From 2b3a806038c406115965ee78b89781f15ed6df6d Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Fri, 20 Mar 2026 20:27:50 +0200 Subject: [PATCH v11 09/14] refactor predicate.c: Move all the initialization together The ShmemInit function is very complicated currently. These refactorings move it in a direction that is more natural with the new shmem callbacks. --- src/backend/storage/lmgr/predicate.c | 164 +++++++++++++-------------- 1 file changed, 79 insertions(+), 85 deletions(-) diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c index 13a6a4b93a6..af03071a71f 100644 --- a/src/backend/storage/lmgr/predicate.c +++ b/src/backend/storage/lmgr/predicate.c @@ -1144,19 +1144,6 @@ PredicateLockShmemInit(void) HASH_ELEM | HASH_BLOBS | HASH_PARTITION | HASH_FIXED_SIZE); - /* - * Reserve a dummy entry in the hash table; we use it to make sure there's - * always one entry available when we need to split or combine a page, - * because running out of space there could mean aborting a - * non-serializable transaction. - */ - if (!IsUnderPostmaster) - { - (void) hash_search(PredicateLockTargetHash, &ScratchTargetTag, - HASH_ENTER, &found); - Assert(!found); - } - /* Pre-calculate the hash and partition lock of the scratch entry */ ScratchTargetTagHash = PredicateLockTargetTagHashCode(&ScratchTargetTag); ScratchPartitionLock = PredicateLockHashPartitionLock(ScratchTargetTagHash); @@ -1200,49 +1187,6 @@ PredicateLockShmemInit(void) requestSize, &found); Assert(found == IsUnderPostmaster); - if (!found) - { - int i; - - /* clean everything, both the header and the element */ - memset(PredXact, 0, requestSize); - - dlist_init(&PredXact->availableList); - dlist_init(&PredXact->activeList); - PredXact->SxactGlobalXmin = InvalidTransactionId; - PredXact->SxactGlobalXminCount = 0; - PredXact->WritableSxactCount = 0; - PredXact->LastSxactCommitSeqNo = FirstNormalSerCommitSeqNo - 1; - PredXact->CanPartialClearThrough = 0; - PredXact->HavePartialClearedThrough = 0; - PredXact->element - = (SERIALIZABLEXACT *) ((char *) PredXact + PredXactListDataSize); - /* Add all elements to available list, clean. */ - for (i = 0; i < max_serializable_xacts; i++) - { - LWLockInitialize(&PredXact->element[i].perXactPredicateListLock, - LWTRANCHE_PER_XACT_PREDICATE_LIST); - dlist_push_tail(&PredXact->availableList, &PredXact->element[i].xactLink); - } - PredXact->OldCommittedSxact = CreatePredXact(); - SetInvalidVirtualTransactionId(PredXact->OldCommittedSxact->vxid); - PredXact->OldCommittedSxact->prepareSeqNo = 0; - PredXact->OldCommittedSxact->commitSeqNo = 0; - PredXact->OldCommittedSxact->SeqNo.lastCommitBeforeSnapshot = 0; - dlist_init(&PredXact->OldCommittedSxact->outConflicts); - dlist_init(&PredXact->OldCommittedSxact->inConflicts); - dlist_init(&PredXact->OldCommittedSxact->predicateLocks); - dlist_node_init(&PredXact->OldCommittedSxact->finishedLink); - dlist_init(&PredXact->OldCommittedSxact->possibleUnsafeConflicts); - PredXact->OldCommittedSxact->topXid = InvalidTransactionId; - PredXact->OldCommittedSxact->finishedBefore = InvalidTransactionId; - PredXact->OldCommittedSxact->xmin = InvalidTransactionId; - PredXact->OldCommittedSxact->flags = SXACT_FLAG_COMMITTED; - PredXact->OldCommittedSxact->pid = 0; - PredXact->OldCommittedSxact->pgprocno = INVALID_PROC_NUMBER; - } - /* This never changes, so let's keep a local copy. */ - OldCommittedSxact = PredXact->OldCommittedSxact; /* * Allocate hash table for SERIALIZABLEXID structs. This stores per-xid @@ -1278,23 +1222,6 @@ PredicateLockShmemInit(void) requestSize, &found); Assert(found == IsUnderPostmaster); - if (!found) - { - int i; - - /* clean everything, including the elements */ - memset(RWConflictPool, 0, requestSize); - - dlist_init(&RWConflictPool->availableList); - RWConflictPool->element = (RWConflict) ((char *) RWConflictPool + - RWConflictPoolHeaderDataSize); - /* Add all elements to available list, clean. */ - for (i = 0; i < max_rw_conflicts; i++) - { - dlist_push_tail(&RWConflictPool->availableList, - &RWConflictPool->element[i].outLink); - } - } /* * Create or attach to the header for the list of finished serializable @@ -1305,8 +1232,6 @@ PredicateLockShmemInit(void) sizeof(dlist_head), &found); Assert(found == IsUnderPostmaster); - if (!found) - dlist_init(FinishedSerializableTransactions); /* * Initialize the SLRU storage for old committed serializable @@ -1328,19 +1253,88 @@ PredicateLockShmemInit(void) */ serialControl = (SerialControl) ShmemInitStruct("SerialControlData", sizeof(SerialControlData), &found); - Assert(found == IsUnderPostmaster); - if (!found) + + /* + * If we just attached to existing shared memory (EXEC_BACKEND), we're all + * done. Otherwise, during postmaster startup proceed to initialize the + * shared memory. + */ + if (IsUnderPostmaster) { - /* - * Set control information to reflect empty SLRU. - */ - LWLockAcquire(SerialControlLock, LW_EXCLUSIVE); - serialControl->headPage = -1; - serialControl->headXid = InvalidTransactionId; - serialControl->tailXid = InvalidTransactionId; - LWLockRelease(SerialControlLock); + /* This never changes, so let's keep a local copy. */ + OldCommittedSxact = PredXact->OldCommittedSxact; + return; + } + + /* + * Reserve a dummy entry in the hash table; we use it to make sure there's + * always one entry available when we need to split or combine a page, + * because running out of space there could mean aborting a + * non-serializable transaction. + */ + (void) hash_search(PredicateLockTargetHash, &ScratchTargetTag, + HASH_ENTER, &found); + Assert(!found); + + /* Initialize PredXact list */ + dlist_init(&PredXact->availableList); + dlist_init(&PredXact->activeList); + PredXact->SxactGlobalXmin = InvalidTransactionId; + PredXact->SxactGlobalXminCount = 0; + PredXact->WritableSxactCount = 0; + PredXact->LastSxactCommitSeqNo = FirstNormalSerCommitSeqNo - 1; + PredXact->CanPartialClearThrough = 0; + PredXact->HavePartialClearedThrough = 0; + PredXact->element + = (SERIALIZABLEXACT *) ((char *) PredXact + PredXactListDataSize); + /* Add all elements to available list, clean. */ + for (int i = 0; i < max_serializable_xacts; i++) + { + LWLockInitialize(&PredXact->element[i].perXactPredicateListLock, + LWTRANCHE_PER_XACT_PREDICATE_LIST); + dlist_push_tail(&PredXact->availableList, &PredXact->element[i].xactLink); } + PredXact->OldCommittedSxact = CreatePredXact(); + SetInvalidVirtualTransactionId(PredXact->OldCommittedSxact->vxid); + PredXact->OldCommittedSxact->prepareSeqNo = 0; + PredXact->OldCommittedSxact->commitSeqNo = 0; + PredXact->OldCommittedSxact->SeqNo.lastCommitBeforeSnapshot = 0; + dlist_init(&PredXact->OldCommittedSxact->outConflicts); + dlist_init(&PredXact->OldCommittedSxact->inConflicts); + dlist_init(&PredXact->OldCommittedSxact->predicateLocks); + dlist_node_init(&PredXact->OldCommittedSxact->finishedLink); + dlist_init(&PredXact->OldCommittedSxact->possibleUnsafeConflicts); + PredXact->OldCommittedSxact->topXid = InvalidTransactionId; + PredXact->OldCommittedSxact->finishedBefore = InvalidTransactionId; + PredXact->OldCommittedSxact->xmin = InvalidTransactionId; + PredXact->OldCommittedSxact->flags = SXACT_FLAG_COMMITTED; + PredXact->OldCommittedSxact->pid = 0; + PredXact->OldCommittedSxact->pgprocno = INVALID_PROC_NUMBER; + + /* This never changes, so let's keep a local copy. */ + OldCommittedSxact = PredXact->OldCommittedSxact; + + /* Initialize the rw-conflict pool */ + dlist_init(&RWConflictPool->availableList); + RWConflictPool->element = (RWConflict) ((char *) RWConflictPool + + RWConflictPoolHeaderDataSize); + /* Add all elements to available list, clean. */ + for (int i = 0; i < max_rw_conflicts; i++) + { + dlist_push_tail(&RWConflictPool->availableList, + &RWConflictPool->element[i].outLink); + } + + /* Initialize the list of finished serializable transactions */ + dlist_init(FinishedSerializableTransactions); + + /* Initialize SerialControl to reflect empty SLRU. */ + LWLockAcquire(SerialControlLock, LW_EXCLUSIVE); + serialControl->headPage = -1; + serialControl->headXid = InvalidTransactionId; + serialControl->tailXid = InvalidTransactionId; + LWLockRelease(SerialControlLock); } /* -- 2.47.3