predicate.h File Reference

#include "access/transam.h"
#include "storage/itemptr.h"
#include "utils/relcache.h"
#include "utils/snapshot.h"

Include dependency graph for predicate.h:

This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Typedefs
typedef struct VirtualTransactionId	VirtualTransactionId
typedef void *	SerializableXactHandle

Functions
void	CheckPointPredicate (void)
bool	PageIsPredicateLocked (Relation relation, BlockNumber blkno)
Snapshot	GetSerializableTransactionSnapshot (Snapshot snapshot)
void	SetSerializableTransactionSnapshot (Snapshot snapshot, VirtualTransactionId *sourcevxid, int sourcepid)
void	RegisterPredicateLockingXid (TransactionId xid)
void	PredicateLockRelation (Relation relation, Snapshot snapshot)
void	PredicateLockPage (Relation relation, BlockNumber blkno, Snapshot snapshot)
void	PredicateLockTID (Relation relation, const ItemPointerData *tid, Snapshot snapshot, TransactionId tuple_xid)
void	PredicateLockPageSplit (Relation relation, BlockNumber oldblkno, BlockNumber newblkno)
void	PredicateLockPageCombine (Relation relation, BlockNumber oldblkno, BlockNumber newblkno)
void	TransferPredicateLocksToHeapRelation (Relation relation)
void	ReleasePredicateLocks (bool isCommit, bool isReadOnlySafe)
bool	CheckForSerializableConflictOutNeeded (Relation relation, Snapshot snapshot)
void	CheckForSerializableConflictOut (Relation relation, TransactionId xid, Snapshot snapshot)
void	CheckForSerializableConflictIn (Relation relation, const ItemPointerData *tid, BlockNumber blkno)
void	CheckTableForSerializableConflictIn (Relation relation)
void	PreCommit_CheckForSerializationFailure (void)
void	AtPrepare_PredicateLocks (void)
void	PostPrepare_PredicateLocks (FullTransactionId fxid)
void	PredicateLockTwoPhaseFinish (FullTransactionId fxid, bool isCommit)
void	predicatelock_twophase_recover (FullTransactionId fxid, uint16 info, void *recdata, uint32 len)
SerializableXactHandle	ShareSerializableXact (void)
void	AttachSerializableXact (SerializableXactHandle handle)

Variables
PGDLLIMPORT int	max_predicate_locks_per_xact
PGDLLIMPORT int	max_predicate_locks_per_relation
PGDLLIMPORT int	max_predicate_locks_per_page

Typedef Documentation

SerializableXactHandle

typedef void* SerializableXactHandle

Definition at line 39 of file predicate.h.

VirtualTransactionId

typedef struct VirtualTransactionId VirtualTransactionId

Definition at line 25 of file predicate.h.

Function Documentation

AtPrepare_PredicateLocks()

void AtPrepare_PredicateLocks ( void  )

extern

Definition at line 4719 of file predicate.c.

{
    SERIALIZABLEXACT *sxact;
    TwoPhasePredicateRecord record;
    TwoPhasePredicateXactRecord *xactRecord;
    TwoPhasePredicateLockRecord *lockRecord;
    dlist_iter  iter;
 
    sxact = MySerializableXact;
    xactRecord = &(record.data.xactRecord);
    lockRecord = &(record.data.lockRecord);
 
    if (MySerializableXact == InvalidSerializableXact)
        return;
 
    /* Generate an xact record for our SERIALIZABLEXACT */
    record.type = TWOPHASEPREDICATERECORD_XACT;
    xactRecord->xmin = MySerializableXact->xmin;
    xactRecord->flags = MySerializableXact->flags;
 
    /*
     * Note that we don't include the list of conflicts in our out in the
     * statefile, because new conflicts can be added even after the
     * transaction prepares. We'll just make a conservative assumption during
     * recovery instead.
     */
 
    RegisterTwoPhaseRecord(TWOPHASE_RM_PREDICATELOCK_ID, 0,
                           &record, sizeof(record));
 
    /*
     * Generate a lock record for each lock.
     *
     * To do this, we need to walk the predicate lock list in our sxact rather
     * than using the local predicate lock table because the latter is not
     * guaranteed to be accurate.
     */
    LWLockAcquire(SerializablePredicateListLock, LW_SHARED);
 
    /*
     * No need to take sxact->perXactPredicateListLock in parallel mode
     * because there cannot be any parallel workers running while we are
     * preparing a transaction.
     */
    Assert(!IsParallelWorker() && !ParallelContextActive());
 
    dlist_foreach(iter, &sxact->predicateLocks)
    {
        PREDICATELOCK *predlock =
            dlist_container(PREDICATELOCK, xactLink, iter.cur);
 
        record.type = TWOPHASEPREDICATERECORD_LOCK;
        lockRecord->target = predlock->tag.myTarget->tag;
 
        RegisterTwoPhaseRecord(TWOPHASE_RM_PREDICATELOCK_ID, 0,
                               &record, sizeof(record));
    }
 
    LWLockRelease(SerializablePredicateListLock);
}

References Assert, dlist_iter::cur, TwoPhasePredicateRecord::data, dlist_container, dlist_foreach, fb(), SERIALIZABLEXACT::flags, TwoPhasePredicateXactRecord::flags, InvalidSerializableXact, IsParallelWorker, TwoPhasePredicateRecord::lockRecord, LW_SHARED, LWLockAcquire(), LWLockRelease(), MySerializableXact, ParallelContextActive(), RegisterTwoPhaseRecord(), TwoPhasePredicateLockRecord::target, TWOPHASE_RM_PREDICATELOCK_ID, TWOPHASEPREDICATERECORD_LOCK, TWOPHASEPREDICATERECORD_XACT, TwoPhasePredicateRecord::type, TwoPhasePredicateRecord::xactRecord, SERIALIZABLEXACT::xmin, and TwoPhasePredicateXactRecord::xmin.

Referenced by PrepareTransaction().

AttachSerializableXact()

void AttachSerializableXact ( SerializableXactHandle  handle )

extern

Definition at line 4985 of file predicate.c.

{
 
    Assert(MySerializableXact == InvalidSerializableXact);
 
    MySerializableXact = (SERIALIZABLEXACT *) handle;
    if (MySerializableXact != InvalidSerializableXact)
        CreateLocalPredicateLockHash();
}

References Assert, CreateLocalPredicateLockHash(), InvalidSerializableXact, and MySerializableXact.

Referenced by ParallelWorkerMain().

CheckForSerializableConflictIn()

void CheckForSerializableConflictIn ( Relation  relation, const ItemPointerData *  tid, BlockNumber  blkno  )

extern

Definition at line 4265 of file predicate.c.

{
    PREDICATELOCKTARGETTAG targettag;
 
    if (!SerializationNeededForWrite(relation))
        return;
 
    /* Check if someone else has already decided that we need to die */
    if (SxactIsDoomed(MySerializableXact))
        ereport(ERROR,
                (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                 errmsg("could not serialize access due to read/write dependencies among transactions"),
                 errdetail_internal("Reason code: Canceled on identification as a pivot, during conflict in checking."),
                 errhint("The transaction might succeed if retried.")));
 
    /*
     * We're doing a write which might cause rw-conflicts now or later.
     * Memorize that fact.
     */
    MyXactDidWrite = true;
 
    /*
     * It is important that we check for locks from the finest granularity to
     * the coarsest granularity, so that granularity promotion doesn't cause
     * us to miss a lock.  The new (coarser) lock will be acquired before the
     * old (finer) locks are released.
     *
     * It is not possible to take and hold a lock across the checks for all
     * granularities because each target could be in a separate partition.
     */
    if (tid != NULL)
    {
        SET_PREDICATELOCKTARGETTAG_TUPLE(targettag,
                                         relation->rd_locator.dbOid,
                                         relation->rd_id,
                                         ItemPointerGetBlockNumber(tid),
                                         ItemPointerGetOffsetNumber(tid));
        CheckTargetForConflictsIn(&targettag);
    }
 
    if (blkno != InvalidBlockNumber)
    {
        SET_PREDICATELOCKTARGETTAG_PAGE(targettag,
                                        relation->rd_locator.dbOid,
                                        relation->rd_id,
                                        blkno);
        CheckTargetForConflictsIn(&targettag);
    }
 
    SET_PREDICATELOCKTARGETTAG_RELATION(targettag,
                                        relation->rd_locator.dbOid,
                                        relation->rd_id);
    CheckTargetForConflictsIn(&targettag);
}

References CheckTargetForConflictsIn(), RelFileLocator::dbOid, ereport, errcode(), ERRCODE_T_R_SERIALIZATION_FAILURE, errdetail_internal(), errhint(), errmsg, ERROR, fb(), InvalidBlockNumber, ItemPointerGetBlockNumber(), ItemPointerGetOffsetNumber(), MySerializableXact, MyXactDidWrite, RelationData::rd_id, RelationData::rd_locator, SerializationNeededForWrite(), SET_PREDICATELOCKTARGETTAG_PAGE, SET_PREDICATELOCKTARGETTAG_RELATION, SET_PREDICATELOCKTARGETTAG_TUPLE, and SxactIsDoomed.

Referenced by _bt_check_unique(), _bt_doinsert(), _hash_doinsert(), ginEntryInsert(), ginFindLeafPage(), ginHeapTupleFastInsert(), gistinserttuples(), heap_delete(), heap_insert(), heap_multi_insert(), heap_update(), and index_insert().

CheckForSerializableConflictOut()

void CheckForSerializableConflictOut ( Relation  relation, TransactionId  xid, Snapshot  snapshot  )

extern

Definition at line 3952 of file predicate.c.

{
    SERIALIZABLEXIDTAG sxidtag;
    SERIALIZABLEXID *sxid;
    SERIALIZABLEXACT *sxact;
 
    if (!SerializationNeededForRead(relation, snapshot))
        return;
 
    /* Check if someone else has already decided that we need to die */
    if (SxactIsDoomed(MySerializableXact))
    {
        ereport(ERROR,
                (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                 errmsg("could not serialize access due to read/write dependencies among transactions"),
                 errdetail_internal("Reason code: Canceled on identification as a pivot, during conflict out checking."),
                 errhint("The transaction might succeed if retried.")));
    }
    Assert(TransactionIdIsValid(xid));
 
    if (TransactionIdEquals(xid, GetTopTransactionIdIfAny()))
        return;
 
    /*
     * Find sxact or summarized info for the top level xid.
     */
    sxidtag.xid = xid;
    LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
    sxid = (SERIALIZABLEXID *)
        hash_search(SerializableXidHash, &sxidtag, HASH_FIND, NULL);
    if (!sxid)
    {
        /*
         * Transaction not found in "normal" SSI structures.  Check whether it
         * got pushed out to SLRU storage for "old committed" transactions.
         */
        SerCommitSeqNo conflictCommitSeqNo;
 
        conflictCommitSeqNo = SerialGetMinConflictCommitSeqNo(xid);
        if (conflictCommitSeqNo != 0)
        {
            if (conflictCommitSeqNo != InvalidSerCommitSeqNo
                && (!SxactIsReadOnly(MySerializableXact)
                    || conflictCommitSeqNo
                    <= MySerializableXact->SeqNo.lastCommitBeforeSnapshot))
                ereport(ERROR,
                        (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                         errmsg("could not serialize access due to read/write dependencies among transactions"),
                         errdetail_internal("Reason code: Canceled on conflict out to old pivot %u.", xid),
                         errhint("The transaction might succeed if retried.")));
 
            if (SxactHasSummaryConflictIn(MySerializableXact)
                || !dlist_is_empty(&MySerializableXact->inConflicts))
                ereport(ERROR,
                        (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                         errmsg("could not serialize access due to read/write dependencies among transactions"),
                         errdetail_internal("Reason code: Canceled on identification as a pivot, with conflict out to old committed transaction %u.", xid),
                         errhint("The transaction might succeed if retried.")));
 
            MySerializableXact->flags |= SXACT_FLAG_SUMMARY_CONFLICT_OUT;
        }
 
        /* It's not serializable or otherwise not important. */
        LWLockRelease(SerializableXactHashLock);
        return;
    }
    sxact = sxid->myXact;
    Assert(TransactionIdEquals(sxact->topXid, xid));
    if (sxact == MySerializableXact || SxactIsDoomed(sxact))
    {
        /* Can't conflict with ourself or a transaction that will roll back. */
        LWLockRelease(SerializableXactHashLock);
        return;
    }
 
    /*
     * We have a conflict out to a transaction which has a conflict out to a
     * summarized transaction.  That summarized transaction must have
     * committed first, and we can't tell when it committed in relation to our
     * snapshot acquisition, so something needs to be canceled.
     */
    if (SxactHasSummaryConflictOut(sxact))
    {
        if (!SxactIsPrepared(sxact))
        {
            sxact->flags |= SXACT_FLAG_DOOMED;
            LWLockRelease(SerializableXactHashLock);
            return;
        }
        else
        {
            LWLockRelease(SerializableXactHashLock);
            ereport(ERROR,
                    (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                     errmsg("could not serialize access due to read/write dependencies among transactions"),
                     errdetail_internal("Reason code: Canceled on conflict out to old pivot."),
                     errhint("The transaction might succeed if retried.")));
        }
    }
 
    /*
     * If this is a read-only transaction and the writing transaction has
     * committed, and it doesn't have a rw-conflict to a transaction which
     * committed before it, no conflict.
     */
    if (SxactIsReadOnly(MySerializableXact)
        && SxactIsCommitted(sxact)
        && !SxactHasSummaryConflictOut(sxact)
        && (!SxactHasConflictOut(sxact)
            || MySerializableXact->SeqNo.lastCommitBeforeSnapshot < sxact->SeqNo.earliestOutConflictCommit))
    {
        /* Read-only transaction will appear to run first.  No conflict. */
        LWLockRelease(SerializableXactHashLock);
        return;
    }
 
    if (!XidIsConcurrent(xid))
    {
        /* This write was already in our snapshot; no conflict. */
        LWLockRelease(SerializableXactHashLock);
        return;
    }
 
    if (RWConflictExists(MySerializableXact, sxact))
    {
        /* We don't want duplicate conflict records in the list. */
        LWLockRelease(SerializableXactHashLock);
        return;
    }
 
    /*
     * Flag the conflict.  But first, if this conflict creates a dangerous
     * structure, ereport an error.
     */
    FlagRWConflict(MySerializableXact, sxact);
    LWLockRelease(SerializableXactHashLock);
}

References Assert, dlist_is_empty(), ereport, errcode(), ERRCODE_T_R_SERIALIZATION_FAILURE, errdetail_internal(), errhint(), errmsg, ERROR, fb(), FlagRWConflict(), SERIALIZABLEXACT::flags, GetTopTransactionIdIfAny(), HASH_FIND, hash_search(), SERIALIZABLEXACT::inConflicts, InvalidSerCommitSeqNo, SERIALIZABLEXACT::lastCommitBeforeSnapshot, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MySerializableXact, RWConflictExists(), SERIALIZABLEXACT::SeqNo, SerialGetMinConflictCommitSeqNo(), SerializableXidHash, SerializationNeededForRead(), SXACT_FLAG_DOOMED, SXACT_FLAG_SUMMARY_CONFLICT_OUT, SxactHasConflictOut, SxactHasSummaryConflictIn, SxactHasSummaryConflictOut, SxactIsCommitted, SxactIsDoomed, SxactIsPrepared, SxactIsReadOnly, TransactionIdEquals, TransactionIdIsValid, and XidIsConcurrent().

Referenced by HeapCheckForSerializableConflictOut().

CheckForSerializableConflictOutNeeded()

bool CheckForSerializableConflictOutNeeded ( Relation  relation, Snapshot  snapshot  )

extern

Definition at line 3920 of file predicate.c.

{
    if (!SerializationNeededForRead(relation, snapshot))
        return false;
 
    /* Check if someone else has already decided that we need to die */
    if (SxactIsDoomed(MySerializableXact))
    {
        ereport(ERROR,
                (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                 errmsg("could not serialize access due to read/write dependencies among transactions"),
                 errdetail_internal("Reason code: Canceled on identification as a pivot, during conflict out checking."),
                 errhint("The transaction might succeed if retried.")));
    }
 
    return true;
}

References ereport, errcode(), ERRCODE_T_R_SERIALIZATION_FAILURE, errdetail_internal(), errhint(), errmsg, ERROR, MySerializableXact, SerializationNeededForRead(), and SxactIsDoomed.

Referenced by heap_prepare_pagescan(), and HeapCheckForSerializableConflictOut().

CheckPointPredicate()

void CheckPointPredicate ( void  )

extern

Definition at line 1022 of file predicate.c.

{
    int64       truncateCutoffPage;
 
    LWLockAcquire(SerialControlLock, LW_EXCLUSIVE);
 
    /* Exit quickly if the SLRU is currently not in use. */
    if (serialControl->headPage < 0)
    {
        LWLockRelease(SerialControlLock);
        return;
    }
 
    if (TransactionIdIsValid(serialControl->tailXid))
    {
        int64       tailPage;
 
        tailPage = SerialPage(serialControl->tailXid);
 
        /*
         * It is possible for the tailXid to be ahead of the headXid.  This
         * occurs if we checkpoint while there are in-progress serializable
         * transaction(s) advancing the tail but we are yet to summarize the
         * transactions.  In this case, we cutoff up to the headPage and the
         * next summary will advance the headXid.
         */
        if (SerialPagePrecedesLogically(tailPage, serialControl->headPage))
        {
            /* We can truncate the SLRU up to the page containing tailXid */
            truncateCutoffPage = tailPage;
        }
        else
            truncateCutoffPage = serialControl->headPage;
    }
    else
    {
        /*----------
         * The SLRU is no longer needed. Truncate to head before we set head
         * invalid.
         *
         * XXX: It's possible that the SLRU is not needed again until XID
         * wrap-around has happened, so that the segment containing headPage
         * that we leave behind will appear to be new again. In that case it
         * won't be removed until XID horizon advances enough to make it
         * current again.
         *
         * XXX: This should happen in vac_truncate_clog(), not in checkpoints.
         * Consider this scenario, starting from a system with no in-progress
         * transactions and VACUUM FREEZE having maximized oldestXact:
         * - Start a SERIALIZABLE transaction.
         * - Start, finish, and summarize a SERIALIZABLE transaction, creating
         *   one SLRU page.
         * - Consume XIDs to reach xidStopLimit.
         * - Finish all transactions.  Due to the long-running SERIALIZABLE
         *   transaction, earlier checkpoints did not touch headPage.  The
         *   next checkpoint will change it, but that checkpoint happens after
         *   the end of the scenario.
         * - VACUUM to advance XID limits.
         * - Consume ~2M XIDs, crossing the former xidWrapLimit.
         * - Start, finish, and summarize a SERIALIZABLE transaction.
         *   SerialAdd() declines to create the targetPage, because headPage
         *   is not regarded as in the past relative to that targetPage.  The
         *   transaction instigating the summarize fails in
         *   SimpleLruReadPage().
         */
        truncateCutoffPage = serialControl->headPage;
        serialControl->headPage = -1;
    }
 
    LWLockRelease(SerialControlLock);
 
    /*
     * Truncate away pages that are no longer required.  Note that no
     * additional locking is required, because this is only called as part of
     * a checkpoint, and the validity limits have already been determined.
     */
    SimpleLruTruncate(SerialSlruCtl, truncateCutoffPage);
 
    /*
     * Write dirty SLRU pages to disk
     *
     * This is not actually necessary from a correctness point of view. We do
     * it merely as a debugging aid.
     *
     * We're doing this after the truncation to avoid writing pages right
     * before deleting the file in which they sit, which would be completely
     * pointless.
     */
    SimpleLruWriteAll(SerialSlruCtl, true);
}

References fb(), SerialControlData::headPage, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), serialControl, SerialPage, SerialPagePrecedesLogically(), SerialSlruCtl, SimpleLruTruncate(), SimpleLruWriteAll(), SerialControlData::tailXid, and TransactionIdIsValid.

Referenced by CheckPointGuts().

CheckTableForSerializableConflictIn()

void CheckTableForSerializableConflictIn ( Relation  relation )

extern

Definition at line 4348 of file predicate.c.

{
    HASH_SEQ_STATUS seqstat;
    PREDICATELOCKTARGET *target;
    Oid         dbId;
    Oid         heapId;
    int         i;
 
    /*
     * Bail out quickly if there are no serializable transactions running.
     * It's safe to check this without taking locks because the caller is
     * holding an ACCESS EXCLUSIVE lock on the relation.  No new locks which
     * would matter here can be acquired while that is held.
     */
    if (!TransactionIdIsValid(PredXact->SxactGlobalXmin))
        return;
 
    if (!SerializationNeededForWrite(relation))
        return;
 
    /*
     * We're doing a write which might cause rw-conflicts now or later.
     * Memorize that fact.
     */
    MyXactDidWrite = true;
 
    Assert(relation->rd_index == NULL); /* not an index relation */
 
    dbId = relation->rd_locator.dbOid;
    heapId = relation->rd_id;
 
    LWLockAcquire(SerializablePredicateListLock, LW_EXCLUSIVE);
    for (i = 0; i < NUM_PREDICATELOCK_PARTITIONS; i++)
        LWLockAcquire(PredicateLockHashPartitionLockByIndex(i), LW_SHARED);
    LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
 
    /* Scan through target list */
    hash_seq_init(&seqstat, PredicateLockTargetHash);
 
    while ((target = (PREDICATELOCKTARGET *) hash_seq_search(&seqstat)))
    {
        dlist_mutable_iter iter;
 
        /*
         * Check whether this is a target which needs attention.
         */
        if (GET_PREDICATELOCKTARGETTAG_RELATION(target->tag) != heapId)
            continue;           /* wrong relation id */
        if (GET_PREDICATELOCKTARGETTAG_DB(target->tag) != dbId)
            continue;           /* wrong database id */
 
        /*
         * Loop through locks for this target and flag conflicts.
         */
        dlist_foreach_modify(iter, &target->predicateLocks)
        {
            PREDICATELOCK *predlock =
                dlist_container(PREDICATELOCK, targetLink, iter.cur);
 
            if (predlock->tag.myXact != MySerializableXact
                && !RWConflictExists(predlock->tag.myXact, MySerializableXact))
            {
                FlagRWConflict(predlock->tag.myXact, MySerializableXact);
            }
        }
    }
 
    /* Release locks in reverse order */
    LWLockRelease(SerializableXactHashLock);
    for (i = NUM_PREDICATELOCK_PARTITIONS - 1; i >= 0; i--)
        LWLockRelease(PredicateLockHashPartitionLockByIndex(i));
    LWLockRelease(SerializablePredicateListLock);
}

References Assert, dlist_mutable_iter::cur, RelFileLocator::dbOid, dlist_container, dlist_foreach_modify, fb(), FlagRWConflict(), GET_PREDICATELOCKTARGETTAG_DB, GET_PREDICATELOCKTARGETTAG_RELATION, hash_seq_init(), hash_seq_search(), i, LW_EXCLUSIVE, LW_SHARED, LWLockAcquire(), LWLockRelease(), MySerializableXact, MyXactDidWrite, NUM_PREDICATELOCK_PARTITIONS, PredicateLockHashPartitionLockByIndex, PREDICATELOCKTARGET::predicateLocks, PredicateLockTargetHash, PredXact, RelationData::rd_id, RelationData::rd_index, RelationData::rd_locator, RWConflictExists(), SerializationNeededForWrite(), PredXactListData::SxactGlobalXmin, PREDICATELOCKTARGET::tag, and TransactionIdIsValid.

Referenced by ExecuteTruncateGuts(), and heap_drop_with_catalog().

GetSerializableTransactionSnapshot()

Snapshot GetSerializableTransactionSnapshot ( Snapshot  snapshot )

extern

Definition at line 1611 of file predicate.c.

{
    Assert(IsolationIsSerializable());
 
    /*
     * Can't use serializable mode while recovery is still active, as it is,
     * for example, on a hot standby.  We could get here despite the check in
     * check_transaction_isolation() if default_transaction_isolation is set
     * to serializable, so phrase the hint accordingly.
     */
    if (RecoveryInProgress())
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot use serializable mode in a hot standby"),
                 errdetail("\"default_transaction_isolation\" is set to \"serializable\"."),
                 errhint("You can use \"SET default_transaction_isolation = 'repeatable read'\" to change the default.")));
 
    /*
     * A special optimization is available for SERIALIZABLE READ ONLY
     * DEFERRABLE transactions -- we can wait for a suitable snapshot and
     * thereby avoid all SSI overhead once it's running.
     */
    if (XactReadOnly && XactDeferrable)
        return GetSafeSnapshot(snapshot);
 
    return GetSerializableTransactionSnapshotInt(snapshot,
                                                 NULL, InvalidPid);
}

References Assert, ereport, errcode(), errdetail(), errhint(), errmsg, ERROR, fb(), GetSafeSnapshot(), GetSerializableTransactionSnapshotInt(), InvalidPid, IsolationIsSerializable, RecoveryInProgress(), XactDeferrable, and XactReadOnly.

Referenced by GetTransactionSnapshot().

PageIsPredicateLocked()

bool PageIsPredicateLocked ( Relation  relation, BlockNumber  blkno  )

extern

Definition at line 1937 of file predicate.c.

{
    PREDICATELOCKTARGETTAG targettag;
    uint32      targettaghash;
    LWLock     *partitionLock;
    PREDICATELOCKTARGET *target;
 
    SET_PREDICATELOCKTARGETTAG_PAGE(targettag,
                                    relation->rd_locator.dbOid,
                                    relation->rd_id,
                                    blkno);
 
    targettaghash = PredicateLockTargetTagHashCode(&targettag);
    partitionLock = PredicateLockHashPartitionLock(targettaghash);
    LWLockAcquire(partitionLock, LW_SHARED);
    target = (PREDICATELOCKTARGET *)
        hash_search_with_hash_value(PredicateLockTargetHash,
                                    &targettag, targettaghash,
                                    HASH_FIND, NULL);
    LWLockRelease(partitionLock);
 
    return (target != NULL);
}

References RelFileLocator::dbOid, fb(), HASH_FIND, hash_search_with_hash_value(), LW_SHARED, LWLockAcquire(), LWLockRelease(), PredicateLockHashPartitionLock, PredicateLockTargetHash, PredicateLockTargetTagHashCode, RelationData::rd_id, RelationData::rd_locator, and SET_PREDICATELOCKTARGETTAG_PAGE.

PostPrepare_PredicateLocks()

void PostPrepare_PredicateLocks ( FullTransactionId  fxid )

extern

Definition at line 4788 of file predicate.c.

{
    if (MySerializableXact == InvalidSerializableXact)
        return;
 
    Assert(SxactIsPrepared(MySerializableXact));
 
    MySerializableXact->pid = 0;
    MySerializableXact->pgprocno = INVALID_PROC_NUMBER;
 
    hash_destroy(LocalPredicateLockHash);
    LocalPredicateLockHash = NULL;
 
    MySerializableXact = InvalidSerializableXact;
    MyXactDidWrite = false;
}

References Assert, fb(), hash_destroy(), INVALID_PROC_NUMBER, InvalidSerializableXact, LocalPredicateLockHash, MySerializableXact, MyXactDidWrite, SERIALIZABLEXACT::pgprocno, SERIALIZABLEXACT::pid, and SxactIsPrepared.

Referenced by PrepareTransaction().

PreCommit_CheckForSerializationFailure()

void PreCommit_CheckForSerializationFailure ( void  )

extern

Definition at line 4632 of file predicate.c.

{
    dlist_iter  near_iter;
 
    if (MySerializableXact == InvalidSerializableXact)
        return;
 
    Assert(IsolationIsSerializable());
 
    LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
 
    /*
     * Check if someone else has already decided that we need to die.  Since
     * we set our own DOOMED flag when partially releasing, ignore in that
     * case.
     */
    if (SxactIsDoomed(MySerializableXact) &&
        !SxactIsPartiallyReleased(MySerializableXact))
    {
        LWLockRelease(SerializableXactHashLock);
        ereport(ERROR,
                (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                 errmsg("could not serialize access due to read/write dependencies among transactions"),
                 errdetail_internal("Reason code: Canceled on identification as a pivot, during commit attempt."),
                 errhint("The transaction might succeed if retried.")));
    }
 
    dlist_foreach(near_iter, &MySerializableXact->inConflicts)
    {
        RWConflict  nearConflict =
            dlist_container(RWConflictData, inLink, near_iter.cur);
 
        if (!SxactIsCommitted(nearConflict->sxactOut)
            && !SxactIsDoomed(nearConflict->sxactOut))
        {
            dlist_iter  far_iter;
 
            dlist_foreach(far_iter, &nearConflict->sxactOut->inConflicts)
            {
                RWConflict  farConflict =
                    dlist_container(RWConflictData, inLink, far_iter.cur);
 
                if (farConflict->sxactOut == MySerializableXact
                    || (!SxactIsCommitted(farConflict->sxactOut)
                        && !SxactIsReadOnly(farConflict->sxactOut)
                        && !SxactIsDoomed(farConflict->sxactOut)))
                {
                    /*
                     * Normally, we kill the pivot transaction to make sure we
                     * make progress if the failing transaction is retried.
                     * However, we can't kill it if it's already prepared, so
                     * in that case we commit suicide instead.
                     */
                    if (SxactIsPrepared(nearConflict->sxactOut))
                    {
                        LWLockRelease(SerializableXactHashLock);
                        ereport(ERROR,
                                (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                                 errmsg("could not serialize access due to read/write dependencies among transactions"),
                                 errdetail_internal("Reason code: Canceled on commit attempt with conflict in from prepared pivot."),
                                 errhint("The transaction might succeed if retried.")));
                    }
                    nearConflict->sxactOut->flags |= SXACT_FLAG_DOOMED;
                    break;
                }
            }
        }
    }
 
    MySerializableXact->prepareSeqNo = ++(PredXact->LastSxactCommitSeqNo);
    MySerializableXact->flags |= SXACT_FLAG_PREPARED;
 
    LWLockRelease(SerializableXactHashLock);
}

References Assert, dlist_container, dlist_foreach, ereport, errcode(), ERRCODE_T_R_SERIALIZATION_FAILURE, errdetail_internal(), errhint(), errmsg, ERROR, fb(), SERIALIZABLEXACT::flags, SERIALIZABLEXACT::inConflicts, InvalidSerializableXact, IsolationIsSerializable, PredXactListData::LastSxactCommitSeqNo, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MySerializableXact, PredXact, SERIALIZABLEXACT::prepareSeqNo, SXACT_FLAG_DOOMED, SXACT_FLAG_PREPARED, SxactIsCommitted, SxactIsDoomed, SxactIsPartiallyReleased, SxactIsPrepared, and SxactIsReadOnly.

Referenced by CommitTransaction(), and PrepareTransaction().

predicatelock_twophase_recover()

void predicatelock_twophase_recover ( FullTransactionId  fxid, uint16  info, void *  recdata, uint32  len  )

extern

Definition at line 4838 of file predicate.c.

{
    TwoPhasePredicateRecord *record;
    TransactionId xid = XidFromFullTransactionId(fxid);
 
    Assert(len == sizeof(TwoPhasePredicateRecord));
 
    record = (TwoPhasePredicateRecord *) recdata;
 
    Assert((record->type == TWOPHASEPREDICATERECORD_XACT) ||
           (record->type == TWOPHASEPREDICATERECORD_LOCK));
 
    if (record->type == TWOPHASEPREDICATERECORD_XACT)
    {
        /* Per-transaction record. Set up a SERIALIZABLEXACT. */
        TwoPhasePredicateXactRecord *xactRecord;
        SERIALIZABLEXACT *sxact;
        SERIALIZABLEXID *sxid;
        SERIALIZABLEXIDTAG sxidtag;
        bool        found;
 
        xactRecord = (TwoPhasePredicateXactRecord *) &record->data.xactRecord;
 
        LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
        sxact = CreatePredXact();
        if (!sxact)
            ereport(ERROR,
                    (errcode(ERRCODE_OUT_OF_MEMORY),
                     errmsg("out of shared memory")));
 
        /* vxid for a prepared xact is INVALID_PROC_NUMBER/xid; no pid */
        sxact->vxid.procNumber = INVALID_PROC_NUMBER;
        sxact->vxid.localTransactionId = (LocalTransactionId) xid;
        sxact->pid = 0;
        sxact->pgprocno = INVALID_PROC_NUMBER;
 
        /* a prepared xact hasn't committed yet */
        sxact->prepareSeqNo = RecoverySerCommitSeqNo;
        sxact->commitSeqNo = InvalidSerCommitSeqNo;
        sxact->finishedBefore = InvalidTransactionId;
 
        sxact->SeqNo.lastCommitBeforeSnapshot = RecoverySerCommitSeqNo;
 
        /*
         * Don't need to track this; no transactions running at the time the
         * recovered xact started are still active, except possibly other
         * prepared xacts and we don't care whether those are RO_SAFE or not.
         */
        dlist_init(&(sxact->possibleUnsafeConflicts));
 
        dlist_init(&(sxact->predicateLocks));
        dlist_node_init(&sxact->finishedLink);
 
        sxact->topXid = xid;
        sxact->xmin = xactRecord->xmin;
        sxact->flags = xactRecord->flags;
        Assert(SxactIsPrepared(sxact));
        if (!SxactIsReadOnly(sxact))
        {
            ++(PredXact->WritableSxactCount);
            Assert(PredXact->WritableSxactCount <=
                   (MaxBackends + max_prepared_xacts));
        }
 
        /*
         * We don't know whether the transaction had any conflicts or not, so
         * we'll conservatively assume that it had both a conflict in and a
         * conflict out, and represent that with the summary conflict flags.
         */
        dlist_init(&(sxact->outConflicts));
        dlist_init(&(sxact->inConflicts));
        sxact->flags |= SXACT_FLAG_SUMMARY_CONFLICT_IN;
        sxact->flags |= SXACT_FLAG_SUMMARY_CONFLICT_OUT;
 
        /* Register the transaction's xid */
        sxidtag.xid = xid;
        sxid = (SERIALIZABLEXID *) hash_search(SerializableXidHash,
                                               &sxidtag,
                                               HASH_ENTER, &found);
        Assert(sxid != NULL);
        Assert(!found);
        sxid->myXact = sxact;
 
        /*
         * Update global xmin. Note that this is a special case compared to
         * registering a normal transaction, because the global xmin might go
         * backwards. That's OK, because until recovery is over we're not
         * going to complete any transactions or create any non-prepared
         * transactions, so there's no danger of throwing away.
         */
        if ((!TransactionIdIsValid(PredXact->SxactGlobalXmin)) ||
            (TransactionIdFollows(PredXact->SxactGlobalXmin, sxact->xmin)))
        {
            PredXact->SxactGlobalXmin = sxact->xmin;
            PredXact->SxactGlobalXminCount = 1;
            SerialSetActiveSerXmin(sxact->xmin);
        }
        else if (TransactionIdEquals(sxact->xmin, PredXact->SxactGlobalXmin))
        {
            Assert(PredXact->SxactGlobalXminCount > 0);
            PredXact->SxactGlobalXminCount++;
        }
 
        LWLockRelease(SerializableXactHashLock);
    }
    else if (record->type == TWOPHASEPREDICATERECORD_LOCK)
    {
        /* Lock record. Recreate the PREDICATELOCK */
        TwoPhasePredicateLockRecord *lockRecord;
        SERIALIZABLEXID *sxid;
        SERIALIZABLEXACT *sxact;
        SERIALIZABLEXIDTAG sxidtag;
        uint32      targettaghash;
 
        lockRecord = (TwoPhasePredicateLockRecord *) &record->data.lockRecord;
        targettaghash = PredicateLockTargetTagHashCode(&lockRecord->target);
 
        LWLockAcquire(SerializableXactHashLock, LW_SHARED);
        sxidtag.xid = xid;
        sxid = (SERIALIZABLEXID *)
            hash_search(SerializableXidHash, &sxidtag, HASH_FIND, NULL);
        LWLockRelease(SerializableXactHashLock);
 
        Assert(sxid != NULL);
        sxact = sxid->myXact;
        Assert(sxact != InvalidSerializableXact);
 
        CreatePredicateLock(&lockRecord->target, targettaghash, sxact);
    }
}

References Assert, CreatePredicateLock(), CreatePredXact(), TwoPhasePredicateRecord::data, dlist_init(), dlist_node_init(), ereport, errcode(), errmsg, ERROR, fb(), TwoPhasePredicateXactRecord::flags, HASH_ENTER, HASH_FIND, hash_search(), INVALID_PROC_NUMBER, InvalidSerCommitSeqNo, InvalidSerializableXact, InvalidTransactionId, len, TwoPhasePredicateRecord::lockRecord, LW_EXCLUSIVE, LW_SHARED, LWLockAcquire(), LWLockRelease(), max_prepared_xacts, MaxBackends, PredicateLockTargetTagHashCode, PredXact, RecoverySerCommitSeqNo, SerializableXidHash, SerialSetActiveSerXmin(), SXACT_FLAG_SUMMARY_CONFLICT_IN, SXACT_FLAG_SUMMARY_CONFLICT_OUT, PredXactListData::SxactGlobalXmin, PredXactListData::SxactGlobalXminCount, SxactIsPrepared, SxactIsReadOnly, TwoPhasePredicateLockRecord::target, TransactionIdEquals, TransactionIdFollows(), TransactionIdIsValid, TWOPHASEPREDICATERECORD_LOCK, TWOPHASEPREDICATERECORD_XACT, TwoPhasePredicateRecord::type, PredXactListData::WritableSxactCount, TwoPhasePredicateRecord::xactRecord, XidFromFullTransactionId, and TwoPhasePredicateXactRecord::xmin.

PredicateLockPage()

void PredicateLockPage ( Relation  relation, BlockNumber  blkno, Snapshot  snapshot  )

extern

Definition at line 2528 of file predicate.c.

{
    PREDICATELOCKTARGETTAG tag;
 
    if (!SerializationNeededForRead(relation, snapshot))
        return;
 
    SET_PREDICATELOCKTARGETTAG_PAGE(tag,
                                    relation->rd_locator.dbOid,
                                    relation->rd_id,
                                    blkno);
    PredicateLockAcquire(&tag);
}

References RelFileLocator::dbOid, PredicateLockAcquire(), RelationData::rd_id, RelationData::rd_locator, SerializationNeededForRead(), and SET_PREDICATELOCKTARGETTAG_PAGE.

Referenced by _bt_readpage(), _hash_first(), _hash_readnext(), collectMatchBitmap(), gistScanPage(), IndexOnlyNext(), moveRightIfItNeeded(), scanPendingInsert(), and startScanEntry().

PredicateLockPageCombine()

void PredicateLockPageCombine ( Relation  relation, BlockNumber  oldblkno, BlockNumber  newblkno  )

extern

Definition at line 3158 of file predicate.c.

{
    /*
     * Page combines differ from page splits in that we ought to be able to
     * remove the locks on the old page after transferring them to the new
     * page, instead of duplicating them. However, because we can't edit other
     * backends' local lock tables, removing the old lock would leave them
     * with an entry in their LocalPredicateLockHash for a lock they're not
     * holding, which isn't acceptable. So we wind up having to do the same
     * work as a page split, acquiring a lock on the new page and keeping the
     * old page locked too. That can lead to some false positives, but should
     * be rare in practice.
     */
    PredicateLockPageSplit(relation, oldblkno, newblkno);
}

References fb(), and PredicateLockPageSplit().

Referenced by _bt_mark_page_halfdead(), and ginDeletePostingPage().

PredicateLockPageSplit()

void PredicateLockPageSplit ( Relation  relation, BlockNumber  oldblkno, BlockNumber  newblkno  )

extern

Definition at line 3073 of file predicate.c.

{
    PREDICATELOCKTARGETTAG oldtargettag;
    PREDICATELOCKTARGETTAG newtargettag;
    bool        success;
 
    /*
     * Bail out quickly if there are no serializable transactions running.
     *
     * It's safe to do this check without taking any additional locks. Even if
     * a serializable transaction starts concurrently, we know it can't take
     * any SIREAD locks on the page being split because the caller is holding
     * the associated buffer page lock. Memory reordering isn't an issue; the
     * memory barrier in the LWLock acquisition guarantees that this read
     * occurs while the buffer page lock is held.
     */
    if (!TransactionIdIsValid(PredXact->SxactGlobalXmin))
        return;
 
    if (!PredicateLockingNeededForRelation(relation))
        return;
 
    Assert(oldblkno != newblkno);
    Assert(BlockNumberIsValid(oldblkno));
    Assert(BlockNumberIsValid(newblkno));
 
    SET_PREDICATELOCKTARGETTAG_PAGE(oldtargettag,
                                    relation->rd_locator.dbOid,
                                    relation->rd_id,
                                    oldblkno);
    SET_PREDICATELOCKTARGETTAG_PAGE(newtargettag,
                                    relation->rd_locator.dbOid,
                                    relation->rd_id,
                                    newblkno);
 
    LWLockAcquire(SerializablePredicateListLock, LW_EXCLUSIVE);
 
    /*
     * Try copying the locks over to the new page's tag, creating it if
     * necessary.
     */
    success = TransferPredicateLocksToNewTarget(oldtargettag,
                                                newtargettag,
                                                false);
 
    if (!success)
    {
        /*
         * No more predicate lock entries are available. Failure isn't an
         * option here, so promote the page lock to a relation lock.
         */
 
        /* Get the parent relation lock's lock tag */
        success = GetParentPredicateLockTag(&oldtargettag,
                                            &newtargettag);
        Assert(success);
 
        /*
         * Move the locks to the parent. This shouldn't fail.
         *
         * Note that here we are removing locks held by other backends,
         * leading to a possible inconsistency in their local lock hash table.
         * This is OK because we're replacing it with a lock that covers the
         * old one.
         */
        success = TransferPredicateLocksToNewTarget(oldtargettag,
                                                    newtargettag,
                                                    true);
        Assert(success);
    }
 
    LWLockRelease(SerializablePredicateListLock);
}

References Assert, BlockNumberIsValid(), RelFileLocator::dbOid, fb(), GetParentPredicateLockTag(), LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), PredicateLockingNeededForRelation(), PredXact, RelationData::rd_id, RelationData::rd_locator, SET_PREDICATELOCKTARGETTAG_PAGE, success, PredXactListData::SxactGlobalXmin, TransactionIdIsValid, and TransferPredicateLocksToNewTarget().

Referenced by _bt_insertonpg(), _hash_splitbucket(), createPostingTree(), ginPlaceToPage(), gistplacetopage(), and PredicateLockPageCombine().

PredicateLockRelation()

void PredicateLockRelation ( Relation  relation, Snapshot  snapshot  )

extern

Definition at line 2505 of file predicate.c.

{
    PREDICATELOCKTARGETTAG tag;
 
    if (!SerializationNeededForRead(relation, snapshot))
        return;
 
    SET_PREDICATELOCKTARGETTAG_RELATION(tag,
                                        relation->rd_locator.dbOid,
                                        relation->rd_id);
    PredicateLockAcquire(&tag);
}

References RelFileLocator::dbOid, PredicateLockAcquire(), RelationData::rd_id, RelationData::rd_locator, SerializationNeededForRead(), and SET_PREDICATELOCKTARGETTAG_RELATION.

Referenced by _bt_endpoint(), _bt_first(), heap_beginscan(), and index_beginscan_internal().

PredicateLockTID()

void PredicateLockTID ( Relation  relation, const ItemPointerData *  tid, Snapshot  snapshot, TransactionId  tuple_xid  )

extern

Definition at line 2550 of file predicate.c.

{
    PREDICATELOCKTARGETTAG tag;
 
    if (!SerializationNeededForRead(relation, snapshot))
        return;
 
    /*
     * Return if this xact wrote it.
     */
    if (relation->rd_index == NULL)
    {
        /* If we wrote it; we already have a write lock. */
        if (TransactionIdIsCurrentTransactionId(tuple_xid))
            return;
    }
 
    /*
     * Do quick-but-not-definitive test for a relation lock first.  This will
     * never cause a return when the relation is *not* locked, but will
     * occasionally let the check continue when there really *is* a relation
     * level lock.
     */
    SET_PREDICATELOCKTARGETTAG_RELATION(tag,
                                        relation->rd_locator.dbOid,
                                        relation->rd_id);
    if (PredicateLockExists(&tag))
        return;
 
    SET_PREDICATELOCKTARGETTAG_TUPLE(tag,
                                     relation->rd_locator.dbOid,
                                     relation->rd_id,
                                     ItemPointerGetBlockNumber(tid),
                                     ItemPointerGetOffsetNumber(tid));
    PredicateLockAcquire(&tag);
}

References RelFileLocator::dbOid, fb(), ItemPointerGetBlockNumber(), ItemPointerGetOffsetNumber(), PredicateLockAcquire(), PredicateLockExists(), RelationData::rd_id, RelationData::rd_index, RelationData::rd_locator, SerializationNeededForRead(), SET_PREDICATELOCKTARGETTAG_RELATION, SET_PREDICATELOCKTARGETTAG_TUPLE, and TransactionIdIsCurrentTransactionId().

Referenced by BitmapHeapScanNextBlock(), heap_fetch(), and heap_hot_search_buffer().

PredicateLockTwoPhaseFinish()

void PredicateLockTwoPhaseFinish ( FullTransactionId  fxid, bool  isCommit  )

extern

Definition at line 4811 of file predicate.c.

{
    SERIALIZABLEXID *sxid;
    SERIALIZABLEXIDTAG sxidtag;
 
    sxidtag.xid = XidFromFullTransactionId(fxid);
 
    LWLockAcquire(SerializableXactHashLock, LW_SHARED);
    sxid = (SERIALIZABLEXID *)
        hash_search(SerializableXidHash, &sxidtag, HASH_FIND, NULL);
    LWLockRelease(SerializableXactHashLock);
 
    /* xid will not be found if it wasn't a serializable transaction */
    if (sxid == NULL)
        return;
 
    /* Release its locks */
    MySerializableXact = sxid->myXact;
    MyXactDidWrite = true;      /* conservatively assume that we wrote
                                 * something */
    ReleasePredicateLocks(isCommit, false);
}

References fb(), HASH_FIND, hash_search(), LW_SHARED, LWLockAcquire(), LWLockRelease(), MySerializableXact, MyXactDidWrite, ReleasePredicateLocks(), SerializableXidHash, SERIALIZABLEXIDTAG::xid, and XidFromFullTransactionId.

Referenced by FinishPreparedTransaction().

RegisterPredicateLockingXid()

void RegisterPredicateLockingXid ( TransactionId  xid )

extern

Definition at line 1888 of file predicate.c.

{
    SERIALIZABLEXIDTAG sxidtag;
    SERIALIZABLEXID *sxid;
    bool        found;
 
    /*
     * If we're not tracking predicate lock data for this transaction, we
     * should ignore the request and return quickly.
     */
    if (MySerializableXact == InvalidSerializableXact)
        return;
 
    /* We should have a valid XID and be at the top level. */
    Assert(TransactionIdIsValid(xid));
 
    LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
 
    /* This should only be done once per transaction. */
    Assert(MySerializableXact->topXid == InvalidTransactionId);
 
    MySerializableXact->topXid = xid;
 
    sxidtag.xid = xid;
    sxid = (SERIALIZABLEXID *) hash_search(SerializableXidHash,
                                           &sxidtag,
                                           HASH_ENTER, &found);
    Assert(!found);
 
    /* Initialize the structure. */
    sxid->myXact = MySerializableXact;
    LWLockRelease(SerializableXactHashLock);
}

References Assert, fb(), HASH_ENTER, hash_search(), InvalidSerializableXact, InvalidTransactionId, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MySerializableXact, SerializableXidHash, SERIALIZABLEXACT::topXid, and TransactionIdIsValid.

Referenced by AssignTransactionId().

ReleasePredicateLocks()

void ReleasePredicateLocks ( bool  isCommit, bool  isReadOnlySafe  )

extern

Definition at line 3241 of file predicate.c.

{
    bool        partiallyReleasing = false;
    bool        needToClear;
    SERIALIZABLEXACT *roXact;
    dlist_mutable_iter iter;
 
    /*
     * We can't trust XactReadOnly here, because a transaction which started
     * as READ WRITE can show as READ ONLY later, e.g., within
     * subtransactions.  We want to flag a transaction as READ ONLY if it
     * commits without writing so that de facto READ ONLY transactions get the
     * benefit of some RO optimizations, so we will use this local variable to
     * get some cleanup logic right which is based on whether the transaction
     * was declared READ ONLY at the top level.
     */
    bool        topLevelIsDeclaredReadOnly;
 
    /* We can't be both committing and releasing early due to RO_SAFE. */
    Assert(!(isCommit && isReadOnlySafe));
 
    /* Are we at the end of a transaction, that is, a commit or abort? */
    if (!isReadOnlySafe)
    {
        /*
         * Parallel workers mustn't release predicate locks at the end of
         * their transaction.  The leader will do that at the end of its
         * transaction.
         */
        if (IsParallelWorker())
        {
            ReleasePredicateLocksLocal();
            return;
        }
 
        /*
         * By the time the leader in a parallel query reaches end of
         * transaction, it has waited for all workers to exit.
         */
        Assert(!ParallelContextActive());
 
        /*
         * If the leader in a parallel query earlier stashed a partially
         * released SERIALIZABLEXACT for final clean-up at end of transaction
         * (because workers might still have been accessing it), then it's
         * time to restore it.
         */
        if (SavedSerializableXact != InvalidSerializableXact)
        {
            Assert(MySerializableXact == InvalidSerializableXact);
            MySerializableXact = SavedSerializableXact;
            SavedSerializableXact = InvalidSerializableXact;
            Assert(SxactIsPartiallyReleased(MySerializableXact));
        }
    }
 
    if (MySerializableXact == InvalidSerializableXact)
    {
        Assert(LocalPredicateLockHash == NULL);
        return;
    }
 
    LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
 
    /*
     * If the transaction is committing, but it has been partially released
     * already, then treat this as a roll back.  It was marked as rolled back.
     */
    if (isCommit && SxactIsPartiallyReleased(MySerializableXact))
        isCommit = false;
 
    /*
     * If we're called in the middle of a transaction because we discovered
     * that the SXACT_FLAG_RO_SAFE flag was set, then we'll partially release
     * it (that is, release the predicate locks and conflicts, but not the
     * SERIALIZABLEXACT itself) if we're the first backend to have noticed.
     */
    if (isReadOnlySafe && IsInParallelMode())
    {
        /*
         * The leader needs to stash a pointer to it, so that it can
         * completely release it at end-of-transaction.
         */
        if (!IsParallelWorker())
            SavedSerializableXact = MySerializableXact;
 
        /*
         * The first backend to reach this condition will partially release
         * the SERIALIZABLEXACT.  All others will just clear their
         * backend-local state so that they stop doing SSI checks for the rest
         * of the transaction.
         */
        if (SxactIsPartiallyReleased(MySerializableXact))
        {
            LWLockRelease(SerializableXactHashLock);
            ReleasePredicateLocksLocal();
            return;
        }
        else
        {
            MySerializableXact->flags |= SXACT_FLAG_PARTIALLY_RELEASED;
            partiallyReleasing = true;
            /* ... and proceed to perform the partial release below. */
        }
    }
    Assert(!isCommit || SxactIsPrepared(MySerializableXact));
    Assert(!isCommit || !SxactIsDoomed(MySerializableXact));
    Assert(!SxactIsCommitted(MySerializableXact));
    Assert(SxactIsPartiallyReleased(MySerializableXact)
           || !SxactIsRolledBack(MySerializableXact));
 
    /* may not be serializable during COMMIT/ROLLBACK PREPARED */
    Assert(MySerializableXact->pid == 0 || IsolationIsSerializable());
 
    /* We'd better not already be on the cleanup list. */
    Assert(!SxactIsOnFinishedList(MySerializableXact));
 
    topLevelIsDeclaredReadOnly = SxactIsReadOnly(MySerializableXact);
 
    /*
     * We don't hold XidGenLock lock here, assuming that TransactionId is
     * atomic!
     *
     * If this value is changing, we don't care that much whether we get the
     * old or new value -- it is just used to determine how far
     * SxactGlobalXmin must advance before this transaction can be fully
     * cleaned up.  The worst that could happen is we wait for one more
     * transaction to complete before freeing some RAM; correctness of visible
     * behavior is not affected.
     */
    MySerializableXact->finishedBefore = XidFromFullTransactionId(TransamVariables->nextXid);
 
    /*
     * If it's not a commit it's either a rollback or a read-only transaction
     * flagged SXACT_FLAG_RO_SAFE, and we can clear our locks immediately.
     */
    if (isCommit)
    {
        MySerializableXact->flags |= SXACT_FLAG_COMMITTED;
        MySerializableXact->commitSeqNo = ++(PredXact->LastSxactCommitSeqNo);
        /* Recognize implicit read-only transaction (commit without write). */
        if (!MyXactDidWrite)
            MySerializableXact->flags |= SXACT_FLAG_READ_ONLY;
    }
    else
    {
        /*
         * The DOOMED flag indicates that we intend to roll back this
         * transaction and so it should not cause serialization failures for
         * other transactions that conflict with it. Note that this flag might
         * already be set, if another backend marked this transaction for
         * abort.
         *
         * The ROLLED_BACK flag further indicates that ReleasePredicateLocks
         * has been called, and so the SerializableXact is eligible for
         * cleanup. This means it should not be considered when calculating
         * SxactGlobalXmin.
         */
        MySerializableXact->flags |= SXACT_FLAG_DOOMED;
        MySerializableXact->flags |= SXACT_FLAG_ROLLED_BACK;
 
        /*
         * If the transaction was previously prepared, but is now failing due
         * to a ROLLBACK PREPARED or (hopefully very rare) error after the
         * prepare, clear the prepared flag.  This simplifies conflict
         * checking.
         */
        MySerializableXact->flags &= ~SXACT_FLAG_PREPARED;
    }
 
    if (!topLevelIsDeclaredReadOnly)
    {
        Assert(PredXact->WritableSxactCount > 0);
        if (--(PredXact->WritableSxactCount) == 0)
        {
            /*
             * Release predicate locks and rw-conflicts in for all committed
             * transactions.  There are no longer any transactions which might
             * conflict with the locks and no chance for new transactions to
             * overlap.  Similarly, existing conflicts in can't cause pivots,
             * and any conflicts in which could have completed a dangerous
             * structure would already have caused a rollback, so any
             * remaining ones must be benign.
             */
            PredXact->CanPartialClearThrough = PredXact->LastSxactCommitSeqNo;
        }
    }
    else
    {
        /*
         * Read-only transactions: clear the list of transactions that might
         * make us unsafe. Note that we use 'inLink' for the iteration as
         * opposed to 'outLink' for the r/w xacts.
         */
        dlist_foreach_modify(iter, &MySerializableXact->possibleUnsafeConflicts)
        {
            RWConflict  possibleUnsafeConflict =
                dlist_container(RWConflictData, inLink, iter.cur);
 
            Assert(!SxactIsReadOnly(possibleUnsafeConflict->sxactOut));
            Assert(MySerializableXact == possibleUnsafeConflict->sxactIn);
 
            ReleaseRWConflict(possibleUnsafeConflict);
        }
    }
 
    /* Check for conflict out to old committed transactions. */
    if (isCommit
        && !SxactIsReadOnly(MySerializableXact)
        && SxactHasSummaryConflictOut(MySerializableXact))
    {
        /*
         * we don't know which old committed transaction we conflicted with,
         * so be conservative and use FirstNormalSerCommitSeqNo here
         */
        MySerializableXact->SeqNo.earliestOutConflictCommit =
            FirstNormalSerCommitSeqNo;
        MySerializableXact->flags |= SXACT_FLAG_CONFLICT_OUT;
    }
 
    /*
     * Release all outConflicts to committed transactions.  If we're rolling
     * back clear them all.  Set SXACT_FLAG_CONFLICT_OUT if any point to
     * previously committed transactions.
     */
    dlist_foreach_modify(iter, &MySerializableXact->outConflicts)
    {
        RWConflict  conflict =
            dlist_container(RWConflictData, outLink, iter.cur);
 
        if (isCommit
            && !SxactIsReadOnly(MySerializableXact)
            && SxactIsCommitted(conflict->sxactIn))
        {
            if ((MySerializableXact->flags & SXACT_FLAG_CONFLICT_OUT) == 0
                || conflict->sxactIn->prepareSeqNo < MySerializableXact->SeqNo.earliestOutConflictCommit)
                MySerializableXact->SeqNo.earliestOutConflictCommit = conflict->sxactIn->prepareSeqNo;
            MySerializableXact->flags |= SXACT_FLAG_CONFLICT_OUT;
        }
 
        if (!isCommit
            || SxactIsCommitted(conflict->sxactIn)
            || (conflict->sxactIn->SeqNo.lastCommitBeforeSnapshot >= PredXact->LastSxactCommitSeqNo))
            ReleaseRWConflict(conflict);
    }
 
    /*
     * Release all inConflicts from committed and read-only transactions. If
     * we're rolling back, clear them all.
     */
    dlist_foreach_modify(iter, &MySerializableXact->inConflicts)
    {
        RWConflict  conflict =
            dlist_container(RWConflictData, inLink, iter.cur);
 
        if (!isCommit
            || SxactIsCommitted(conflict->sxactOut)
            || SxactIsReadOnly(conflict->sxactOut))
            ReleaseRWConflict(conflict);
    }
 
    if (!topLevelIsDeclaredReadOnly)
    {
        /*
         * Remove ourselves from the list of possible conflicts for concurrent
         * READ ONLY transactions, flagging them as unsafe if we have a
         * conflict out. If any are waiting DEFERRABLE transactions, wake them
         * up if they are known safe or known unsafe.
         */
        dlist_foreach_modify(iter, &MySerializableXact->possibleUnsafeConflicts)
        {
            RWConflict  possibleUnsafeConflict =
                dlist_container(RWConflictData, outLink, iter.cur);
 
            roXact = possibleUnsafeConflict->sxactIn;
            Assert(MySerializableXact == possibleUnsafeConflict->sxactOut);
            Assert(SxactIsReadOnly(roXact));
 
            /* Mark conflicted if necessary. */
            if (isCommit
                && MyXactDidWrite
                && SxactHasConflictOut(MySerializableXact)
                && (MySerializableXact->SeqNo.earliestOutConflictCommit
                    <= roXact->SeqNo.lastCommitBeforeSnapshot))
            {
                /*
                 * This releases possibleUnsafeConflict (as well as all other
                 * possible conflicts for roXact)
                 */
                FlagSxactUnsafe(roXact);
            }
            else
            {
                ReleaseRWConflict(possibleUnsafeConflict);
 
                /*
                 * If we were the last possible conflict, flag it safe. The
                 * transaction can now safely release its predicate locks (but
                 * that transaction's backend has to do that itself).
                 */
                if (dlist_is_empty(&roXact->possibleUnsafeConflicts))
                    roXact->flags |= SXACT_FLAG_RO_SAFE;
            }
 
            /*
             * Wake up the process for a waiting DEFERRABLE transaction if we
             * now know it's either safe or conflicted.
             */
            if (SxactIsDeferrableWaiting(roXact) &&
                (SxactIsROUnsafe(roXact) || SxactIsROSafe(roXact)))
                ProcSendSignal(roXact->pgprocno);
        }
    }
 
    /*
     * Check whether it's time to clean up old transactions. This can only be
     * done when the last serializable transaction with the oldest xmin among
     * serializable transactions completes.  We then find the "new oldest"
     * xmin and purge any transactions which finished before this transaction
     * was launched.
     *
     * For parallel queries in read-only transactions, it might run twice. We
     * only release the reference on the first call.
     */
    needToClear = false;
    if ((partiallyReleasing ||
         !SxactIsPartiallyReleased(MySerializableXact)) &&
        TransactionIdEquals(MySerializableXact->xmin,
                            PredXact->SxactGlobalXmin))
    {
        Assert(PredXact->SxactGlobalXminCount > 0);
        if (--(PredXact->SxactGlobalXminCount) == 0)
        {
            SetNewSxactGlobalXmin();
            needToClear = true;
        }
    }
 
    LWLockRelease(SerializableXactHashLock);
 
    LWLockAcquire(SerializableFinishedListLock, LW_EXCLUSIVE);
 
    /* Add this to the list of transactions to check for later cleanup. */
    if (isCommit)
        dlist_push_tail(FinishedSerializableTransactions,
                        &MySerializableXact->finishedLink);
 
    /*
     * If we're releasing a RO_SAFE transaction in parallel mode, we'll only
     * partially release it.  That's necessary because other backends may have
     * a reference to it.  The leader will release the SERIALIZABLEXACT itself
     * at the end of the transaction after workers have stopped running.
     */
    if (!isCommit)
        ReleaseOneSerializableXact(MySerializableXact,
                                   isReadOnlySafe && IsInParallelMode(),
                                   false);
 
    LWLockRelease(SerializableFinishedListLock);
 
    if (needToClear)
        ClearOldPredicateLocks();
 
    ReleasePredicateLocksLocal();
}

References Assert, PredXactListData::CanPartialClearThrough, ClearOldPredicateLocks(), SERIALIZABLEXACT::commitSeqNo, dlist_mutable_iter::cur, dlist_container, dlist_foreach_modify, dlist_is_empty(), dlist_push_tail(), SERIALIZABLEXACT::earliestOutConflictCommit, fb(), SERIALIZABLEXACT::finishedBefore, SERIALIZABLEXACT::finishedLink, FinishedSerializableTransactions, FirstNormalSerCommitSeqNo, SERIALIZABLEXACT::flags, FlagSxactUnsafe(), SERIALIZABLEXACT::inConflicts, InvalidSerializableXact, IsInParallelMode(), IsolationIsSerializable, IsParallelWorker, PredXactListData::LastSxactCommitSeqNo, LocalPredicateLockHash, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MySerializableXact, MyXactDidWrite, TransamVariablesData::nextXid, SERIALIZABLEXACT::outConflicts, ParallelContextActive(), SERIALIZABLEXACT::pid, SERIALIZABLEXACT::possibleUnsafeConflicts, PredXact, ProcSendSignal(), ReleaseOneSerializableXact(), ReleasePredicateLocksLocal(), ReleaseRWConflict(), SavedSerializableXact, SERIALIZABLEXACT::SeqNo, SetNewSxactGlobalXmin(), SXACT_FLAG_COMMITTED, SXACT_FLAG_CONFLICT_OUT, SXACT_FLAG_DOOMED, SXACT_FLAG_PARTIALLY_RELEASED, SXACT_FLAG_READ_ONLY, SXACT_FLAG_RO_SAFE, SXACT_FLAG_ROLLED_BACK, PredXactListData::SxactGlobalXmin, PredXactListData::SxactGlobalXminCount, SxactHasConflictOut, SxactHasSummaryConflictOut, SxactIsCommitted, SxactIsDeferrableWaiting, SxactIsDoomed, SxactIsOnFinishedList, SxactIsPartiallyReleased, SxactIsPrepared, SxactIsReadOnly, SxactIsRolledBack, SxactIsROSafe, SxactIsROUnsafe, TransactionIdEquals, TransamVariables, PredXactListData::WritableSxactCount, XidFromFullTransactionId, and SERIALIZABLEXACT::xmin.

Referenced by GetSafeSnapshot(), PredicateLockTwoPhaseFinish(), ResourceOwnerReleaseInternal(), and SerializationNeededForRead().

SetSerializableTransactionSnapshot()

void SetSerializableTransactionSnapshot ( Snapshot  snapshot, VirtualTransactionId *  sourcevxid, int  sourcepid  )

extern

Definition at line 1651 of file predicate.c.

{
    Assert(IsolationIsSerializable());
 
    /*
     * If this is called by parallel.c in a parallel worker, we don't want to
     * create a SERIALIZABLEXACT just yet because the leader's
     * SERIALIZABLEXACT will be installed with AttachSerializableXact().  We
     * also don't want to reject SERIALIZABLE READ ONLY DEFERRABLE in this
     * case, because the leader has already determined that the snapshot it
     * has passed us is safe.  So there is nothing for us to do.
     */
    if (IsParallelWorker())
        return;
 
    /*
     * We do not allow SERIALIZABLE READ ONLY DEFERRABLE transactions to
     * import snapshots, since there's no way to wait for a safe snapshot when
     * we're using the snap we're told to.  (XXX instead of throwing an error,
     * we could just ignore the XactDeferrable flag?)
     */
    if (XactReadOnly && XactDeferrable)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("a snapshot-importing transaction must not be READ ONLY DEFERRABLE")));
 
    (void) GetSerializableTransactionSnapshotInt(snapshot, sourcevxid,
                                                 sourcepid);
}

References Assert, ereport, errcode(), errmsg, ERROR, fb(), GetSerializableTransactionSnapshotInt(), IsolationIsSerializable, IsParallelWorker, XactDeferrable, and XactReadOnly.

Referenced by SetTransactionSnapshot().

ShareSerializableXact()

SerializableXactHandle ShareSerializableXact ( void  )

extern

Definition at line 4976 of file predicate.c.

{
    return MySerializableXact;
}

References MySerializableXact.

Referenced by InitializeParallelDSM().

TransferPredicateLocksToHeapRelation()

void TransferPredicateLocksToHeapRelation ( Relation  relation )

extern

Definition at line 3052 of file predicate.c.

{
    DropAllPredicateLocksFromTable(relation, true);
}

References DropAllPredicateLocksFromTable().

Referenced by ATRewriteTable(), cluster_rel(), index_concurrently_set_dead(), index_drop(), rebuild_relation_finish_concurrent(), and reindex_index().

Variable Documentation

max_predicate_locks_per_page

PGDLLIMPORT int max_predicate_locks_per_page

extern

Definition at line 375 of file predicate.c.

Referenced by MaxPredicateChildLocks().

max_predicate_locks_per_relation

PGDLLIMPORT int max_predicate_locks_per_relation

extern

Definition at line 374 of file predicate.c.

Referenced by MaxPredicateChildLocks().

max_predicate_locks_per_xact

PGDLLIMPORT int max_predicate_locks_per_xact

extern

Definition at line 373 of file predicate.c.

Referenced by CreateLocalPredicateLockHash(), and MaxPredicateChildLocks().