Here's an updated patch. I haven't added commentary or documentation to account for the new assumption, per Matthias' comment and Robert's discussion thereof.
-- Álvaro Herrera 39°49'30"S 73°17'W "Cada quien es cada cual y baja las escaleras como quiere" (JMSerrat)
>From 4e1cf2ee0e6c9fb49fc2bc5932d3a59d65ee9ea7 Mon Sep 17 00:00:00 2001 From: Alvaro Herrera <alvhe...@alvh.no-ip.org> Date: Fri, 15 Jan 2021 14:03:14 -0300 Subject: [PATCH v2] Teach VACUUM to ignore CIC Discussion: https://postgr.es/m/20210115133858.GA18931@alvherre.pgsql --- src/backend/storage/ipc/procarray.c | 40 +++++++++++++++++++++++------ src/backend/utils/misc/guc.c | 2 +- 2 files changed, 33 insertions(+), 9 deletions(-) diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index a5daea8957..88b8271c22 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -1610,7 +1610,12 @@ TransactionIdIsActive(TransactionId xid) * relations that's not required, since only backends in my own database could * ever see the tuples in them. Also, we can ignore concurrently running lazy * VACUUMs because (a) they must be working on other tables, and (b) they - * don't need to do snapshot-based lookups. + * don't need to do snapshot-based lookups. Also, for the non-catalog + * horizon, we can ignore CREATE INDEX CONCURRENTLY and REINDEX CONCURRENTLY + * when they are working on non-partial, non-expressional indexes, for the + * same reasons and because they can't run in transaction blocks. (They are + * not possible to ignore for catalogs, because CIC and RC do some catalog + * operations.) * * This also computes a horizon used to truncate pg_subtrans. For that * backends in all databases have to be considered, and concurrently running @@ -1660,9 +1665,6 @@ ComputeXidHorizons(ComputeXidHorizonsResult *h) bool in_recovery = RecoveryInProgress(); TransactionId *other_xids = ProcGlobal->xids; - /* inferred after ProcArrayLock is released */ - h->catalog_oldest_nonremovable = InvalidTransactionId; - LWLockAcquire(ProcArrayLock, LW_SHARED); h->latest_completed = ShmemVariableCache->latestCompletedXid; @@ -1682,6 +1684,7 @@ ComputeXidHorizons(ComputeXidHorizonsResult *h) h->oldest_considered_running = initial; h->shared_oldest_nonremovable = initial; + h->catalog_oldest_nonremovable = initial; h->data_oldest_nonremovable = initial; /* @@ -1752,7 +1755,7 @@ ComputeXidHorizons(ComputeXidHorizonsResult *h) if (statusFlags & (PROC_IN_VACUUM | PROC_IN_LOGICAL_DECODING)) continue; - /* shared tables need to take backends in all database into account */ + /* shared tables need to take backends in all databases into account */ h->shared_oldest_nonremovable = TransactionIdOlder(h->shared_oldest_nonremovable, xmin); @@ -1768,16 +1771,33 @@ ComputeXidHorizons(ComputeXidHorizonsResult *h) * to prune still needed data away). If the current backend never * connects to a database that is harmless, because * data_oldest_nonremovable will never be utilized. + * + * Additionally, processes doing CREATE INDEX CONCURRENTLY and REINDEX + * CONCURRENTLY on "safe" indexes can be ignored for non-catalog + * horizon. (But not for catalogs: some transactions in CIC/RC do + * catalog updates.) */ if (in_recovery || MyDatabaseId == InvalidOid || proc->databaseId == MyDatabaseId || proc->databaseId == 0) /* always include WalSender */ { - h->data_oldest_nonremovable = - TransactionIdOlder(h->data_oldest_nonremovable, xmin); + if (statusFlags & PROC_IN_SAFE_IC) + h->catalog_oldest_nonremovable = + TransactionIdOlder(h->catalog_oldest_nonremovable, xmin); + else + { + h->data_oldest_nonremovable = + TransactionIdOlder(h->data_oldest_nonremovable, xmin); + h->catalog_oldest_nonremovable = + TransactionIdOlder(h->catalog_oldest_nonremovable, xmin); + } } } + /* catalog horizon should never be later than data */ + Assert(TransactionIdPrecedesOrEquals(h->catalog_oldest_nonremovable, + h->data_oldest_nonremovable)); + /* * If in recovery fetch oldest xid in KnownAssignedXids, will be applied * after lock is released. @@ -1799,6 +1819,8 @@ ComputeXidHorizons(ComputeXidHorizonsResult *h) TransactionIdOlder(h->shared_oldest_nonremovable, kaxmin); h->data_oldest_nonremovable = TransactionIdOlder(h->data_oldest_nonremovable, kaxmin); + h->catalog_oldest_nonremovable = + TransactionIdOlder(h->catalog_oldest_nonremovable, kaxmin); /* temp relations cannot be accessed in recovery */ } else @@ -1825,6 +1847,9 @@ ComputeXidHorizons(ComputeXidHorizonsResult *h) h->data_oldest_nonremovable = TransactionIdRetreatedBy(h->data_oldest_nonremovable, vacuum_defer_cleanup_age); + h->catalog_oldest_nonremovable = + TransactionIdRetreatedBy(h->catalog_oldest_nonremovable, + vacuum_defer_cleanup_age); /* defer doesn't apply to temp relations */ } @@ -1847,7 +1872,6 @@ ComputeXidHorizons(ComputeXidHorizonsResult *h) h->shared_oldest_nonremovable = TransactionIdOlder(h->shared_oldest_nonremovable, h->slot_catalog_xmin); - h->catalog_oldest_nonremovable = h->data_oldest_nonremovable; h->catalog_oldest_nonremovable = TransactionIdOlder(h->catalog_oldest_nonremovable, h->slot_catalog_xmin); diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index 260ec7b97e..d626731723 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -2583,7 +2583,7 @@ static struct config_int ConfigureNamesInt[] = NULL }, &vacuum_defer_cleanup_age, - 0, 0, 1000000, + 0, 0, 1000000, /* see ComputeXidHorizons */ NULL, NULL, NULL }, -- 2.20.1
