Update copyright for the year 2010.

[postgresql] / src / backend / utils / cache / relcache.c

/*-------------------------------------------------------------------------
 *
 * relcache.c
 *        POSTGRES relation descriptor cache code
 *
 * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *        $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.295 2010/01/02 16:57:55 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
/*
 * INTERFACE ROUTINES
 *              RelationCacheInitialize                 - initialize relcache (to empty)
 *              RelationCacheInitializePhase2   - initialize shared-catalog entries
 *              RelationCacheInitializePhase3   - finish initializing relcache
 *              RelationIdGetRelation                   - get a reldesc by relation id
 *              RelationClose                                   - close an open relation
 *
 * NOTES
 *              The following code contains many undocumented hacks.  Please be
 *              careful....
 */
#include "postgres.h"

#include <sys/file.h>
#include <fcntl.h>
#include <unistd.h>

#include "access/genam.h"
#include "access/reloptions.h"
#include "access/sysattr.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/index.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_amop.h"
#include "catalog/pg_amproc.h"
#include "catalog/pg_attrdef.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_database.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_rewrite.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_type.h"
#include "commands/trigger.h"
#include "miscadmin.h"
#include "optimizer/clauses.h"
#include "optimizer/planmain.h"
#include "optimizer/prep.h"
#include "optimizer/var.h"
#include "rewrite/rewriteDefine.h"
#include "storage/fd.h"
#include "storage/lmgr.h"
#include "storage/smgr.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/relcache.h"
#include "utils/resowner.h"
#include "utils/syscache.h"
#include "utils/tqual.h"
#include "utils/typcache.h"


/*
 *              name of relcache init file(s), used to speed up backend startup
 */
#define RELCACHE_INIT_FILENAME  "pg_internal.init"

#define RELCACHE_INIT_FILEMAGIC         0x573265        /* version ID value */

/*
 *              hardcoded tuple descriptors.  see include/catalog/pg_attribute.h
 */
static const FormData_pg_attribute Desc_pg_class[Natts_pg_class] = {Schema_pg_class};
static const FormData_pg_attribute Desc_pg_attribute[Natts_pg_attribute] = {Schema_pg_attribute};
static const FormData_pg_attribute Desc_pg_proc[Natts_pg_proc] = {Schema_pg_proc};
static const FormData_pg_attribute Desc_pg_type[Natts_pg_type] = {Schema_pg_type};
static const FormData_pg_attribute Desc_pg_database[Natts_pg_database] = {Schema_pg_database};
static const FormData_pg_attribute Desc_pg_index[Natts_pg_index] = {Schema_pg_index};

/*
 *              Hash tables that index the relation cache
 *
 *              We used to index the cache by both name and OID, but now there
 *              is only an index by OID.
 */
typedef struct relidcacheent
{
        Oid                     reloid;
        Relation        reldesc;
} RelIdCacheEnt;

static HTAB *RelationIdCache;

/*
 * This flag is false until we have prepared the critical relcache entries
 * that are needed to do indexscans on the tables read by relcache building.
 */
bool            criticalRelcachesBuilt = false;

/*
 * This flag is false until we have prepared the critical relcache entries
 * for shared catalogs (specifically, pg_database and its indexes).
 */
bool            criticalSharedRelcachesBuilt = false;

/*
 * This counter counts relcache inval events received since backend startup
 * (but only for rels that are actually in cache).      Presently, we use it only
 * to detect whether data about to be written by write_relcache_init_file()
 * might already be obsolete.
 */
static long relcacheInvalsReceived = 0L;

/*
 * This list remembers the OIDs of the non-shared relations cached in the
 * database's local relcache init file.  Note that there is no corresponding
 * list for the shared relcache init file, for reasons explained in the
 * comments for RelationCacheInitFileRemove.
 */
static List *initFileRelationIds = NIL;

/*
 * This flag lets us optimize away work in AtEO(Sub)Xact_RelationCache().
 */
static bool need_eoxact_work = false;


/*
 *              macros to manipulate the lookup hashtables
 */
#define RelationCacheInsert(RELATION)   \
do { \
        RelIdCacheEnt *idhentry; bool found; \
        idhentry = (RelIdCacheEnt*)hash_search(RelationIdCache, \
                                                                                   (void *) &(RELATION->rd_id), \
                                                                                   HASH_ENTER, &found); \
        /* used to give notice if found -- now just keep quiet */ \
        idhentry->reldesc = RELATION; \
} while(0)

#define RelationIdCacheLookup(ID, RELATION) \
do { \
        RelIdCacheEnt *hentry; \
        hentry = (RelIdCacheEnt*)hash_search(RelationIdCache, \
                                                                                 (void *) &(ID), \
                                                                                 HASH_FIND, NULL); \
        if (hentry) \
                RELATION = hentry->reldesc; \
        else \
                RELATION = NULL; \
} while(0)

#define RelationCacheDelete(RELATION) \
do { \
        RelIdCacheEnt *idhentry; \
        idhentry = (RelIdCacheEnt*)hash_search(RelationIdCache, \
                                                                                   (void *) &(RELATION->rd_id), \
                                                                                   HASH_REMOVE, NULL); \
        if (idhentry == NULL) \
                elog(WARNING, "trying to delete a rd_id reldesc that does not exist"); \
} while(0)


/*
 * Special cache for opclass-related information
 *
 * Note: only default operators and support procs get cached, ie, those with
 * lefttype = righttype = opcintype.
 */
typedef struct opclasscacheent
{
        Oid                     opclassoid;             /* lookup key: OID of opclass */
        bool            valid;                  /* set TRUE after successful fill-in */
        StrategyNumber numStrats;       /* max # of strategies (from pg_am) */
        StrategyNumber numSupport;      /* max # of support procs (from pg_am) */
        Oid                     opcfamily;              /* OID of opclass's family */
        Oid                     opcintype;              /* OID of opclass's declared input type */
        Oid                *operatorOids;       /* strategy operators' OIDs */
        RegProcedure *supportProcs; /* support procs */
} OpClassCacheEnt;

static HTAB *OpClassCache = NULL;


/* non-export function prototypes */

static void RelationClearRelation(Relation relation, bool rebuild);

static void RelationReloadIndexInfo(Relation relation);
static void RelationFlushRelation(Relation relation);
static bool load_relcache_init_file(bool shared);
static void write_relcache_init_file(bool shared);
static void write_item(const void *data, Size len, FILE *fp);

static void formrdesc(const char *relationName, Oid relationReltype,
                  bool isshared, bool hasoids,
                  int natts, const FormData_pg_attribute *attrs);

static HeapTuple ScanPgRelation(Oid targetRelId, bool indexOK);
static Relation AllocateRelationDesc(Relation relation, Form_pg_class relp);
static void RelationParseRelOptions(Relation relation, HeapTuple tuple);
static void RelationBuildTupleDesc(Relation relation);
static Relation RelationBuildDesc(Oid targetRelId, Relation oldrelation);
static void RelationInitPhysicalAddr(Relation relation);
static void load_critical_index(Oid indexoid);
static TupleDesc GetPgClassDescriptor(void);
static TupleDesc GetPgIndexDescriptor(void);
static void AttrDefaultFetch(Relation relation);
static void CheckConstraintFetch(Relation relation);
static List *insert_ordered_oid(List *list, Oid datum);
static void IndexSupportInitialize(oidvector *indclass,
                                           Oid *indexOperator,
                                           RegProcedure *indexSupport,
                                           Oid *opFamily,
                                           Oid *opcInType,
                                           StrategyNumber maxStrategyNumber,
                                           StrategyNumber maxSupportNumber,
                                           AttrNumber maxAttributeNumber);
static OpClassCacheEnt *LookupOpclassInfo(Oid operatorClassOid,
                                  StrategyNumber numStrats,
                                  StrategyNumber numSupport);
static void RelationCacheInitFileRemoveInDir(const char *tblspcpath);
static void unlink_initfile(const char *initfilename);


/*
 *              ScanPgRelation
 *
 *              This is used by RelationBuildDesc to find a pg_class
 *              tuple matching targetRelId.  The caller must hold at least
 *              AccessShareLock on the target relid to prevent concurrent-update
 *              scenarios --- else our SnapshotNow scan might fail to find any
 *              version that it thinks is live.
 *
 *              NB: the returned tuple has been copied into palloc'd storage
 *              and must eventually be freed with heap_freetuple.
 */
static HeapTuple
ScanPgRelation(Oid targetRelId, bool indexOK)
{
        HeapTuple       pg_class_tuple;
        Relation        pg_class_desc;
        SysScanDesc pg_class_scan;
        ScanKeyData key[1];

        /*
         * If something goes wrong during backend startup, we might find ourselves
         * trying to read pg_class before we've selected a database.  That ain't
         * gonna work, so bail out with a useful error message.  If this happens,
         * it probably means a relcache entry that needs to be nailed isn't.
         */
        if (!OidIsValid(MyDatabaseId))
                elog(FATAL, "cannot read pg_class without having selected a database");

        /*
         * form a scan key
         */
        ScanKeyInit(&key[0],
                                ObjectIdAttributeNumber,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(targetRelId));

        /*
         * Open pg_class and fetch a tuple.  Force heap scan if we haven't yet
         * built the critical relcache entries (this includes initdb and startup
         * without a pg_internal.init file).  The caller can also force a heap
         * scan by setting indexOK == false.
         */
        pg_class_desc = heap_open(RelationRelationId, AccessShareLock);
        pg_class_scan = systable_beginscan(pg_class_desc, ClassOidIndexId,
                                                                           indexOK && criticalRelcachesBuilt,
                                                                           SnapshotNow,
                                                                           1, key);

        pg_class_tuple = systable_getnext(pg_class_scan);

        /*
         * Must copy tuple before releasing buffer.
         */
        if (HeapTupleIsValid(pg_class_tuple))
                pg_class_tuple = heap_copytuple(pg_class_tuple);

        /* all done */
        systable_endscan(pg_class_scan);
        heap_close(pg_class_desc, AccessShareLock);

        return pg_class_tuple;
}

/*
 *              AllocateRelationDesc
 *
 *              This is used to allocate memory for a new relation descriptor
 *              and initialize the rd_rel field.
 *
 *              If 'relation' is NULL, allocate a new RelationData object.
 *              If not, reuse the given object (that path is taken only when
 *              we have to rebuild a relcache entry during RelationClearRelation).
 */
static Relation
AllocateRelationDesc(Relation relation, Form_pg_class relp)
{
        MemoryContext oldcxt;
        Form_pg_class relationForm;

        /* Relcache entries must live in CacheMemoryContext */
        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

        /*
         * allocate space for new relation descriptor, if needed
         */
        if (relation == NULL)
                relation = (Relation) palloc(sizeof(RelationData));

        /*
         * clear all fields of reldesc
         */
        MemSet(relation, 0, sizeof(RelationData));
        relation->rd_targblock = InvalidBlockNumber;
        relation->rd_fsm_nblocks = InvalidBlockNumber;
        relation->rd_vm_nblocks = InvalidBlockNumber;

        /* make sure relation is marked as having no open file yet */
        relation->rd_smgr = NULL;

        /*
         * Copy the relation tuple form
         *
         * We only allocate space for the fixed fields, ie, CLASS_TUPLE_SIZE. The
         * variable-length fields (relacl, reloptions) are NOT stored in the
         * relcache --- there'd be little point in it, since we don't copy the
         * tuple's nulls bitmap and hence wouldn't know if the values are valid.
         * Bottom line is that relacl *cannot* be retrieved from the relcache. Get
         * it from the syscache if you need it.  The same goes for the original
         * form of reloptions (however, we do store the parsed form of reloptions
         * in rd_options).
         */
        relationForm = (Form_pg_class) palloc(CLASS_TUPLE_SIZE);

        memcpy(relationForm, relp, CLASS_TUPLE_SIZE);

        /* initialize relation tuple form */
        relation->rd_rel = relationForm;

        /* and allocate attribute tuple form storage */
        relation->rd_att = CreateTemplateTupleDesc(relationForm->relnatts,
                                                                                           relationForm->relhasoids);
        /* which we mark as a reference-counted tupdesc */
        relation->rd_att->tdrefcount = 1;

        MemoryContextSwitchTo(oldcxt);

        return relation;
}

/*
 * RelationParseRelOptions
 *              Convert pg_class.reloptions into pre-parsed rd_options
 *
 * tuple is the real pg_class tuple (not rd_rel!) for relation
 *
 * Note: rd_rel and (if an index) rd_am must be valid already
 */
static void
RelationParseRelOptions(Relation relation, HeapTuple tuple)
{
        bytea      *options;

        relation->rd_options = NULL;

        /* Fall out if relkind should not have options */
        switch (relation->rd_rel->relkind)
        {
                case RELKIND_RELATION:
                case RELKIND_TOASTVALUE:
                case RELKIND_UNCATALOGED:
                case RELKIND_INDEX:
                        break;
                default:
                        return;
        }

        /*
         * Fetch reloptions from tuple; have to use a hardwired descriptor because
         * we might not have any other for pg_class yet (consider executing this
         * code for pg_class itself)
         */
        options = extractRelOptions(tuple,
                                                                GetPgClassDescriptor(),
                                                                relation->rd_rel->relkind == RELKIND_INDEX ?
                                                                relation->rd_am->amoptions : InvalidOid);

        /* Copy parsed data into CacheMemoryContext */
        if (options)
        {
                relation->rd_options = MemoryContextAlloc(CacheMemoryContext,
                                                                                                  VARSIZE(options));
                memcpy(relation->rd_options, options, VARSIZE(options));
        }
}

/*
 *              RelationBuildTupleDesc
 *
 *              Form the relation's tuple descriptor from information in
 *              the pg_attribute, pg_attrdef & pg_constraint system catalogs.
 */
static void
RelationBuildTupleDesc(Relation relation)
{
        HeapTuple       pg_attribute_tuple;
        Relation        pg_attribute_desc;
        SysScanDesc pg_attribute_scan;
        ScanKeyData skey[2];
        int                     need;
        TupleConstr *constr;
        AttrDefault *attrdef = NULL;
        int                     ndef = 0;

        /* copy some fields from pg_class row to rd_att */
        relation->rd_att->tdtypeid = relation->rd_rel->reltype;
        relation->rd_att->tdtypmod = -1;        /* unnecessary, but... */
        relation->rd_att->tdhasoid = relation->rd_rel->relhasoids;

        constr = (TupleConstr *) MemoryContextAlloc(CacheMemoryContext,
                                                                                                sizeof(TupleConstr));
        constr->has_not_null = false;

        /*
         * Form a scan key that selects only user attributes (attnum > 0).
         * (Eliminating system attribute rows at the index level is lots faster
         * than fetching them.)
         */
        ScanKeyInit(&skey[0],
                                Anum_pg_attribute_attrelid,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(RelationGetRelid(relation)));
        ScanKeyInit(&skey[1],
                                Anum_pg_attribute_attnum,
                                BTGreaterStrategyNumber, F_INT2GT,
                                Int16GetDatum(0));

        /*
         * Open pg_attribute and begin a scan.  Force heap scan if we haven't yet
         * built the critical relcache entries (this includes initdb and startup
         * without a pg_internal.init file).
         */
        pg_attribute_desc = heap_open(AttributeRelationId, AccessShareLock);
        pg_attribute_scan = systable_beginscan(pg_attribute_desc,
                                                                                   AttributeRelidNumIndexId,
                                                                                   criticalRelcachesBuilt,
                                                                                   SnapshotNow,
                                                                                   2, skey);

        /*
         * add attribute data to relation->rd_att
         */
        need = relation->rd_rel->relnatts;

        while (HeapTupleIsValid(pg_attribute_tuple = systable_getnext(pg_attribute_scan)))
        {
                Form_pg_attribute attp;

                attp = (Form_pg_attribute) GETSTRUCT(pg_attribute_tuple);

                if (attp->attnum <= 0 ||
                        attp->attnum > relation->rd_rel->relnatts)
                        elog(ERROR, "invalid attribute number %d for %s",
                                 attp->attnum, RelationGetRelationName(relation));

                memcpy(relation->rd_att->attrs[attp->attnum - 1],
                           attp,
                           ATTRIBUTE_FIXED_PART_SIZE);

                /* Update constraint/default info */
                if (attp->attnotnull)
                        constr->has_not_null = true;

                if (attp->atthasdef)
                {
                        if (attrdef == NULL)
                                attrdef = (AttrDefault *)
                                        MemoryContextAllocZero(CacheMemoryContext,
                                                                                   relation->rd_rel->relnatts *
                                                                                   sizeof(AttrDefault));
                        attrdef[ndef].adnum = attp->attnum;
                        attrdef[ndef].adbin = NULL;
                        ndef++;
                }
                need--;
                if (need == 0)
                        break;
        }

        /*
         * end the scan and close the attribute relation
         */
        systable_endscan(pg_attribute_scan);
        heap_close(pg_attribute_desc, AccessShareLock);

        if (need != 0)
                elog(ERROR, "catalog is missing %d attribute(s) for relid %u",
                         need, RelationGetRelid(relation));

        /*
         * The attcacheoff values we read from pg_attribute should all be -1
         * ("unknown").  Verify this if assert checking is on.  They will be
         * computed when and if needed during tuple access.
         */
#ifdef USE_ASSERT_CHECKING
        {
                int                     i;

                for (i = 0; i < relation->rd_rel->relnatts; i++)
                        Assert(relation->rd_att->attrs[i]->attcacheoff == -1);
        }
#endif

        /*
         * However, we can easily set the attcacheoff value for the first
         * attribute: it must be zero.  This eliminates the need for special cases
         * for attnum=1 that used to exist in fastgetattr() and index_getattr().
         */
        if (relation->rd_rel->relnatts > 0)
                relation->rd_att->attrs[0]->attcacheoff = 0;

        /*
         * Set up constraint/default info
         */
        if (constr->has_not_null || ndef > 0 || relation->rd_rel->relchecks)
        {
                relation->rd_att->constr = constr;

                if (ndef > 0)                   /* DEFAULTs */
                {
                        if (ndef < relation->rd_rel->relnatts)
                                constr->defval = (AttrDefault *)
                                        repalloc(attrdef, ndef * sizeof(AttrDefault));
                        else
                                constr->defval = attrdef;
                        constr->num_defval = ndef;
                        AttrDefaultFetch(relation);
                }
                else
                        constr->num_defval = 0;

                if (relation->rd_rel->relchecks > 0)    /* CHECKs */
                {
                        constr->num_check = relation->rd_rel->relchecks;
                        constr->check = (ConstrCheck *)
                                MemoryContextAllocZero(CacheMemoryContext,
                                                                        constr->num_check * sizeof(ConstrCheck));
                        CheckConstraintFetch(relation);
                }
                else
                        constr->num_check = 0;
        }
        else
        {
                pfree(constr);
                relation->rd_att->constr = NULL;
        }
}

/*
 *              RelationBuildRuleLock
 *
 *              Form the relation's rewrite rules from information in
 *              the pg_rewrite system catalog.
 *
 * Note: The rule parsetrees are potentially very complex node structures.
 * To allow these trees to be freed when the relcache entry is flushed,
 * we make a private memory context to hold the RuleLock information for
 * each relcache entry that has associated rules.  The context is used
 * just for rule info, not for any other subsidiary data of the relcache
 * entry, because that keeps the update logic in RelationClearRelation()
 * manageable.  The other subsidiary data structures are simple enough
 * to be easy to free explicitly, anyway.
 */
static void
RelationBuildRuleLock(Relation relation)
{
        MemoryContext rulescxt;
        MemoryContext oldcxt;
        HeapTuple       rewrite_tuple;
        Relation        rewrite_desc;
        TupleDesc       rewrite_tupdesc;
        SysScanDesc rewrite_scan;
        ScanKeyData key;
        RuleLock   *rulelock;
        int                     numlocks;
        RewriteRule **rules;
        int                     maxlocks;

        /*
         * Make the private context.  Parameters are set on the assumption that
         * it'll probably not contain much data.
         */
        rulescxt = AllocSetContextCreate(CacheMemoryContext,
                                                                         RelationGetRelationName(relation),
                                                                         ALLOCSET_SMALL_MINSIZE,
                                                                         ALLOCSET_SMALL_INITSIZE,
                                                                         ALLOCSET_SMALL_MAXSIZE);
        relation->rd_rulescxt = rulescxt;

        /*
         * allocate an array to hold the rewrite rules (the array is extended if
         * necessary)
         */
        maxlocks = 4;
        rules = (RewriteRule **)
                MemoryContextAlloc(rulescxt, sizeof(RewriteRule *) * maxlocks);
        numlocks = 0;

        /*
         * form a scan key
         */
        ScanKeyInit(&key,
                                Anum_pg_rewrite_ev_class,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(RelationGetRelid(relation)));

        /*
         * open pg_rewrite and begin a scan
         *
         * Note: since we scan the rules using RewriteRelRulenameIndexId, we will
         * be reading the rules in name order, except possibly during
         * emergency-recovery operations (ie, IgnoreSystemIndexes). This in turn
         * ensures that rules will be fired in name order.
         */
        rewrite_desc = heap_open(RewriteRelationId, AccessShareLock);
        rewrite_tupdesc = RelationGetDescr(rewrite_desc);
        rewrite_scan = systable_beginscan(rewrite_desc,
                                                                          RewriteRelRulenameIndexId,
                                                                          true, SnapshotNow,
                                                                          1, &key);

        while (HeapTupleIsValid(rewrite_tuple = systable_getnext(rewrite_scan)))
        {
                Form_pg_rewrite rewrite_form = (Form_pg_rewrite) GETSTRUCT(rewrite_tuple);
                bool            isnull;
                Datum           rule_datum;
                char       *rule_str;
                RewriteRule *rule;

                rule = (RewriteRule *) MemoryContextAlloc(rulescxt,
                                                                                                  sizeof(RewriteRule));

                rule->ruleId = HeapTupleGetOid(rewrite_tuple);

                rule->event = rewrite_form->ev_type - '0';
                rule->attrno = rewrite_form->ev_attr;
                rule->enabled = rewrite_form->ev_enabled;
                rule->isInstead = rewrite_form->is_instead;

                /*
                 * Must use heap_getattr to fetch ev_action and ev_qual.  Also, the
                 * rule strings are often large enough to be toasted.  To avoid
                 * leaking memory in the caller's context, do the detoasting here so
                 * we can free the detoasted version.
                 */
                rule_datum = heap_getattr(rewrite_tuple,
                                                                  Anum_pg_rewrite_ev_action,
                                                                  rewrite_tupdesc,
                                                                  &isnull);
                Assert(!isnull);
                rule_str = TextDatumGetCString(rule_datum);
                oldcxt = MemoryContextSwitchTo(rulescxt);
                rule->actions = (List *) stringToNode(rule_str);
                MemoryContextSwitchTo(oldcxt);
                pfree(rule_str);

                rule_datum = heap_getattr(rewrite_tuple,
                                                                  Anum_pg_rewrite_ev_qual,
                                                                  rewrite_tupdesc,
                                                                  &isnull);
                Assert(!isnull);
                rule_str = TextDatumGetCString(rule_datum);
                oldcxt = MemoryContextSwitchTo(rulescxt);
                rule->qual = (Node *) stringToNode(rule_str);
                MemoryContextSwitchTo(oldcxt);
                pfree(rule_str);

                /*
                 * We want the rule's table references to be checked as though by the
                 * table owner, not the user referencing the rule.      Therefore, scan
                 * through the rule's actions and set the checkAsUser field on all
                 * rtable entries.      We have to look at the qual as well, in case it
                 * contains sublinks.
                 *
                 * The reason for doing this when the rule is loaded, rather than when
                 * it is stored, is that otherwise ALTER TABLE OWNER would have to
                 * grovel through stored rules to update checkAsUser fields. Scanning
                 * the rule tree during load is relatively cheap (compared to
                 * constructing it in the first place), so we do it here.
                 */
                setRuleCheckAsUser((Node *) rule->actions, relation->rd_rel->relowner);
                setRuleCheckAsUser(rule->qual, relation->rd_rel->relowner);

                if (numlocks >= maxlocks)
                {
                        maxlocks *= 2;
                        rules = (RewriteRule **)
                                repalloc(rules, sizeof(RewriteRule *) * maxlocks);
                }
                rules[numlocks++] = rule;
        }

        /*
         * end the scan and close the attribute relation
         */
        systable_endscan(rewrite_scan);
        heap_close(rewrite_desc, AccessShareLock);

        /*
         * there might not be any rules (if relhasrules is out-of-date)
         */
        if (numlocks == 0)
        {
                relation->rd_rules = NULL;
                relation->rd_rulescxt = NULL;
                MemoryContextDelete(rulescxt);
                return;
        }

        /*
         * form a RuleLock and insert into relation
         */
        rulelock = (RuleLock *) MemoryContextAlloc(rulescxt, sizeof(RuleLock));
        rulelock->numLocks = numlocks;
        rulelock->rules = rules;

        relation->rd_rules = rulelock;
}

/*
 *              equalRuleLocks
 *
 *              Determine whether two RuleLocks are equivalent
 *
 *              Probably this should be in the rules code someplace...
 */
static bool
equalRuleLocks(RuleLock *rlock1, RuleLock *rlock2)
{
        int                     i;

        /*
         * As of 7.3 we assume the rule ordering is repeatable, because
         * RelationBuildRuleLock should read 'em in a consistent order.  So just
         * compare corresponding slots.
         */
        if (rlock1 != NULL)
        {
                if (rlock2 == NULL)
                        return false;
                if (rlock1->numLocks != rlock2->numLocks)
                        return false;
                for (i = 0; i < rlock1->numLocks; i++)
                {
                        RewriteRule *rule1 = rlock1->rules[i];
                        RewriteRule *rule2 = rlock2->rules[i];

                        if (rule1->ruleId != rule2->ruleId)
                                return false;
                        if (rule1->event != rule2->event)
                                return false;
                        if (rule1->attrno != rule2->attrno)
                                return false;
                        if (rule1->enabled != rule2->enabled)
                                return false;
                        if (rule1->isInstead != rule2->isInstead)
                                return false;
                        if (!equal(rule1->qual, rule2->qual))
                                return false;
                        if (!equal(rule1->actions, rule2->actions))
                                return false;
                }
        }
        else if (rlock2 != NULL)
                return false;
        return true;
}


/*
 *              RelationBuildDesc
 *
 *              Build a relation descriptor --- either a new one, or by
 *              recycling the given old relation object.  The latter case
 *              supports rebuilding a relcache entry without invalidating
 *              pointers to it.  The caller must hold at least
 *              AccessShareLock on the target relid.
 *
 *              Returns NULL if no pg_class row could be found for the given relid
 *              (suggesting we are trying to access a just-deleted relation).
 *              Any other error is reported via elog.
 */
static Relation
RelationBuildDesc(Oid targetRelId, Relation oldrelation)
{
        Relation        relation;
        Oid                     relid;
        HeapTuple       pg_class_tuple;
        Form_pg_class relp;
        MemoryContext oldcxt;

        /*
         * find the tuple in pg_class corresponding to the given relation id
         */
        pg_class_tuple = ScanPgRelation(targetRelId, true);

        /*
         * if no such tuple exists, return NULL
         */
        if (!HeapTupleIsValid(pg_class_tuple))
                return NULL;

        /*
         * get information from the pg_class_tuple
         */
        relid = HeapTupleGetOid(pg_class_tuple);
        relp = (Form_pg_class) GETSTRUCT(pg_class_tuple);

        /*
         * allocate storage for the relation descriptor, and copy pg_class_tuple
         * to relation->rd_rel.
         */
        relation = AllocateRelationDesc(oldrelation, relp);

        /*
         * initialize the relation's relation id (relation->rd_id)
         */
        RelationGetRelid(relation) = relid;

        /*
         * normal relations are not nailed into the cache; nor can a pre-existing
         * relation be new.  It could be temp though.  (Actually, it could be new
         * too, but it's okay to forget that fact if forced to flush the entry.)
         */
        relation->rd_refcnt = 0;
        relation->rd_isnailed = false;
        relation->rd_createSubid = InvalidSubTransactionId;
        relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;
        relation->rd_istemp = relation->rd_rel->relistemp;
        if (relation->rd_istemp)
                relation->rd_islocaltemp = isTempOrToastNamespace(relation->rd_rel->relnamespace);
        else
                relation->rd_islocaltemp = false;

        /*
         * initialize the tuple descriptor (relation->rd_att).
         */
        RelationBuildTupleDesc(relation);

        /*
         * Fetch rules and triggers that affect this relation
         */
        if (relation->rd_rel->relhasrules)
                RelationBuildRuleLock(relation);
        else
        {
                relation->rd_rules = NULL;
                relation->rd_rulescxt = NULL;
        }

        if (relation->rd_rel->relhastriggers)
                RelationBuildTriggers(relation);
        else
                relation->trigdesc = NULL;

        /*
         * if it's an index, initialize index-related information
         */
        if (OidIsValid(relation->rd_rel->relam))
                RelationInitIndexAccessInfo(relation);

        /* extract reloptions if any */
        RelationParseRelOptions(relation, pg_class_tuple);

        /*
         * initialize the relation lock manager information
         */
        RelationInitLockInfo(relation);         /* see lmgr.c */

        /*
         * initialize physical addressing information for the relation
         */
        RelationInitPhysicalAddr(relation);

        /* make sure relation is marked as having no open file yet */
        relation->rd_smgr = NULL;

        /*
         * now we can free the memory allocated for pg_class_tuple
         */
        heap_freetuple(pg_class_tuple);

        /*
         * Insert newly created relation into relcache hash tables.
         */
        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
        RelationCacheInsert(relation);
        MemoryContextSwitchTo(oldcxt);

        /* It's fully valid */
        relation->rd_isvalid = true;

        return relation;
}

/*
 * Initialize the physical addressing info (RelFileNode) for a relcache entry
 */
static void
RelationInitPhysicalAddr(Relation relation)
{
        if (relation->rd_rel->reltablespace)
                relation->rd_node.spcNode = relation->rd_rel->reltablespace;
        else
                relation->rd_node.spcNode = MyDatabaseTableSpace;
        if (relation->rd_rel->relisshared)
                relation->rd_node.dbNode = InvalidOid;
        else
                relation->rd_node.dbNode = MyDatabaseId;
        relation->rd_node.relNode = relation->rd_rel->relfilenode;
}

/*
 * Initialize index-access-method support data for an index relation
 */
void
RelationInitIndexAccessInfo(Relation relation)
{
        HeapTuple       tuple;
        Form_pg_am      aform;
        Datum           indclassDatum;
        Datum           indoptionDatum;
        bool            isnull;
        oidvector  *indclass;
        int2vector *indoption;
        MemoryContext indexcxt;
        MemoryContext oldcontext;
        int                     natts;
        uint16          amstrategies;
        uint16          amsupport;

        /*
         * Make a copy of the pg_index entry for the index.  Since pg_index
         * contains variable-length and possibly-null fields, we have to do this
         * honestly rather than just treating it as a Form_pg_index struct.
         */
        tuple = SearchSysCache(INDEXRELID,
                                                   ObjectIdGetDatum(RelationGetRelid(relation)),
                                                   0, 0, 0);
        if (!HeapTupleIsValid(tuple))
                elog(ERROR, "cache lookup failed for index %u",
                         RelationGetRelid(relation));
        oldcontext = MemoryContextSwitchTo(CacheMemoryContext);
        relation->rd_indextuple = heap_copytuple(tuple);
        relation->rd_index = (Form_pg_index) GETSTRUCT(relation->rd_indextuple);
        MemoryContextSwitchTo(oldcontext);
        ReleaseSysCache(tuple);

        /*
         * Make a copy of the pg_am entry for the index's access method
         */
        tuple = SearchSysCache(AMOID,
                                                   ObjectIdGetDatum(relation->rd_rel->relam),
                                                   0, 0, 0);
        if (!HeapTupleIsValid(tuple))
                elog(ERROR, "cache lookup failed for access method %u",
                         relation->rd_rel->relam);
        aform = (Form_pg_am) MemoryContextAlloc(CacheMemoryContext, sizeof *aform);
        memcpy(aform, GETSTRUCT(tuple), sizeof *aform);
        ReleaseSysCache(tuple);
        relation->rd_am = aform;

        natts = relation->rd_rel->relnatts;
        if (natts != relation->rd_index->indnatts)
                elog(ERROR, "relnatts disagrees with indnatts for index %u",
                         RelationGetRelid(relation));
        amstrategies = aform->amstrategies;
        amsupport = aform->amsupport;

        /*
         * Make the private context to hold index access info.  The reason we need
         * a context, and not just a couple of pallocs, is so that we won't leak
         * any subsidiary info attached to fmgr lookup records.
         *
         * Context parameters are set on the assumption that it'll probably not
         * contain much data.
         */
        indexcxt = AllocSetContextCreate(CacheMemoryContext,
                                                                         RelationGetRelationName(relation),
                                                                         ALLOCSET_SMALL_MINSIZE,
                                                                         ALLOCSET_SMALL_INITSIZE,
                                                                         ALLOCSET_SMALL_MAXSIZE);
        relation->rd_indexcxt = indexcxt;

        /*
         * Allocate arrays to hold data
         */
        relation->rd_aminfo = (RelationAmInfo *)
                MemoryContextAllocZero(indexcxt, sizeof(RelationAmInfo));

        relation->rd_opfamily = (Oid *)
                MemoryContextAllocZero(indexcxt, natts * sizeof(Oid));
        relation->rd_opcintype = (Oid *)
                MemoryContextAllocZero(indexcxt, natts * sizeof(Oid));

        if (amstrategies > 0)
                relation->rd_operator = (Oid *)
                        MemoryContextAllocZero(indexcxt,
                                                                   natts * amstrategies * sizeof(Oid));
        else
                relation->rd_operator = NULL;

        if (amsupport > 0)
        {
                int                     nsupport = natts * amsupport;

                relation->rd_support = (RegProcedure *)
                        MemoryContextAllocZero(indexcxt, nsupport * sizeof(RegProcedure));
                relation->rd_supportinfo = (FmgrInfo *)
                        MemoryContextAllocZero(indexcxt, nsupport * sizeof(FmgrInfo));
        }
        else
        {
                relation->rd_support = NULL;
                relation->rd_supportinfo = NULL;
        }

        relation->rd_indoption = (int16 *)
                MemoryContextAllocZero(indexcxt, natts * sizeof(int16));

        /*
         * indclass cannot be referenced directly through the C struct, because it
         * comes after the variable-width indkey field.  Must extract the datum
         * the hard way...
         */
        indclassDatum = fastgetattr(relation->rd_indextuple,
                                                                Anum_pg_index_indclass,
                                                                GetPgIndexDescriptor(),
                                                                &isnull);
        Assert(!isnull);
        indclass = (oidvector *) DatumGetPointer(indclassDatum);

        /*
         * Fill the operator and support procedure OID arrays, as well as the info
         * about opfamilies and opclass input types.  (aminfo and supportinfo are
         * left as zeroes, and are filled on-the-fly when used)
         */
        IndexSupportInitialize(indclass,
                                                   relation->rd_operator, relation->rd_support,
                                                   relation->rd_opfamily, relation->rd_opcintype,
                                                   amstrategies, amsupport, natts);

        /*
         * Similarly extract indoption and copy it to the cache entry
         */
        indoptionDatum = fastgetattr(relation->rd_indextuple,
                                                                 Anum_pg_index_indoption,
                                                                 GetPgIndexDescriptor(),
                                                                 &isnull);
        Assert(!isnull);
        indoption = (int2vector *) DatumGetPointer(indoptionDatum);
        memcpy(relation->rd_indoption, indoption->values, natts * sizeof(int16));

        /*
         * expressions, predicate, exclusion caches will be filled later
         */
        relation->rd_indexprs = NIL;
        relation->rd_indpred = NIL;
        relation->rd_exclops = NULL;
        relation->rd_exclprocs = NULL;
        relation->rd_exclstrats = NULL;
        relation->rd_amcache = NULL;
}

/*
 * IndexSupportInitialize
 *              Initializes an index's cached opclass information,
 *              given the index's pg_index.indclass entry.
 *
 * Data is returned into *indexOperator, *indexSupport, *opFamily, and
 * *opcInType, which are arrays allocated by the caller.
 *
 * The caller also passes maxStrategyNumber, maxSupportNumber, and
 * maxAttributeNumber, since these indicate the size of the arrays
 * it has allocated --- but in practice these numbers must always match
 * those obtainable from the system catalog entries for the index and
 * access method.
 */
static void
IndexSupportInitialize(oidvector *indclass,
                                           Oid *indexOperator,
                                           RegProcedure *indexSupport,
                                           Oid *opFamily,
                                           Oid *opcInType,
                                           StrategyNumber maxStrategyNumber,
                                           StrategyNumber maxSupportNumber,
                                           AttrNumber maxAttributeNumber)
{
        int                     attIndex;

        for (attIndex = 0; attIndex < maxAttributeNumber; attIndex++)
        {
                OpClassCacheEnt *opcentry;

                if (!OidIsValid(indclass->values[attIndex]))
                        elog(ERROR, "bogus pg_index tuple");

                /* look up the info for this opclass, using a cache */
                opcentry = LookupOpclassInfo(indclass->values[attIndex],
                                                                         maxStrategyNumber,
                                                                         maxSupportNumber);

                /* copy cached data into relcache entry */
                opFamily[attIndex] = opcentry->opcfamily;
                opcInType[attIndex] = opcentry->opcintype;
                if (maxStrategyNumber > 0)
                        memcpy(&indexOperator[attIndex * maxStrategyNumber],
                                   opcentry->operatorOids,
                                   maxStrategyNumber * sizeof(Oid));
                if (maxSupportNumber > 0)
                        memcpy(&indexSupport[attIndex * maxSupportNumber],
                                   opcentry->supportProcs,
                                   maxSupportNumber * sizeof(RegProcedure));
        }
}

/*
 * LookupOpclassInfo
 *
 * This routine maintains a per-opclass cache of the information needed
 * by IndexSupportInitialize().  This is more efficient than relying on
 * the catalog cache, because we can load all the info about a particular
 * opclass in a single indexscan of pg_amproc or pg_amop.
 *
 * The information from pg_am about expected range of strategy and support
 * numbers is passed in, rather than being looked up, mainly because the
 * caller will have it already.
 *
 * Note there is no provision for flushing the cache.  This is OK at the
 * moment because there is no way to ALTER any interesting properties of an
 * existing opclass --- all you can do is drop it, which will result in
 * a useless but harmless dead entry in the cache.      To support altering
 * opclass membership (not the same as opfamily membership!), we'd need to
 * be able to flush this cache as well as the contents of relcache entries
 * for indexes.
 */
static OpClassCacheEnt *
LookupOpclassInfo(Oid operatorClassOid,
                                  StrategyNumber numStrats,
                                  StrategyNumber numSupport)
{
        OpClassCacheEnt *opcentry;
        bool            found;
        Relation        rel;
        SysScanDesc scan;
        ScanKeyData skey[3];
        HeapTuple       htup;
        bool            indexOK;

        if (OpClassCache == NULL)
        {
                /* First time through: initialize the opclass cache */
                HASHCTL         ctl;

                MemSet(&ctl, 0, sizeof(ctl));
                ctl.keysize = sizeof(Oid);
                ctl.entrysize = sizeof(OpClassCacheEnt);
                ctl.hash = oid_hash;
                OpClassCache = hash_create("Operator class cache", 64,
                                                                   &ctl, HASH_ELEM | HASH_FUNCTION);

                /* Also make sure CacheMemoryContext exists */
                if (!CacheMemoryContext)
                        CreateCacheMemoryContext();
        }

        opcentry = (OpClassCacheEnt *) hash_search(OpClassCache,
                                                                                           (void *) &operatorClassOid,
                                                                                           HASH_ENTER, &found);

        if (!found)
        {
                /* Need to allocate memory for new entry */
                opcentry->valid = false;        /* until known OK */
                opcentry->numStrats = numStrats;
                opcentry->numSupport = numSupport;

                if (numStrats > 0)
                        opcentry->operatorOids = (Oid *)
                                MemoryContextAllocZero(CacheMemoryContext,
                                                                           numStrats * sizeof(Oid));
                else
                        opcentry->operatorOids = NULL;

                if (numSupport > 0)
                        opcentry->supportProcs = (RegProcedure *)
                                MemoryContextAllocZero(CacheMemoryContext,
                                                                           numSupport * sizeof(RegProcedure));
                else
                        opcentry->supportProcs = NULL;
        }
        else
        {
                Assert(numStrats == opcentry->numStrats);
                Assert(numSupport == opcentry->numSupport);
        }

        /*
         * When testing for cache-flush hazards, we intentionally disable the
         * operator class cache and force reloading of the info on each call. This
         * is helpful because we want to test the case where a cache flush occurs
         * while we are loading the info, and it's very hard to provoke that if
         * this happens only once per opclass per backend.
         */
#if defined(CLOBBER_CACHE_ALWAYS)
        opcentry->valid = false;
#endif

        if (opcentry->valid)
                return opcentry;

        /*
         * Need to fill in new entry.
         *
         * To avoid infinite recursion during startup, force heap scans if we're
         * looking up info for the opclasses used by the indexes we would like to
         * reference here.
         */
        indexOK = criticalRelcachesBuilt ||
                (operatorClassOid != OID_BTREE_OPS_OID &&
                 operatorClassOid != INT2_BTREE_OPS_OID);

        /*
         * We have to fetch the pg_opclass row to determine its opfamily and
         * opcintype, which are needed to look up the operators and functions.
         * It'd be convenient to use the syscache here, but that probably doesn't
         * work while bootstrapping.
         */
        ScanKeyInit(&skey[0],
                                ObjectIdAttributeNumber,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(operatorClassOid));
        rel = heap_open(OperatorClassRelationId, AccessShareLock);
        scan = systable_beginscan(rel, OpclassOidIndexId, indexOK,
                                                          SnapshotNow, 1, skey);

        if (HeapTupleIsValid(htup = systable_getnext(scan)))
        {
                Form_pg_opclass opclassform = (Form_pg_opclass) GETSTRUCT(htup);

                opcentry->opcfamily = opclassform->opcfamily;
                opcentry->opcintype = opclassform->opcintype;
        }
        else
                elog(ERROR, "could not find tuple for opclass %u", operatorClassOid);

        systable_endscan(scan);
        heap_close(rel, AccessShareLock);


        /*
         * Scan pg_amop to obtain operators for the opclass.  We only fetch the
         * default ones (those with lefttype = righttype = opcintype).
         */
        if (numStrats > 0)
        {
                ScanKeyInit(&skey[0],
                                        Anum_pg_amop_amopfamily,
                                        BTEqualStrategyNumber, F_OIDEQ,
                                        ObjectIdGetDatum(opcentry->opcfamily));
                ScanKeyInit(&skey[1],
                                        Anum_pg_amop_amoplefttype,
                                        BTEqualStrategyNumber, F_OIDEQ,
                                        ObjectIdGetDatum(opcentry->opcintype));
                ScanKeyInit(&skey[2],
                                        Anum_pg_amop_amoprighttype,
                                        BTEqualStrategyNumber, F_OIDEQ,
                                        ObjectIdGetDatum(opcentry->opcintype));
                rel = heap_open(AccessMethodOperatorRelationId, AccessShareLock);
                scan = systable_beginscan(rel, AccessMethodStrategyIndexId, indexOK,
                                                                  SnapshotNow, 3, skey);

                while (HeapTupleIsValid(htup = systable_getnext(scan)))
                {
                        Form_pg_amop amopform = (Form_pg_amop) GETSTRUCT(htup);

                        if (amopform->amopstrategy <= 0 ||
                                (StrategyNumber) amopform->amopstrategy > numStrats)
                                elog(ERROR, "invalid amopstrategy number %d for opclass %u",
                                         amopform->amopstrategy, operatorClassOid);
                        opcentry->operatorOids[amopform->amopstrategy - 1] =
                                amopform->amopopr;
                }

                systable_endscan(scan);
                heap_close(rel, AccessShareLock);
        }

        /*
         * Scan pg_amproc to obtain support procs for the opclass.      We only fetch
         * the default ones (those with lefttype = righttype = opcintype).
         */
        if (numSupport > 0)
        {
                ScanKeyInit(&skey[0],
                                        Anum_pg_amproc_amprocfamily,
                                        BTEqualStrategyNumber, F_OIDEQ,
                                        ObjectIdGetDatum(opcentry->opcfamily));
                ScanKeyInit(&skey[1],
                                        Anum_pg_amproc_amproclefttype,
                                        BTEqualStrategyNumber, F_OIDEQ,
                                        ObjectIdGetDatum(opcentry->opcintype));
                ScanKeyInit(&skey[2],
                                        Anum_pg_amproc_amprocrighttype,
                                        BTEqualStrategyNumber, F_OIDEQ,
                                        ObjectIdGetDatum(opcentry->opcintype));
                rel = heap_open(AccessMethodProcedureRelationId, AccessShareLock);
                scan = systable_beginscan(rel, AccessMethodProcedureIndexId, indexOK,
                                                                  SnapshotNow, 3, skey);

                while (HeapTupleIsValid(htup = systable_getnext(scan)))
                {
                        Form_pg_amproc amprocform = (Form_pg_amproc) GETSTRUCT(htup);

                        if (amprocform->amprocnum <= 0 ||
                                (StrategyNumber) amprocform->amprocnum > numSupport)
                                elog(ERROR, "invalid amproc number %d for opclass %u",
                                         amprocform->amprocnum, operatorClassOid);

                        opcentry->supportProcs[amprocform->amprocnum - 1] =
                                amprocform->amproc;
                }

                systable_endscan(scan);
                heap_close(rel, AccessShareLock);
        }

        opcentry->valid = true;
        return opcentry;
}


/*
 *              formrdesc
 *
 *              This is a special cut-down version of RelationBuildDesc(),
 *              used while initializing the relcache.
 *              The relation descriptor is built just from the supplied parameters,
 *              without actually looking at any system table entries.  We cheat
 *              quite a lot since we only need to work for a few basic system
 *              catalogs.
 *
 * formrdesc is currently used for: pg_database, pg_class, pg_attribute,
 * pg_proc, and pg_type (see RelationCacheInitializePhase2/3).
 *
 * Note that these catalogs can't have constraints (except attnotnull),
 * default values, rules, or triggers, since we don't cope with any of that.
 * (Well, actually, this only matters for properties that need to be valid
 * during bootstrap or before RelationCacheInitializePhase3 runs, and none of
 * these properties matter then...)
 *
 * NOTE: we assume we are already switched into CacheMemoryContext.
 */
static void
formrdesc(const char *relationName, Oid relationReltype,
                  bool isshared, bool hasoids,
                  int natts, const FormData_pg_attribute *attrs)
{
        Relation        relation;
        int                     i;
        bool            has_not_null;

        /*
         * allocate new relation desc, clear all fields of reldesc
         */
        relation = (Relation) palloc0(sizeof(RelationData));
        relation->rd_targblock = InvalidBlockNumber;
        relation->rd_fsm_nblocks = InvalidBlockNumber;
        relation->rd_vm_nblocks = InvalidBlockNumber;

        /* make sure relation is marked as having no open file yet */
        relation->rd_smgr = NULL;

        /*
         * initialize reference count: 1 because it is nailed in cache
         */
        relation->rd_refcnt = 1;

        /*
         * all entries built with this routine are nailed-in-cache; none are for
         * new or temp relations.
         */
        relation->rd_isnailed = true;
        relation->rd_createSubid = InvalidSubTransactionId;
        relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;
        relation->rd_istemp = false;
        relation->rd_islocaltemp = false;

        /*
         * initialize relation tuple form
         *
         * The data we insert here is pretty incomplete/bogus, but it'll serve to
         * get us launched.  RelationCacheInitializePhase3() will read the real
         * data from pg_class and replace what we've done here.  Note in particular
         * that relowner is left as zero; this cues RelationCacheInitializePhase3
         * that the real data isn't there yet.
         */
        relation->rd_rel = (Form_pg_class) palloc0(CLASS_TUPLE_SIZE);

        namestrcpy(&relation->rd_rel->relname, relationName);
        relation->rd_rel->relnamespace = PG_CATALOG_NAMESPACE;
        relation->rd_rel->reltype = relationReltype;

        /*
         * It's important to distinguish between shared and non-shared relations,
         * even at bootstrap time, to make sure we know where they are stored.
         */
        relation->rd_rel->relisshared = isshared;
        if (isshared)
                relation->rd_rel->reltablespace = GLOBALTABLESPACE_OID;

        /*
         * Likewise, we must know if a relation is temp ... but formrdesc is not
         * used for any temp relations.
         */
        relation->rd_rel->relistemp = false;

        relation->rd_rel->relpages = 1;
        relation->rd_rel->reltuples = 1;
        relation->rd_rel->relkind = RELKIND_RELATION;
        relation->rd_rel->relhasoids = hasoids;
        relation->rd_rel->relnatts = (int16) natts;

        /*
         * initialize attribute tuple form
         *
         * Unlike the case with the relation tuple, this data had better be right
         * because it will never be replaced.  The input values must be correctly
         * defined by macros in src/include/catalog/ headers.
         */
        relation->rd_att = CreateTemplateTupleDesc(natts, hasoids);
        relation->rd_att->tdrefcount = 1;       /* mark as refcounted */

        relation->rd_att->tdtypeid = relationReltype;
        relation->rd_att->tdtypmod = -1;        /* unnecessary, but... */

        /*
         * initialize tuple desc info
         */
        has_not_null = false;
        for (i = 0; i < natts; i++)
        {
                memcpy(relation->rd_att->attrs[i],
                           &attrs[i],
                           ATTRIBUTE_FIXED_PART_SIZE);
                has_not_null |= attrs[i].attnotnull;
                /* make sure attcacheoff is valid */
                relation->rd_att->attrs[i]->attcacheoff = -1;
        }

        /* initialize first attribute's attcacheoff, cf RelationBuildTupleDesc */
        relation->rd_att->attrs[0]->attcacheoff = 0;

        /* mark not-null status */
        if (has_not_null)
        {
                TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));

                constr->has_not_null = true;
                relation->rd_att->constr = constr;
        }

        /*
         * initialize relation id from info in att array (my, this is ugly)
         */
        RelationGetRelid(relation) = relation->rd_att->attrs[0]->attrelid;
        relation->rd_rel->relfilenode = RelationGetRelid(relation);

        /*
         * initialize the relation lock manager information
         */
        RelationInitLockInfo(relation);         /* see lmgr.c */

        /*
         * initialize physical addressing information for the relation
         */
        RelationInitPhysicalAddr(relation);

        /*
         * initialize the rel-has-index flag, using hardwired knowledge
         */
        if (IsBootstrapProcessingMode())
        {
                /* In bootstrap mode, we have no indexes */
                relation->rd_rel->relhasindex = false;
        }
        else
        {
                /* Otherwise, all the rels formrdesc is used for have indexes */
                relation->rd_rel->relhasindex = true;
        }

        /*
         * add new reldesc to relcache
         */
        RelationCacheInsert(relation);

        /* It's fully valid */
        relation->rd_isvalid = true;
}


/* ----------------------------------------------------------------
 *                               Relation Descriptor Lookup Interface
 * ----------------------------------------------------------------
 */

/*
 *              RelationIdGetRelation
 *
 *              Lookup a reldesc by OID; make one if not already in cache.
 *
 *              Returns NULL if no pg_class row could be found for the given relid
 *              (suggesting we are trying to access a just-deleted relation).
 *              Any other error is reported via elog.
 *
 *              NB: caller should already have at least AccessShareLock on the
 *              relation ID, else there are nasty race conditions.
 *
 *              NB: relation ref count is incremented, or set to 1 if new entry.
 *              Caller should eventually decrement count.  (Usually,
 *              that happens by calling RelationClose().)
 */
Relation
RelationIdGetRelation(Oid relationId)
{
        Relation        rd;

        /*
         * first try to find reldesc in the cache
         */
        RelationIdCacheLookup(relationId, rd);

        if (RelationIsValid(rd))
        {
                RelationIncrementReferenceCount(rd);
                /* revalidate nailed index if necessary */
                if (!rd->rd_isvalid)
                        RelationReloadIndexInfo(rd);
                return rd;
        }

        /*
         * no reldesc in the cache, so have RelationBuildDesc() build one and add
         * it.
         */
        rd = RelationBuildDesc(relationId, NULL);
        if (RelationIsValid(rd))
                RelationIncrementReferenceCount(rd);
        return rd;
}

/* ----------------------------------------------------------------
 *                              cache invalidation support routines
 * ----------------------------------------------------------------
 */

/*
 * RelationIncrementReferenceCount
 *              Increments relation reference count.
 *
 * Note: bootstrap mode has its own weird ideas about relation refcount
 * behavior; we ought to fix it someday, but for now, just disable
 * reference count ownership tracking in bootstrap mode.
 */
void
RelationIncrementReferenceCount(Relation rel)
{
        ResourceOwnerEnlargeRelationRefs(CurrentResourceOwner);
        rel->rd_refcnt += 1;
        if (!IsBootstrapProcessingMode())
                ResourceOwnerRememberRelationRef(CurrentResourceOwner, rel);
}

/*
 * RelationDecrementReferenceCount
 *              Decrements relation reference count.
 */
void
RelationDecrementReferenceCount(Relation rel)
{
        Assert(rel->rd_refcnt > 0);
        rel->rd_refcnt -= 1;
        if (!IsBootstrapProcessingMode())
                ResourceOwnerForgetRelationRef(CurrentResourceOwner, rel);
}

/*
 * RelationClose - close an open relation
 *
 *      Actually, we just decrement the refcount.
 *
 *      NOTE: if compiled with -DRELCACHE_FORCE_RELEASE then relcache entries
 *      will be freed as soon as their refcount goes to zero.  In combination
 *      with aset.c's CLOBBER_FREED_MEMORY option, this provides a good test
 *      to catch references to already-released relcache entries.  It slows
 *      things down quite a bit, however.
 */
void
RelationClose(Relation relation)
{
        /* Note: no locking manipulations needed */
        RelationDecrementReferenceCount(relation);

#ifdef RELCACHE_FORCE_RELEASE
        if (RelationHasReferenceCountZero(relation) &&
                relation->rd_createSubid == InvalidSubTransactionId &&
                relation->rd_newRelfilenodeSubid == InvalidSubTransactionId)
                RelationClearRelation(relation, false);
#endif
}

/*
 * RelationReloadIndexInfo - reload minimal information for an open index
 *
 *      This function is used only for indexes.  A relcache inval on an index
 *      can mean that its pg_class or pg_index row changed.  There are only
 *      very limited changes that are allowed to an existing index's schema,
 *      so we can update the relcache entry without a complete rebuild; which
 *      is fortunate because we can't rebuild an index entry that is "nailed"
 *      and/or in active use.  We support full replacement of the pg_class row,
 *      as well as updates of a few simple fields of the pg_index row.
 *
 *      We can't necessarily reread the catalog rows right away; we might be
 *      in a failed transaction when we receive the SI notification.  If so,
 *      RelationClearRelation just marks the entry as invalid by setting
 *      rd_isvalid to false.  This routine is called to fix the entry when it
 *      is next needed.
 *
 *      We assume that at the time we are called, we have at least AccessShareLock
 *      on the target index.  (Note: in the calls from RelationClearRelation,
 *      this is legitimate because we know the rel has positive refcount.)
 */
static void
RelationReloadIndexInfo(Relation relation)
{
        bool            indexOK;
        HeapTuple       pg_class_tuple;
        Form_pg_class relp;

        /* Should be called only for invalidated indexes */
        Assert(relation->rd_rel->relkind == RELKIND_INDEX &&
                   !relation->rd_isvalid);
        /* Should be closed at smgr level */
        Assert(relation->rd_smgr == NULL);

        /*
         * Must reset targblock, fsm_nblocks and vm_nblocks in case rel was
         * truncated
         */
        relation->rd_targblock = InvalidBlockNumber;
        relation->rd_fsm_nblocks = InvalidBlockNumber;
        relation->rd_vm_nblocks = InvalidBlockNumber;
        /* Must free any AM cached data, too */
        if (relation->rd_amcache)
                pfree(relation->rd_amcache);
        relation->rd_amcache = NULL;

        /*
         * If it's a shared index, we might be called before backend startup
         * has finished selecting a database, in which case we have no way to
         * read pg_class yet.  However, a shared index can never have any
         * significant schema updates, so it's okay to ignore the invalidation
         * signal.  Just mark it valid and return without doing anything more.
         */
        if (relation->rd_rel->relisshared && !criticalRelcachesBuilt)
        {
                relation->rd_isvalid = true;
                return;
        }

        /*
         * Read the pg_class row
         *
         * Don't try to use an indexscan of pg_class_oid_index to reload the info
         * for pg_class_oid_index ...
         */
        indexOK = (RelationGetRelid(relation) != ClassOidIndexId);
        pg_class_tuple = ScanPgRelation(RelationGetRelid(relation), indexOK);
        if (!HeapTupleIsValid(pg_class_tuple))
                elog(ERROR, "could not find pg_class tuple for index %u",
                         RelationGetRelid(relation));
        relp = (Form_pg_class) GETSTRUCT(pg_class_tuple);
        memcpy(relation->rd_rel, relp, CLASS_TUPLE_SIZE);
        /* Reload reloptions in case they changed */
        if (relation->rd_options)
                pfree(relation->rd_options);
        RelationParseRelOptions(relation, pg_class_tuple);
        /* done with pg_class tuple */
        heap_freetuple(pg_class_tuple);
        /* We must recalculate physical address in case it changed */
        RelationInitPhysicalAddr(relation);

        /*
         * For a non-system index, there are fields of the pg_index row that are
         * allowed to change, so re-read that row and update the relcache entry.
         * Most of the info derived from pg_index (such as support function lookup
         * info) cannot change, and indeed the whole point of this routine is to
         * update the relcache entry without clobbering that data; so wholesale
         * replacement is not appropriate.
         */
        if (!IsSystemRelation(relation))
        {
                HeapTuple       tuple;
                Form_pg_index index;

                tuple = SearchSysCache(INDEXRELID,
                                                           ObjectIdGetDatum(RelationGetRelid(relation)),
                                                           0, 0, 0);
                if (!HeapTupleIsValid(tuple))
                        elog(ERROR, "cache lookup failed for index %u",
                                 RelationGetRelid(relation));
                index = (Form_pg_index) GETSTRUCT(tuple);

                relation->rd_index->indisvalid = index->indisvalid;
                relation->rd_index->indcheckxmin = index->indcheckxmin;
                relation->rd_index->indisready = index->indisready;
                HeapTupleHeaderSetXmin(relation->rd_indextuple->t_data,
                                                           HeapTupleHeaderGetXmin(tuple->t_data));

                ReleaseSysCache(tuple);
        }

        /* Okay, now it's valid again */
        relation->rd_isvalid = true;
}

/*
 * RelationClearRelation
 *
 *       Physically blow away a relation cache entry, or reset it and rebuild
 *       it from scratch (that is, from catalog entries).  The latter path is
 *       usually used when we are notified of a change to an open relation
 *       (one with refcount > 0).  However, this routine just does whichever
 *       it's told to do; callers must determine which they want.
 *
 *       NB: when rebuilding, we'd better hold some lock on the relation.
 *       In current usages this is presumed true because it has refcnt > 0.
 */
static void
RelationClearRelation(Relation relation, bool rebuild)
{
        Oid                     old_reltype = relation->rd_rel->reltype;
        MemoryContext oldcxt;

        /*
         * Make sure smgr and lower levels close the relation's files, if they
         * weren't closed already.  If the relation is not getting deleted, the
         * next smgr access should reopen the files automatically.      This ensures
         * that the low-level file access state is updated after, say, a vacuum
         * truncation.
         */
        RelationCloseSmgr(relation);

        /*
         * Never, never ever blow away a nailed-in system relation, because we'd
         * be unable to recover.  However, we must reset rd_targblock, in case we
         * got called because of a relation cache flush that was triggered by
         * VACUUM.
         *
         * If it's a nailed index, then we need to re-read the pg_class row to see
         * if its relfilenode changed.  We can't necessarily do that here, because
         * we might be in a failed transaction.  We assume it's okay to do it if
         * there are open references to the relcache entry (cf notes for
         * AtEOXact_RelationCache).  Otherwise just mark the entry as possibly
         * invalid, and it'll be fixed when next opened.
         */
        if (relation->rd_isnailed)
        {
                relation->rd_targblock = InvalidBlockNumber;
                relation->rd_fsm_nblocks = InvalidBlockNumber;
                relation->rd_vm_nblocks = InvalidBlockNumber;
                if (relation->rd_rel->relkind == RELKIND_INDEX)
                {
                        relation->rd_isvalid = false;           /* needs to be revalidated */
                        if (relation->rd_refcnt > 1)
                                RelationReloadIndexInfo(relation);
                }
                return;
        }

        /*
         * Even non-system indexes should not be blown away if they are open and
         * have valid index support information.  This avoids problems with active
         * use of the index support information.  As with nailed indexes, we
         * re-read the pg_class row to handle possible physical relocation of the
         * index, and we check for pg_index updates too.
         */
        if (relation->rd_rel->relkind == RELKIND_INDEX &&
                relation->rd_refcnt > 0 &&
                relation->rd_indexcxt != NULL)
        {
                relation->rd_isvalid = false;   /* needs to be revalidated */
                RelationReloadIndexInfo(relation);
                return;
        }

        /*
         * Remove relation from hash tables
         *
         * Note: we might be reinserting it momentarily, but we must not have it
         * visible in the hash tables until it's valid again, so don't try to
         * optimize this away...
         */
        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
        RelationCacheDelete(relation);
        MemoryContextSwitchTo(oldcxt);

        /* Clear out catcache's entries for this relation */
        CatalogCacheFlushRelation(RelationGetRelid(relation));

        /*
         * Free all the subsidiary data structures of the relcache entry. We
         * cannot free rd_att if we are trying to rebuild the entry, however,
         * because pointers to it may be cached in various places. The rule
         * manager might also have pointers into the rewrite rules. So to begin
         * with, we can only get rid of these fields:
         */
        FreeTriggerDesc(relation->trigdesc);
        if (relation->rd_indextuple)
                pfree(relation->rd_indextuple);
        if (relation->rd_am)
                pfree(relation->rd_am);
        if (relation->rd_rel)
                pfree(relation->rd_rel);
        if (relation->rd_options)
                pfree(relation->rd_options);
        list_free(relation->rd_indexlist);
        bms_free(relation->rd_indexattr);
        if (relation->rd_indexcxt)
                MemoryContextDelete(relation->rd_indexcxt);

        /*
         * If we're really done with the relcache entry, blow it away. But if
         * someone is still using it, reconstruct the whole deal without moving
         * the physical RelationData record (so that the someone's pointer is
         * still valid).
         */
        if (!rebuild)
        {
                /* ok to zap remaining substructure */
                flush_rowtype_cache(old_reltype);
                /* can't use DecrTupleDescRefCount here */
                Assert(relation->rd_att->tdrefcount > 0);
                if (--relation->rd_att->tdrefcount == 0)
                        FreeTupleDesc(relation->rd_att);
                if (relation->rd_rulescxt)
                        MemoryContextDelete(relation->rd_rulescxt);
                pfree(relation);
        }
        else
        {
                /*
                 * When rebuilding an open relcache entry, must preserve ref count and
                 * rd_createSubid/rd_newRelfilenodeSubid state.  Also attempt to
                 * preserve the tupledesc and rewrite-rule substructures in place.
                 * (Note: the refcount mechanism for tupledescs may eventually ensure
                 * that we don't really need to preserve the tupledesc in-place, but
                 * for now there are still a lot of places that assume an open rel's
                 * tupledesc won't move.)
                 *
                 * Note that this process does not touch CurrentResourceOwner; which
                 * is good because whatever ref counts the entry may have do not
                 * necessarily belong to that resource owner.
                 */
                Oid                     save_relid = RelationGetRelid(relation);
                int                     old_refcnt = relation->rd_refcnt;
                SubTransactionId old_createSubid = relation->rd_createSubid;
                SubTransactionId old_newRelfilenodeSubid = relation->rd_newRelfilenodeSubid;
                struct PgStat_TableStatus *old_pgstat_info = relation->pgstat_info;
                TupleDesc       old_att = relation->rd_att;
                RuleLock   *old_rules = relation->rd_rules;
                MemoryContext old_rulescxt = relation->rd_rulescxt;

                if (RelationBuildDesc(save_relid, relation) != relation)
                {
                        /* Should only get here if relation was deleted */
                        flush_rowtype_cache(old_reltype);
                        Assert(old_att->tdrefcount > 0);
                        if (--old_att->tdrefcount == 0)
                                FreeTupleDesc(old_att);
                        if (old_rulescxt)
                                MemoryContextDelete(old_rulescxt);
                        pfree(relation);
                        elog(ERROR, "relation %u deleted while still in use", save_relid);
                }
                relation->rd_refcnt = old_refcnt;
                relation->rd_createSubid = old_createSubid;
                relation->rd_newRelfilenodeSubid = old_newRelfilenodeSubid;
                relation->pgstat_info = old_pgstat_info;

                if (equalTupleDescs(old_att, relation->rd_att))
                {
                        /* needn't flush typcache here */
                        Assert(relation->rd_att->tdrefcount == 1);
                        if (--relation->rd_att->tdrefcount == 0)
                                FreeTupleDesc(relation->rd_att);
                        relation->rd_att = old_att;
                }
                else
                {
                        flush_rowtype_cache(old_reltype);
                        Assert(old_att->tdrefcount > 0);
                        if (--old_att->tdrefcount == 0)
                                FreeTupleDesc(old_att);
                }
                if (equalRuleLocks(old_rules, relation->rd_rules))
                {
                        if (relation->rd_rulescxt)
                                MemoryContextDelete(relation->rd_rulescxt);
                        relation->rd_rules = old_rules;
                        relation->rd_rulescxt = old_rulescxt;
                }
                else
                {
                        if (old_rulescxt)
                                MemoryContextDelete(old_rulescxt);
                }
        }
}

/*
 * RelationFlushRelation
 *
 *       Rebuild the relation if it is open (refcount > 0), else blow it away.
 */
static void
RelationFlushRelation(Relation relation)
{
        bool            rebuild;

        if (relation->rd_createSubid != InvalidSubTransactionId ||
                relation->rd_newRelfilenodeSubid != InvalidSubTransactionId)
        {
                /*
                 * New relcache entries are always rebuilt, not flushed; else we'd
                 * forget the "new" status of the relation, which is a useful
                 * optimization to have.  Ditto for the new-relfilenode status.
                 */
                rebuild = true;
        }
        else
        {
                /*
                 * Pre-existing rels can be dropped from the relcache if not open.
                 */
                rebuild = !RelationHasReferenceCountZero(relation);
        }

        RelationClearRelation(relation, rebuild);
}

/*
 * RelationForgetRelation - unconditionally remove a relcache entry
 *
 *                 External interface for destroying a relcache entry when we
 *                 drop the relation.
 */
void
RelationForgetRelation(Oid rid)
{
        Relation        relation;

        RelationIdCacheLookup(rid, relation);

        if (!PointerIsValid(relation))
                return;                                 /* not in cache, nothing to do */

        if (!RelationHasReferenceCountZero(relation))
                elog(ERROR, "relation %u is still open", rid);

        /* Unconditionally destroy the relcache entry */
        RelationClearRelation(relation, false);
}

/*
 *              RelationCacheInvalidateEntry
 *
 *              This routine is invoked for SI cache flush messages.
 *
 * Any relcache entry matching the relid must be flushed.  (Note: caller has
 * already determined that the relid belongs to our database or is a shared
 * relation.)
 *
 * We used to skip local relations, on the grounds that they could
 * not be targets of cross-backend SI update messages; but it seems
 * safer to process them, so that our *own* SI update messages will
 * have the same effects during CommandCounterIncrement for both
 * local and nonlocal relations.
 */
void
RelationCacheInvalidateEntry(Oid relationId)
{
        Relation        relation;

        RelationIdCacheLookup(relationId, relation);

        if (PointerIsValid(relation))
        {
                relcacheInvalsReceived++;
                RelationFlushRelation(relation);
        }
}

/*
 * RelationCacheInvalidate
 *       Blow away cached relation descriptors that have zero reference counts,
 *       and rebuild those with positive reference counts.      Also reset the smgr
 *       relation cache.
 *
 *       This is currently used only to recover from SI message buffer overflow,
 *       so we do not touch new-in-transaction relations; they cannot be targets
 *       of cross-backend SI updates (and our own updates now go through a
 *       separate linked list that isn't limited by the SI message buffer size).
 *       Likewise, we need not discard new-relfilenode-in-transaction hints,
 *       since any invalidation of those would be a local event.
 *
 *       We do this in two phases: the first pass deletes deletable items, and
 *       the second one rebuilds the rebuildable items.  This is essential for
 *       safety, because hash_seq_search only copes with concurrent deletion of
 *       the element it is currently visiting.  If a second SI overflow were to
 *       occur while we are walking the table, resulting in recursive entry to
 *       this routine, we could crash because the inner invocation blows away
 *       the entry next to be visited by the outer scan.  But this way is OK,
 *       because (a) during the first pass we won't process any more SI messages,
 *       so hash_seq_search will complete safely; (b) during the second pass we
 *       only hold onto pointers to nondeletable entries.
 *
 *       The two-phase approach also makes it easy to ensure that we process
 *       nailed-in-cache indexes before other nondeletable items, and that we
 *       process pg_class_oid_index first of all.  In scenarios where a nailed
 *       index has been given a new relfilenode, we have to detect that update
 *       before the nailed index is used in reloading any other relcache entry.
 */
void
RelationCacheInvalidate(void)
{
        HASH_SEQ_STATUS status;
        RelIdCacheEnt *idhentry;
        Relation        relation;
        List       *rebuildFirstList = NIL;
        List       *rebuildList = NIL;
        ListCell   *l;

        /* Phase 1 */
        hash_seq_init(&status, RelationIdCache);

        while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
        {
                relation = idhentry->reldesc;

                /* Must close all smgr references to avoid leaving dangling ptrs */
                RelationCloseSmgr(relation);

                /* Ignore new relations, since they are never SI targets */
                if (relation->rd_createSubid != InvalidSubTransactionId)
                        continue;

                relcacheInvalsReceived++;

                if (RelationHasReferenceCountZero(relation))
                {
                        /* Delete this entry immediately */
                        Assert(!relation->rd_isnailed);
                        RelationClearRelation(relation, false);
                }
                else
                {
                        /*
                         * Add this entry to list of stuff to rebuild in second pass.
                         * pg_class_oid_index goes on the front of rebuildFirstList, other
                         * nailed indexes on the back, and everything else into
                         * rebuildList (in no particular order).
                         */
                        if (relation->rd_isnailed &&
                                relation->rd_rel->relkind == RELKIND_INDEX)
                        {
                                if (RelationGetRelid(relation) == ClassOidIndexId)
                                        rebuildFirstList = lcons(relation, rebuildFirstList);
                                else
                                        rebuildFirstList = lappend(rebuildFirstList, relation);
                        }
                        else
                                rebuildList = lcons(relation, rebuildList);
                }
        }

        /*
         * Now zap any remaining smgr cache entries.  This must happen before we
         * start to rebuild entries, since that may involve catalog fetches which
         * will re-open catalog files.
         */
        smgrcloseall();

        /* Phase 2: rebuild the items found to need rebuild in phase 1 */
        foreach(l, rebuildFirstList)
        {
                relation = (Relation) lfirst(l);
                RelationClearRelation(relation, true);
        }
        list_free(rebuildFirstList);
        foreach(l, rebuildList)
        {
                relation = (Relation) lfirst(l);
                RelationClearRelation(relation, true);
        }
        list_free(rebuildList);
}

/*
 * AtEOXact_RelationCache
 *
 *      Clean up the relcache at main-transaction commit or abort.
 *
 * Note: this must be called *before* processing invalidation messages.
 * In the case of abort, we don't want to try to rebuild any invalidated
 * cache entries (since we can't safely do database accesses).  Therefore
 * we must reset refcnts before handling pending invalidations.
 *
 * As of PostgreSQL 8.1, relcache refcnts should get released by the
 * ResourceOwner mechanism.  This routine just does a debugging
 * cross-check that no pins remain.  However, we also need to do special
 * cleanup when the current transaction created any relations or made use
 * of forced index lists.
 */
void
AtEOXact_RelationCache(bool isCommit)
{
        HASH_SEQ_STATUS status;
        RelIdCacheEnt *idhentry;

        /*
         * To speed up transaction exit, we want to avoid scanning the relcache
         * unless there is actually something for this routine to do.  Other than
         * the debug-only Assert checks, most transactions don't create any work
         * for us to do here, so we keep a static flag that gets set if there is
         * anything to do.      (Currently, this means either a relation is created in
         * the current xact, or one is given a new relfilenode, or an index list
         * is forced.)  For simplicity, the flag remains set till end of top-level
         * transaction, even though we could clear it at subtransaction end in
         * some cases.
         */
        if (!need_eoxact_work
#ifdef USE_ASSERT_CHECKING
                && !assert_enabled
#endif
                )
                return;

        hash_seq_init(&status, RelationIdCache);

        while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
        {
                Relation        relation = idhentry->reldesc;

                /*
                 * The relcache entry's ref count should be back to its normal
                 * not-in-a-transaction state: 0 unless it's nailed in cache.
                 *
                 * In bootstrap mode, this is NOT true, so don't check it --- the
                 * bootstrap code expects relations to stay open across start/commit
                 * transaction calls.  (That seems bogus, but it's not worth fixing.)
                 */
#ifdef USE_ASSERT_CHECKING
                if (!IsBootstrapProcessingMode())
                {
                        int                     expected_refcnt;

                        expected_refcnt = relation->rd_isnailed ? 1 : 0;
                        Assert(relation->rd_refcnt == expected_refcnt);
                }
#endif

                /*
                 * Is it a relation created in the current transaction?
                 *
                 * During commit, reset the flag to zero, since we are now out of the
                 * creating transaction.  During abort, simply delete the relcache
                 * entry --- it isn't interesting any longer.  (NOTE: if we have
                 * forgotten the new-ness of a new relation due to a forced cache
                 * flush, the entry will get deleted anyway by shared-cache-inval
                 * processing of the aborted pg_class insertion.)
                 */
                if (relation->rd_createSubid != InvalidSubTransactionId)
                {
                        if (isCommit)
                                relation->rd_createSubid = InvalidSubTransactionId;
                        else
                        {
                                RelationClearRelation(relation, false);
                                continue;
                        }
                }

                /*
                 * Likewise, reset the hint about the relfilenode being new.
                 */
                relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;

                /*
                 * Flush any temporary index list.
                 */
                if (relation->rd_indexvalid == 2)
                {
                        list_free(relation->rd_indexlist);
                        relation->rd_indexlist = NIL;
                        relation->rd_oidindex = InvalidOid;
                        relation->rd_indexvalid = 0;
                }
        }

        /* Once done with the transaction, we can reset need_eoxact_work */
        need_eoxact_work = false;
}

/*
 * AtEOSubXact_RelationCache
 *
 *      Clean up the relcache at sub-transaction commit or abort.
 *
 * Note: this must be called *before* processing invalidation messages.
 */
void
AtEOSubXact_RelationCache(bool isCommit, SubTransactionId mySubid,
                                                  SubTransactionId parentSubid)
{
        HASH_SEQ_STATUS status;
        RelIdCacheEnt *idhentry;

        /*
         * Skip the relcache scan if nothing to do --- see notes for
         * AtEOXact_RelationCache.
         */
        if (!need_eoxact_work)
                return;

        hash_seq_init(&status, RelationIdCache);

        while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
        {
                Relation        relation = idhentry->reldesc;

                /*
                 * Is it a relation created in the current subtransaction?
                 *
                 * During subcommit, mark it as belonging to the parent, instead.
                 * During subabort, simply delete the relcache entry.
                 */
                if (relation->rd_createSubid == mySubid)
                {
                        if (isCommit)
                                relation->rd_createSubid = parentSubid;
                        else
                        {
                                Assert(RelationHasReferenceCountZero(relation));
                                RelationClearRelation(relation, false);
                                continue;
                        }
                }

                /*
                 * Likewise, update or drop any new-relfilenode-in-subtransaction
                 * hint.
                 */
                if (relation->rd_newRelfilenodeSubid == mySubid)
                {
                        if (isCommit)
                                relation->rd_newRelfilenodeSubid = parentSubid;
                        else
                                relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;
                }

                /*
                 * Flush any temporary index list.
                 */
                if (relation->rd_indexvalid == 2)
                {
                        list_free(relation->rd_indexlist);
                        relation->rd_indexlist = NIL;
                        relation->rd_oidindex = InvalidOid;
                        relation->rd_indexvalid = 0;
                }
        }
}

/*
 * RelationCacheMarkNewRelfilenode
 *
 *      Mark the rel as having been given a new relfilenode in the current
 *      (sub) transaction.      This is a hint that can be used to optimize
 *      later operations on the rel in the same transaction.
 */
void
RelationCacheMarkNewRelfilenode(Relation rel)
{
        /* Mark it... */
        rel->rd_newRelfilenodeSubid = GetCurrentSubTransactionId();
        /* ... and now we have eoxact cleanup work to do */
        need_eoxact_work = true;
}


/*
 *              RelationBuildLocalRelation
 *                      Build a relcache entry for an about-to-be-created relation,
 *                      and enter it into the relcache.
 */
Relation
RelationBuildLocalRelation(const char *relname,
                                                   Oid relnamespace,
                                                   TupleDesc tupDesc,
                                                   Oid relid,
                                                   Oid reltablespace,
                                                   bool shared_relation)
{
        Relation        rel;
        MemoryContext oldcxt;
        int                     natts = tupDesc->natts;
        int                     i;
        bool            has_not_null;
        bool            nailit;

        AssertArg(natts >= 0);

        /*
         * check for creation of a rel that must be nailed in cache.
         *
         * XXX this list had better match the relations specially handled in
         * RelationCacheInitializePhase2/3.
         */
        switch (relid)
        {
                case DatabaseRelationId:
                case RelationRelationId:
                case AttributeRelationId:
                case ProcedureRelationId:
                case TypeRelationId:
                        nailit = true;
                        break;
                default:
                        nailit = false;
                        break;
        }

        /*
         * check that hardwired list of shared rels matches what's in the
         * bootstrap .bki file.  If you get a failure here during initdb, you
         * probably need to fix IsSharedRelation() to match whatever you've done
         * to the set of shared relations.
         */
        if (shared_relation != IsSharedRelation(relid))
                elog(ERROR, "shared_relation flag for \"%s\" does not match IsSharedRelation(%u)",
                         relname, relid);

        /*
         * switch to the cache context to create the relcache entry.
         */
        if (!CacheMemoryContext)
                CreateCacheMemoryContext();

        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

        /*
         * allocate a new relation descriptor and fill in basic state fields.
         */
        rel = (Relation) palloc0(sizeof(RelationData));

        rel->rd_targblock = InvalidBlockNumber;
        rel->rd_fsm_nblocks = InvalidBlockNumber;
        rel->rd_vm_nblocks = InvalidBlockNumber;

        /* make sure relation is marked as having no open file yet */
        rel->rd_smgr = NULL;

        /* mark it nailed if appropriate */
        rel->rd_isnailed = nailit;

        rel->rd_refcnt = nailit ? 1 : 0;

        /* it's being created in this transaction */
        rel->rd_createSubid = GetCurrentSubTransactionId();
        rel->rd_newRelfilenodeSubid = InvalidSubTransactionId;

        /* must flag that we have rels created in this transaction */
        need_eoxact_work = true;

        /* it is temporary if and only if it is in my temp-table namespace */
        rel->rd_istemp = isTempOrToastNamespace(relnamespace);
        rel->rd_islocaltemp = rel->rd_istemp;

        /*
         * create a new tuple descriptor from the one passed in.  We do this
         * partly to copy it into the cache context, and partly because the new
         * relation can't have any defaults or constraints yet; they have to be
         * added in later steps, because they require additions to multiple system
         * catalogs.  We can copy attnotnull constraints here, however.
         */
        rel->rd_att = CreateTupleDescCopy(tupDesc);
        rel->rd_att->tdrefcount = 1;    /* mark as refcounted */
        has_not_null = false;
        for (i = 0; i < natts; i++)
        {
                rel->rd_att->attrs[i]->attnotnull = tupDesc->attrs[i]->attnotnull;
                has_not_null |= tupDesc->attrs[i]->attnotnull;
        }

        if (has_not_null)
        {
                TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));

                constr->has_not_null = true;
                rel->rd_att->constr = constr;
        }

        /*
         * initialize relation tuple form (caller may add/override data later)
         */
        rel->rd_rel = (Form_pg_class) palloc0(CLASS_TUPLE_SIZE);

        namestrcpy(&rel->rd_rel->relname, relname);
        rel->rd_rel->relnamespace = relnamespace;

        rel->rd_rel->relkind = RELKIND_UNCATALOGED;
        rel->rd_rel->relhasoids = rel->rd_att->tdhasoid;
        rel->rd_rel->relnatts = natts;
        rel->rd_rel->reltype = InvalidOid;
        /* needed when bootstrapping: */
        rel->rd_rel->relowner = BOOTSTRAP_SUPERUSERID;

        /*
         * Insert relation physical and logical identifiers (OIDs) into the right
         * places.      Note that the physical ID (relfilenode) is initially the same
         * as the logical ID (OID).
         */
        rel->rd_rel->relisshared = shared_relation;
        rel->rd_rel->relistemp = rel->rd_istemp;

        RelationGetRelid(rel) = relid;

        for (i = 0; i < natts; i++)
                rel->rd_att->attrs[i]->attrelid = relid;

        rel->rd_rel->relfilenode = relid;
        rel->rd_rel->reltablespace = reltablespace;

        RelationInitLockInfo(rel);      /* see lmgr.c */

        RelationInitPhysicalAddr(rel);

        /*
         * Okay to insert into the relcache hash tables.
         */
        RelationCacheInsert(rel);

        /*
         * done building relcache entry.
         */
        MemoryContextSwitchTo(oldcxt);

        /* It's fully valid */
        rel->rd_isvalid = true;

        /*
         * Caller expects us to pin the returned entry.
         */
        RelationIncrementReferenceCount(rel);

        return rel;
}

/*
 *              RelationCacheInitialize
 *
 *              This initializes the relation descriptor cache.  At the time
 *              that this is invoked, we can't do database access yet (mainly
 *              because the transaction subsystem is not up); all we are doing
 *              is making an empty cache hashtable.  This must be done before
 *              starting the initialization transaction, because otherwise
 *              AtEOXact_RelationCache would crash if that transaction aborts
 *              before we can get the relcache set up.
 */

#define INITRELCACHESIZE                400

void
RelationCacheInitialize(void)
{
        HASHCTL         ctl;

        /*
         * make sure cache memory context exists
         */
        if (!CacheMemoryContext)
                CreateCacheMemoryContext();

        /*
         * create hashtable that indexes the relcache
         */
        MemSet(&ctl, 0, sizeof(ctl));
        ctl.keysize = sizeof(Oid);
        ctl.entrysize = sizeof(RelIdCacheEnt);
        ctl.hash = oid_hash;
        RelationIdCache = hash_create("Relcache by OID", INITRELCACHESIZE,
                                                                  &ctl, HASH_ELEM | HASH_FUNCTION);
}

/*
 *              RelationCacheInitializePhase2
 *
 *              This is called to prepare for access to pg_database during startup.
 *              We must at least set up a nailed reldesc for pg_database.  Ideally
 *              we'd like to have reldescs for its indexes, too.  We attempt to
 *              load this information from the shared relcache init file.  If that's
 *              missing or broken, just make a phony entry for pg_database.
 *              RelationCacheInitializePhase3 will clean up as needed.
 */
void
RelationCacheInitializePhase2(void)
{
        MemoryContext oldcxt;

        /*
         * In bootstrap mode, pg_database isn't there yet anyway, so do nothing.
         */
        if (IsBootstrapProcessingMode())
                return;

        /*
         * switch to cache memory context
         */
        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

        /*
         * Try to load the shared relcache cache file.  If unsuccessful,
         * bootstrap the cache with a pre-made descriptor for pg_database.
         */
        if (!load_relcache_init_file(true))
        {
                formrdesc("pg_database", DatabaseRelation_Rowtype_Id, true,
                                  true, Natts_pg_database, Desc_pg_database);

#define NUM_CRITICAL_SHARED_RELS        1       /* fix if you change list above */
        }

        MemoryContextSwitchTo(oldcxt);
}

/*
 *              RelationCacheInitializePhase3
 *
 *              This is called as soon as the catcache and transaction system
 *              are functional and we have determined MyDatabaseId.  At this point
 *              we can actually read data from the database's system catalogs.
 *              We first try to read pre-computed relcache entries from the local
 *              relcache init file.  If that's missing or broken, make phony entries
 *              for the minimum set of nailed-in-cache relations.  Then (unless
 *              bootstrapping) make sure we have entries for the critical system
 *              indexes.  Once we've done all this, we have enough infrastructure to
 *              open any system catalog or use any catcache.  The last step is to
 *              rewrite the cache files if needed.
 */
void
RelationCacheInitializePhase3(void)
{
        HASH_SEQ_STATUS status;
        RelIdCacheEnt *idhentry;
        MemoryContext oldcxt;
        bool            needNewCacheFile = !criticalSharedRelcachesBuilt;

        /*
         * switch to cache memory context
         */
        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

        /*
         * Try to load the local relcache cache file.  If unsuccessful,
         * bootstrap the cache with pre-made descriptors for the critical
         * "nailed-in" system catalogs.
         */
        if (IsBootstrapProcessingMode() ||
                !load_relcache_init_file(false))
        {
                needNewCacheFile = true;

                formrdesc("pg_class", RelationRelation_Rowtype_Id, false,
                                  true, Natts_pg_class, Desc_pg_class);
                formrdesc("pg_attribute", AttributeRelation_Rowtype_Id, false,
                                  false, Natts_pg_attribute, Desc_pg_attribute);
                formrdesc("pg_proc", ProcedureRelation_Rowtype_Id, false,
                                  true, Natts_pg_proc, Desc_pg_proc);
                formrdesc("pg_type", TypeRelation_Rowtype_Id, false,
                                  true, Natts_pg_type, Desc_pg_type);

#define NUM_CRITICAL_LOCAL_RELS 4       /* fix if you change list above */
        }

        MemoryContextSwitchTo(oldcxt);

        /* In bootstrap mode, the faked-up formrdesc info is all we'll have */
        if (IsBootstrapProcessingMode())
                return;

        /*
         * If we didn't get the critical system indexes loaded into relcache, do
         * so now.      These are critical because the catcache and/or opclass cache
         * depend on them for fetches done during relcache load.  Thus, we have an
         * infinite-recursion problem.  We can break the recursion by doing
         * heapscans instead of indexscans at certain key spots. To avoid hobbling
         * performance, we only want to do that until we have the critical indexes
         * loaded into relcache.  Thus, the flag criticalRelcachesBuilt is used to
         * decide whether to do heapscan or indexscan at the key spots, and we set
         * it true after we've loaded the critical indexes.
         *
         * The critical indexes are marked as "nailed in cache", partly to make it
         * easy for load_relcache_init_file to count them, but mainly because we
         * cannot flush and rebuild them once we've set criticalRelcachesBuilt to
         * true.  (NOTE: perhaps it would be possible to reload them by
         * temporarily setting criticalRelcachesBuilt to false again.  For now,
         * though, we just nail 'em in.)
         *
         * RewriteRelRulenameIndexId and TriggerRelidNameIndexId are not critical
         * in the same way as the others, because the critical catalogs don't
         * (currently) have any rules or triggers, and so these indexes can be
         * rebuilt without inducing recursion.  However they are used during
         * relcache load when a rel does have rules or triggers, so we choose to
         * nail them for performance reasons.
         */
        if (!criticalRelcachesBuilt)
        {
                load_critical_index(ClassOidIndexId);
                load_critical_index(AttributeRelidNumIndexId);
                load_critical_index(IndexRelidIndexId);
                load_critical_index(OpclassOidIndexId);
                load_critical_index(AccessMethodStrategyIndexId);
                load_critical_index(AccessMethodProcedureIndexId);
                load_critical_index(OperatorOidIndexId);
                load_critical_index(RewriteRelRulenameIndexId);
                load_critical_index(TriggerRelidNameIndexId);

#define NUM_CRITICAL_LOCAL_INDEXES      9               /* fix if you change list above */

                criticalRelcachesBuilt = true;
        }

        /*
         * Process critical shared indexes too.
         *
         * DatabaseNameIndexId isn't critical for relcache loading, but rather
         * for initial lookup of MyDatabaseId, without which we'll never find
         * any non-shared catalogs at all.  Autovacuum calls InitPostgres with
         * a database OID, so it instead depends on DatabaseOidIndexId.
         */
        if (!criticalSharedRelcachesBuilt)
        {
                load_critical_index(DatabaseNameIndexId);
                load_critical_index(DatabaseOidIndexId);

#define NUM_CRITICAL_SHARED_INDEXES     2               /* fix if you change list above */

                criticalSharedRelcachesBuilt = true;
        }

        /*
         * Now, scan all the relcache entries and update anything that might be
         * wrong in the results from formrdesc or the relcache cache file. If we
         * faked up relcache entries using formrdesc, then read the real pg_class
         * rows and replace the fake entries with them. Also, if any of the
         * relcache entries have rules or triggers, load that info the hard way
         * since it isn't recorded in the cache file.
         *
         * Whenever we access the catalogs to read data, there is a possibility
         * of a shared-inval cache flush causing relcache entries to be removed.
         * Since hash_seq_search only guarantees to still work after the *current*
         * entry is removed, it's unsafe to continue the hashtable scan afterward.
         * We handle this by restarting the scan from scratch after each access.
         * This is theoretically O(N^2), but the number of entries that actually
         * need to be fixed is small enough that it doesn't matter.
         */
        hash_seq_init(&status, RelationIdCache);

        while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
        {
                Relation        relation = idhentry->reldesc;
                bool            restart = false;

                /*
                 * Make sure *this* entry doesn't get flushed while we work with it.
                 */
                RelationIncrementReferenceCount(relation);

                /*
                 * If it's a faked-up entry, read the real pg_class tuple.
                 */
                if (relation->rd_rel->relowner == InvalidOid)
                {
                        HeapTuple       htup;
                        Form_pg_class relp;

                        htup = SearchSysCache(RELOID,
                                                                ObjectIdGetDatum(RelationGetRelid(relation)),
                                                                  0, 0, 0);
                        if (!HeapTupleIsValid(htup))
                                elog(FATAL, "cache lookup failed for relation %u",
                                         RelationGetRelid(relation));
                        relp = (Form_pg_class) GETSTRUCT(htup);

                        /*
                         * Copy tuple to relation->rd_rel. (See notes in
                         * AllocateRelationDesc())
                         */
                        memcpy((char *) relation->rd_rel, (char *) relp, CLASS_TUPLE_SIZE);

                        /* Update rd_options while we have the tuple */
                        if (relation->rd_options)
                                pfree(relation->rd_options);
                        RelationParseRelOptions(relation, htup);

                        /*
                         * Check the values in rd_att were set up correctly.  (We cannot
                         * just copy them over now: formrdesc must have set up the
                         * rd_att data correctly to start with, because it may already
                         * have been copied into one or more catcache entries.)
                         */
                        Assert(relation->rd_att->tdtypeid == relp->reltype);
                        Assert(relation->rd_att->tdtypmod == -1);
                        Assert(relation->rd_att->tdhasoid == relp->relhasoids);

                        ReleaseSysCache(htup);

                        /* relowner had better be OK now, else we'll loop forever */
                        if (relation->rd_rel->relowner == InvalidOid)
                                elog(ERROR, "invalid relowner in pg_class entry for \"%s\"",
                                         RelationGetRelationName(relation));

                        restart = true;
                }

                /*
                 * Fix data that isn't saved in relcache cache file.
                 *
                 * relhasrules or relhastriggers could possibly be wrong or out of
                 * date.  If we don't actually find any rules or triggers, clear the
                 * local copy of the flag so that we don't get into an infinite loop
                 * here.  We don't make any attempt to fix the pg_class entry, though.
                 */
                if (relation->rd_rel->relhasrules && relation->rd_rules == NULL)
                {
                        RelationBuildRuleLock(relation);
                        if (relation->rd_rules == NULL)
                                relation->rd_rel->relhasrules = false;
                        restart = true;
                }
                if (relation->rd_rel->relhastriggers && relation->trigdesc == NULL)
                {
                        RelationBuildTriggers(relation);
                        if (relation->trigdesc == NULL)
                                relation->rd_rel->relhastriggers = false;
                        restart = true;
                }

                /* Release hold on the relation */
                RelationDecrementReferenceCount(relation);

                /* Now, restart the hashtable scan if needed */
                if (restart)
                {
                        hash_seq_term(&status);
                        hash_seq_init(&status, RelationIdCache);
                }
        }

        /*
         * Lastly, write out new relcache cache files if needed.  We don't bother
         * to distinguish cases where only one of the two needs an update.
         */
        if (needNewCacheFile)
        {
                /*
                 * Force all the catcaches to finish initializing and thereby open the
                 * catalogs and indexes they use.  This will preload the relcache with
                 * entries for all the most important system catalogs and indexes, so
                 * that the init files will be most useful for future backends.
                 */
                InitCatalogCachePhase2();

                /* reset initFileRelationIds list; we'll fill it during write */
                initFileRelationIds = NIL;

                /* now write the files */
                write_relcache_init_file(true);
                write_relcache_init_file(false);
        }
}

/*
 * Load one critical system index into the relcache
 */
static void
load_critical_index(Oid indexoid)
{
        Relation        ird;

        LockRelationOid(indexoid, AccessShareLock);
        ird = RelationBuildDesc(indexoid, NULL);
        if (ird == NULL)
                elog(PANIC, "could not open critical system index %u", indexoid);
        ird->rd_isnailed = true;
        ird->rd_refcnt = 1;
        UnlockRelationOid(indexoid, AccessShareLock);
}

/*
 * GetPgClassDescriptor -- get a predefined tuple descriptor for pg_class
 * GetPgIndexDescriptor -- get a predefined tuple descriptor for pg_index
 *
 * We need this kluge because we have to be able to access non-fixed-width
 * fields of pg_class and pg_index before we have the standard catalog caches
 * available.  We use predefined data that's set up in just the same way as
 * the bootstrapped reldescs used by formrdesc().  The resulting tupdesc is
 * not 100% kosher: it does not have the correct rowtype OID in tdtypeid, nor
 * does it have a TupleConstr field.  But it's good enough for the purpose of
 * extracting fields.
 */
static TupleDesc
BuildHardcodedDescriptor(int natts, const FormData_pg_attribute *attrs,
                                                 bool hasoids)
{
        TupleDesc       result;
        MemoryContext oldcxt;
        int                     i;

        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

        result = CreateTemplateTupleDesc(natts, hasoids);
        result->tdtypeid = RECORDOID;           /* not right, but we don't care */
        result->tdtypmod = -1;

        for (i = 0; i < natts; i++)
        {
                memcpy(result->attrs[i], &attrs[i], ATTRIBUTE_FIXED_PART_SIZE);
                /* make sure attcacheoff is valid */
                result->attrs[i]->attcacheoff = -1;
        }

        /* initialize first attribute's attcacheoff, cf RelationBuildTupleDesc */
        result->attrs[0]->attcacheoff = 0;

        /* Note: we don't bother to set up a TupleConstr entry */

        MemoryContextSwitchTo(oldcxt);

        return result;
}

static TupleDesc
GetPgClassDescriptor(void)
{
        static TupleDesc pgclassdesc = NULL;

        /* Already done? */
        if (pgclassdesc == NULL)
                pgclassdesc = BuildHardcodedDescriptor(Natts_pg_class,
                                                                                           Desc_pg_class,
                                                                                           true);

        return pgclassdesc;
}

static TupleDesc
GetPgIndexDescriptor(void)
{
        static TupleDesc pgindexdesc = NULL;

        /* Already done? */
        if (pgindexdesc == NULL)
                pgindexdesc = BuildHardcodedDescriptor(Natts_pg_index,
                                                                                           Desc_pg_index,
                                                                                           false);

        return pgindexdesc;
}

/*
 * Load any default attribute value definitions for the relation.
 */
static void
AttrDefaultFetch(Relation relation)
{
        AttrDefault *attrdef = relation->rd_att->constr->defval;
        int                     ndef = relation->rd_att->constr->num_defval;
        Relation        adrel;
        SysScanDesc adscan;
        ScanKeyData skey;
        HeapTuple       htup;
        Datum           val;
        bool            isnull;
        int                     found;
        int                     i;

        ScanKeyInit(&skey,
                                Anum_pg_attrdef_adrelid,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(RelationGetRelid(relation)));

        adrel = heap_open(AttrDefaultRelationId, AccessShareLock);
        adscan = systable_beginscan(adrel, AttrDefaultIndexId, true,
                                                                SnapshotNow, 1, &skey);
        found = 0;

        while (HeapTupleIsValid(htup = systable_getnext(adscan)))
        {
                Form_pg_attrdef adform = (Form_pg_attrdef) GETSTRUCT(htup);

                for (i = 0; i < ndef; i++)
                {
                        if (adform->adnum != attrdef[i].adnum)
                                continue;
                        if (attrdef[i].adbin != NULL)
                                elog(WARNING, "multiple attrdef records found for attr %s of rel %s",
                                NameStr(relation->rd_att->attrs[adform->adnum - 1]->attname),
                                         RelationGetRelationName(relation));
                        else
                                found++;

                        val = fastgetattr(htup,
                                                          Anum_pg_attrdef_adbin,
                                                          adrel->rd_att, &isnull);
                        if (isnull)
                                elog(WARNING, "null adbin for attr %s of rel %s",
                                NameStr(relation->rd_att->attrs[adform->adnum - 1]->attname),
                                         RelationGetRelationName(relation));
                        else
                                attrdef[i].adbin = MemoryContextStrdup(CacheMemoryContext,
                                                                                                   TextDatumGetCString(val));
                        break;
                }

                if (i >= ndef)
                        elog(WARNING, "unexpected attrdef record found for attr %d of rel %s",
                                 adform->adnum, RelationGetRelationName(relation));
        }

        systable_endscan(adscan);
        heap_close(adrel, AccessShareLock);

        if (found != ndef)
                elog(WARNING, "%d attrdef record(s) missing for rel %s",
                         ndef - found, RelationGetRelationName(relation));
}

/*
 * Load any check constraints for the relation.
 */
static void
CheckConstraintFetch(Relation relation)
{
        ConstrCheck *check = relation->rd_att->constr->check;
        int                     ncheck = relation->rd_att->constr->num_check;
        Relation        conrel;
        SysScanDesc conscan;
        ScanKeyData skey[1];
        HeapTuple       htup;
        Datum           val;
        bool            isnull;
        int                     found = 0;

        ScanKeyInit(&skey[0],
                                Anum_pg_constraint_conrelid,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(RelationGetRelid(relation)));

        conrel = heap_open(ConstraintRelationId, AccessShareLock);
        conscan = systable_beginscan(conrel, ConstraintRelidIndexId, true,
                                                                 SnapshotNow, 1, skey);

        while (HeapTupleIsValid(htup = systable_getnext(conscan)))
        {
                Form_pg_constraint conform = (Form_pg_constraint) GETSTRUCT(htup);

                /* We want check constraints only */
                if (conform->contype != CONSTRAINT_CHECK)
                        continue;

                if (found >= ncheck)
                        elog(ERROR, "unexpected constraint record found for rel %s",
                                 RelationGetRelationName(relation));

                check[found].ccname = MemoryContextStrdup(CacheMemoryContext,
                                                                                                  NameStr(conform->conname));

                /* Grab and test conbin is actually set */
                val = fastgetattr(htup,
                                                  Anum_pg_constraint_conbin,
                                                  conrel->rd_att, &isnull);
                if (isnull)
                        elog(ERROR, "null conbin for rel %s",
                                 RelationGetRelationName(relation));

                check[found].ccbin = MemoryContextStrdup(CacheMemoryContext,
                                                                                                 TextDatumGetCString(val));
                found++;
        }

        systable_endscan(conscan);
        heap_close(conrel, AccessShareLock);

        if (found != ncheck)
                elog(ERROR, "%d constraint record(s) missing for rel %s",
                         ncheck - found, RelationGetRelationName(relation));
}

/*
 * RelationGetIndexList -- get a list of OIDs of indexes on this relation
 *
 * The index list is created only if someone requests it.  We scan pg_index
 * to find relevant indexes, and add the list to the relcache entry so that
 * we won't have to compute it again.  Note that shared cache inval of a
 * relcache entry will delete the old list and set rd_indexvalid to 0,
 * so that we must recompute the index list on next request.  This handles
 * creation or deletion of an index.
 *
 * The returned list is guaranteed to be sorted in order by OID.  This is
 * needed by the executor, since for index types that we obtain exclusive
 * locks on when updating the index, all backends must lock the indexes in
 * the same order or we will get deadlocks (see ExecOpenIndices()).  Any
 * consistent ordering would do, but ordering by OID is easy.
 *
 * Since shared cache inval causes the relcache's copy of the list to go away,
 * we return a copy of the list palloc'd in the caller's context.  The caller
 * may list_free() the returned list after scanning it. This is necessary
 * since the caller will typically be doing syscache lookups on the relevant
 * indexes, and syscache lookup could cause SI messages to be processed!
 *
 * We also update rd_oidindex, which this module treats as effectively part
 * of the index list.  rd_oidindex is valid when rd_indexvalid isn't zero;
 * it is the pg_class OID of a unique index on OID when the relation has one,
 * and InvalidOid if there is no such index.
 */
List *
RelationGetIndexList(Relation relation)
{
        Relation        indrel;
        SysScanDesc indscan;
        ScanKeyData skey;
        HeapTuple       htup;
        List       *result;
        Oid                     oidIndex;
        MemoryContext oldcxt;

        /* Quick exit if we already computed the list. */
        if (relation->rd_indexvalid != 0)
                return list_copy(relation->rd_indexlist);

        /*
         * We build the list we intend to return (in the caller's context) while
         * doing the scan.      After successfully completing the scan, we copy that
         * list into the relcache entry.  This avoids cache-context memory leakage
         * if we get some sort of error partway through.
         */
        result = NIL;
        oidIndex = InvalidOid;

        /* Prepare to scan pg_index for entries having indrelid = this rel. */
        ScanKeyInit(&skey,
                                Anum_pg_index_indrelid,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(RelationGetRelid(relation)));

        indrel = heap_open(IndexRelationId, AccessShareLock);
        indscan = systable_beginscan(indrel, IndexIndrelidIndexId, true,
                                                                 SnapshotNow, 1, &skey);

        while (HeapTupleIsValid(htup = systable_getnext(indscan)))
        {
                Form_pg_index index = (Form_pg_index) GETSTRUCT(htup);

                /* Add index's OID to result list in the proper order */
                result = insert_ordered_oid(result, index->indexrelid);

                /* Check to see if it is a unique, non-partial btree index on OID */
                if (index->indnatts == 1 &&
                        index->indisunique && index->indimmediate &&
                        index->indkey.values[0] == ObjectIdAttributeNumber &&
                        index->indclass.values[0] == OID_BTREE_OPS_OID &&
                        heap_attisnull(htup, Anum_pg_index_indpred))
                        oidIndex = index->indexrelid;
        }

        systable_endscan(indscan);
        heap_close(indrel, AccessShareLock);

        /* Now save a copy of the completed list in the relcache entry. */
        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
        relation->rd_indexlist = list_copy(result);
        relation->rd_oidindex = oidIndex;
        relation->rd_indexvalid = 1;
        MemoryContextSwitchTo(oldcxt);

        return result;
}

/*
 * insert_ordered_oid
 *              Insert a new Oid into a sorted list of Oids, preserving ordering
 *
 * Building the ordered list this way is O(N^2), but with a pretty small
 * constant, so for the number of entries we expect it will probably be
 * faster than trying to apply qsort().  Most tables don't have very many
 * indexes...
 */
static List *
insert_ordered_oid(List *list, Oid datum)
{
        ListCell   *prev;

        /* Does the datum belong at the front? */
        if (list == NIL || datum < linitial_oid(list))
                return lcons_oid(datum, list);
        /* No, so find the entry it belongs after */
        prev = list_head(list);
        for (;;)
        {
                ListCell   *curr = lnext(prev);

                if (curr == NULL || datum < lfirst_oid(curr))
                        break;                          /* it belongs after 'prev', before 'curr' */

                prev = curr;
        }
        /* Insert datum into list after 'prev' */
        lappend_cell_oid(list, prev, datum);
        return list;
}

/*
 * RelationSetIndexList -- externally force the index list contents
 *
 * This is used to temporarily override what we think the set of valid
 * indexes is (including the presence or absence of an OID index).
 * The forcing will be valid only until transaction commit or abort.
 *
 * This should only be applied to nailed relations, because in a non-nailed
 * relation the hacked index list could be lost at any time due to SI
 * messages.  In practice it is only used on pg_class (see REINDEX).
 *
 * It is up to the caller to make sure the given list is correctly ordered.
 *
 * We deliberately do not change rd_indexattr here: even when operating
 * with a temporary partial index list, HOT-update decisions must be made
 * correctly with respect to the full index set.  It is up to the caller
 * to ensure that a correct rd_indexattr set has been cached before first
 * calling RelationSetIndexList; else a subsequent inquiry might cause a
 * wrong rd_indexattr set to get computed and cached.
 */
void
RelationSetIndexList(Relation relation, List *indexIds, Oid oidIndex)
{
        MemoryContext oldcxt;

        Assert(relation->rd_isnailed);
        /* Copy the list into the cache context (could fail for lack of mem) */
        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
        indexIds = list_copy(indexIds);
        MemoryContextSwitchTo(oldcxt);
        /* Okay to replace old list */
        list_free(relation->rd_indexlist);
        relation->rd_indexlist = indexIds;
        relation->rd_oidindex = oidIndex;
        relation->rd_indexvalid = 2;    /* mark list as forced */
        /* must flag that we have a forced index list */
        need_eoxact_work = true;
}

/*
 * RelationGetOidIndex -- get the pg_class OID of the relation's OID index
 *
 * Returns InvalidOid if there is no such index.
 */
Oid
RelationGetOidIndex(Relation relation)
{
        List       *ilist;

        /*
         * If relation doesn't have OIDs at all, caller is probably confused. (We
         * could just silently return InvalidOid, but it seems better to throw an
         * assertion.)
         */
        Assert(relation->rd_rel->relhasoids);

        if (relation->rd_indexvalid == 0)
        {
                /* RelationGetIndexList does the heavy lifting. */
                ilist = RelationGetIndexList(relation);
                list_free(ilist);
                Assert(relation->rd_indexvalid != 0);
        }

        return relation->rd_oidindex;
}

/*
 * RelationGetIndexExpressions -- get the index expressions for an index
 *
 * We cache the result of transforming pg_index.indexprs into a node tree.
 * If the rel is not an index or has no expressional columns, we return NIL.
 * Otherwise, the returned tree is copied into the caller's memory context.
 * (We don't want to return a pointer to the relcache copy, since it could
 * disappear due to relcache invalidation.)
 */
List *
RelationGetIndexExpressions(Relation relation)
{
        List       *result;
        Datum           exprsDatum;
        bool            isnull;
        char       *exprsString;
        MemoryContext oldcxt;

        /* Quick exit if we already computed the result. */
        if (relation->rd_indexprs)
                return (List *) copyObject(relation->rd_indexprs);

        /* Quick exit if there is nothing to do. */
        if (relation->rd_indextuple == NULL ||
                heap_attisnull(relation->rd_indextuple, Anum_pg_index_indexprs))
                return NIL;

        /*
         * We build the tree we intend to return in the caller's context. After
         * successfully completing the work, we copy it into the relcache entry.
         * This avoids problems if we get some sort of error partway through.
         */
        exprsDatum = heap_getattr(relation->rd_indextuple,
                                                          Anum_pg_index_indexprs,
                                                          GetPgIndexDescriptor(),
                                                          &isnull);
        Assert(!isnull);
        exprsString = TextDatumGetCString(exprsDatum);
        result = (List *) stringToNode(exprsString);
        pfree(exprsString);

        /*
         * Run the expressions through eval_const_expressions. This is not just an
         * optimization, but is necessary, because the planner will be comparing
         * them to similarly-processed qual clauses, and may fail to detect valid
         * matches without this.  We don't bother with canonicalize_qual, however.
         */
        result = (List *) eval_const_expressions(NULL, (Node *) result);

        /*
         * Also mark any coercion format fields as "don't care", so that the
         * planner can match to both explicit and implicit coercions.
         */
        set_coercionform_dontcare((Node *) result);

        /* May as well fix opfuncids too */
        fix_opfuncids((Node *) result);

        /* Now save a copy of the completed tree in the relcache entry. */
        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
        relation->rd_indexprs = (List *) copyObject(result);
        MemoryContextSwitchTo(oldcxt);

        return result;
}

/*
 * RelationGetIndexPredicate -- get the index predicate for an index
 *
 * We cache the result of transforming pg_index.indpred into an implicit-AND
 * node tree (suitable for ExecQual).
 * If the rel is not an index or has no predicate, we return NIL.
 * Otherwise, the returned tree is copied into the caller's memory context.
 * (We don't want to return a pointer to the relcache copy, since it could
 * disappear due to relcache invalidation.)
 */
List *
RelationGetIndexPredicate(Relation relation)
{
        List       *result;
        Datum           predDatum;
        bool            isnull;
        char       *predString;
        MemoryContext oldcxt;

        /* Quick exit if we already computed the result. */
        if (relation->rd_indpred)
                return (List *) copyObject(relation->rd_indpred);

        /* Quick exit if there is nothing to do. */
        if (relation->rd_indextuple == NULL ||
                heap_attisnull(relation->rd_indextuple, Anum_pg_index_indpred))
                return NIL;

        /*
         * We build the tree we intend to return in the caller's context. After
         * successfully completing the work, we copy it into the relcache entry.
         * This avoids problems if we get some sort of error partway through.
         */
        predDatum = heap_getattr(relation->rd_indextuple,
                                                         Anum_pg_index_indpred,
                                                         GetPgIndexDescriptor(),
                                                         &isnull);
        Assert(!isnull);
        predString = TextDatumGetCString(predDatum);
        result = (List *) stringToNode(predString);
        pfree(predString);

        /*
         * Run the expression through const-simplification and canonicalization.
         * This is not just an optimization, but is necessary, because the planner
         * will be comparing it to similarly-processed qual clauses, and may fail
         * to detect valid matches without this.  This must match the processing
         * done to qual clauses in preprocess_expression()!  (We can skip the
         * stuff involving subqueries, however, since we don't allow any in index
         * predicates.)
         */
        result = (List *) eval_const_expressions(NULL, (Node *) result);

        result = (List *) canonicalize_qual((Expr *) result);

        /*
         * Also mark any coercion format fields as "don't care", so that the
         * planner can match to both explicit and implicit coercions.
         */
        set_coercionform_dontcare((Node *) result);

        /* Also convert to implicit-AND format */
        result = make_ands_implicit((Expr *) result);

        /* May as well fix opfuncids too */
        fix_opfuncids((Node *) result);

        /* Now save a copy of the completed tree in the relcache entry. */
        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
        relation->rd_indpred = (List *) copyObject(result);
        MemoryContextSwitchTo(oldcxt);

        return result;
}

/*
 * RelationGetIndexAttrBitmap -- get a bitmap of index attribute numbers
 *
 * The result has a bit set for each attribute used anywhere in the index
 * definitions of all the indexes on this relation.  (This includes not only
 * simple index keys, but attributes used in expressions and partial-index
 * predicates.)
 *
 * Attribute numbers are offset by FirstLowInvalidHeapAttributeNumber so that
 * we can include system attributes (e.g., OID) in the bitmap representation.
 *
 * The returned result is palloc'd in the caller's memory context and should
 * be bms_free'd when not needed anymore.
 */
Bitmapset *
RelationGetIndexAttrBitmap(Relation relation)
{
        Bitmapset  *indexattrs;
        List       *indexoidlist;
        ListCell   *l;
        MemoryContext oldcxt;

        /* Quick exit if we already computed the result. */
        if (relation->rd_indexattr != NULL)
                return bms_copy(relation->rd_indexattr);

        /* Fast path if definitely no indexes */
        if (!RelationGetForm(relation)->relhasindex)
                return NULL;

        /*
         * Get cached list of index OIDs
         */
        indexoidlist = RelationGetIndexList(relation);

        /* Fall out if no indexes (but relhasindex was set) */
        if (indexoidlist == NIL)
                return NULL;

        /*
         * For each index, add referenced attributes to indexattrs.
         */
        indexattrs = NULL;
        foreach(l, indexoidlist)
        {
                Oid                     indexOid = lfirst_oid(l);
                Relation        indexDesc;
                IndexInfo  *indexInfo;
                int                     i;

                indexDesc = index_open(indexOid, AccessShareLock);

                /* Extract index key information from the index's pg_index row */
                indexInfo = BuildIndexInfo(indexDesc);

                /* Collect simple attribute references */
                for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
                {
                        int                     attrnum = indexInfo->ii_KeyAttrNumbers[i];

                        if (attrnum != 0)
                                indexattrs = bms_add_member(indexattrs,
                                                           attrnum - FirstLowInvalidHeapAttributeNumber);
                }

                /* Collect all attributes used in expressions, too */
                pull_varattnos((Node *) indexInfo->ii_Expressions, &indexattrs);

                /* Collect all attributes in the index predicate, too */
                pull_varattnos((Node *) indexInfo->ii_Predicate, &indexattrs);

                index_close(indexDesc, AccessShareLock);
        }

        list_free(indexoidlist);

        /* Now save a copy of the bitmap in the relcache entry. */
        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
        relation->rd_indexattr = bms_copy(indexattrs);
        MemoryContextSwitchTo(oldcxt);

        /* We return our original working copy for caller to play with */
        return indexattrs;
}

/*
 * RelationGetExclusionInfo -- get info about index's exclusion constraint
 *
 * This should be called only for an index that is known to have an
 * associated exclusion constraint.  It returns arrays (palloc'd in caller's
 * context) of the exclusion operator OIDs, their underlying functions'
 * OIDs, and their strategy numbers in the index's opclasses.  We cache
 * all this information since it requires a fair amount of work to get.
 */
void
RelationGetExclusionInfo(Relation indexRelation,
                                                 Oid **operators,
                                                 Oid **procs,
                                                 uint16 **strategies)
{
        int                     ncols = indexRelation->rd_rel->relnatts;
        Oid                *ops;
        Oid                *funcs;
        uint16     *strats;
        Relation        conrel;
        SysScanDesc     conscan;
        ScanKeyData     skey[1];
        HeapTuple       htup;
        bool            found;
        MemoryContext oldcxt;
        int                     i;

        /* Allocate result space in caller context */
        *operators = ops = (Oid *) palloc(sizeof(Oid) * ncols);
        *procs = funcs = (Oid *) palloc(sizeof(Oid) * ncols);
        *strategies = strats = (uint16 *) palloc(sizeof(uint16) * ncols);

        /* Quick exit if we have the data cached already */
        if (indexRelation->rd_exclstrats != NULL)
        {
                memcpy(ops, indexRelation->rd_exclops, sizeof(Oid) * ncols);
                memcpy(funcs, indexRelation->rd_exclprocs, sizeof(Oid) * ncols);
                memcpy(strats, indexRelation->rd_exclstrats, sizeof(uint16) * ncols);
                return;
        }

        /*
         * Search pg_constraint for the constraint associated with the index.
         * To make this not too painfully slow, we use the index on conrelid;
         * that will hold the parent relation's OID not the index's own OID.
         */
        ScanKeyInit(&skey[0],
                                Anum_pg_constraint_conrelid,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(indexRelation->rd_index->indrelid));

        conrel = heap_open(ConstraintRelationId, AccessShareLock);
        conscan = systable_beginscan(conrel, ConstraintRelidIndexId, true,
                                                                 SnapshotNow, 1, skey);
        found = false;

        while (HeapTupleIsValid(htup = systable_getnext(conscan)))
        {
                Form_pg_constraint       conform = (Form_pg_constraint) GETSTRUCT(htup);
                Datum           val;
                bool            isnull;
                ArrayType  *arr;
                int                     nelem;

                /* We want the exclusion constraint owning the index */
                if (conform->contype != CONSTRAINT_EXCLUSION ||
                        conform->conindid != RelationGetRelid(indexRelation))
                        continue;

                /* There should be only one */
                if (found)
                        elog(ERROR, "unexpected exclusion constraint record found for rel %s",
                                 RelationGetRelationName(indexRelation));
                found = true;

                /* Extract the operator OIDS from conexclop */
                val = fastgetattr(htup,
                                                  Anum_pg_constraint_conexclop,
                                                  conrel->rd_att, &isnull);
                if (isnull)
                        elog(ERROR, "null conexclop for rel %s",
                                 RelationGetRelationName(indexRelation));

                arr = DatumGetArrayTypeP(val);  /* ensure not toasted */
                nelem = ARR_DIMS(arr)[0];
                if (ARR_NDIM(arr) != 1 ||
                        nelem != ncols ||
                        ARR_HASNULL(arr) ||
                        ARR_ELEMTYPE(arr) != OIDOID)
                        elog(ERROR, "conexclop is not a 1-D Oid array");

                memcpy(ops, ARR_DATA_PTR(arr), sizeof(Oid) * ncols);
        }

        systable_endscan(conscan);
        heap_close(conrel, AccessShareLock);

        if (!found)
                elog(ERROR, "exclusion constraint record missing for rel %s",
                         RelationGetRelationName(indexRelation));

        /* We need the func OIDs and strategy numbers too */
        for (i = 0; i < ncols; i++)
        {
                funcs[i] = get_opcode(ops[i]);
                strats[i] = get_op_opfamily_strategy(ops[i],
                                                                                         indexRelation->rd_opfamily[i]);
                /* shouldn't fail, since it was checked at index creation */
                if (strats[i] == InvalidStrategy)
                        elog(ERROR, "could not find strategy for operator %u in family %u",
                                 ops[i], indexRelation->rd_opfamily[i]);
        }

        /* Save a copy of the results in the relcache entry. */
        oldcxt = MemoryContextSwitchTo(indexRelation->rd_indexcxt);
        indexRelation->rd_exclops = (Oid *) palloc(sizeof(Oid) * ncols);
        indexRelation->rd_exclprocs = (Oid *) palloc(sizeof(Oid) * ncols);
        indexRelation->rd_exclstrats = (uint16 *) palloc(sizeof(uint16) * ncols);
        memcpy(indexRelation->rd_exclops, ops, sizeof(Oid) * ncols);
        memcpy(indexRelation->rd_exclprocs, funcs, sizeof(Oid) * ncols);
        memcpy(indexRelation->rd_exclstrats, strats, sizeof(uint16) * ncols);
        MemoryContextSwitchTo(oldcxt);
}


/*
 *      load_relcache_init_file, write_relcache_init_file
 *
 *              In late 1992, we started regularly having databases with more than
 *              a thousand classes in them.  With this number of classes, it became
 *              critical to do indexed lookups on the system catalogs.
 *
 *              Bootstrapping these lookups is very hard.  We want to be able to
 *              use an index on pg_attribute, for example, but in order to do so,
 *              we must have read pg_attribute for the attributes in the index,
 *              which implies that we need to use the index.
 *
 *              In order to get around the problem, we do the following:
 *
 *                 +  When the database system is initialized (at initdb time), we
 *                        don't use indexes.  We do sequential scans.
 *
 *                 +  When the backend is started up in normal mode, we load an image
 *                        of the appropriate relation descriptors, in internal format,
 *                        from an initialization file in the data/base/... directory.
 *
 *                 +  If the initialization file isn't there, then we create the
 *                        relation descriptors using sequential scans and write 'em to
 *                        the initialization file for use by subsequent backends.
 *
 *              As of Postgres 8.5, there is one local initialization file in each
 *              database, plus one shared initialization file for shared catalogs.
 *
 *              We could dispense with the initialization files and just build the
 *              critical reldescs the hard way on every backend startup, but that
 *              slows down backend startup noticeably.
 *
 *              We can in fact go further, and save more relcache entries than
 *              just the ones that are absolutely critical; this allows us to speed
 *              up backend startup by not having to build such entries the hard way.
 *              Presently, all the catalog and index entries that are referred to
 *              by catcaches are stored in the initialization files.
 *
 *              The same mechanism that detects when catcache and relcache entries
 *              need to be invalidated (due to catalog updates) also arranges to
 *              unlink the initialization files when the contents may be out of date.
 *              The files will then be rebuilt during the next backend startup.
 */

/*
 * load_relcache_init_file -- attempt to load cache from the shared
 * or local cache init file
 *
 * If successful, return TRUE and set criticalRelcachesBuilt or
 * criticalSharedRelcachesBuilt to true.
 * If not successful, return FALSE.
 *
 * NOTE: we assume we are already switched into CacheMemoryContext.
 */
static bool
load_relcache_init_file(bool shared)
{
        FILE       *fp;
        char            initfilename[MAXPGPATH];
        Relation   *rels;
        int                     relno,
                                num_rels,
                                max_rels,
                                nailed_rels,
                                nailed_indexes,
                                magic;
        int                     i;

        if (shared)
                snprintf(initfilename, sizeof(initfilename), "global/%s",
                                 RELCACHE_INIT_FILENAME);
        else
                snprintf(initfilename, sizeof(initfilename), "%s/%s",
                                 DatabasePath, RELCACHE_INIT_FILENAME);

        fp = AllocateFile(initfilename, PG_BINARY_R);
        if (fp == NULL)
                return false;

        /*
         * Read the index relcache entries from the file.  Note we will not enter
         * any of them into the cache if the read fails partway through; this
         * helps to guard against broken init files.
         */
        max_rels = 100;
        rels = (Relation *) palloc(max_rels * sizeof(Relation));
        num_rels = 0;
        nailed_rels = nailed_indexes = 0;

        /* check for correct magic number (compatible version) */
        if (fread(&magic, 1, sizeof(magic), fp) != sizeof(magic))
                goto read_failed;
        if (magic != RELCACHE_INIT_FILEMAGIC)
                goto read_failed;

        for (relno = 0;; relno++)
        {
                Size            len;
                size_t          nread;
                Relation        rel;
                Form_pg_class relform;
                bool            has_not_null;

                /* first read the relation descriptor length */
                nread = fread(&len, 1, sizeof(len), fp);
                if (nread != sizeof(len))
                {
                        if (nread == 0)
                                break;                  /* end of file */
                        goto read_failed;
                }

                /* safety check for incompatible relcache layout */
                if (len != sizeof(RelationData))
                        goto read_failed;

                /* allocate another relcache header */
                if (num_rels >= max_rels)
                {
                        max_rels *= 2;
                        rels = (Relation *) repalloc(rels, max_rels * sizeof(Relation));
                }

                rel = rels[num_rels++] = (Relation) palloc(len);

                /* then, read the Relation structure */
                if (fread(rel, 1, len, fp) != len)
                        goto read_failed;

                /* next read the relation tuple form */
                if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                        goto read_failed;

                relform = (Form_pg_class) palloc(len);
                if (fread(relform, 1, len, fp) != len)
                        goto read_failed;

                rel->rd_rel = relform;

                /* initialize attribute tuple forms */
                rel->rd_att = CreateTemplateTupleDesc(relform->relnatts,
                                                                                          relform->relhasoids);
                rel->rd_att->tdrefcount = 1;    /* mark as refcounted */

                rel->rd_att->tdtypeid = relform->reltype;
                rel->rd_att->tdtypmod = -1;             /* unnecessary, but... */

                /* next read all the attribute tuple form data entries */
                has_not_null = false;
                for (i = 0; i < relform->relnatts; i++)
                {
                        if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                                goto read_failed;
                        if (len != ATTRIBUTE_FIXED_PART_SIZE)
                                goto read_failed;
                        if (fread(rel->rd_att->attrs[i], 1, len, fp) != len)
                                goto read_failed;

                        has_not_null |= rel->rd_att->attrs[i]->attnotnull;
                }

                /* next read the access method specific field */
                if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                        goto read_failed;
                if (len > 0)
                {
                        rel->rd_options = palloc(len);
                        if (fread(rel->rd_options, 1, len, fp) != len)
                                goto read_failed;
                        if (len != VARSIZE(rel->rd_options))
                                goto read_failed;               /* sanity check */
                }
                else
                {
                        rel->rd_options = NULL;
                }

                /* mark not-null status */
                if (has_not_null)
                {
                        TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));

                        constr->has_not_null = true;
                        rel->rd_att->constr = constr;
                }

                /* If it's an index, there's more to do */
                if (rel->rd_rel->relkind == RELKIND_INDEX)
                {
                        Form_pg_am      am;
                        MemoryContext indexcxt;
                        Oid                *opfamily;
                        Oid                *opcintype;
                        Oid                *operator;
                        RegProcedure *support;
                        int                     nsupport;
                        int16      *indoption;

                        /* Count nailed indexes to ensure we have 'em all */
                        if (rel->rd_isnailed)
                                nailed_indexes++;

                        /* next, read the pg_index tuple */
                        if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                                goto read_failed;

                        rel->rd_indextuple = (HeapTuple) palloc(len);
                        if (fread(rel->rd_indextuple, 1, len, fp) != len)
                                goto read_failed;

                        /* Fix up internal pointers in the tuple -- see heap_copytuple */
                        rel->rd_indextuple->t_data = (HeapTupleHeader) ((char *) rel->rd_indextuple + HEAPTUPLESIZE);
                        rel->rd_index = (Form_pg_index) GETSTRUCT(rel->rd_indextuple);

                        /* next, read the access method tuple form */
                        if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                                goto read_failed;

                        am = (Form_pg_am) palloc(len);
                        if (fread(am, 1, len, fp) != len)
                                goto read_failed;
                        rel->rd_am = am;

                        /*
                         * prepare index info context --- parameters should match
                         * RelationInitIndexAccessInfo
                         */
                        indexcxt = AllocSetContextCreate(CacheMemoryContext,
                                                                                         RelationGetRelationName(rel),
                                                                                         ALLOCSET_SMALL_MINSIZE,
                                                                                         ALLOCSET_SMALL_INITSIZE,
                                                                                         ALLOCSET_SMALL_MAXSIZE);
                        rel->rd_indexcxt = indexcxt;

                        /* next, read the vector of opfamily OIDs */
                        if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                                goto read_failed;

                        opfamily = (Oid *) MemoryContextAlloc(indexcxt, len);
                        if (fread(opfamily, 1, len, fp) != len)
                                goto read_failed;

                        rel->rd_opfamily = opfamily;

                        /* next, read the vector of opcintype OIDs */
                        if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                                goto read_failed;

                        opcintype = (Oid *) MemoryContextAlloc(indexcxt, len);
                        if (fread(opcintype, 1, len, fp) != len)
                                goto read_failed;

                        rel->rd_opcintype = opcintype;

                        /* next, read the vector of operator OIDs */
                        if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                                goto read_failed;

                        operator = (Oid *) MemoryContextAlloc(indexcxt, len);
                        if (fread(operator, 1, len, fp) != len)
                                goto read_failed;

                        rel->rd_operator = operator;

                        /* next, read the vector of support procedures */
                        if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                                goto read_failed;
                        support = (RegProcedure *) MemoryContextAlloc(indexcxt, len);
                        if (fread(support, 1, len, fp) != len)
                                goto read_failed;

                        rel->rd_support = support;

                        /* finally, read the vector of indoption values */
                        if (fread(&len, 1, sizeof(len), fp) != sizeof(len))
                                goto read_failed;

                        indoption = (int16 *) MemoryContextAlloc(indexcxt, len);
                        if (fread(indoption, 1, len, fp) != len)
                                goto read_failed;

                        rel->rd_indoption = indoption;

                        /* set up zeroed fmgr-info vectors */
                        rel->rd_aminfo = (RelationAmInfo *)
                                MemoryContextAllocZero(indexcxt, sizeof(RelationAmInfo));
                        nsupport = relform->relnatts * am->amsupport;
                        rel->rd_supportinfo = (FmgrInfo *)
                                MemoryContextAllocZero(indexcxt, nsupport * sizeof(FmgrInfo));
                }
                else
                {
                        /* Count nailed rels to ensure we have 'em all */
                        if (rel->rd_isnailed)
                                nailed_rels++;

                        Assert(rel->rd_index == NULL);
                        Assert(rel->rd_indextuple == NULL);
                        Assert(rel->rd_am == NULL);
                        Assert(rel->rd_indexcxt == NULL);
                        Assert(rel->rd_aminfo == NULL);
                        Assert(rel->rd_opfamily == NULL);
                        Assert(rel->rd_opcintype == NULL);
                        Assert(rel->rd_operator == NULL);
                        Assert(rel->rd_support == NULL);
                        Assert(rel->rd_supportinfo == NULL);
                        Assert(rel->rd_indoption == NULL);
                }

                /*
                 * Rules and triggers are not saved (mainly because the internal
                 * format is complex and subject to change).  They must be rebuilt if
                 * needed by RelationCacheInitializePhase3.  This is not expected to
                 * be a big performance hit since few system catalogs have such. Ditto
                 * for index expressions, predicates, and exclusion info.
                 */
                rel->rd_rules = NULL;
                rel->rd_rulescxt = NULL;
                rel->trigdesc = NULL;
                rel->rd_indexprs = NIL;
                rel->rd_indpred = NIL;
                rel->rd_exclops = NULL;
                rel->rd_exclprocs = NULL;
                rel->rd_exclstrats = NULL;

                /*
                 * Reset transient-state fields in the relcache entry
                 */
                rel->rd_smgr = NULL;
                rel->rd_targblock = InvalidBlockNumber;
                rel->rd_fsm_nblocks = InvalidBlockNumber;
                rel->rd_vm_nblocks = InvalidBlockNumber;
                if (rel->rd_isnailed)
                        rel->rd_refcnt = 1;
                else
                        rel->rd_refcnt = 0;
                rel->rd_indexvalid = 0;
                rel->rd_indexlist = NIL;
                rel->rd_indexattr = NULL;
                rel->rd_oidindex = InvalidOid;
                rel->rd_createSubid = InvalidSubTransactionId;
                rel->rd_newRelfilenodeSubid = InvalidSubTransactionId;
                rel->rd_amcache = NULL;
                MemSet(&rel->pgstat_info, 0, sizeof(rel->pgstat_info));

                /*
                 * Recompute lock and physical addressing info.  This is needed in
                 * case the pg_internal.init file was copied from some other database
                 * by CREATE DATABASE.
                 */
                RelationInitLockInfo(rel);
                RelationInitPhysicalAddr(rel);
        }

        /*
         * We reached the end of the init file without apparent problem. Did we
         * get the right number of nailed items?  (This is a useful crosscheck in
         * case the set of critical rels or indexes changes.)
         */
        if (shared)
        {
                if (nailed_rels != NUM_CRITICAL_SHARED_RELS ||
                        nailed_indexes != NUM_CRITICAL_SHARED_INDEXES)
                        goto read_failed;
        }
        else
        {
                if (nailed_rels != NUM_CRITICAL_LOCAL_RELS ||
                        nailed_indexes != NUM_CRITICAL_LOCAL_INDEXES)
                        goto read_failed;
        }

        /*
         * OK, all appears well.
         *
         * Now insert all the new relcache entries into the cache.
         */
        for (relno = 0; relno < num_rels; relno++)
        {
                RelationCacheInsert(rels[relno]);
                /* also make a list of their OIDs, for RelationIdIsInInitFile */
                if (!shared)
                        initFileRelationIds = lcons_oid(RelationGetRelid(rels[relno]),
                                                                                        initFileRelationIds);
        }

        pfree(rels);
        FreeFile(fp);

        if (shared)
                criticalSharedRelcachesBuilt = true;
        else
                criticalRelcachesBuilt = true;
        return true;

        /*
         * init file is broken, so do it the hard way.  We don't bother trying to
         * free the clutter we just allocated; it's not in the relcache so it
         * won't hurt.
         */
read_failed:
        pfree(rels);
        FreeFile(fp);

        return false;
}

/*
 * Write out a new initialization file with the current contents
 * of the relcache (either shared rels or local rels, as indicated).
 */
static void
write_relcache_init_file(bool shared)
{
        FILE       *fp;
        char            tempfilename[MAXPGPATH];
        char            finalfilename[MAXPGPATH];
        int                     magic;
        HASH_SEQ_STATUS status;
        RelIdCacheEnt *idhentry;
        MemoryContext oldcxt;
        int                     i;

        /*
         * We must write a temporary file and rename it into place. Otherwise,
         * another backend starting at about the same time might crash trying to
         * read the partially-complete file.
         */
        if (shared)
        {
                snprintf(tempfilename, sizeof(tempfilename), "global/%s.%d",
                                 RELCACHE_INIT_FILENAME, MyProcPid);
                snprintf(finalfilename, sizeof(finalfilename), "global/%s",
                                 RELCACHE_INIT_FILENAME);
        }
        else
        {
                snprintf(tempfilename, sizeof(tempfilename), "%s/%s.%d",
                                 DatabasePath, RELCACHE_INIT_FILENAME, MyProcPid);
                snprintf(finalfilename, sizeof(finalfilename), "%s/%s",
                                 DatabasePath, RELCACHE_INIT_FILENAME);
        }

        unlink(tempfilename);           /* in case it exists w/wrong permissions */

        fp = AllocateFile(tempfilename, PG_BINARY_W);
        if (fp == NULL)
        {
                /*
                 * We used to consider this a fatal error, but we might as well
                 * continue with backend startup ...
                 */
                ereport(WARNING,
                                (errcode_for_file_access(),
                                 errmsg("could not create relation-cache initialization file \"%s\": %m",
                                                tempfilename),
                          errdetail("Continuing anyway, but there's something wrong.")));
                return;
        }

        /*
         * Write a magic number to serve as a file version identifier.  We can
         * change the magic number whenever the relcache layout changes.
         */
        magic = RELCACHE_INIT_FILEMAGIC;
        if (fwrite(&magic, 1, sizeof(magic), fp) != sizeof(magic))
                elog(FATAL, "could not write init file");

        /*
         * Write all the appropriate reldescs (in no particular order).
         */
        hash_seq_init(&status, RelationIdCache);

        while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
        {
                Relation        rel = idhentry->reldesc;
                Form_pg_class relform = rel->rd_rel;

                /* ignore if not correct group */
                if (relform->relisshared != shared)
                        continue;

                /* first write the relcache entry proper */
                write_item(rel, sizeof(RelationData), fp);

                /* next write the relation tuple form */
                write_item(relform, CLASS_TUPLE_SIZE, fp);

                /* next, do all the attribute tuple form data entries */
                for (i = 0; i < relform->relnatts; i++)
                {
                        write_item(rel->rd_att->attrs[i], ATTRIBUTE_FIXED_PART_SIZE, fp);
                }

                /* next, do the access method specific field */
                write_item(rel->rd_options,
                                   (rel->rd_options ? VARSIZE(rel->rd_options) : 0),
                                   fp);

                /* If it's an index, there's more to do */
                if (rel->rd_rel->relkind == RELKIND_INDEX)
                {
                        Form_pg_am      am = rel->rd_am;

                        /* write the pg_index tuple */
                        /* we assume this was created by heap_copytuple! */
                        write_item(rel->rd_indextuple,
                                           HEAPTUPLESIZE + rel->rd_indextuple->t_len,
                                           fp);

                        /* next, write the access method tuple form */
                        write_item(am, sizeof(FormData_pg_am), fp);

                        /* next, write the vector of opfamily OIDs */
                        write_item(rel->rd_opfamily,
                                           relform->relnatts * sizeof(Oid),
                                           fp);

                        /* next, write the vector of opcintype OIDs */
                        write_item(rel->rd_opcintype,
                                           relform->relnatts * sizeof(Oid),
                                           fp);

                        /* next, write the vector of operator OIDs */
                        write_item(rel->rd_operator,
                                           relform->relnatts * (am->amstrategies * sizeof(Oid)),
                                           fp);

                        /* next, write the vector of support procedures */
                        write_item(rel->rd_support,
                                  relform->relnatts * (am->amsupport * sizeof(RegProcedure)),
                                           fp);

                        /* finally, write the vector of indoption values */
                        write_item(rel->rd_indoption,
                                           relform->relnatts * sizeof(int16),
                                           fp);
                }

                /* also make a list of their OIDs, for RelationIdIsInInitFile */
                if (!shared)
                {
                        oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
                        initFileRelationIds = lcons_oid(RelationGetRelid(rel),
                                                                                        initFileRelationIds);
                        MemoryContextSwitchTo(oldcxt);
                }
        }

        if (FreeFile(fp))
                elog(FATAL, "could not write init file");

        /*
         * Now we have to check whether the data we've so painstakingly
         * accumulated is already obsolete due to someone else's just-committed
         * catalog changes.  If so, we just delete the temp file and leave it to
         * the next backend to try again.  (Our own relcache entries will be
         * updated by SI message processing, but we can't be sure whether what we
         * wrote out was up-to-date.)
         *
         * This mustn't run concurrently with RelationCacheInitFileInvalidate, so
         * grab a serialization lock for the duration.
         */
        LWLockAcquire(RelCacheInitLock, LW_EXCLUSIVE);

        /* Make sure we have seen all incoming SI messages */
        AcceptInvalidationMessages();

        /*
         * If we have received any SI relcache invals since backend start, assume
         * we may have written out-of-date data.
         */
        if (relcacheInvalsReceived == 0L)
        {
                /*
                 * OK, rename the temp file to its final name, deleting any
                 * previously-existing init file.
                 *
                 * Note: a failure here is possible under Cygwin, if some other
                 * backend is holding open an unlinked-but-not-yet-gone init file. So
                 * treat this as a noncritical failure; just remove the useless temp
                 * file on failure.
                 */
                if (rename(tempfilename, finalfilename) < 0)
                        unlink(tempfilename);
        }
        else
        {
                /* Delete the already-obsolete temp file */
                unlink(tempfilename);
        }

        LWLockRelease(RelCacheInitLock);
}

/* write a chunk of data preceded by its length */
static void
write_item(const void *data, Size len, FILE *fp)
{
        if (fwrite(&len, 1, sizeof(len), fp) != sizeof(len))
                elog(FATAL, "could not write init file");
        if (fwrite(data, 1, len, fp) != len)
                elog(FATAL, "could not write init file");
}

/*
 * Detect whether a given relation (identified by OID) is one of the ones
 * we store in the local relcache init file.
 *
 * Note that we effectively assume that all backends running in a database
 * would choose to store the same set of relations in the init file;
 * otherwise there are cases where we'd fail to detect the need for an init
 * file invalidation.  This does not seem likely to be a problem in practice.
 */
bool
RelationIdIsInInitFile(Oid relationId)
{
        return list_member_oid(initFileRelationIds, relationId);
}

/*
 * Invalidate (remove) the init file during commit of a transaction that
 * changed one or more of the relation cache entries that are kept in the
 * local init file.
 *
 * We actually need to remove the init file twice: once just before sending
 * the SI messages that include relcache inval for such relations, and once
 * just after sending them.  The unlink before ensures that a backend that's
 * currently starting cannot read the now-obsolete init file and then miss
 * the SI messages that will force it to update its relcache entries.  (This
 * works because the backend startup sequence gets into the PGPROC array before
 * trying to load the init file.)  The unlink after is to synchronize with a
 * backend that may currently be trying to write an init file based on data
 * that we've just rendered invalid.  Such a backend will see the SI messages,
 * but we can't leave the init file sitting around to fool later backends.
 *
 * Ignore any failure to unlink the file, since it might not be there if
 * no backend has been started since the last removal.
 *
 * Notice this deals only with the local init file, not the shared init file.
 * The reason is that there can never be a "significant" change to the
 * relcache entry of a shared relation; the most that could happen is
 * updates of noncritical fields such as relpages/reltuples.  So, while
 * it's worth updating the shared init file from time to time, it can never
 * be invalid enough to make it necessary to remove it.
 */
void
RelationCacheInitFileInvalidate(bool beforeSend)
{
        char            initfilename[MAXPGPATH];

        snprintf(initfilename, sizeof(initfilename), "%s/%s",
                         DatabasePath, RELCACHE_INIT_FILENAME);

        if (beforeSend)
        {
                /* no interlock needed here */
                unlink(initfilename);
        }
        else
        {
                /*
                 * We need to interlock this against write_relcache_init_file, to
                 * guard against possibility that someone renames a new-but-
                 * already-obsolete init file into place just after we unlink. With
                 * the interlock, it's certain that write_relcache_init_file will
                 * notice our SI inval message before renaming into place, or else
                 * that we will execute second and successfully unlink the file.
                 */
                LWLockAcquire(RelCacheInitLock, LW_EXCLUSIVE);
                unlink(initfilename);
                LWLockRelease(RelCacheInitLock);
        }
}

/*
 * Remove the init files during postmaster startup.
 *
 * We used to keep the init files across restarts, but that is unsafe in PITR
 * scenarios, and even in simple crash-recovery cases there are windows for
 * the init files to become out-of-sync with the database.  So now we just
 * remove them during startup and expect the first backend launch to rebuild
 * them.  Of course, this has to happen in each database of the cluster.
 */
void
RelationCacheInitFileRemove(void)
{
        const char *tblspcdir = "pg_tblspc";
        DIR                *dir;
        struct dirent *de;
        char            path[MAXPGPATH];

        /*
         * We zap the shared cache file too.  In theory it can't get out of sync
         * enough to be a problem, but in data-corruption cases, who knows ...
         */
        snprintf(path, sizeof(path), "global/%s",
                         RELCACHE_INIT_FILENAME);
        unlink_initfile(path);

        /* Scan everything in the default tablespace */
        RelationCacheInitFileRemoveInDir("base");

        /* Scan the tablespace link directory to find non-default tablespaces */
        dir = AllocateDir(tblspcdir);
        if (dir == NULL)
        {
                elog(LOG, "could not open tablespace link directory \"%s\": %m",
                         tblspcdir);
                return;
        }

        while ((de = ReadDir(dir, tblspcdir)) != NULL)
        {
                if (strspn(de->d_name, "0123456789") == strlen(de->d_name))
                {
                        /* Scan the tablespace dir for per-database dirs */
                        snprintf(path, sizeof(path), "%s/%s",
                                         tblspcdir, de->d_name);
                        RelationCacheInitFileRemoveInDir(path);
                }
        }

        FreeDir(dir);
}

/* Process one per-tablespace directory for RelationCacheInitFileRemove */
static void
RelationCacheInitFileRemoveInDir(const char *tblspcpath)
{
        DIR                *dir;
        struct dirent *de;
        char            initfilename[MAXPGPATH];

        /* Scan the tablespace directory to find per-database directories */
        dir = AllocateDir(tblspcpath);
        if (dir == NULL)
        {
                elog(LOG, "could not open tablespace directory \"%s\": %m",
                         tblspcpath);
                return;
        }

        while ((de = ReadDir(dir, tblspcpath)) != NULL)
        {
                if (strspn(de->d_name, "0123456789") == strlen(de->d_name))
                {
                        /* Try to remove the init file in each database */
                        snprintf(initfilename, sizeof(initfilename), "%s/%s/%s",
                                         tblspcpath, de->d_name, RELCACHE_INIT_FILENAME);
                        unlink_initfile(initfilename);
                }
        }

        FreeDir(dir);
}

static void
unlink_initfile(const char *initfilename)
{
        if (unlink(initfilename) < 0)
        {
                /* It might not be there, but log any error other than ENOENT */
                if (errno != ENOENT)
                        elog(LOG, "could not remove cache file \"%s\": %m", initfilename);
        }
}