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

/*-------------------------------------------------------------------------
 *
 * inval.c
 *        POSTGRES cache invalidation dispatcher code.
 *
 *      This is subtle stuff, so pay attention:
 *
 *      When a tuple is updated or deleted, our standard time qualification rules
 *      consider that it is *still valid* so long as we are in the same command,
 *      ie, until the next CommandCounterIncrement() or transaction commit.
 *      (See utils/time/tqual.c, and note that system catalogs are generally
 *      scanned under SnapshotNow rules by the system, or plain user snapshots
 *      for user queries.)      At the command boundary, the old tuple stops
 *      being valid and the new version, if any, becomes valid.  Therefore,
 *      we cannot simply flush a tuple from the system caches during heap_update()
 *      or heap_delete().  The tuple is still good at that point; what's more,
 *      even if we did flush it, it might be reloaded into the caches by a later
 *      request in the same command.  So the correct behavior is to keep a list
 *      of outdated (updated/deleted) tuples and then do the required cache
 *      flushes at the next command boundary.  We must also keep track of
 *      inserted tuples so that we can flush "negative" cache entries that match
 *      the new tuples; again, that mustn't happen until end of command.
 *
 *      Once we have finished the command, we still need to remember inserted
 *      tuples (including new versions of updated tuples), so that we can flush
 *      them from the caches if we abort the transaction.  Similarly, we'd better
 *      be able to flush "negative" cache entries that may have been loaded in
 *      place of deleted tuples, so we still need the deleted ones too.
 *
 *      If we successfully complete the transaction, we have to broadcast all
 *      these invalidation events to other backends (via the SI message queue)
 *      so that they can flush obsolete entries from their caches.      Note we have
 *      to record the transaction commit before sending SI messages, otherwise
 *      the other backends won't see our updated tuples as good.
 *
 *      When a subtransaction aborts, we can process and discard any events
 *      it has queued.  When a subtransaction commits, we just add its events
 *      to the pending lists of the parent transaction.
 *
 *      In short, we need to remember until xact end every insert or delete
 *      of a tuple that might be in the system caches.  Updates are treated as
 *      two events, delete + insert, for simplicity.  (There are cases where
 *      it'd be possible to record just one event, but we don't currently try.)
 *
 *      We do not need to register EVERY tuple operation in this way, just those
 *      on tuples in relations that have associated catcaches.  We do, however,
 *      have to register every operation on every tuple that *could* be in a
 *      catcache, whether or not it currently is in our cache.  Also, if the
 *      tuple is in a relation that has multiple catcaches, we need to register
 *      an invalidation message for each such catcache.  catcache.c's
 *      PrepareToInvalidateCacheTuple() routine provides the knowledge of which
 *      catcaches may need invalidation for a given tuple.
 *
 *      Also, whenever we see an operation on a pg_class or pg_attribute tuple,
 *      we register a relcache flush operation for the relation described by that
 *      tuple.  pg_class updates trigger an smgr flush operation as well.
 *
 *      We keep the relcache and smgr flush requests in lists separate from the
 *      catcache tuple flush requests.  This allows us to issue all the pending
 *      catcache flushes before we issue relcache flushes, which saves us from
 *      loading a catcache tuple during relcache load only to flush it again
 *      right away.  Also, we avoid queuing multiple relcache flush requests for
 *      the same relation, since a relcache flush is relatively expensive to do.
 *      (XXX is it worth testing likewise for duplicate catcache flush entries?
 *      Probably not.)
 *
 *      If a relcache flush is issued for a system relation that we preload
 *      from the relcache init file, we must also delete the init file so that
 *      it will be rebuilt during the next backend restart.  The actual work of
 *      manipulating the init file is in relcache.c, but we keep track of the
 *      need for it here.
 *
 *      The request lists proper are kept in CurTransactionContext of their
 *      creating (sub)transaction, since they can be forgotten on abort of that
 *      transaction but must be kept till top-level commit otherwise.  For
 *      simplicity we keep the controlling list-of-lists in TopTransactionContext.
 *
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *        $PostgreSQL: pgsql/src/backend/utils/cache/inval.c,v 1.86 2008/06/19 21:32:56 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/twophase_rmgr.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "miscadmin.h"
#include "storage/sinval.h"
#include "storage/smgr.h"
#include "utils/inval.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/syscache.h"


/*
 * To minimize palloc traffic, we keep pending requests in successively-
 * larger chunks (a slightly more sophisticated version of an expansible
 * array).      All request types can be stored as SharedInvalidationMessage
 * records.  The ordering of requests within a list is never significant.
 */
typedef struct InvalidationChunk
{
        struct InvalidationChunk *next;         /* list link */
        int                     nitems;                 /* # items currently stored in chunk */
        int                     maxitems;               /* size of allocated array in this chunk */
        SharedInvalidationMessage msgs[1];      /* VARIABLE LENGTH ARRAY */
} InvalidationChunk;                    /* VARIABLE LENGTH STRUCTURE */

typedef struct InvalidationListHeader
{
        InvalidationChunk *cclist;      /* list of chunks holding catcache msgs */
        InvalidationChunk *rclist;      /* list of chunks holding relcache/smgr msgs */
} InvalidationListHeader;

/*----------------
 * Invalidation info is divided into two lists:
 *      1) events so far in current command, not yet reflected to caches.
 *      2) events in previous commands of current transaction; these have
 *         been reflected to local caches, and must be either broadcast to
 *         other backends or rolled back from local cache when we commit
 *         or abort the transaction.
 * Actually, we need two such lists for each level of nested transaction,
 * so that we can discard events from an aborted subtransaction.  When
 * a subtransaction commits, we append its lists to the parent's lists.
 *
 * The relcache-file-invalidated flag can just be a simple boolean,
 * since we only act on it at transaction commit; we don't care which
 * command of the transaction set it.
 *----------------
 */

typedef struct TransInvalidationInfo
{
        /* Back link to parent transaction's info */
        struct TransInvalidationInfo *parent;

        /* Subtransaction nesting depth */
        int                     my_level;

        /* head of current-command event list */
        InvalidationListHeader CurrentCmdInvalidMsgs;

        /* head of previous-commands event list */
        InvalidationListHeader PriorCmdInvalidMsgs;

        /* init file must be invalidated? */
        bool            RelcacheInitFileInval;
} TransInvalidationInfo;

static TransInvalidationInfo *transInvalInfo = NULL;

/*
 * Dynamically-registered callback functions.  Current implementation
 * assumes there won't be very many of these at once; could improve if needed.
 */

#define MAX_CACHE_CALLBACKS 20

static struct CACHECALLBACK
{
        int16           id;                             /* cache number or message type id */
        CacheCallbackFunction function;
        Datum           arg;
}       cache_callback_list[MAX_CACHE_CALLBACKS];

static int      cache_callback_count = 0;

/* info values for 2PC callback */
#define TWOPHASE_INFO_MSG                       0       /* SharedInvalidationMessage */
#define TWOPHASE_INFO_FILE_BEFORE       1       /* relcache file inval */
#define TWOPHASE_INFO_FILE_AFTER        2       /* relcache file inval */

static void PersistInvalidationMessage(SharedInvalidationMessage *msg);


/* ----------------------------------------------------------------
 *                              Invalidation list support functions
 *
 * These three routines encapsulate processing of the "chunked"
 * representation of what is logically just a list of messages.
 * ----------------------------------------------------------------
 */

/*
 * AddInvalidationMessage
 *              Add an invalidation message to a list (of chunks).
 *
 * Note that we do not pay any great attention to maintaining the original
 * ordering of the messages.
 */
static void
AddInvalidationMessage(InvalidationChunk **listHdr,
                                           SharedInvalidationMessage *msg)
{
        InvalidationChunk *chunk = *listHdr;

        if (chunk == NULL)
        {
                /* First time through; create initial chunk */
#define FIRSTCHUNKSIZE 32
                chunk = (InvalidationChunk *)
                        MemoryContextAlloc(CurTransactionContext,
                                                           sizeof(InvalidationChunk) +
                                        (FIRSTCHUNKSIZE - 1) *sizeof(SharedInvalidationMessage));
                chunk->nitems = 0;
                chunk->maxitems = FIRSTCHUNKSIZE;
                chunk->next = *listHdr;
                *listHdr = chunk;
        }
        else if (chunk->nitems >= chunk->maxitems)
        {
                /* Need another chunk; double size of last chunk */
                int                     chunksize = 2 * chunk->maxitems;

                chunk = (InvalidationChunk *)
                        MemoryContextAlloc(CurTransactionContext,
                                                           sizeof(InvalidationChunk) +
                                                 (chunksize - 1) *sizeof(SharedInvalidationMessage));
                chunk->nitems = 0;
                chunk->maxitems = chunksize;
                chunk->next = *listHdr;
                *listHdr = chunk;
        }
        /* Okay, add message to current chunk */
        chunk->msgs[chunk->nitems] = *msg;
        chunk->nitems++;
}

/*
 * Append one list of invalidation message chunks to another, resetting
 * the source chunk-list pointer to NULL.
 */
static void
AppendInvalidationMessageList(InvalidationChunk **destHdr,
                                                          InvalidationChunk **srcHdr)
{
        InvalidationChunk *chunk = *srcHdr;

        if (chunk == NULL)
                return;                                 /* nothing to do */

        while (chunk->next != NULL)
                chunk = chunk->next;

        chunk->next = *destHdr;

        *destHdr = *srcHdr;

        *srcHdr = NULL;
}

/*
 * Process a list of invalidation messages.
 *
 * This is a macro that executes the given code fragment for each message in
 * a message chunk list.  The fragment should refer to the message as *msg.
 */
#define ProcessMessageList(listHdr, codeFragment) \
        do { \
                InvalidationChunk *_chunk; \
                for (_chunk = (listHdr); _chunk != NULL; _chunk = _chunk->next) \
                { \
                        int             _cindex; \
                        for (_cindex = 0; _cindex < _chunk->nitems; _cindex++) \
                        { \
                                SharedInvalidationMessage *msg = &_chunk->msgs[_cindex]; \
                                codeFragment; \
                        } \
                } \
        } while (0)

/*
 * Process a list of invalidation messages group-wise.
 *
 * As above, but the code fragment can handle an array of messages.
 * The fragment should refer to the messages as msgs[], with n entries.
 */
#define ProcessMessageListMulti(listHdr, codeFragment) \
        do { \
                InvalidationChunk *_chunk; \
                for (_chunk = (listHdr); _chunk != NULL; _chunk = _chunk->next) \
                { \
                        SharedInvalidationMessage *msgs = _chunk->msgs; \
                        int             n = _chunk->nitems; \
                        codeFragment; \
                } \
        } while (0)


/* ----------------------------------------------------------------
 *                              Invalidation set support functions
 *
 * These routines understand about the division of a logical invalidation
 * list into separate physical lists for catcache and relcache/smgr entries.
 * ----------------------------------------------------------------
 */

/*
 * Add a catcache inval entry
 */
static void
AddCatcacheInvalidationMessage(InvalidationListHeader *hdr,
                                                           int id, uint32 hashValue,
                                                           ItemPointer tuplePtr, Oid dbId)
{
        SharedInvalidationMessage msg;

        msg.cc.id = (int16) id;
        msg.cc.tuplePtr = *tuplePtr;
        msg.cc.dbId = dbId;
        msg.cc.hashValue = hashValue;
        AddInvalidationMessage(&hdr->cclist, &msg);
}

/*
 * Add a relcache inval entry
 */
static void
AddRelcacheInvalidationMessage(InvalidationListHeader *hdr,
                                                           Oid dbId, Oid relId)
{
        SharedInvalidationMessage msg;

        /* Don't add a duplicate item */
        /* We assume dbId need not be checked because it will never change */
        ProcessMessageList(hdr->rclist,
                                           if (msg->rc.id == SHAREDINVALRELCACHE_ID &&
                                                   msg->rc.relId == relId)
                                           return);

        /* OK, add the item */
        msg.rc.id = SHAREDINVALRELCACHE_ID;
        msg.rc.dbId = dbId;
        msg.rc.relId = relId;
        AddInvalidationMessage(&hdr->rclist, &msg);
}

/*
 * Add an smgr inval entry
 */
static void
AddSmgrInvalidationMessage(InvalidationListHeader *hdr,
                                                   RelFileNode rnode)
{
        SharedInvalidationMessage msg;

        /* Don't add a duplicate item */
        ProcessMessageList(hdr->rclist,
                                           if (msg->sm.id == SHAREDINVALSMGR_ID &&
                                                   RelFileNodeEquals(msg->sm.rnode, rnode))
                                           return);

        /* OK, add the item */
        msg.sm.id = SHAREDINVALSMGR_ID;
        msg.sm.rnode = rnode;
        AddInvalidationMessage(&hdr->rclist, &msg);
}

/*
 * Append one list of invalidation messages to another, resetting
 * the source list to empty.
 */
static void
AppendInvalidationMessages(InvalidationListHeader *dest,
                                                   InvalidationListHeader *src)
{
        AppendInvalidationMessageList(&dest->cclist, &src->cclist);
        AppendInvalidationMessageList(&dest->rclist, &src->rclist);
}

/*
 * Execute the given function for all the messages in an invalidation list.
 * The list is not altered.
 *
 * catcache entries are processed first, for reasons mentioned above.
 */
static void
ProcessInvalidationMessages(InvalidationListHeader *hdr,
                                                        void (*func) (SharedInvalidationMessage *msg))
{
        ProcessMessageList(hdr->cclist, func(msg));
        ProcessMessageList(hdr->rclist, func(msg));
}

/*
 * As above, but the function is able to process an array of messages
 * rather than just one at a time.
 */
static void
ProcessInvalidationMessagesMulti(InvalidationListHeader *hdr,
                                                                 void (*func) (const SharedInvalidationMessage *msgs, int n))
{
        ProcessMessageListMulti(hdr->cclist, func(msgs, n));
        ProcessMessageListMulti(hdr->rclist, func(msgs, n));
}

/* ----------------------------------------------------------------
 *                                        private support functions
 * ----------------------------------------------------------------
 */

/*
 * RegisterCatcacheInvalidation
 *
 * Register an invalidation event for a catcache tuple entry.
 */
static void
RegisterCatcacheInvalidation(int cacheId,
                                                         uint32 hashValue,
                                                         ItemPointer tuplePtr,
                                                         Oid dbId)
{
        AddCatcacheInvalidationMessage(&transInvalInfo->CurrentCmdInvalidMsgs,
                                                                   cacheId, hashValue, tuplePtr, dbId);
}

/*
 * RegisterRelcacheInvalidation
 *
 * As above, but register a relcache invalidation event.
 */
static void
RegisterRelcacheInvalidation(Oid dbId, Oid relId)
{
        AddRelcacheInvalidationMessage(&transInvalInfo->CurrentCmdInvalidMsgs,
                                                                   dbId, relId);

        /*
         * Most of the time, relcache invalidation is associated with system
         * catalog updates, but there are a few cases where it isn't.  Quick
         * hack to ensure that the next CommandCounterIncrement() will think
         * that we need to do CommandEndInvalidationMessages().
         */
        (void) GetCurrentCommandId(true);

        /*
         * If the relation being invalidated is one of those cached in the
         * relcache init file, mark that we need to zap that file at commit.
         */
        if (RelationIdIsInInitFile(relId))
                transInvalInfo->RelcacheInitFileInval = true;
}

/*
 * RegisterSmgrInvalidation
 *
 * As above, but register an smgr invalidation event.
 */
static void
RegisterSmgrInvalidation(RelFileNode rnode)
{
        AddSmgrInvalidationMessage(&transInvalInfo->CurrentCmdInvalidMsgs,
                                                           rnode);

        /*
         * As above, just in case there is not an associated catalog change.
         */
        (void) GetCurrentCommandId(true);
}

/*
 * LocalExecuteInvalidationMessage
 *
 * Process a single invalidation message (which could be of any type).
 * Only the local caches are flushed; this does not transmit the message
 * to other backends.
 */
static void
LocalExecuteInvalidationMessage(SharedInvalidationMessage *msg)
{
        int                     i;

        if (msg->id >= 0)
        {
                if (msg->cc.dbId == MyDatabaseId || msg->cc.dbId == 0)
                {
                        CatalogCacheIdInvalidate(msg->cc.id,
                                                                         msg->cc.hashValue,
                                                                         &msg->cc.tuplePtr);

                        for (i = 0; i < cache_callback_count; i++)
                        {
                                struct CACHECALLBACK *ccitem = cache_callback_list + i;

                                if (ccitem->id == msg->cc.id)
                                        (*ccitem->function) (ccitem->arg, InvalidOid);
                        }
                }
        }
        else if (msg->id == SHAREDINVALRELCACHE_ID)
        {
                if (msg->rc.dbId == MyDatabaseId || msg->rc.dbId == InvalidOid)
                {
                        RelationCacheInvalidateEntry(msg->rc.relId);

                        for (i = 0; i < cache_callback_count; i++)
                        {
                                struct CACHECALLBACK *ccitem = cache_callback_list + i;

                                if (ccitem->id == SHAREDINVALRELCACHE_ID)
                                        (*ccitem->function) (ccitem->arg, msg->rc.relId);
                        }
                }
        }
        else if (msg->id == SHAREDINVALSMGR_ID)
        {
                /*
                 * We could have smgr entries for relations of other databases, so no
                 * short-circuit test is possible here.
                 */
                smgrclosenode(msg->sm.rnode);
        }
        else
                elog(FATAL, "unrecognized SI message id: %d", msg->id);
}

/*
 *              InvalidateSystemCaches
 *
 *              This blows away all tuples in the system catalog caches and
 *              all the cached relation descriptors and smgr cache entries.
 *              Relation descriptors that have positive refcounts are then rebuilt.
 *
 *              We call this when we see a shared-inval-queue overflow signal,
 *              since that tells us we've lost some shared-inval messages and hence
 *              don't know what needs to be invalidated.
 */
static void
InvalidateSystemCaches(void)
{
        int                     i;

        ResetCatalogCaches();
        RelationCacheInvalidate();      /* gets smgr cache too */

        for (i = 0; i < cache_callback_count; i++)
        {
                struct CACHECALLBACK *ccitem = cache_callback_list + i;

                (*ccitem->function) (ccitem->arg, InvalidOid);
        }
}

/*
 * PrepareForTupleInvalidation
 *              Detect whether invalidation of this tuple implies invalidation
 *              of catalog/relation cache entries; if so, register inval events.
 */
static void
PrepareForTupleInvalidation(Relation relation, HeapTuple tuple)
{
        Oid                     tupleRelId;
        Oid                     databaseId;
        Oid                     relationId;

        /* Do nothing during bootstrap */
        if (IsBootstrapProcessingMode())
                return;

        /*
         * We only need to worry about invalidation for tuples that are in system
         * relations; user-relation tuples are never in catcaches and can't affect
         * the relcache either.
         */
        if (!IsSystemRelation(relation))
                return;

        /*
         * TOAST tuples can likewise be ignored here. Note that TOAST tables are
         * considered system relations so they are not filtered by the above test.
         */
        if (IsToastRelation(relation))
                return;

        /*
         * First let the catcache do its thing
         */
        PrepareToInvalidateCacheTuple(relation, tuple,
                                                                  RegisterCatcacheInvalidation);

        /*
         * Now, is this tuple one of the primary definers of a relcache entry?
         */
        tupleRelId = RelationGetRelid(relation);

        if (tupleRelId == RelationRelationId)
        {
                Form_pg_class classtup = (Form_pg_class) GETSTRUCT(tuple);
                RelFileNode rnode;

                relationId = HeapTupleGetOid(tuple);
                if (classtup->relisshared)
                        databaseId = InvalidOid;
                else
                        databaseId = MyDatabaseId;

                /*
                 * We need to send out an smgr inval as well as a relcache inval. This
                 * is needed because other backends might possibly possess smgr cache
                 * but not relcache entries for the target relation.
                 *
                 * Note: during a pg_class row update that assigns a new relfilenode
                 * or reltablespace value, we will be called on both the old and new
                 * tuples, and thus will broadcast invalidation messages showing both
                 * the old and new RelFileNode values.  This ensures that other
                 * backends will close smgr references to the old file.
                 *
                 * XXX possible future cleanup: it might be better to trigger smgr
                 * flushes explicitly, rather than indirectly from pg_class updates.
                 */
                if (classtup->reltablespace)
                        rnode.spcNode = classtup->reltablespace;
                else
                        rnode.spcNode = MyDatabaseTableSpace;
                rnode.dbNode = databaseId;
                rnode.relNode = classtup->relfilenode;
                RegisterSmgrInvalidation(rnode);
        }
        else if (tupleRelId == AttributeRelationId)
        {
                Form_pg_attribute atttup = (Form_pg_attribute) GETSTRUCT(tuple);

                relationId = atttup->attrelid;

                /*
                 * KLUGE ALERT: we always send the relcache event with MyDatabaseId,
                 * even if the rel in question is shared (which we can't easily tell).
                 * This essentially means that only backends in this same database
                 * will react to the relcache flush request.  This is in fact
                 * appropriate, since only those backends could see our pg_attribute
                 * change anyway.  It looks a bit ugly though.  (In practice, shared
                 * relations can't have schema changes after bootstrap, so we should
                 * never come here for a shared rel anyway.)
                 */
                databaseId = MyDatabaseId;
        }
        else if (tupleRelId == IndexRelationId)
        {
                Form_pg_index indextup = (Form_pg_index) GETSTRUCT(tuple);

                /*
                 * When a pg_index row is updated, we should send out a relcache inval
                 * for the index relation.      As above, we don't know the shared status
                 * of the index, but in practice it doesn't matter since indexes of
                 * shared catalogs can't have such updates.
                 */
                relationId = indextup->indexrelid;
                databaseId = MyDatabaseId;
        }
        else
                return;

        /*
         * Yes.  We need to register a relcache invalidation event.
         */
        RegisterRelcacheInvalidation(databaseId, relationId);
}


/* ----------------------------------------------------------------
 *                                        public functions
 * ----------------------------------------------------------------
 */

/*
 * AcceptInvalidationMessages
 *              Read and process invalidation messages from the shared invalidation
 *              message queue.
 *
 * Note:
 *              This should be called as the first step in processing a transaction.
 */
void
AcceptInvalidationMessages(void)
{
        ReceiveSharedInvalidMessages(LocalExecuteInvalidationMessage,
                                                                 InvalidateSystemCaches);

        /*
         * Test code to force cache flushes anytime a flush could happen.
         *
         * If used with CLOBBER_FREED_MEMORY, CLOBBER_CACHE_ALWAYS provides a
         * fairly thorough test that the system contains no cache-flush hazards.
         * However, it also makes the system unbelievably slow --- the regression
         * tests take about 100 times longer than normal.
         *
         * If you're a glutton for punishment, try CLOBBER_CACHE_RECURSIVELY. This
         * slows things by at least a factor of 10000, so I wouldn't suggest
         * trying to run the entire regression tests that way.  It's useful to try
         * a few simple tests, to make sure that cache reload isn't subject to
         * internal cache-flush hazards, but after you've done a few thousand
         * recursive reloads it's unlikely you'll learn more.
         */
#if defined(CLOBBER_CACHE_ALWAYS)
        {
                static bool in_recursion = false;

                if (!in_recursion)
                {
                        in_recursion = true;
                        InvalidateSystemCaches();
                        in_recursion = false;
                }
        }
#elif defined(CLOBBER_CACHE_RECURSIVELY)
        InvalidateSystemCaches();
#endif
}

/*
 * AtStart_Inval
 *              Initialize inval lists at start of a main transaction.
 */
void
AtStart_Inval(void)
{
        Assert(transInvalInfo == NULL);
        transInvalInfo = (TransInvalidationInfo *)
                MemoryContextAllocZero(TopTransactionContext,
                                                           sizeof(TransInvalidationInfo));
        transInvalInfo->my_level = GetCurrentTransactionNestLevel();
}

/*
 * AtPrepare_Inval
 *              Save the inval lists state at 2PC transaction prepare.
 *
 * In this phase we just generate 2PC records for all the pending invalidation
 * work.
 */
void
AtPrepare_Inval(void)
{
        /* Must be at top of stack */
        Assert(transInvalInfo != NULL && transInvalInfo->parent == NULL);

        /*
         * Relcache init file invalidation requires processing both before and
         * after we send the SI messages.
         */
        if (transInvalInfo->RelcacheInitFileInval)
                RegisterTwoPhaseRecord(TWOPHASE_RM_INVAL_ID, TWOPHASE_INFO_FILE_BEFORE,
                                                           NULL, 0);

        AppendInvalidationMessages(&transInvalInfo->PriorCmdInvalidMsgs,
                                                           &transInvalInfo->CurrentCmdInvalidMsgs);

        ProcessInvalidationMessages(&transInvalInfo->PriorCmdInvalidMsgs,
                                                                PersistInvalidationMessage);

        if (transInvalInfo->RelcacheInitFileInval)
                RegisterTwoPhaseRecord(TWOPHASE_RM_INVAL_ID, TWOPHASE_INFO_FILE_AFTER,
                                                           NULL, 0);
}

/*
 * PostPrepare_Inval
 *              Clean up after successful PREPARE.
 *
 * Here, we want to act as though the transaction aborted, so that we will
 * undo any syscache changes it made, thereby bringing us into sync with the
 * outside world, which doesn't believe the transaction committed yet.
 *
 * If the prepared transaction is later aborted, there is nothing more to
 * do; if it commits, we will receive the consequent inval messages just
 * like everyone else.
 */
void
PostPrepare_Inval(void)
{
        AtEOXact_Inval(false);
}

/*
 * AtSubStart_Inval
 *              Initialize inval lists at start of a subtransaction.
 */
void
AtSubStart_Inval(void)
{
        TransInvalidationInfo *myInfo;

        Assert(transInvalInfo != NULL);
        myInfo = (TransInvalidationInfo *)
                MemoryContextAllocZero(TopTransactionContext,
                                                           sizeof(TransInvalidationInfo));
        myInfo->parent = transInvalInfo;
        myInfo->my_level = GetCurrentTransactionNestLevel();
        transInvalInfo = myInfo;
}

/*
 * PersistInvalidationMessage
 *              Write an invalidation message to the 2PC state file.
 */
static void
PersistInvalidationMessage(SharedInvalidationMessage *msg)
{
        RegisterTwoPhaseRecord(TWOPHASE_RM_INVAL_ID, TWOPHASE_INFO_MSG,
                                                   msg, sizeof(SharedInvalidationMessage));
}

/*
 * inval_twophase_postcommit
 *              Process an invalidation message from the 2PC state file.
 */
void
inval_twophase_postcommit(TransactionId xid, uint16 info,
                                                  void *recdata, uint32 len)
{
        SharedInvalidationMessage *msg;

        switch (info)
        {
                case TWOPHASE_INFO_MSG:
                        msg = (SharedInvalidationMessage *) recdata;
                        Assert(len == sizeof(SharedInvalidationMessage));
                        SendSharedInvalidMessages(msg, 1);
                        break;
                case TWOPHASE_INFO_FILE_BEFORE:
                        RelationCacheInitFileInvalidate(true);
                        break;
                case TWOPHASE_INFO_FILE_AFTER:
                        RelationCacheInitFileInvalidate(false);
                        break;
                default:
                        Assert(false);
                        break;
        }
}


/*
 * AtEOXact_Inval
 *              Process queued-up invalidation messages at end of main transaction.
 *
 * If isCommit, we must send out the messages in our PriorCmdInvalidMsgs list
 * to the shared invalidation message queue.  Note that these will be read
 * not only by other backends, but also by our own backend at the next
 * transaction start (via AcceptInvalidationMessages).  This means that
 * we can skip immediate local processing of anything that's still in
 * CurrentCmdInvalidMsgs, and just send that list out too.
 *
 * If not isCommit, we are aborting, and must locally process the messages
 * in PriorCmdInvalidMsgs.      No messages need be sent to other backends,
 * since they'll not have seen our changed tuples anyway.  We can forget
 * about CurrentCmdInvalidMsgs too, since those changes haven't touched
 * the caches yet.
 *
 * In any case, reset the various lists to empty.  We need not physically
 * free memory here, since TopTransactionContext is about to be emptied
 * anyway.
 *
 * Note:
 *              This should be called as the last step in processing a transaction.
 */
void
AtEOXact_Inval(bool isCommit)
{
        if (isCommit)
        {
                /* Must be at top of stack */
                Assert(transInvalInfo != NULL && transInvalInfo->parent == NULL);

                /*
                 * Relcache init file invalidation requires processing both before and
                 * after we send the SI messages.  However, we need not do anything
                 * unless we committed.
                 */
                if (transInvalInfo->RelcacheInitFileInval)
                        RelationCacheInitFileInvalidate(true);

                AppendInvalidationMessages(&transInvalInfo->PriorCmdInvalidMsgs,
                                                                   &transInvalInfo->CurrentCmdInvalidMsgs);

                ProcessInvalidationMessagesMulti(&transInvalInfo->PriorCmdInvalidMsgs,
                                                                                 SendSharedInvalidMessages);

                if (transInvalInfo->RelcacheInitFileInval)
                        RelationCacheInitFileInvalidate(false);
        }
        else if (transInvalInfo != NULL)
        {
                /* Must be at top of stack */
                Assert(transInvalInfo->parent == NULL);

                ProcessInvalidationMessages(&transInvalInfo->PriorCmdInvalidMsgs,
                                                                        LocalExecuteInvalidationMessage);
        }

        /* Need not free anything explicitly */
        transInvalInfo = NULL;
}

/*
 * AtEOSubXact_Inval
 *              Process queued-up invalidation messages at end of subtransaction.
 *
 * If isCommit, process CurrentCmdInvalidMsgs if any (there probably aren't),
 * and then attach both CurrentCmdInvalidMsgs and PriorCmdInvalidMsgs to the
 * parent's PriorCmdInvalidMsgs list.
 *
 * If not isCommit, we are aborting, and must locally process the messages
 * in PriorCmdInvalidMsgs.      No messages need be sent to other backends.
 * We can forget about CurrentCmdInvalidMsgs too, since those changes haven't
 * touched the caches yet.
 *
 * In any case, pop the transaction stack.      We need not physically free memory
 * here, since CurTransactionContext is about to be emptied anyway
 * (if aborting).  Beware of the possibility of aborting the same nesting
 * level twice, though.
 */
void
AtEOSubXact_Inval(bool isCommit)
{
        int                     my_level = GetCurrentTransactionNestLevel();
        TransInvalidationInfo *myInfo = transInvalInfo;

        if (isCommit)
        {
                /* Must be at non-top of stack */
                Assert(myInfo != NULL && myInfo->parent != NULL);
                Assert(myInfo->my_level == my_level);

                /* If CurrentCmdInvalidMsgs still has anything, fix it */
                CommandEndInvalidationMessages();

                /* Pass up my inval messages to parent */
                AppendInvalidationMessages(&myInfo->parent->PriorCmdInvalidMsgs,
                                                                   &myInfo->PriorCmdInvalidMsgs);

                /* Pending relcache inval becomes parent's problem too */
                if (myInfo->RelcacheInitFileInval)
                        myInfo->parent->RelcacheInitFileInval = true;

                /* Pop the transaction state stack */
                transInvalInfo = myInfo->parent;

                /* Need not free anything else explicitly */
                pfree(myInfo);
        }
        else if (myInfo != NULL && myInfo->my_level == my_level)
        {
                /* Must be at non-top of stack */
                Assert(myInfo->parent != NULL);

                ProcessInvalidationMessages(&myInfo->PriorCmdInvalidMsgs,
                                                                        LocalExecuteInvalidationMessage);

                /* Pop the transaction state stack */
                transInvalInfo = myInfo->parent;

                /* Need not free anything else explicitly */
                pfree(myInfo);
        }
}

/*
 * CommandEndInvalidationMessages
 *              Process queued-up invalidation messages at end of one command
 *              in a transaction.
 *
 * Here, we send no messages to the shared queue, since we don't know yet if
 * we will commit.      We do need to locally process the CurrentCmdInvalidMsgs
 * list, so as to flush our caches of any entries we have outdated in the
 * current command.  We then move the current-cmd list over to become part
 * of the prior-cmds list.
 *
 * Note:
 *              This should be called during CommandCounterIncrement(),
 *              after we have advanced the command ID.
 */
void
CommandEndInvalidationMessages(void)
{
        /*
         * You might think this shouldn't be called outside any transaction, but
         * bootstrap does it, and also ABORT issued when not in a transaction. So
         * just quietly return if no state to work on.
         */
        if (transInvalInfo == NULL)
                return;

        ProcessInvalidationMessages(&transInvalInfo->CurrentCmdInvalidMsgs,
                                                                LocalExecuteInvalidationMessage);
        AppendInvalidationMessages(&transInvalInfo->PriorCmdInvalidMsgs,
                                                           &transInvalInfo->CurrentCmdInvalidMsgs);
}


/*
 * BeginNonTransactionalInvalidation
 *              Prepare for invalidation messages for nontransactional updates.
 *
 * A nontransactional invalidation is one that must be sent whether or not
 * the current transaction eventually commits.  We arrange for all invals
 * queued between this call and EndNonTransactionalInvalidation() to be sent
 * immediately when the latter is called.
 *
 * Currently, this is only used by heap_page_prune(), and only when it is
 * invoked during VACUUM FULL's first pass over a table.  We expect therefore
 * that we are not inside a subtransaction and there are no already-pending
 * invalidations.  This could be relaxed by setting up a new nesting level of
 * invalidation data, but for now there's no need.  Note that heap_page_prune
 * knows that this function does not change any state, and therefore there's
 * no need to worry about cleaning up if there's an elog(ERROR) before
 * reaching EndNonTransactionalInvalidation (the invals will just be thrown
 * away if that happens).
 */
void
BeginNonTransactionalInvalidation(void)
{
        /* Must be at top of stack */
        Assert(transInvalInfo != NULL && transInvalInfo->parent == NULL);

        /* Must not have any previously-queued activity */
        Assert(transInvalInfo->PriorCmdInvalidMsgs.cclist == NULL);
        Assert(transInvalInfo->PriorCmdInvalidMsgs.rclist == NULL);
        Assert(transInvalInfo->CurrentCmdInvalidMsgs.cclist == NULL);
        Assert(transInvalInfo->CurrentCmdInvalidMsgs.rclist == NULL);
        Assert(transInvalInfo->RelcacheInitFileInval == false);
}

/*
 * EndNonTransactionalInvalidation
 *              Process queued-up invalidation messages for nontransactional updates.
 *
 * We expect to find messages in CurrentCmdInvalidMsgs only (else there
 * was a CommandCounterIncrement within the "nontransactional" update).
 * We must process them locally and send them out to the shared invalidation
 * message queue.
 *
 * We must also reset the lists to empty and explicitly free memory (we can't
 * rely on end-of-transaction cleanup for that).
 */
void
EndNonTransactionalInvalidation(void)
{
        InvalidationChunk *chunk;
        InvalidationChunk *next;

        /* Must be at top of stack */
        Assert(transInvalInfo != NULL && transInvalInfo->parent == NULL);

        /* Must not have any prior-command messages */
        Assert(transInvalInfo->PriorCmdInvalidMsgs.cclist == NULL);
        Assert(transInvalInfo->PriorCmdInvalidMsgs.rclist == NULL);

        /*
         * At present, this function is only used for CTID-changing updates;
         * since the relcache init file doesn't store any tuple CTIDs, we
         * don't have to invalidate it.  That might not be true forever
         * though, in which case we'd need code similar to AtEOXact_Inval.
         */

        /* Send out the invals */
        ProcessInvalidationMessages(&transInvalInfo->CurrentCmdInvalidMsgs,
                                                                LocalExecuteInvalidationMessage);
        ProcessInvalidationMessagesMulti(&transInvalInfo->CurrentCmdInvalidMsgs,
                                                                         SendSharedInvalidMessages);

        /* Clean up and release memory */
        for (chunk = transInvalInfo->CurrentCmdInvalidMsgs.cclist;
                 chunk != NULL;
                 chunk = next)
        {
                next = chunk->next;
                pfree(chunk);
        }
        for (chunk = transInvalInfo->CurrentCmdInvalidMsgs.rclist;
                 chunk != NULL;
                 chunk = next)
        {
                next = chunk->next;
                pfree(chunk);
        }
        transInvalInfo->CurrentCmdInvalidMsgs.cclist = NULL;
        transInvalInfo->CurrentCmdInvalidMsgs.rclist = NULL;
        transInvalInfo->RelcacheInitFileInval = false;
}


/*
 * CacheInvalidateHeapTuple
 *              Register the given tuple for invalidation at end of command
 *              (ie, current command is creating or outdating this tuple).
 */
void
CacheInvalidateHeapTuple(Relation relation, HeapTuple tuple)
{
        PrepareForTupleInvalidation(relation, tuple);
}

/*
 * CacheInvalidateRelcache
 *              Register invalidation of the specified relation's relcache entry
 *              at end of command.
 *
 * This is used in places that need to force relcache rebuild but aren't
 * changing any of the tuples recognized as contributors to the relcache
 * entry by PrepareForTupleInvalidation.  (An example is dropping an index.)
 * We assume in particular that relfilenode/reltablespace aren't changing
 * (so the rd_node value is still good).
 *
 * XXX most callers of this probably don't need to force an smgr flush.
 */
void
CacheInvalidateRelcache(Relation relation)
{
        Oid                     databaseId;
        Oid                     relationId;

        relationId = RelationGetRelid(relation);
        if (relation->rd_rel->relisshared)
                databaseId = InvalidOid;
        else
                databaseId = MyDatabaseId;

        RegisterRelcacheInvalidation(databaseId, relationId);
        RegisterSmgrInvalidation(relation->rd_node);
}

/*
 * CacheInvalidateRelcacheByTuple
 *              As above, but relation is identified by passing its pg_class tuple.
 */
void
CacheInvalidateRelcacheByTuple(HeapTuple classTuple)
{
        Form_pg_class classtup = (Form_pg_class) GETSTRUCT(classTuple);
        Oid                     databaseId;
        Oid                     relationId;
        RelFileNode rnode;

        relationId = HeapTupleGetOid(classTuple);
        if (classtup->relisshared)
                databaseId = InvalidOid;
        else
                databaseId = MyDatabaseId;
        if (classtup->reltablespace)
                rnode.spcNode = classtup->reltablespace;
        else
                rnode.spcNode = MyDatabaseTableSpace;
        rnode.dbNode = databaseId;
        rnode.relNode = classtup->relfilenode;

        RegisterRelcacheInvalidation(databaseId, relationId);
        RegisterSmgrInvalidation(rnode);
}

/*
 * CacheInvalidateRelcacheByRelid
 *              As above, but relation is identified by passing its OID.
 *              This is the least efficient of the three options; use one of
 *              the above routines if you have a Relation or pg_class tuple.
 */
void
CacheInvalidateRelcacheByRelid(Oid relid)
{
        HeapTuple       tup;

        tup = SearchSysCache(RELOID,
                                                 ObjectIdGetDatum(relid),
                                                 0, 0, 0);
        if (!HeapTupleIsValid(tup))
                elog(ERROR, "cache lookup failed for relation %u", relid);
        CacheInvalidateRelcacheByTuple(tup);
        ReleaseSysCache(tup);
}

/*
 * CacheRegisterSyscacheCallback
 *              Register the specified function to be called for all future
 *              invalidation events in the specified cache.
 *
 * NOTE: currently, the OID argument to the callback routine is not
 * provided for syscache callbacks; the routine doesn't really get any
 * useful info as to exactly what changed.      It should treat every call
 * as a "cache flush" request.
 */
void
CacheRegisterSyscacheCallback(int cacheid,
                                                          CacheCallbackFunction func,
                                                          Datum arg)
{
        if (cache_callback_count >= MAX_CACHE_CALLBACKS)
                elog(FATAL, "out of cache_callback_list slots");

        cache_callback_list[cache_callback_count].id = cacheid;
        cache_callback_list[cache_callback_count].function = func;
        cache_callback_list[cache_callback_count].arg = arg;

        ++cache_callback_count;
}

/*
 * CacheRegisterRelcacheCallback
 *              Register the specified function to be called for all future
 *              relcache invalidation events.  The OID of the relation being
 *              invalidated will be passed to the function.
 *
 * NOTE: InvalidOid will be passed if a cache reset request is received.
 * In this case the called routines should flush all cached state.
 */
void
CacheRegisterRelcacheCallback(CacheCallbackFunction func,
                                                          Datum arg)
{
        if (cache_callback_count >= MAX_CACHE_CALLBACKS)
                elog(FATAL, "out of cache_callback_list slots");

        cache_callback_list[cache_callback_count].id = SHAREDINVALRELCACHE_ID;
        cache_callback_list[cache_callback_count].function = func;
        cache_callback_list[cache_callback_count].arg = arg;

        ++cache_callback_count;
}