From 3763c4813593af7267c37203a09e3d04037cf304 Mon Sep 17 00:00:00 2001 From: Junwang Zhao Date: Wed, 30 Apr 2025 10:20:16 +0000 Subject: [PATCH v1] Introduce autovacuum vacuum strategy Add a new configuration option `autovacuum_vacuum_strategy` to control the order in which tables are vacuumed by the autovacuum process. Two strategies are supported for now: 1. Sequential: Tables are vacuumed in the order they are collected. 2. Random: The list of tables is rotated around a randomly chosen pivot before vacuuming to avoid always starting with the same table, which prevents vacuuming starvation for some tables. The default strategy is `sequential`. Signed-off-by: Junwang Zhao --- src/backend/postmaster/autovacuum.c | 33 +++++++++++++++++++ src/backend/utils/misc/guc_tables.c | 10 ++++++ src/backend/utils/misc/postgresql.conf.sample | 1 + src/include/postmaster/autovacuum.h | 7 ++++ src/include/utils/guc.h | 1 + 5 files changed, 52 insertions(+) diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c index 16756152b71..2452d893533 100644 --- a/src/backend/postmaster/autovacuum.c +++ b/src/backend/postmaster/autovacuum.c @@ -79,6 +79,7 @@ #include "catalog/pg_namespace.h" #include "commands/dbcommands.h" #include "commands/vacuum.h" +#include "common/pg_prng.h" #include "common/int.h" #include "lib/ilist.h" #include "libpq/pqsignal.h" @@ -132,9 +133,16 @@ int autovacuum_multixact_freeze_max_age; double autovacuum_vac_cost_delay; int autovacuum_vac_cost_limit; +int autovacuum_vac_strategy; int Log_autovacuum_min_duration = 600000; +const struct config_enum_entry autovacuum_vac_strategy_options[] = { + {"sequential", AUTOVACUUM_VAC_STRATEGY_SEQUENTIAL, false}, + {"random", AUTOVACUUM_VAC_STRATEGY_RANDOM, false}, + {NULL, 0, false} +}; + /* the minimum allowed time between two awakenings of the launcher */ #define MIN_AUTOVAC_SLEEPTIME 100.0 /* milliseconds */ #define MAX_AUTOVAC_SLEEPTIME 300 /* seconds */ @@ -2267,6 +2275,30 @@ do_autovacuum(void) "Autovacuum Portal", ALLOCSET_DEFAULT_SIZES); + /* + * Randomly rotate the list of tables to vacuum. This is to avoid always + * vacuuming the same table first, which could lead to spinning on the + * same table or vacuuming starvation. + */ + if (list_length(table_oids) > 1 && autovacuum_vac_strategy == AUTOVACUUM_VAC_STRATEGY_RANDOM) + { + + int rand = 0; + static pg_prng_state prng_state; + List *tmp_oids = NIL; + + pg_prng_seed(&prng_state, (uint64) (getpid() ^ time(NULL))); + rand = (int) pg_prng_uint64_range(&prng_state, 0, + list_length(table_oids) - 1); + if (rand != 0) + { + tmp_oids = list_copy_tail(table_oids, rand); + table_oids = list_copy_head(table_oids, + list_length(table_oids) - rand); + table_oids = list_concat(table_oids, tmp_oids); + } + } + /* * Perform operations on collected tables. */ @@ -3282,6 +3314,7 @@ AutoVacuumRequestWork(AutoVacuumWorkItemType type, Oid relationId, workitem->avw_used = true; workitem->avw_active = false; workitem->avw_type = type; + workitem->avw_database = MyDatabaseId; workitem->avw_relation = relationId; workitem->avw_blockNumber = blkno; diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c index 2f8cbd86759..c928106fd50 100644 --- a/src/backend/utils/misc/guc_tables.c +++ b/src/backend/utils/misc/guc_tables.c @@ -5418,6 +5418,16 @@ struct config_enum ConfigureNamesEnum[] = NULL, assign_io_method, NULL }, + { + {"autovacuum_vacuum_strategy", PGC_SIGHUP, VACUUM_AUTOVACUUM, + gettext_noop("Vacuum strategy for autovacuum."), + NULL + }, + &autovacuum_vac_strategy, + AUTOVACUUM_VAC_STRATEGY_SEQUENTIAL, autovacuum_vac_strategy_options, + NULL, NULL, NULL + }, + /* End-of-list marker */ { {NULL, 0, 0, NULL, NULL}, NULL, 0, NULL, NULL, NULL, NULL diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 34826d01380..5c44944008f 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -713,6 +713,7 @@ autovacuum_worker_slots = 16 # autovacuum worker slots to allocate #autovacuum_vacuum_cost_limit = -1 # default vacuum cost limit for # autovacuum, -1 means use # vacuum_cost_limit +#autovacuum_vacuum_strategy = sequential # - Cost-Based Vacuum Delay - diff --git a/src/include/postmaster/autovacuum.h b/src/include/postmaster/autovacuum.h index e8135f41a1c..218ea4ee1c8 100644 --- a/src/include/postmaster/autovacuum.h +++ b/src/include/postmaster/autovacuum.h @@ -25,6 +25,12 @@ typedef enum AVW_BRINSummarizeRange, } AutoVacuumWorkItemType; +/* Autovacuum vacuum strategies */ +enum AutovacuumVacStrategy +{ + AUTOVACUUM_VAC_STRATEGY_SEQUENTIAL = 0, + AUTOVACUUM_VAC_STRATEGY_RANDOM, +}; /* GUC variables */ extern PGDLLIMPORT bool autovacuum_start_daemon; @@ -43,6 +49,7 @@ extern PGDLLIMPORT int autovacuum_freeze_max_age; extern PGDLLIMPORT int autovacuum_multixact_freeze_max_age; extern PGDLLIMPORT double autovacuum_vac_cost_delay; extern PGDLLIMPORT int autovacuum_vac_cost_limit; +extern PGDLLIMPORT int autovacuum_vac_strategy; /* autovacuum launcher PID, only valid when worker is shutting down */ extern PGDLLIMPORT int AutovacuumLauncherPid; diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h index f619100467d..2f5c5363b03 100644 --- a/src/include/utils/guc.h +++ b/src/include/utils/guc.h @@ -322,6 +322,7 @@ extern PGDLLIMPORT const struct config_enum_entry io_method_options[]; extern PGDLLIMPORT const struct config_enum_entry recovery_target_action_options[]; extern PGDLLIMPORT const struct config_enum_entry wal_level_options[]; extern PGDLLIMPORT const struct config_enum_entry wal_sync_method_options[]; +extern PGDLLIMPORT const struct config_enum_entry autovacuum_vac_strategy_options[]; /* * Functions exported by guc.c -- 2.39.5