Define integer limits independently from the system definitions.

[postgresql] / src / include / storage / predicate_internals.h

/*-------------------------------------------------------------------------
 *
 * predicate_internals.h
 *        POSTGRES internal predicate locking definitions.
 *
 *
 * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/storage/predicate_internals.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef PREDICATE_INTERNALS_H
#define PREDICATE_INTERNALS_H

#include "storage/lock.h"

/*
 * Commit number.
 */
typedef uint64 SerCommitSeqNo;

/*
 * Reserved commit sequence numbers:
 *      - 0 is reserved to indicate a non-existent SLRU entry; it cannot be
 *        used as a SerCommitSeqNo, even an invalid one
 *      - InvalidSerCommitSeqNo is used to indicate a transaction that
 *        hasn't committed yet, so use a number greater than all valid
 *        ones to make comparison do the expected thing
 *      - RecoverySerCommitSeqNo is used to refer to transactions that
 *        happened before a crash/recovery, since we restart the sequence
 *        at that point.  It's earlier than all normal sequence numbers,
 *        and is only used by recovered prepared transactions
 */
#define InvalidSerCommitSeqNo           ((SerCommitSeqNo) PG_UINT64_MAX)
#define RecoverySerCommitSeqNo          ((SerCommitSeqNo) 1)
#define FirstNormalSerCommitSeqNo       ((SerCommitSeqNo) 2)

/*
 * The SERIALIZABLEXACT struct contains information needed for each
 * serializable database transaction to support SSI techniques.
 *
 * A home-grown list is maintained in shared memory to manage these.
 * An entry is used when the serializable transaction acquires a snapshot.
 * Unless the transaction is rolled back, this entry must generally remain
 * until all concurrent transactions have completed.  (There are special
 * optimizations for READ ONLY transactions which often allow them to be
 * cleaned up earlier.)  A transaction which is rolled back is cleaned up
 * as soon as possible.
 *
 * Eligibility for cleanup of committed transactions is generally determined
 * by comparing the transaction's finishedBefore field to
 * SerializableGlobalXmin.
 */
typedef struct SERIALIZABLEXACT
{
        VirtualTransactionId vxid;      /* The executing process always has one of
                                                                 * these. */

        /*
         * We use two numbers to track the order that transactions commit. Before
         * commit, a transaction is marked as prepared, and prepareSeqNo is set.
         * Shortly after commit, it's marked as committed, and commitSeqNo is set.
         * This doesn't give a strict commit order, but these two values together
         * are good enough for us, as we can always err on the safe side and
         * assume that there's a conflict, if we can't be sure of the exact
         * ordering of two commits.
         *
         * Note that a transaction is marked as prepared for a short period during
         * commit processing, even if two-phase commit is not used. But with
         * two-phase commit, a transaction can stay in prepared state for some
         * time.
         */
        SerCommitSeqNo prepareSeqNo;
        SerCommitSeqNo commitSeqNo;

        /* these values are not both interesting at the same time */
        union
        {
                SerCommitSeqNo earliestOutConflictCommit;               /* when committed with
                                                                                                                 * conflict out */
                SerCommitSeqNo lastCommitBeforeSnapshot;                /* when not committed or
                                                                                                                 * no conflict out */
        }                       SeqNo;
        SHM_QUEUE       outConflicts;   /* list of write transactions whose data we
                                                                 * couldn't read. */
        SHM_QUEUE       inConflicts;    /* list of read transactions which couldn't
                                                                 * see our write. */
        SHM_QUEUE       predicateLocks; /* list of associated PREDICATELOCK objects */
        SHM_QUEUE       finishedLink;   /* list link in
                                                                 * FinishedSerializableTransactions */

        /*
         * for r/o transactions: list of concurrent r/w transactions that we could
         * potentially have conflicts with, and vice versa for r/w transactions
         */
        SHM_QUEUE       possibleUnsafeConflicts;

        TransactionId topXid;           /* top level xid for the transaction, if one
                                                                 * exists; else invalid */
        TransactionId finishedBefore;           /* invalid means still running; else
                                                                                 * the struct expires when no
                                                                                 * serializable xids are before this. */
        TransactionId xmin;                     /* the transaction's snapshot xmin */
        uint32          flags;                  /* OR'd combination of values defined below */
        int                     pid;                    /* pid of associated process */
} SERIALIZABLEXACT;

#define SXACT_FLAG_COMMITTED                    0x00000001              /* already committed */
#define SXACT_FLAG_PREPARED                             0x00000002              /* about to commit */
#define SXACT_FLAG_ROLLED_BACK                  0x00000004              /* already rolled back */
#define SXACT_FLAG_DOOMED                               0x00000008              /* will roll back */
/*
 * The following flag actually means that the flagged transaction has a
 * conflict out *to a transaction which committed ahead of it*.  It's hard
 * to get that into a name of a reasonable length.
 */
#define SXACT_FLAG_CONFLICT_OUT                 0x00000010
#define SXACT_FLAG_READ_ONLY                    0x00000020
#define SXACT_FLAG_DEFERRABLE_WAITING   0x00000040
#define SXACT_FLAG_RO_SAFE                              0x00000080
#define SXACT_FLAG_RO_UNSAFE                    0x00000100
#define SXACT_FLAG_SUMMARY_CONFLICT_IN  0x00000200
#define SXACT_FLAG_SUMMARY_CONFLICT_OUT 0x00000400

/*
 * The following types are used to provide an ad hoc list for holding
 * SERIALIZABLEXACT objects.  An HTAB is overkill, since there is no need to
 * access these by key -- there are direct pointers to these objects where
 * needed.  If a shared memory list is created, these types can probably be
 * eliminated in favor of using the general solution.
 */
typedef struct PredXactListElementData
{
        SHM_QUEUE       link;
        SERIALIZABLEXACT sxact;
}       PredXactListElementData;

typedef struct PredXactListElementData *PredXactListElement;

#define PredXactListElementDataSize \
                ((Size)MAXALIGN(sizeof(PredXactListElementData)))

typedef struct PredXactListData
{
        SHM_QUEUE       availableList;
        SHM_QUEUE       activeList;

        /*
         * These global variables are maintained when registering and cleaning up
         * serializable transactions.  They must be global across all backends,
         * but are not needed outside the predicate.c source file. Protected by
         * SerializableXactHashLock.
         */
        TransactionId SxactGlobalXmin;          /* global xmin for active serializable
                                                                                 * transactions */
        int                     SxactGlobalXminCount;   /* how many active serializable
                                                                                 * transactions have this xmin */
        int                     WritableSxactCount;             /* how many non-read-only serializable
                                                                                 * transactions are active */
        SerCommitSeqNo LastSxactCommitSeqNo;            /* a strictly monotonically
                                                                                                 * increasing number for
                                                                                                 * commits of serializable
                                                                                                 * transactions */
        /* Protected by SerializableXactHashLock. */
        SerCommitSeqNo CanPartialClearThrough;          /* can clear predicate locks
                                                                                                 * and inConflicts for
                                                                                                 * committed transactions
                                                                                                 * through this seq no */
        /* Protected by SerializableFinishedListLock. */
        SerCommitSeqNo HavePartialClearedThrough;       /* have cleared through this
                                                                                                 * seq no */
        SERIALIZABLEXACT *OldCommittedSxact;            /* shared copy of dummy sxact */

        PredXactListElement element;
}       PredXactListData;

typedef struct PredXactListData *PredXactList;

#define PredXactListDataSize \
                ((Size)MAXALIGN(sizeof(PredXactListData)))


/*
 * The following types are used to provide lists of rw-conflicts between
 * pairs of transactions.  Since exactly the same information is needed,
 * they are also used to record possible unsafe transaction relationships
 * for purposes of identifying safe snapshots for read-only transactions.
 *
 * When a RWConflictData is not in use to record either type of relationship
 * between a pair of transactions, it is kept on an "available" list.  The
 * outLink field is used for maintaining that list.
 */
typedef struct RWConflictData
{
        SHM_QUEUE       outLink;                /* link for list of conflicts out from a sxact */
        SHM_QUEUE       inLink;                 /* link for list of conflicts in to a sxact */
        SERIALIZABLEXACT *sxactOut;
        SERIALIZABLEXACT *sxactIn;
}       RWConflictData;

typedef struct RWConflictData *RWConflict;

#define RWConflictDataSize \
                ((Size)MAXALIGN(sizeof(RWConflictData)))

typedef struct RWConflictPoolHeaderData
{
        SHM_QUEUE       availableList;
        RWConflict      element;
}       RWConflictPoolHeaderData;

typedef struct RWConflictPoolHeaderData *RWConflictPoolHeader;

#define RWConflictPoolHeaderDataSize \
                ((Size)MAXALIGN(sizeof(RWConflictPoolHeaderData)))


/*
 * The SERIALIZABLEXIDTAG struct identifies an xid assigned to a serializable
 * transaction or any of its subtransactions.
 */
typedef struct SERIALIZABLEXIDTAG
{
        TransactionId xid;
} SERIALIZABLEXIDTAG;

/*
 * The SERIALIZABLEXID struct provides a link from a TransactionId for a
 * serializable transaction to the related SERIALIZABLEXACT record, even if
 * the transaction has completed and its connection has been closed.
 *
 * These are created as new top level transaction IDs are first assigned to
 * transactions which are participating in predicate locking.  This may
 * never happen for a particular transaction if it doesn't write anything.
 * They are removed with their related serializable transaction objects.
 *
 * The SubTransGetTopmostTransaction method is used where necessary to get
 * from an XID which might be from a subtransaction to the top level XID.
 */
typedef struct SERIALIZABLEXID
{
        /* hash key */
        SERIALIZABLEXIDTAG tag;

        /* data */
        SERIALIZABLEXACT *myXact;       /* pointer to the top level transaction data */
} SERIALIZABLEXID;


/*
 * The PREDICATELOCKTARGETTAG struct identifies a database object which can
 * be the target of predicate locks.
 *
 * Note that the hash function being used doesn't properly respect tag
 * length -- if the length of the structure isn't a multiple of four bytes it
 * will go to a four byte boundary past the end of the tag.  If you change
 * this struct, make sure any slack space is initialized, so that any random
 * bytes in the middle or at the end are not included in the hash.
 *
 * TODO SSI: If we always use the same fields for the same type of value, we
 * should rename these.  Holding off until it's clear there are no exceptions.
 * Since indexes are relations with blocks and tuples, it's looking likely that
 * the rename will be possible.  If not, we may need to divide the last field
 * and use part of it for a target type, so that we know how to interpret the
 * data..
 */
typedef struct PREDICATELOCKTARGETTAG
{
        uint32          locktag_field1; /* a 32-bit ID field */
        uint32          locktag_field2; /* a 32-bit ID field */
        uint32          locktag_field3; /* a 32-bit ID field */
        uint32          locktag_field4; /* a 32-bit ID field */
} PREDICATELOCKTARGETTAG;

/*
 * The PREDICATELOCKTARGET struct represents a database object on which there
 * are predicate locks.
 *
 * A hash list of these objects is maintained in shared memory.  An entry is
 * added when a predicate lock is requested on an object which doesn't
 * already have one.  An entry is removed when the last lock is removed from
 * its list.
 */
typedef struct PREDICATELOCKTARGET
{
        /* hash key */
        PREDICATELOCKTARGETTAG tag; /* unique identifier of lockable object */

        /* data */
        SHM_QUEUE       predicateLocks; /* list of PREDICATELOCK objects assoc. with
                                                                 * predicate lock target */
} PREDICATELOCKTARGET;


/*
 * The PREDICATELOCKTAG struct identifies an individual predicate lock.
 *
 * It is the combination of predicate lock target (which is a lockable
 * object) and a serializable transaction which has acquired a lock on that
 * target.
 */
typedef struct PREDICATELOCKTAG
{
        PREDICATELOCKTARGET *myTarget;
        SERIALIZABLEXACT *myXact;
} PREDICATELOCKTAG;

/*
 * The PREDICATELOCK struct represents an individual lock.
 *
 * An entry can be created here when the related database object is read, or
 * by promotion of multiple finer-grained targets.  All entries related to a
 * serializable transaction are removed when that serializable transaction is
 * cleaned up.  Entries can also be removed when they are combined into a
 * single coarser-grained lock entry.
 */
typedef struct PREDICATELOCK
{
        /* hash key */
        PREDICATELOCKTAG tag;           /* unique identifier of lock */

        /* data */
        SHM_QUEUE       targetLink;             /* list link in PREDICATELOCKTARGET's list of
                                                                 * predicate locks */
        SHM_QUEUE       xactLink;               /* list link in SERIALIZABLEXACT's list of
                                                                 * predicate locks */
        SerCommitSeqNo commitSeqNo; /* only used for summarized predicate locks */
} PREDICATELOCK;


/*
 * The LOCALPREDICATELOCK struct represents a local copy of data which is
 * also present in the PREDICATELOCK table, organized for fast access without
 * needing to acquire a LWLock.  It is strictly for optimization.
 *
 * Each serializable transaction creates its own local hash table to hold a
 * collection of these.  This information is used to determine when a number
 * of fine-grained locks should be promoted to a single coarser-grained lock.
 * The information is maintained more-or-less in parallel to the
 * PREDICATELOCK data, but because this data is not protected by locks and is
 * only used in an optimization heuristic, it is allowed to drift in a few
 * corner cases where maintaining exact data would be expensive.
 *
 * The hash table is created when the serializable transaction acquires its
 * snapshot, and its memory is released upon completion of the transaction.
 */
typedef struct LOCALPREDICATELOCK
{
        /* hash key */
        PREDICATELOCKTARGETTAG tag; /* unique identifier of lockable object */

        /* data */
        bool            held;                   /* is lock held, or just its children?  */
        int                     childLocks;             /* number of child locks currently held */
} LOCALPREDICATELOCK;


/*
 * The types of predicate locks which can be acquired.
 */
typedef enum PredicateLockTargetType
{
        PREDLOCKTAG_RELATION,
        PREDLOCKTAG_PAGE,
        PREDLOCKTAG_TUPLE
        /* TODO SSI: Other types may be needed for index locking */
} PredicateLockTargetType;


/*
 * This structure is used to quickly capture a copy of all predicate
 * locks.  This is currently used only by the pg_lock_status function,
 * which in turn is used by the pg_locks view.
 */
typedef struct PredicateLockData
{
        int                     nelements;
        PREDICATELOCKTARGETTAG *locktags;
        SERIALIZABLEXACT *xacts;
} PredicateLockData;


/*
 * These macros define how we map logical IDs of lockable objects into the
 * physical fields of PREDICATELOCKTARGETTAG.   Use these to set up values,
 * rather than accessing the fields directly.  Note multiple eval of target!
 */
#define SET_PREDICATELOCKTARGETTAG_RELATION(locktag,dboid,reloid) \
        ((locktag).locktag_field1 = (dboid), \
         (locktag).locktag_field2 = (reloid), \
         (locktag).locktag_field3 = InvalidBlockNumber, \
         (locktag).locktag_field4 = InvalidOffsetNumber)

#define SET_PREDICATELOCKTARGETTAG_PAGE(locktag,dboid,reloid,blocknum) \
        ((locktag).locktag_field1 = (dboid), \
         (locktag).locktag_field2 = (reloid), \
         (locktag).locktag_field3 = (blocknum), \
         (locktag).locktag_field4 = InvalidOffsetNumber)

#define SET_PREDICATELOCKTARGETTAG_TUPLE(locktag,dboid,reloid,blocknum,offnum) \
        ((locktag).locktag_field1 = (dboid), \
         (locktag).locktag_field2 = (reloid), \
         (locktag).locktag_field3 = (blocknum), \
         (locktag).locktag_field4 = (offnum))

#define GET_PREDICATELOCKTARGETTAG_DB(locktag) \
        ((Oid) (locktag).locktag_field1)
#define GET_PREDICATELOCKTARGETTAG_RELATION(locktag) \
        ((Oid) (locktag).locktag_field2)
#define GET_PREDICATELOCKTARGETTAG_PAGE(locktag) \
        ((BlockNumber) (locktag).locktag_field3)
#define GET_PREDICATELOCKTARGETTAG_OFFSET(locktag) \
        ((OffsetNumber) (locktag).locktag_field4)
#define GET_PREDICATELOCKTARGETTAG_TYPE(locktag)                                                         \
        (((locktag).locktag_field4 != InvalidOffsetNumber) ? PREDLOCKTAG_TUPLE : \
         (((locktag).locktag_field3 != InvalidBlockNumber) ? PREDLOCKTAG_PAGE :   \
          PREDLOCKTAG_RELATION))

/*
 * Two-phase commit statefile records. There are two types: for each
 * transaction, we generate one per-transaction record and a variable
 * number of per-predicate-lock records.
 */
typedef enum TwoPhasePredicateRecordType
{
        TWOPHASEPREDICATERECORD_XACT,
        TWOPHASEPREDICATERECORD_LOCK
} TwoPhasePredicateRecordType;

/*
 * Per-transaction information to reconstruct a SERIALIZABLEXACT. Not
 * much is needed because most of it not meaningful for a recovered
 * prepared transaction.
 *
 * In particular, we do not record the in and out conflict lists for a
 * prepared transaction because the associated SERIALIZABLEXACTs will
 * not be available after recovery. Instead, we simply record the
 * existence of each type of conflict by setting the transaction's
 * summary conflict in/out flag.
 */
typedef struct TwoPhasePredicateXactRecord
{
        TransactionId xmin;
        uint32          flags;
} TwoPhasePredicateXactRecord;

/* Per-lock state */
typedef struct TwoPhasePredicateLockRecord
{
        PREDICATELOCKTARGETTAG target;
        uint32          filler;                 /* to avoid length change in back-patched fix */
} TwoPhasePredicateLockRecord;

typedef struct TwoPhasePredicateRecord
{
        TwoPhasePredicateRecordType type;
        union
        {
                TwoPhasePredicateXactRecord xactRecord;
                TwoPhasePredicateLockRecord lockRecord;
        }                       data;
} TwoPhasePredicateRecord;

/*
 * Define a macro to use for an "empty" SERIALIZABLEXACT reference.
 */
#define InvalidSerializableXact ((SERIALIZABLEXACT *) NULL)


/*
 * Function definitions for functions needing awareness of predicate
 * locking internals.
 */
extern PredicateLockData *GetPredicateLockStatusData(void);

#endif   /* PREDICATE_INTERNALS_H */