From d9d076222f5b94a85e0e318339cfc44b8f26022d Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Tue, 23 Feb 2021 12:15:09 -0300 Subject: [PATCH] VACUUM: ignore indexing operations with CONCURRENTLY As envisioned in commit c98763bf51bf, it is possible for VACUUM to ignore certain transactions that are executing CREATE INDEX CONCURRENTLY and REINDEX CONCURRENTLY for the purposes of computing Xmin; that's because we know those transactions are not going to examine any other tables, and are not going to execute anything else in the same transaction. (Only operations on "safe" indexes can be ignored: those on indexes that are neither partial nor expressional). This is extremely useful in cases where CIC/RC can run for a very long time, because that used to be a significant headache for concurrent vacuuming of other tables. Reviewed-by: Matthias van de Meent Reviewed-by: Masahiko Sawada Discussion: https://postgr.es/m/20210115133858.GA18931@alvherre.pgsql --- doc/src/sgml/ref/create_index.sgml | 2 ++ doc/src/sgml/ref/reindex.sgml | 2 ++ src/backend/storage/ipc/procarray.c | 42 +++++++++++++++++++++++------ src/backend/utils/misc/guc.c | 2 +- 4 files changed, 39 insertions(+), 9 deletions(-) diff --git a/doc/src/sgml/ref/create_index.sgml b/doc/src/sgml/ref/create_index.sgml index a5271a9f8f2..965dcf472ca 100644 --- a/doc/src/sgml/ref/create_index.sgml +++ b/doc/src/sgml/ref/create_index.sgml @@ -855,6 +855,8 @@ Indexes: Like any long-running transaction, CREATE INDEX on a table can affect which tuples can be removed by concurrent VACUUM on any other table. + Excepted from this are operations with the CONCURRENTLY + option for indexes that are not partial and do not index any expressions. diff --git a/doc/src/sgml/ref/reindex.sgml b/doc/src/sgml/ref/reindex.sgml index 07795b57372..b22d39eba92 100644 --- a/doc/src/sgml/ref/reindex.sgml +++ b/doc/src/sgml/ref/reindex.sgml @@ -478,6 +478,8 @@ Indexes: Like any long-running transaction, REINDEX on a table can affect which tuples can be removed by concurrent VACUUM on any other table. + Excepted from this are operations with the CONCURRENTLY + option for indexes that are not partial and do not index any expressions. diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index a5daea89571..d736d06d288 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -1610,7 +1610,13 @@ 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. Similarly, 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.) Do note that this means that CIC and RC must use a lock level + * that conflicts with VACUUM. * * 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 +1666,6 @@ 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 +1685,7 @@ 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 +1756,7 @@ 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); @@ -1773,11 +1777,26 @@ ComputeXidHorizons(ComputeXidHorizonsResult *h) MyDatabaseId == InvalidOid || proc->databaseId == MyDatabaseId || proc->databaseId == 0) /* always include WalSender */ { - h->data_oldest_nonremovable = - TransactionIdOlder(h->data_oldest_nonremovable, xmin); + /* + * We can ignore this backend if it's running CREATE INDEX + * CONCURRENTLY or REINDEX CONCURRENTLY on a "safe" index -- but + * only on vacuums of user-defined tables. + */ + if (!(statusFlags & PROC_IN_SAFE_IC)) + h->data_oldest_nonremovable = + TransactionIdOlder(h->data_oldest_nonremovable, xmin); + + /* Catalog tables need to consider all backends in this db */ + 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 +1818,8 @@ 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 +1846,9 @@ 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 +1871,9 @@ 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_xmin); 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 260ec7b97e9..d626731723b 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 }, -- 2.39.5