/*------------------------------------------------------------------------- * * autovacuum.c * * PostgreSQL Integrated Autovacuum Daemon * * The autovacuum system is structured in two different kinds of processes: the * autovacuum launcher and the autovacuum worker. The launcher is an * always-running process, started by the postmaster when the autovacuum GUC * parameter is set. The launcher schedules autovacuum workers to be started * when appropriate. The workers are the processes which execute the actual * vacuuming; they connect to a database as determined in the launcher, and * once connected they examine the catalogs to select the tables to vacuum. * * The autovacuum launcher cannot start the worker processes by itself, * because doing so would cause robustness issues (namely, failure to shut * them down on exceptional conditions, and also, since the launcher is * connected to shared memory and is thus subject to corruption there, it is * not as robust as the postmaster). So it leaves that task to the postmaster. * * There is an autovacuum shared memory area, where the launcher stores * information about the database it wants vacuumed. When it wants a new * worker to start, it sets a flag in shared memory and sends a signal to the * postmaster. Then postmaster knows nothing more than it must start a worker; * so it forks a new child, which turns into a worker. This new process * connects to shared memory, and there it can inspect the information that the * launcher has set up. * * If the fork() call fails in the postmaster, it sets a flag in the shared * memory area, and sends a signal to the launcher. The launcher, upon * noticing the flag, can try starting the worker again by resending the * signal. Note that the failure can only be transient (fork failure due to * high load, memory pressure, too many processes, etc); more permanent * problems, like failure to connect to a database, are detected later in the * worker and dealt with just by having the worker exit normally. The launcher * will launch a new worker again later, per schedule. * * When the worker is done vacuuming it sends SIGUSR2 to the launcher. The * launcher then wakes up and is able to launch another worker, if the schedule * is so tight that a new worker is needed immediately. At this time the * launcher can also balance the settings for the various remaining workers' * cost-based vacuum delay feature. * * Note that there can be more than one worker in a database concurrently. * They will store the table they are currently vacuuming in shared memory, so * that other workers avoid being blocked waiting for the vacuum lock for that * table. They will also fetch the last time the table was vacuumed from * pgstats just before vacuuming each table, to avoid vacuuming a table that * was just finished being vacuumed by another worker and thus is no longer * noted in shared memory. However, there is a small window (due to not yet * holding the relation lock) during which a worker may choose a table that was * already vacuumed; this is a bug in the current design. * * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * src/backend/postmaster/autovacuum.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include #include #include #include "access/heapam.h" #include "access/htup_details.h" #include "access/multixact.h" #include "access/reloptions.h" #include "access/tableam.h" #include "access/transam.h" #include "access/xact.h" #include "catalog/dependency.h" #include "catalog/namespace.h" #include "catalog/pg_database.h" #include "catalog/pg_namespace.h" #include "commands/dbcommands.h" #include "commands/vacuum.h" #include "common/int.h" #include "lib/ilist.h" #include "libpq/pqsignal.h" #include "miscadmin.h" #include "nodes/makefuncs.h" #include "pgstat.h" #include "postmaster/autovacuum.h" #include "postmaster/interrupt.h" #include "postmaster/postmaster.h" #include "storage/bufmgr.h" #include "storage/ipc.h" #include "storage/latch.h" #include "storage/lmgr.h" #include "storage/pmsignal.h" #include "storage/proc.h" #include "storage/procsignal.h" #include "storage/smgr.h" #include "tcop/tcopprot.h" #include "utils/fmgroids.h" #include "utils/fmgrprotos.h" #include "utils/guc_hooks.h" #include "utils/lsyscache.h" #include "utils/memutils.h" #include "utils/ps_status.h" #include "utils/rel.h" #include "utils/snapmgr.h" #include "utils/syscache.h" #include "utils/timeout.h" #include "utils/timestamp.h" /* * GUC parameters */ bool autovacuum_start_daemon = false; int autovacuum_max_workers; int autovacuum_work_mem = -1; int autovacuum_naptime; int autovacuum_vac_thresh; double autovacuum_vac_scale; int autovacuum_vac_ins_thresh; double autovacuum_vac_ins_scale; int autovacuum_anl_thresh; double autovacuum_anl_scale; int autovacuum_freeze_max_age; int autovacuum_multixact_freeze_max_age; double autovacuum_vac_cost_delay; int autovacuum_vac_cost_limit; int Log_autovacuum_min_duration = 600000; /* the minimum allowed time between two awakenings of the launcher */ #define MIN_AUTOVAC_SLEEPTIME 100.0 /* milliseconds */ #define MAX_AUTOVAC_SLEEPTIME 300 /* seconds */ /* * Variables to save the cost-related storage parameters for the current * relation being vacuumed by this autovacuum worker. Using these, we can * ensure we don't overwrite the values of vacuum_cost_delay and * vacuum_cost_limit after reloading the configuration file. They are * initialized to "invalid" values to indicate that no cost-related storage * parameters were specified and will be set in do_autovacuum() after checking * the storage parameters in table_recheck_autovac(). */ static double av_storage_param_cost_delay = -1; static int av_storage_param_cost_limit = -1; /* Flags set by signal handlers */ static volatile sig_atomic_t got_SIGUSR2 = false; /* Comparison points for determining whether freeze_max_age is exceeded */ static TransactionId recentXid; static MultiXactId recentMulti; /* Default freeze ages to use for autovacuum (varies by database) */ static int default_freeze_min_age; static int default_freeze_table_age; static int default_multixact_freeze_min_age; static int default_multixact_freeze_table_age; /* Memory context for long-lived data */ static MemoryContext AutovacMemCxt; /* struct to keep track of databases in launcher */ typedef struct avl_dbase { Oid adl_datid; /* hash key -- must be first */ TimestampTz adl_next_worker; int adl_score; dlist_node adl_node; } avl_dbase; /* struct to keep track of databases in worker */ typedef struct avw_dbase { Oid adw_datid; char *adw_name; TransactionId adw_frozenxid; MultiXactId adw_minmulti; PgStat_StatDBEntry *adw_entry; } avw_dbase; /* struct to keep track of tables to vacuum and/or analyze, in 1st pass */ typedef struct av_relation { Oid ar_toastrelid; /* hash key - must be first */ Oid ar_relid; bool ar_hasrelopts; AutoVacOpts ar_reloptions; /* copy of AutoVacOpts from the main table's * reloptions, or NULL if none */ } av_relation; /* struct to keep track of tables to vacuum and/or analyze, after rechecking */ typedef struct autovac_table { Oid at_relid; VacuumParams at_params; double at_storage_param_vac_cost_delay; int at_storage_param_vac_cost_limit; bool at_dobalance; bool at_sharedrel; char *at_relname; char *at_nspname; char *at_datname; } autovac_table; /*------------- * This struct holds information about a single worker's whereabouts. We keep * an array of these in shared memory, sized according to * autovacuum_max_workers. * * wi_links entry into free list or running list * wi_dboid OID of the database this worker is supposed to work on * wi_tableoid OID of the table currently being vacuumed, if any * wi_sharedrel flag indicating whether table is marked relisshared * wi_proc pointer to PGPROC of the running worker, NULL if not started * wi_launchtime Time at which this worker was launched * wi_dobalance Whether this worker should be included in balance calculations * * All fields are protected by AutovacuumLock, except for wi_tableoid and * wi_sharedrel which are protected by AutovacuumScheduleLock (note these * two fields are read-only for everyone except that worker itself). *------------- */ typedef struct WorkerInfoData { dlist_node wi_links; Oid wi_dboid; Oid wi_tableoid; PGPROC *wi_proc; TimestampTz wi_launchtime; pg_atomic_flag wi_dobalance; bool wi_sharedrel; } WorkerInfoData; typedef struct WorkerInfoData *WorkerInfo; /* * Possible signals received by the launcher from remote processes. These are * stored atomically in shared memory so that other processes can set them * without locking. */ typedef enum { AutoVacForkFailed, /* failed trying to start a worker */ AutoVacRebalance, /* rebalance the cost limits */ AutoVacNumSignals, /* must be last */ } AutoVacuumSignal; /* * Autovacuum workitem array, stored in AutoVacuumShmem->av_workItems. This * list is mostly protected by AutovacuumLock, except that if an item is * marked 'active' other processes must not modify the work-identifying * members. */ typedef struct AutoVacuumWorkItem { AutoVacuumWorkItemType avw_type; bool avw_used; /* below data is valid */ bool avw_active; /* being processed */ Oid avw_database; Oid avw_relation; BlockNumber avw_blockNumber; } AutoVacuumWorkItem; #define NUM_WORKITEMS 256 /*------------- * The main autovacuum shmem struct. On shared memory we store this main * struct and the array of WorkerInfo structs. This struct keeps: * * av_signal set by other processes to indicate various conditions * av_launcherpid the PID of the autovacuum launcher * av_freeWorkers the WorkerInfo freelist * av_runningWorkers the WorkerInfo non-free queue * av_startingWorker pointer to WorkerInfo currently being started (cleared by * the worker itself as soon as it's up and running) * av_workItems work item array * av_nworkersForBalance the number of autovacuum workers to use when * calculating the per worker cost limit * * This struct is protected by AutovacuumLock, except for av_signal and parts * of the worker list (see above). *------------- */ typedef struct { sig_atomic_t av_signal[AutoVacNumSignals]; pid_t av_launcherpid; dlist_head av_freeWorkers; dlist_head av_runningWorkers; WorkerInfo av_startingWorker; AutoVacuumWorkItem av_workItems[NUM_WORKITEMS]; pg_atomic_uint32 av_nworkersForBalance; } AutoVacuumShmemStruct; static AutoVacuumShmemStruct *AutoVacuumShmem; /* * the database list (of avl_dbase elements) in the launcher, and the context * that contains it */ static dlist_head DatabaseList = DLIST_STATIC_INIT(DatabaseList); static MemoryContext DatabaseListCxt = NULL; /* Pointer to my own WorkerInfo, valid on each worker */ static WorkerInfo MyWorkerInfo = NULL; /* PID of launcher, valid only in worker while shutting down */ int AutovacuumLauncherPid = 0; static Oid do_start_worker(void); static void HandleAutoVacLauncherInterrupts(void); static void AutoVacLauncherShutdown(void) pg_attribute_noreturn(); static void launcher_determine_sleep(bool canlaunch, bool recursing, struct timeval *nap); static void launch_worker(TimestampTz now); static List *get_database_list(void); static void rebuild_database_list(Oid newdb); static int db_comparator(const void *a, const void *b); static void autovac_recalculate_workers_for_balance(void); static void do_autovacuum(void); static void FreeWorkerInfo(int code, Datum arg); static autovac_table *table_recheck_autovac(Oid relid, HTAB *table_toast_map, TupleDesc pg_class_desc, int effective_multixact_freeze_max_age); static void recheck_relation_needs_vacanalyze(Oid relid, AutoVacOpts *avopts, Form_pg_class classForm, int effective_multixact_freeze_max_age, bool *dovacuum, bool *doanalyze, bool *wraparound); static void relation_needs_vacanalyze(Oid relid, AutoVacOpts *relopts, Form_pg_class classForm, PgStat_StatTabEntry *tabentry, int effective_multixact_freeze_max_age, bool *dovacuum, bool *doanalyze, bool *wraparound); static void autovacuum_do_vac_analyze(autovac_table *tab, BufferAccessStrategy bstrategy); static AutoVacOpts *extract_autovac_opts(HeapTuple tup, TupleDesc pg_class_desc); static void perform_work_item(AutoVacuumWorkItem *workitem); static void autovac_report_activity(autovac_table *tab); static void autovac_report_workitem(AutoVacuumWorkItem *workitem, const char *nspname, const char *relname); static void avl_sigusr2_handler(SIGNAL_ARGS); /******************************************************************** * AUTOVACUUM LAUNCHER CODE ********************************************************************/ /* * Main entry point for the autovacuum launcher process. */ void AutoVacLauncherMain(char *startup_data, size_t startup_data_len) { sigjmp_buf local_sigjmp_buf; Assert(startup_data_len == 0); /* Release postmaster's working memory context */ if (PostmasterContext) { MemoryContextDelete(PostmasterContext); PostmasterContext = NULL; } MyBackendType = B_AUTOVAC_LAUNCHER; init_ps_display(NULL); ereport(DEBUG1, (errmsg_internal("autovacuum launcher started"))); if (PostAuthDelay) pg_usleep(PostAuthDelay * 1000000L); SetProcessingMode(InitProcessing); /* * Set up signal handlers. We operate on databases much like a regular * backend, so we use the same signal handling. See equivalent code in * tcop/postgres.c. */ pqsignal(SIGHUP, SignalHandlerForConfigReload); pqsignal(SIGINT, StatementCancelHandler); pqsignal(SIGTERM, SignalHandlerForShutdownRequest); /* SIGQUIT handler was already set up by InitPostmasterChild */ InitializeTimeouts(); /* establishes SIGALRM handler */ pqsignal(SIGPIPE, SIG_IGN); pqsignal(SIGUSR1, procsignal_sigusr1_handler); pqsignal(SIGUSR2, avl_sigusr2_handler); pqsignal(SIGFPE, FloatExceptionHandler); pqsignal(SIGCHLD, SIG_DFL); /* * Create a per-backend PGPROC struct in shared memory. We must do this * before we can use LWLocks or access any shared memory. */ InitProcess(); /* Early initialization */ BaseInit(); InitPostgres(NULL, InvalidOid, NULL, InvalidOid, 0, NULL); SetProcessingMode(NormalProcessing); /* * Create a memory context that we will do all our work in. We do this so * that we can reset the context during error recovery and thereby avoid * possible memory leaks. */ AutovacMemCxt = AllocSetContextCreate(TopMemoryContext, "Autovacuum Launcher", ALLOCSET_DEFAULT_SIZES); MemoryContextSwitchTo(AutovacMemCxt); /* * If an exception is encountered, processing resumes here. * * This code is a stripped down version of PostgresMain error recovery. * * Note that we use sigsetjmp(..., 1), so that the prevailing signal mask * (to wit, BlockSig) will be restored when longjmp'ing to here. Thus, * signals other than SIGQUIT will be blocked until we complete error * recovery. It might seem that this policy makes the HOLD_INTERRUPTS() * call redundant, but it is not since InterruptPending might be set * already. */ if (sigsetjmp(local_sigjmp_buf, 1) != 0) { /* since not using PG_TRY, must reset error stack by hand */ error_context_stack = NULL; /* Prevents interrupts while cleaning up */ HOLD_INTERRUPTS(); /* Forget any pending QueryCancel or timeout request */ disable_all_timeouts(false); QueryCancelPending = false; /* second to avoid race condition */ /* Report the error to the server log */ EmitErrorReport(); /* Abort the current transaction in order to recover */ AbortCurrentTransaction(); /* * Release any other resources, for the case where we were not in a * transaction. */ LWLockReleaseAll(); pgstat_report_wait_end(); UnlockBuffers(); /* this is probably dead code, but let's be safe: */ if (AuxProcessResourceOwner) ReleaseAuxProcessResources(false); AtEOXact_Buffers(false); AtEOXact_SMgr(); AtEOXact_Files(false); AtEOXact_HashTables(false); /* * Now return to normal top-level context and clear ErrorContext for * next time. */ MemoryContextSwitchTo(AutovacMemCxt); FlushErrorState(); /* Flush any leaked data in the top-level context */ MemoryContextReset(AutovacMemCxt); /* don't leave dangling pointers to freed memory */ DatabaseListCxt = NULL; dlist_init(&DatabaseList); /* Now we can allow interrupts again */ RESUME_INTERRUPTS(); /* if in shutdown mode, no need for anything further; just go away */ if (ShutdownRequestPending) AutoVacLauncherShutdown(); /* * Sleep at least 1 second after any error. We don't want to be * filling the error logs as fast as we can. */ pg_usleep(1000000L); } /* We can now handle ereport(ERROR) */ PG_exception_stack = &local_sigjmp_buf; /* must unblock signals before calling rebuild_database_list */ sigprocmask(SIG_SETMASK, &UnBlockSig, NULL); /* * Set always-secure search path. Launcher doesn't connect to a database, * so this has no effect. */ SetConfigOption("search_path", "", PGC_SUSET, PGC_S_OVERRIDE); /* * Force zero_damaged_pages OFF in the autovac process, even if it is set * in postgresql.conf. We don't really want such a dangerous option being * applied non-interactively. */ SetConfigOption("zero_damaged_pages", "false", PGC_SUSET, PGC_S_OVERRIDE); /* * Force settable timeouts off to avoid letting these settings prevent * regular maintenance from being executed. */ SetConfigOption("statement_timeout", "0", PGC_SUSET, PGC_S_OVERRIDE); SetConfigOption("transaction_timeout", "0", PGC_SUSET, PGC_S_OVERRIDE); SetConfigOption("lock_timeout", "0", PGC_SUSET, PGC_S_OVERRIDE); SetConfigOption("idle_in_transaction_session_timeout", "0", PGC_SUSET, PGC_S_OVERRIDE); /* * Force default_transaction_isolation to READ COMMITTED. We don't want * to pay the overhead of serializable mode, nor add any risk of causing * deadlocks or delaying other transactions. */ SetConfigOption("default_transaction_isolation", "read committed", PGC_SUSET, PGC_S_OVERRIDE); /* * Even when system is configured to use a different fetch consistency, * for autovac we always want fresh stats. */ SetConfigOption("stats_fetch_consistency", "none", PGC_SUSET, PGC_S_OVERRIDE); /* * In emergency mode, just start a worker (unless shutdown was requested) * and go away. */ if (!AutoVacuumingActive()) { if (!ShutdownRequestPending) do_start_worker(); proc_exit(0); /* done */ } AutoVacuumShmem->av_launcherpid = MyProcPid; /* * Create the initial database list. The invariant we want this list to * keep is that it's ordered by decreasing next_time. As soon as an entry * is updated to a higher time, it will be moved to the front (which is * correct because the only operation is to add autovacuum_naptime to the * entry, and time always increases). */ rebuild_database_list(InvalidOid); /* loop until shutdown request */ while (!ShutdownRequestPending) { struct timeval nap; TimestampTz current_time = 0; bool can_launch; /* * This loop is a bit different from the normal use of WaitLatch, * because we'd like to sleep before the first launch of a child * process. So it's WaitLatch, then ResetLatch, then check for * wakening conditions. */ launcher_determine_sleep(!dlist_is_empty(&AutoVacuumShmem->av_freeWorkers), false, &nap); /* * Wait until naptime expires or we get some type of signal (all the * signal handlers will wake us by calling SetLatch). */ (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH, (nap.tv_sec * 1000L) + (nap.tv_usec / 1000L), WAIT_EVENT_AUTOVACUUM_MAIN); ResetLatch(MyLatch); HandleAutoVacLauncherInterrupts(); /* * a worker finished, or postmaster signaled failure to start a worker */ if (got_SIGUSR2) { got_SIGUSR2 = false; /* rebalance cost limits, if needed */ if (AutoVacuumShmem->av_signal[AutoVacRebalance]) { LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE); AutoVacuumShmem->av_signal[AutoVacRebalance] = false; autovac_recalculate_workers_for_balance(); LWLockRelease(AutovacuumLock); } if (AutoVacuumShmem->av_signal[AutoVacForkFailed]) { /* * If the postmaster failed to start a new worker, we sleep * for a little while and resend the signal. The new worker's * state is still in memory, so this is sufficient. After * that, we restart the main loop. * * XXX should we put a limit to the number of times we retry? * I don't think it makes much sense, because a future start * of a worker will continue to fail in the same way. */ AutoVacuumShmem->av_signal[AutoVacForkFailed] = false; pg_usleep(1000000L); /* 1s */ SendPostmasterSignal(PMSIGNAL_START_AUTOVAC_WORKER); continue; } } /* * There are some conditions that we need to check before trying to * start a worker. First, we need to make sure that there is a worker * slot available. Second, we need to make sure that no other worker * failed while starting up. */ current_time = GetCurrentTimestamp(); LWLockAcquire(AutovacuumLock, LW_SHARED); can_launch = !dlist_is_empty(&AutoVacuumShmem->av_freeWorkers); if (AutoVacuumShmem->av_startingWorker != NULL) { int waittime; WorkerInfo worker = AutoVacuumShmem->av_startingWorker; /* * We can't launch another worker when another one is still * starting up (or failed while doing so), so just sleep for a bit * more; that worker will wake us up again as soon as it's ready. * We will only wait autovacuum_naptime seconds (up to a maximum * of 60 seconds) for this to happen however. Note that failure * to connect to a particular database is not a problem here, * because the worker removes itself from the startingWorker * pointer before trying to connect. Problems detected by the * postmaster (like fork() failure) are also reported and handled * differently. The only problems that may cause this code to * fire are errors in the earlier sections of AutoVacWorkerMain, * before the worker removes the WorkerInfo from the * startingWorker pointer. */ waittime = Min(autovacuum_naptime, 60) * 1000; if (TimestampDifferenceExceeds(worker->wi_launchtime, current_time, waittime)) { LWLockRelease(AutovacuumLock); LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE); /* * No other process can put a worker in starting mode, so if * startingWorker is still INVALID after exchanging our lock, * we assume it's the same one we saw above (so we don't * recheck the launch time). */ if (AutoVacuumShmem->av_startingWorker != NULL) { worker = AutoVacuumShmem->av_startingWorker; worker->wi_dboid = InvalidOid; worker->wi_tableoid = InvalidOid; worker->wi_sharedrel = false; worker->wi_proc = NULL; worker->wi_launchtime = 0; dlist_push_head(&AutoVacuumShmem->av_freeWorkers, &worker->wi_links); AutoVacuumShmem->av_startingWorker = NULL; ereport(WARNING, errmsg("autovacuum worker took too long to start; canceled")); } } else can_launch = false; } LWLockRelease(AutovacuumLock); /* either shared or exclusive */ /* if we can't do anything, just go back to sleep */ if (!can_launch) continue; /* We're OK to start a new worker */ if (dlist_is_empty(&DatabaseList)) { /* * Special case when the list is empty: start a worker right away. * This covers the initial case, when no database is in pgstats * (thus the list is empty). Note that the constraints in * launcher_determine_sleep keep us from starting workers too * quickly (at most once every autovacuum_naptime when the list is * empty). */ launch_worker(current_time); } else { /* * because rebuild_database_list constructs a list with most * distant adl_next_worker first, we obtain our database from the * tail of the list. */ avl_dbase *avdb; avdb = dlist_tail_element(avl_dbase, adl_node, &DatabaseList); /* * launch a worker if next_worker is right now or it is in the * past */ if (TimestampDifferenceExceeds(avdb->adl_next_worker, current_time, 0)) launch_worker(current_time); } } AutoVacLauncherShutdown(); } /* * Process any new interrupts. */ static void HandleAutoVacLauncherInterrupts(void) { /* the normal shutdown case */ if (ShutdownRequestPending) AutoVacLauncherShutdown(); if (ConfigReloadPending) { ConfigReloadPending = false; ProcessConfigFile(PGC_SIGHUP); /* shutdown requested in config file? */ if (!AutoVacuumingActive()) AutoVacLauncherShutdown(); /* rebuild the list in case the naptime changed */ rebuild_database_list(InvalidOid); } /* Process barrier events */ if (ProcSignalBarrierPending) ProcessProcSignalBarrier(); /* Perform logging of memory contexts of this process */ if (LogMemoryContextPending) ProcessLogMemoryContextInterrupt(); /* Process sinval catchup interrupts that happened while sleeping */ ProcessCatchupInterrupt(); } /* * Perform a normal exit from the autovac launcher. */ static void AutoVacLauncherShutdown(void) { ereport(DEBUG1, (errmsg_internal("autovacuum launcher shutting down"))); AutoVacuumShmem->av_launcherpid = 0; proc_exit(0); /* done */ } /* * Determine the time to sleep, based on the database list. * * The "canlaunch" parameter indicates whether we can start a worker right now, * for example due to the workers being all busy. If this is false, we will * cause a long sleep, which will be interrupted when a worker exits. */ static void launcher_determine_sleep(bool canlaunch, bool recursing, struct timeval *nap) { /* * We sleep until the next scheduled vacuum. We trust that when the * database list was built, care was taken so that no entries have times * in the past; if the first entry has too close a next_worker value, or a * time in the past, we will sleep a small nominal time. */ if (!canlaunch) { nap->tv_sec = autovacuum_naptime; nap->tv_usec = 0; } else if (!dlist_is_empty(&DatabaseList)) { TimestampTz current_time = GetCurrentTimestamp(); TimestampTz next_wakeup; avl_dbase *avdb; long secs; int usecs; avdb = dlist_tail_element(avl_dbase, adl_node, &DatabaseList); next_wakeup = avdb->adl_next_worker; TimestampDifference(current_time, next_wakeup, &secs, &usecs); nap->tv_sec = secs; nap->tv_usec = usecs; } else { /* list is empty, sleep for whole autovacuum_naptime seconds */ nap->tv_sec = autovacuum_naptime; nap->tv_usec = 0; } /* * If the result is exactly zero, it means a database had an entry with * time in the past. Rebuild the list so that the databases are evenly * distributed again, and recalculate the time to sleep. This can happen * if there are more tables needing vacuum than workers, and they all take * longer to vacuum than autovacuum_naptime. * * We only recurse once. rebuild_database_list should always return times * in the future, but it seems best not to trust too much on that. */ if (nap->tv_sec == 0 && nap->tv_usec == 0 && !recursing) { rebuild_database_list(InvalidOid); launcher_determine_sleep(canlaunch, true, nap); return; } /* The smallest time we'll allow the launcher to sleep. */ if (nap->tv_sec <= 0 && nap->tv_usec <= MIN_AUTOVAC_SLEEPTIME * 1000) { nap->tv_sec = 0; nap->tv_usec = MIN_AUTOVAC_SLEEPTIME * 1000; } /* * If the sleep time is too large, clamp it to an arbitrary maximum (plus * any fractional seconds, for simplicity). This avoids an essentially * infinite sleep in strange cases like the system clock going backwards a * few years. */ if (nap->tv_sec > MAX_AUTOVAC_SLEEPTIME) nap->tv_sec = MAX_AUTOVAC_SLEEPTIME; } /* * Build an updated DatabaseList. It must only contain databases that appear * in pgstats, and must be sorted by next_worker from highest to lowest, * distributed regularly across the next autovacuum_naptime interval. * * Receives the Oid of the database that made this list be generated (we call * this the "new" database, because when the database was already present on * the list, we expect that this function is not called at all). The * preexisting list, if any, will be used to preserve the order of the * databases in the autovacuum_naptime period. The new database is put at the * end of the interval. The actual values are not saved, which should not be * much of a problem. */ static void rebuild_database_list(Oid newdb) { List *dblist; ListCell *cell; MemoryContext newcxt; MemoryContext oldcxt; MemoryContext tmpcxt; HASHCTL hctl; int score; int nelems; HTAB *dbhash; dlist_iter iter; newcxt = AllocSetContextCreate(AutovacMemCxt, "Autovacuum database list", ALLOCSET_DEFAULT_SIZES); tmpcxt = AllocSetContextCreate(newcxt, "Autovacuum database list (tmp)", ALLOCSET_DEFAULT_SIZES); oldcxt = MemoryContextSwitchTo(tmpcxt); /* * Implementing this is not as simple as it sounds, because we need to put * the new database at the end of the list; next the databases that were * already on the list, and finally (at the tail of the list) all the * other databases that are not on the existing list. * * To do this, we build an empty hash table of scored databases. We will * start with the lowest score (zero) for the new database, then * increasing scores for the databases in the existing list, in order, and * lastly increasing scores for all databases gotten via * get_database_list() that are not already on the hash. * * Then we will put all the hash elements into an array, sort the array by * score, and finally put the array elements into the new doubly linked * list. */ hctl.keysize = sizeof(Oid); hctl.entrysize = sizeof(avl_dbase); hctl.hcxt = tmpcxt; dbhash = hash_create("autovacuum db hash", 20, &hctl, /* magic number here * FIXME */ HASH_ELEM | HASH_BLOBS | HASH_CONTEXT); /* start by inserting the new database */ score = 0; if (OidIsValid(newdb)) { avl_dbase *db; PgStat_StatDBEntry *entry; /* only consider this database if it has a pgstat entry */ entry = pgstat_fetch_stat_dbentry(newdb); if (entry != NULL) { /* we assume it isn't found because the hash was just created */ db = hash_search(dbhash, &newdb, HASH_ENTER, NULL); /* hash_search already filled in the key */ db->adl_score = score++; /* next_worker is filled in later */ } } /* Now insert the databases from the existing list */ dlist_foreach(iter, &DatabaseList) { avl_dbase *avdb = dlist_container(avl_dbase, adl_node, iter.cur); avl_dbase *db; bool found; PgStat_StatDBEntry *entry; /* * skip databases with no stat entries -- in particular, this gets rid * of dropped databases */ entry = pgstat_fetch_stat_dbentry(avdb->adl_datid); if (entry == NULL) continue; db = hash_search(dbhash, &(avdb->adl_datid), HASH_ENTER, &found); if (!found) { /* hash_search already filled in the key */ db->adl_score = score++; /* next_worker is filled in later */ } } /* finally, insert all qualifying databases not previously inserted */ dblist = get_database_list(); foreach(cell, dblist) { avw_dbase *avdb = lfirst(cell); avl_dbase *db; bool found; PgStat_StatDBEntry *entry; /* only consider databases with a pgstat entry */ entry = pgstat_fetch_stat_dbentry(avdb->adw_datid); if (entry == NULL) continue; db = hash_search(dbhash, &(avdb->adw_datid), HASH_ENTER, &found); /* only update the score if the database was not already on the hash */ if (!found) { /* hash_search already filled in the key */ db->adl_score = score++; /* next_worker is filled in later */ } } nelems = score; /* from here on, the allocated memory belongs to the new list */ MemoryContextSwitchTo(newcxt); dlist_init(&DatabaseList); if (nelems > 0) { TimestampTz current_time; int millis_increment; avl_dbase *dbary; avl_dbase *db; HASH_SEQ_STATUS seq; int i; /* put all the hash elements into an array */ dbary = palloc(nelems * sizeof(avl_dbase)); i = 0; hash_seq_init(&seq, dbhash); while ((db = hash_seq_search(&seq)) != NULL) memcpy(&(dbary[i++]), db, sizeof(avl_dbase)); /* sort the array */ qsort(dbary, nelems, sizeof(avl_dbase), db_comparator); /* * Determine the time interval between databases in the schedule. If * we see that the configured naptime would take us to sleep times * lower than our min sleep time (which launcher_determine_sleep is * coded not to allow), silently use a larger naptime (but don't touch * the GUC variable). */ millis_increment = 1000.0 * autovacuum_naptime / nelems; if (millis_increment <= MIN_AUTOVAC_SLEEPTIME) millis_increment = MIN_AUTOVAC_SLEEPTIME * 1.1; current_time = GetCurrentTimestamp(); /* * move the elements from the array into the dlist, setting the * next_worker while walking the array */ for (i = 0; i < nelems; i++) { db = &(dbary[i]); current_time = TimestampTzPlusMilliseconds(current_time, millis_increment); db->adl_next_worker = current_time; /* later elements should go closer to the head of the list */ dlist_push_head(&DatabaseList, &db->adl_node); } } /* all done, clean up memory */ if (DatabaseListCxt != NULL) MemoryContextDelete(DatabaseListCxt); MemoryContextDelete(tmpcxt); DatabaseListCxt = newcxt; MemoryContextSwitchTo(oldcxt); } /* qsort comparator for avl_dbase, using adl_score */ static int db_comparator(const void *a, const void *b) { return pg_cmp_s32(((const avl_dbase *) a)->adl_score, ((const avl_dbase *) b)->adl_score); } /* * do_start_worker * * Bare-bones procedure for starting an autovacuum worker from the launcher. * It determines what database to work on, sets up shared memory stuff and * signals postmaster to start the worker. It fails gracefully if invoked when * autovacuum_workers are already active. * * Return value is the OID of the database that the worker is going to process, * or InvalidOid if no worker was actually started. */ static Oid do_start_worker(void) { List *dblist; ListCell *cell; TransactionId xidForceLimit; MultiXactId multiForceLimit; bool for_xid_wrap; bool for_multi_wrap; avw_dbase *avdb; TimestampTz current_time; bool skipit = false; Oid retval = InvalidOid; MemoryContext tmpcxt, oldcxt; /* return quickly when there are no free workers */ LWLockAcquire(AutovacuumLock, LW_SHARED); if (dlist_is_empty(&AutoVacuumShmem->av_freeWorkers)) { LWLockRelease(AutovacuumLock); return InvalidOid; } LWLockRelease(AutovacuumLock); /* * Create and switch to a temporary context to avoid leaking the memory * allocated for the database list. */ tmpcxt = AllocSetContextCreate(CurrentMemoryContext, "Autovacuum start worker (tmp)", ALLOCSET_DEFAULT_SIZES); oldcxt = MemoryContextSwitchTo(tmpcxt); /* Get a list of databases */ dblist = get_database_list(); /* * Determine the oldest datfrozenxid/relfrozenxid that we will allow to * pass without forcing a vacuum. (This limit can be tightened for * particular tables, but not loosened.) */ recentXid = ReadNextTransactionId(); xidForceLimit = recentXid - autovacuum_freeze_max_age; /* ensure it's a "normal" XID, else TransactionIdPrecedes misbehaves */ /* this can cause the limit to go backwards by 3, but that's OK */ if (xidForceLimit < FirstNormalTransactionId) xidForceLimit -= FirstNormalTransactionId; /* Also determine the oldest datminmxid we will consider. */ recentMulti = ReadNextMultiXactId(); multiForceLimit = recentMulti - MultiXactMemberFreezeThreshold(); if (multiForceLimit < FirstMultiXactId) multiForceLimit -= FirstMultiXactId; /* * Choose a database to connect to. We pick the database that was least * recently auto-vacuumed, or one that needs vacuuming to prevent Xid * wraparound-related data loss. If any db at risk of Xid wraparound is * found, we pick the one with oldest datfrozenxid, independently of * autovacuum times; similarly we pick the one with the oldest datminmxid * if any is in MultiXactId wraparound. Note that those in Xid wraparound * danger are given more priority than those in multi wraparound danger. * * Note that a database with no stats entry is not considered, except for * Xid wraparound purposes. The theory is that if no one has ever * connected to it since the stats were last initialized, it doesn't need * vacuuming. * * XXX This could be improved if we had more info about whether it needs * vacuuming before connecting to it. Perhaps look through the pgstats * data for the database's tables? One idea is to keep track of the * number of new and dead tuples per database in pgstats. However it * isn't clear how to construct a metric that measures that and not cause * starvation for less busy databases. */ avdb = NULL; for_xid_wrap = false; for_multi_wrap = false; current_time = GetCurrentTimestamp(); foreach(cell, dblist) { avw_dbase *tmp = lfirst(cell); dlist_iter iter; /* Check to see if this one is at risk of wraparound */ if (TransactionIdPrecedes(tmp->adw_frozenxid, xidForceLimit)) { if (avdb == NULL || TransactionIdPrecedes(tmp->adw_frozenxid, avdb->adw_frozenxid)) avdb = tmp; for_xid_wrap = true; continue; } else if (for_xid_wrap) continue; /* ignore not-at-risk DBs */ else if (MultiXactIdPrecedes(tmp->adw_minmulti, multiForceLimit)) { if (avdb == NULL || MultiXactIdPrecedes(tmp->adw_minmulti, avdb->adw_minmulti)) avdb = tmp; for_multi_wrap = true; continue; } else if (for_multi_wrap) continue; /* ignore not-at-risk DBs */ /* Find pgstat entry if any */ tmp->adw_entry = pgstat_fetch_stat_dbentry(tmp->adw_datid); /* * Skip a database with no pgstat entry; it means it hasn't seen any * activity. */ if (!tmp->adw_entry) continue; /* * Also, skip a database that appears on the database list as having * been processed recently (less than autovacuum_naptime seconds ago). * We do this so that we don't select a database which we just * selected, but that pgstat hasn't gotten around to updating the last * autovacuum time yet. */ skipit = false; dlist_reverse_foreach(iter, &DatabaseList) { avl_dbase *dbp = dlist_container(avl_dbase, adl_node, iter.cur); if (dbp->adl_datid == tmp->adw_datid) { /* * Skip this database if its next_worker value falls between * the current time and the current time plus naptime. */ if (!TimestampDifferenceExceeds(dbp->adl_next_worker, current_time, 0) && !TimestampDifferenceExceeds(current_time, dbp->adl_next_worker, autovacuum_naptime * 1000)) skipit = true; break; } } if (skipit) continue; /* * Remember the db with oldest autovac time. (If we are here, both * tmp->entry and db->entry must be non-null.) */ if (avdb == NULL || tmp->adw_entry->last_autovac_time < avdb->adw_entry->last_autovac_time) avdb = tmp; } /* Found a database -- process it */ if (avdb != NULL) { WorkerInfo worker; dlist_node *wptr; LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE); /* * Get a worker entry from the freelist. We checked above, so there * really should be a free slot. */ wptr = dlist_pop_head_node(&AutoVacuumShmem->av_freeWorkers); worker = dlist_container(WorkerInfoData, wi_links, wptr); worker->wi_dboid = avdb->adw_datid; worker->wi_proc = NULL; worker->wi_launchtime = GetCurrentTimestamp(); AutoVacuumShmem->av_startingWorker = worker; LWLockRelease(AutovacuumLock); SendPostmasterSignal(PMSIGNAL_START_AUTOVAC_WORKER); retval = avdb->adw_datid; } else if (skipit) { /* * If we skipped all databases on the list, rebuild it, because it * probably contains a dropped database. */ rebuild_database_list(InvalidOid); } MemoryContextSwitchTo(oldcxt); MemoryContextDelete(tmpcxt); return retval; } /* * launch_worker * * Wrapper for starting a worker from the launcher. Besides actually starting * it, update the database list to reflect the next time that another one will * need to be started on the selected database. The actual database choice is * left to do_start_worker. * * This routine is also expected to insert an entry into the database list if * the selected database was previously absent from the list. */ static void launch_worker(TimestampTz now) { Oid dbid; dlist_iter iter; dbid = do_start_worker(); if (OidIsValid(dbid)) { bool found = false; /* * Walk the database list and update the corresponding entry. If the * database is not on the list, we'll recreate the list. */ dlist_foreach(iter, &DatabaseList) { avl_dbase *avdb = dlist_container(avl_dbase, adl_node, iter.cur); if (avdb->adl_datid == dbid) { found = true; /* * add autovacuum_naptime seconds to the current time, and use * that as the new "next_worker" field for this database. */ avdb->adl_next_worker = TimestampTzPlusMilliseconds(now, autovacuum_naptime * 1000); dlist_move_head(&DatabaseList, iter.cur); break; } } /* * If the database was not present in the database list, we rebuild * the list. It's possible that the database does not get into the * list anyway, for example if it's a database that doesn't have a * pgstat entry, but this is not a problem because we don't want to * schedule workers regularly into those in any case. */ if (!found) rebuild_database_list(dbid); } } /* * Called from postmaster to signal a failure to fork a process to become * worker. The postmaster should kill(SIGUSR2) the launcher shortly * after calling this function. */ void AutoVacWorkerFailed(void) { AutoVacuumShmem->av_signal[AutoVacForkFailed] = true; } /* SIGUSR2: a worker is up and running, or just finished, or failed to fork */ static void avl_sigusr2_handler(SIGNAL_ARGS) { got_SIGUSR2 = true; SetLatch(MyLatch); } /******************************************************************** * AUTOVACUUM WORKER CODE ********************************************************************/ /* * Main entry point for autovacuum worker processes. */ void AutoVacWorkerMain(char *startup_data, size_t startup_data_len) { sigjmp_buf local_sigjmp_buf; Oid dbid; Assert(startup_data_len == 0); /* Release postmaster's working memory context */ if (PostmasterContext) { MemoryContextDelete(PostmasterContext); PostmasterContext = NULL; } MyBackendType = B_AUTOVAC_WORKER; init_ps_display(NULL); SetProcessingMode(InitProcessing); /* * Set up signal handlers. We operate on databases much like a regular * backend, so we use the same signal handling. See equivalent code in * tcop/postgres.c. */ pqsignal(SIGHUP, SignalHandlerForConfigReload); /* * SIGINT is used to signal canceling the current table's vacuum; SIGTERM * means abort and exit cleanly, and SIGQUIT means abandon ship. */ pqsignal(SIGINT, StatementCancelHandler); pqsignal(SIGTERM, die); /* SIGQUIT handler was already set up by InitPostmasterChild */ InitializeTimeouts(); /* establishes SIGALRM handler */ pqsignal(SIGPIPE, SIG_IGN); pqsignal(SIGUSR1, procsignal_sigusr1_handler); pqsignal(SIGUSR2, SIG_IGN); pqsignal(SIGFPE, FloatExceptionHandler); pqsignal(SIGCHLD, SIG_DFL); /* * Create a per-backend PGPROC struct in shared memory. We must do this * before we can use LWLocks or access any shared memory. */ InitProcess(); /* Early initialization */ BaseInit(); /* * If an exception is encountered, processing resumes here. * * Unlike most auxiliary processes, we don't attempt to continue * processing after an error; we just clean up and exit. The autovac * launcher is responsible for spawning another worker later. * * Note that we use sigsetjmp(..., 1), so that the prevailing signal mask * (to wit, BlockSig) will be restored when longjmp'ing to here. Thus, * signals other than SIGQUIT will be blocked until we exit. It might * seem that this policy makes the HOLD_INTERRUPTS() call redundant, but * it is not since InterruptPending might be set already. */ if (sigsetjmp(local_sigjmp_buf, 1) != 0) { /* since not using PG_TRY, must reset error stack by hand */ error_context_stack = NULL; /* Prevents interrupts while cleaning up */ HOLD_INTERRUPTS(); /* Report the error to the server log */ EmitErrorReport(); /* * We can now go away. Note that because we called InitProcess, a * callback was registered to do ProcKill, which will clean up * necessary state. */ proc_exit(0); } /* We can now handle ereport(ERROR) */ PG_exception_stack = &local_sigjmp_buf; sigprocmask(SIG_SETMASK, &UnBlockSig, NULL); /* * Set always-secure search path, so malicious users can't redirect user * code (e.g. pg_index.indexprs). (That code runs in a * SECURITY_RESTRICTED_OPERATION sandbox, so malicious users could not * take control of the entire autovacuum worker in any case.) */ SetConfigOption("search_path", "", PGC_SUSET, PGC_S_OVERRIDE); /* * Force zero_damaged_pages OFF in the autovac process, even if it is set * in postgresql.conf. We don't really want such a dangerous option being * applied non-interactively. */ SetConfigOption("zero_damaged_pages", "false", PGC_SUSET, PGC_S_OVERRIDE); /* * Force settable timeouts off to avoid letting these settings prevent * regular maintenance from being executed. */ SetConfigOption("statement_timeout", "0", PGC_SUSET, PGC_S_OVERRIDE); SetConfigOption("transaction_timeout", "0", PGC_SUSET, PGC_S_OVERRIDE); SetConfigOption("lock_timeout", "0", PGC_SUSET, PGC_S_OVERRIDE); SetConfigOption("idle_in_transaction_session_timeout", "0", PGC_SUSET, PGC_S_OVERRIDE); /* * Force default_transaction_isolation to READ COMMITTED. We don't want * to pay the overhead of serializable mode, nor add any risk of causing * deadlocks or delaying other transactions. */ SetConfigOption("default_transaction_isolation", "read committed", PGC_SUSET, PGC_S_OVERRIDE); /* * Force synchronous replication off to allow regular maintenance even if * we are waiting for standbys to connect. This is important to ensure we * aren't blocked from performing anti-wraparound tasks. */ if (synchronous_commit > SYNCHRONOUS_COMMIT_LOCAL_FLUSH) SetConfigOption("synchronous_commit", "local", PGC_SUSET, PGC_S_OVERRIDE); /* * Even when system is configured to use a different fetch consistency, * for autovac we always want fresh stats. */ SetConfigOption("stats_fetch_consistency", "none", PGC_SUSET, PGC_S_OVERRIDE); /* * Get the info about the database we're going to work on. */ LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE); /* * beware of startingWorker being INVALID; this should normally not * happen, but if a worker fails after forking and before this, the * launcher might have decided to remove it from the queue and start * again. */ if (AutoVacuumShmem->av_startingWorker != NULL) { MyWorkerInfo = AutoVacuumShmem->av_startingWorker; dbid = MyWorkerInfo->wi_dboid; MyWorkerInfo->wi_proc = MyProc; /* insert into the running list */ dlist_push_head(&AutoVacuumShmem->av_runningWorkers, &MyWorkerInfo->wi_links); /* * remove from the "starting" pointer, so that the launcher can start * a new worker if required */ AutoVacuumShmem->av_startingWorker = NULL; LWLockRelease(AutovacuumLock); on_shmem_exit(FreeWorkerInfo, 0); /* wake up the launcher */ if (AutoVacuumShmem->av_launcherpid != 0) kill(AutoVacuumShmem->av_launcherpid, SIGUSR2); } else { /* no worker entry for me, go away */ elog(WARNING, "autovacuum worker started without a worker entry"); dbid = InvalidOid; LWLockRelease(AutovacuumLock); } if (OidIsValid(dbid)) { char dbname[NAMEDATALEN]; /* * Report autovac startup to the cumulative stats system. We * deliberately do this before InitPostgres, so that the * last_autovac_time will get updated even if the connection attempt * fails. This is to prevent autovac from getting "stuck" repeatedly * selecting an unopenable database, rather than making any progress * on stuff it can connect to. */ pgstat_report_autovac(dbid); /* * Connect to the selected database, specifying no particular user * * Note: if we have selected a just-deleted database (due to using * stale stats info), we'll fail and exit here. */ InitPostgres(NULL, dbid, NULL, InvalidOid, 0, dbname); SetProcessingMode(NormalProcessing); set_ps_display(dbname); ereport(DEBUG1, (errmsg_internal("autovacuum: processing database \"%s\"", dbname))); if (PostAuthDelay) pg_usleep(PostAuthDelay * 1000000L); /* And do an appropriate amount of work */ recentXid = ReadNextTransactionId(); recentMulti = ReadNextMultiXactId(); do_autovacuum(); } /* * The launcher will be notified of my death in ProcKill, *if* we managed * to get a worker slot at all */ /* All done, go away */ proc_exit(0); } /* * Return a WorkerInfo to the free list */ static void FreeWorkerInfo(int code, Datum arg) { if (MyWorkerInfo != NULL) { LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE); /* * Wake the launcher up so that he can launch a new worker immediately * if required. We only save the launcher's PID in local memory here; * the actual signal will be sent when the PGPROC is recycled. Note * that we always do this, so that the launcher can rebalance the cost * limit setting of the remaining workers. * * We somewhat ignore the risk that the launcher changes its PID * between us reading it and the actual kill; we expect ProcKill to be * called shortly after us, and we assume that PIDs are not reused too * quickly after a process exits. */ AutovacuumLauncherPid = AutoVacuumShmem->av_launcherpid; dlist_delete(&MyWorkerInfo->wi_links); MyWorkerInfo->wi_dboid = InvalidOid; MyWorkerInfo->wi_tableoid = InvalidOid; MyWorkerInfo->wi_sharedrel = false; MyWorkerInfo->wi_proc = NULL; MyWorkerInfo->wi_launchtime = 0; pg_atomic_clear_flag(&MyWorkerInfo->wi_dobalance); dlist_push_head(&AutoVacuumShmem->av_freeWorkers, &MyWorkerInfo->wi_links); /* not mine anymore */ MyWorkerInfo = NULL; /* * now that we're inactive, cause a rebalancing of the surviving * workers */ AutoVacuumShmem->av_signal[AutoVacRebalance] = true; LWLockRelease(AutovacuumLock); } } /* * Update vacuum cost-based delay-related parameters for autovacuum workers and * backends executing VACUUM or ANALYZE using the value of relevant GUCs and * global state. This must be called during setup for vacuum and after every * config reload to ensure up-to-date values. */ void VacuumUpdateCosts(void) { if (MyWorkerInfo) { if (av_storage_param_cost_delay >= 0) vacuum_cost_delay = av_storage_param_cost_delay; else if (autovacuum_vac_cost_delay >= 0) vacuum_cost_delay = autovacuum_vac_cost_delay; else /* fall back to VacuumCostDelay */ vacuum_cost_delay = VacuumCostDelay; AutoVacuumUpdateCostLimit(); } else { /* Must be explicit VACUUM or ANALYZE */ vacuum_cost_delay = VacuumCostDelay; vacuum_cost_limit = VacuumCostLimit; } /* * If configuration changes are allowed to impact VacuumCostActive, make * sure it is updated. */ if (VacuumFailsafeActive) Assert(!VacuumCostActive); else if (vacuum_cost_delay > 0) VacuumCostActive = true; else { VacuumCostActive = false; VacuumCostBalance = 0; } /* * Since the cost logging requires a lock, avoid rendering the log message * in case we are using a message level where the log wouldn't be emitted. */ if (MyWorkerInfo && message_level_is_interesting(DEBUG2)) { Oid dboid, tableoid; Assert(!LWLockHeldByMe(AutovacuumLock)); LWLockAcquire(AutovacuumLock, LW_SHARED); dboid = MyWorkerInfo->wi_dboid; tableoid = MyWorkerInfo->wi_tableoid; LWLockRelease(AutovacuumLock); elog(DEBUG2, "Autovacuum VacuumUpdateCosts(db=%u, rel=%u, dobalance=%s, cost_limit=%d, cost_delay=%g active=%s failsafe=%s)", dboid, tableoid, pg_atomic_unlocked_test_flag(&MyWorkerInfo->wi_dobalance) ? "no" : "yes", vacuum_cost_limit, vacuum_cost_delay, vacuum_cost_delay > 0 ? "yes" : "no", VacuumFailsafeActive ? "yes" : "no"); } } /* * Update vacuum_cost_limit with the correct value for an autovacuum worker, * given the value of other relevant cost limit parameters and the number of * workers across which the limit must be balanced. Autovacuum workers must * call this regularly in case av_nworkersForBalance has been updated by * another worker or by the autovacuum launcher. They must also call it after a * config reload. */ void AutoVacuumUpdateCostLimit(void) { if (!MyWorkerInfo) return; /* * note: in cost_limit, zero also means use value from elsewhere, because * zero is not a valid value. */ if (av_storage_param_cost_limit > 0) vacuum_cost_limit = av_storage_param_cost_limit; else { int nworkers_for_balance; if (autovacuum_vac_cost_limit > 0) vacuum_cost_limit = autovacuum_vac_cost_limit; else vacuum_cost_limit = VacuumCostLimit; /* Only balance limit if no cost-related storage parameters specified */ if (pg_atomic_unlocked_test_flag(&MyWorkerInfo->wi_dobalance)) return; Assert(vacuum_cost_limit > 0); nworkers_for_balance = pg_atomic_read_u32(&AutoVacuumShmem->av_nworkersForBalance); /* There is at least 1 autovac worker (this worker) */ if (nworkers_for_balance <= 0) elog(ERROR, "nworkers_for_balance must be > 0"); vacuum_cost_limit = Max(vacuum_cost_limit / nworkers_for_balance, 1); } } /* * autovac_recalculate_workers_for_balance * Recalculate the number of workers to consider, given cost-related * storage parameters and the current number of active workers. * * Caller must hold the AutovacuumLock in at least shared mode to access * worker->wi_proc. */ static void autovac_recalculate_workers_for_balance(void) { dlist_iter iter; int orig_nworkers_for_balance; int nworkers_for_balance = 0; Assert(LWLockHeldByMe(AutovacuumLock)); orig_nworkers_for_balance = pg_atomic_read_u32(&AutoVacuumShmem->av_nworkersForBalance); dlist_foreach(iter, &AutoVacuumShmem->av_runningWorkers) { WorkerInfo worker = dlist_container(WorkerInfoData, wi_links, iter.cur); if (worker->wi_proc == NULL || pg_atomic_unlocked_test_flag(&worker->wi_dobalance)) continue; nworkers_for_balance++; } if (nworkers_for_balance != orig_nworkers_for_balance) pg_atomic_write_u32(&AutoVacuumShmem->av_nworkersForBalance, nworkers_for_balance); } /* * get_database_list * Return a list of all databases found in pg_database. * * The list and associated data is allocated in the caller's memory context, * which is in charge of ensuring that it's properly cleaned up afterwards. * * Note: this is the only function in which the autovacuum launcher uses a * transaction. Although we aren't attached to any particular database and * therefore can't access most catalogs, we do have enough infrastructure * to do a seqscan on pg_database. */ static List * get_database_list(void) { List *dblist = NIL; Relation rel; TableScanDesc scan; HeapTuple tup; MemoryContext resultcxt; /* This is the context that we will allocate our output data in */ resultcxt = CurrentMemoryContext; /* * Start a transaction so we can access pg_database, and get a snapshot. * We don't have a use for the snapshot itself, but we're interested in * the secondary effect that it sets RecentGlobalXmin. (This is critical * for anything that reads heap pages, because HOT may decide to prune * them even if the process doesn't attempt to modify any tuples.) * * FIXME: This comment is inaccurate / the code buggy. A snapshot that is * not pushed/active does not reliably prevent HOT pruning (->xmin could * e.g. be cleared when cache invalidations are processed). */ StartTransactionCommand(); (void) GetTransactionSnapshot(); rel = table_open(DatabaseRelationId, AccessShareLock); scan = table_beginscan_catalog(rel, 0, NULL); while (HeapTupleIsValid(tup = heap_getnext(scan, ForwardScanDirection))) { Form_pg_database pgdatabase = (Form_pg_database) GETSTRUCT(tup); avw_dbase *avdb; MemoryContext oldcxt; /* * If database has partially been dropped, we can't, nor need to, * vacuum it. */ if (database_is_invalid_form(pgdatabase)) { elog(DEBUG2, "autovacuum: skipping invalid database \"%s\"", NameStr(pgdatabase->datname)); continue; } /* * Allocate our results in the caller's context, not the * transaction's. We do this inside the loop, and restore the original * context at the end, so that leaky things like heap_getnext() are * not called in a potentially long-lived context. */ oldcxt = MemoryContextSwitchTo(resultcxt); avdb = (avw_dbase *) palloc(sizeof(avw_dbase)); avdb->adw_datid = pgdatabase->oid; avdb->adw_name = pstrdup(NameStr(pgdatabase->datname)); avdb->adw_frozenxid = pgdatabase->datfrozenxid; avdb->adw_minmulti = pgdatabase->datminmxid; /* this gets set later: */ avdb->adw_entry = NULL; dblist = lappend(dblist, avdb); MemoryContextSwitchTo(oldcxt); } table_endscan(scan); table_close(rel, AccessShareLock); CommitTransactionCommand(); /* Be sure to restore caller's memory context */ MemoryContextSwitchTo(resultcxt); return dblist; } /* * Process a database table-by-table * * Note that CHECK_FOR_INTERRUPTS is supposed to be used in certain spots in * order not to ignore shutdown commands for too long. */ static void do_autovacuum(void) { Relation classRel; HeapTuple tuple; TableScanDesc relScan; Form_pg_database dbForm; List *table_oids = NIL; List *orphan_oids = NIL; HASHCTL ctl; HTAB *table_toast_map; ListCell *volatile cell; BufferAccessStrategy bstrategy; ScanKeyData key; TupleDesc pg_class_desc; int effective_multixact_freeze_max_age; bool did_vacuum = false; bool found_concurrent_worker = false; int i; /* * StartTransactionCommand and CommitTransactionCommand will automatically * switch to other contexts. We need this one to keep the list of * relations to vacuum/analyze across transactions. */ AutovacMemCxt = AllocSetContextCreate(TopMemoryContext, "Autovacuum worker", ALLOCSET_DEFAULT_SIZES); MemoryContextSwitchTo(AutovacMemCxt); /* Start a transaction so our commands have one to play into. */ StartTransactionCommand(); /* * Compute the multixact age for which freezing is urgent. This is * normally autovacuum_multixact_freeze_max_age, but may be less if we are * short of multixact member space. */ effective_multixact_freeze_max_age = MultiXactMemberFreezeThreshold(); /* * Find the pg_database entry and select the default freeze ages. We use * zero in template and nonconnectable databases, else the system-wide * default. */ tuple = SearchSysCache1(DATABASEOID, ObjectIdGetDatum(MyDatabaseId)); if (!HeapTupleIsValid(tuple)) elog(ERROR, "cache lookup failed for database %u", MyDatabaseId); dbForm = (Form_pg_database) GETSTRUCT(tuple); if (dbForm->datistemplate || !dbForm->datallowconn) { default_freeze_min_age = 0; default_freeze_table_age = 0; default_multixact_freeze_min_age = 0; default_multixact_freeze_table_age = 0; } else { default_freeze_min_age = vacuum_freeze_min_age; default_freeze_table_age = vacuum_freeze_table_age; default_multixact_freeze_min_age = vacuum_multixact_freeze_min_age; default_multixact_freeze_table_age = vacuum_multixact_freeze_table_age; } ReleaseSysCache(tuple); /* StartTransactionCommand changed elsewhere */ MemoryContextSwitchTo(AutovacMemCxt); classRel = table_open(RelationRelationId, AccessShareLock); /* create a copy so we can use it after closing pg_class */ pg_class_desc = CreateTupleDescCopy(RelationGetDescr(classRel)); /* create hash table for toast <-> main relid mapping */ ctl.keysize = sizeof(Oid); ctl.entrysize = sizeof(av_relation); table_toast_map = hash_create("TOAST to main relid map", 100, &ctl, HASH_ELEM | HASH_BLOBS); /* * Scan pg_class to determine which tables to vacuum. * * We do this in two passes: on the first one we collect the list of plain * relations and materialized views, and on the second one we collect * TOAST tables. The reason for doing the second pass is that during it we * want to use the main relation's pg_class.reloptions entry if the TOAST * table does not have any, and we cannot obtain it unless we know * beforehand what's the main table OID. * * We need to check TOAST tables separately because in cases with short, * wide tables there might be proportionally much more activity in the * TOAST table than in its parent. */ relScan = table_beginscan_catalog(classRel, 0, NULL); /* * On the first pass, we collect main tables to vacuum, and also the main * table relid to TOAST relid mapping. */ while ((tuple = heap_getnext(relScan, ForwardScanDirection)) != NULL) { Form_pg_class classForm = (Form_pg_class) GETSTRUCT(tuple); PgStat_StatTabEntry *tabentry; AutoVacOpts *relopts; Oid relid; bool dovacuum; bool doanalyze; bool wraparound; if (classForm->relkind != RELKIND_RELATION && classForm->relkind != RELKIND_MATVIEW) continue; relid = classForm->oid; /* * Check if it is a temp table (presumably, of some other backend's). * We cannot safely process other backends' temp tables. */ if (classForm->relpersistence == RELPERSISTENCE_TEMP) { /* * We just ignore it if the owning backend is still active and * using the temporary schema. Also, for safety, ignore it if the * namespace doesn't exist or isn't a temp namespace after all. */ if (checkTempNamespaceStatus(classForm->relnamespace) == TEMP_NAMESPACE_IDLE) { /* * The table seems to be orphaned -- although it might be that * the owning backend has already deleted it and exited; our * pg_class scan snapshot is not necessarily up-to-date * anymore, so we could be looking at a committed-dead entry. * Remember it so we can try to delete it later. */ orphan_oids = lappend_oid(orphan_oids, relid); } continue; } /* Fetch reloptions and the pgstat entry for this table */ relopts = extract_autovac_opts(tuple, pg_class_desc); tabentry = pgstat_fetch_stat_tabentry_ext(classForm->relisshared, relid); /* Check if it needs vacuum or analyze */ relation_needs_vacanalyze(relid, relopts, classForm, tabentry, effective_multixact_freeze_max_age, &dovacuum, &doanalyze, &wraparound); /* Relations that need work are added to table_oids */ if (dovacuum || doanalyze) table_oids = lappend_oid(table_oids, relid); /* * Remember TOAST associations for the second pass. Note: we must do * this whether or not the table is going to be vacuumed, because we * don't automatically vacuum toast tables along the parent table. */ if (OidIsValid(classForm->reltoastrelid)) { av_relation *hentry; bool found; hentry = hash_search(table_toast_map, &classForm->reltoastrelid, HASH_ENTER, &found); if (!found) { /* hash_search already filled in the key */ hentry->ar_relid = relid; hentry->ar_hasrelopts = false; if (relopts != NULL) { hentry->ar_hasrelopts = true; memcpy(&hentry->ar_reloptions, relopts, sizeof(AutoVacOpts)); } } } } table_endscan(relScan); /* second pass: check TOAST tables */ ScanKeyInit(&key, Anum_pg_class_relkind, BTEqualStrategyNumber, F_CHAREQ, CharGetDatum(RELKIND_TOASTVALUE)); relScan = table_beginscan_catalog(classRel, 1, &key); while ((tuple = heap_getnext(relScan, ForwardScanDirection)) != NULL) { Form_pg_class classForm = (Form_pg_class) GETSTRUCT(tuple); PgStat_StatTabEntry *tabentry; Oid relid; AutoVacOpts *relopts = NULL; bool dovacuum; bool doanalyze; bool wraparound; /* * We cannot safely process other backends' temp tables, so skip 'em. */ if (classForm->relpersistence == RELPERSISTENCE_TEMP) continue; relid = classForm->oid; /* * fetch reloptions -- if this toast table does not have them, try the * main rel */ relopts = extract_autovac_opts(tuple, pg_class_desc); if (relopts == NULL) { av_relation *hentry; bool found; hentry = hash_search(table_toast_map, &relid, HASH_FIND, &found); if (found && hentry->ar_hasrelopts) relopts = &hentry->ar_reloptions; } /* Fetch the pgstat entry for this table */ tabentry = pgstat_fetch_stat_tabentry_ext(classForm->relisshared, relid); relation_needs_vacanalyze(relid, relopts, classForm, tabentry, effective_multixact_freeze_max_age, &dovacuum, &doanalyze, &wraparound); /* ignore analyze for toast tables */ if (dovacuum) table_oids = lappend_oid(table_oids, relid); } table_endscan(relScan); table_close(classRel, AccessShareLock); /* * Recheck orphan temporary tables, and if they still seem orphaned, drop * them. We'll eat a transaction per dropped table, which might seem * excessive, but we should only need to do anything as a result of a * previous backend crash, so this should not happen often enough to * justify "optimizing". Using separate transactions ensures that we * don't bloat the lock table if there are many temp tables to be dropped, * and it ensures that we don't lose work if a deletion attempt fails. */ foreach(cell, orphan_oids) { Oid relid = lfirst_oid(cell); Form_pg_class classForm; ObjectAddress object; /* * Check for user-requested abort. */ CHECK_FOR_INTERRUPTS(); /* * Try to lock the table. If we can't get the lock immediately, * somebody else is using (or dropping) the table, so it's not our * concern anymore. Having the lock prevents race conditions below. */ if (!ConditionalLockRelationOid(relid, AccessExclusiveLock)) continue; /* * Re-fetch the pg_class tuple and re-check whether it still seems to * be an orphaned temp table. If it's not there or no longer the same * relation, ignore it. */ tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relid)); if (!HeapTupleIsValid(tuple)) { /* be sure to drop useless lock so we don't bloat lock table */ UnlockRelationOid(relid, AccessExclusiveLock); continue; } classForm = (Form_pg_class) GETSTRUCT(tuple); /* * Make all the same tests made in the loop above. In event of OID * counter wraparound, the pg_class entry we have now might be * completely unrelated to the one we saw before. */ if (!((classForm->relkind == RELKIND_RELATION || classForm->relkind == RELKIND_MATVIEW) && classForm->relpersistence == RELPERSISTENCE_TEMP)) { UnlockRelationOid(relid, AccessExclusiveLock); continue; } if (checkTempNamespaceStatus(classForm->relnamespace) != TEMP_NAMESPACE_IDLE) { UnlockRelationOid(relid, AccessExclusiveLock); continue; } /* * Try to lock the temp namespace, too. Even though we have lock on * the table itself, there's a risk of deadlock against an incoming * backend trying to clean out the temp namespace, in case this table * has dependencies (such as sequences) that the backend's * performDeletion call might visit in a different order. If we can * get AccessShareLock on the namespace, that's sufficient to ensure * we're not running concurrently with RemoveTempRelations. If we * can't, back off and let RemoveTempRelations do its thing. */ if (!ConditionalLockDatabaseObject(NamespaceRelationId, classForm->relnamespace, 0, AccessShareLock)) { UnlockRelationOid(relid, AccessExclusiveLock); continue; } /* OK, let's delete it */ ereport(LOG, (errmsg("autovacuum: dropping orphan temp table \"%s.%s.%s\"", get_database_name(MyDatabaseId), get_namespace_name(classForm->relnamespace), NameStr(classForm->relname)))); object.classId = RelationRelationId; object.objectId = relid; object.objectSubId = 0; performDeletion(&object, DROP_CASCADE, PERFORM_DELETION_INTERNAL | PERFORM_DELETION_QUIETLY | PERFORM_DELETION_SKIP_EXTENSIONS); /* * To commit the deletion, end current transaction and start a new * one. Note this also releases the locks we took. */ CommitTransactionCommand(); StartTransactionCommand(); /* StartTransactionCommand changed current memory context */ MemoryContextSwitchTo(AutovacMemCxt); } /* * Optionally, create a buffer access strategy object for VACUUM to use. * We use the same BufferAccessStrategy object for all tables VACUUMed by * this worker to prevent autovacuum from blowing out shared buffers. * * VacuumBufferUsageLimit being set to 0 results in * GetAccessStrategyWithSize returning NULL, effectively meaning we can * use up to all of shared buffers. * * If we later enter failsafe mode on any of the tables being vacuumed, we * will cease use of the BufferAccessStrategy only for that table. * * XXX should we consider adding code to adjust the size of this if * VacuumBufferUsageLimit changes? */ bstrategy = GetAccessStrategyWithSize(BAS_VACUUM, VacuumBufferUsageLimit); /* * create a memory context to act as fake PortalContext, so that the * contexts created in the vacuum code are cleaned up for each table. */ PortalContext = AllocSetContextCreate(AutovacMemCxt, "Autovacuum Portal", ALLOCSET_DEFAULT_SIZES); /* * Perform operations on collected tables. */ foreach(cell, table_oids) { Oid relid = lfirst_oid(cell); HeapTuple classTup; autovac_table *tab; bool isshared; bool skipit; dlist_iter iter; CHECK_FOR_INTERRUPTS(); /* * Check for config changes before processing each collected table. */ if (ConfigReloadPending) { ConfigReloadPending = false; ProcessConfigFile(PGC_SIGHUP); /* * You might be tempted to bail out if we see autovacuum is now * disabled. Must resist that temptation -- this might be a * for-wraparound emergency worker, in which case that would be * entirely inappropriate. */ } /* * Find out whether the table is shared or not. (It's slightly * annoying to fetch the syscache entry just for this, but in typical * cases it adds little cost because table_recheck_autovac would * refetch the entry anyway. We could buy that back by copying the * tuple here and passing it to table_recheck_autovac, but that * increases the odds of that function working with stale data.) */ classTup = SearchSysCache1(RELOID, ObjectIdGetDatum(relid)); if (!HeapTupleIsValid(classTup)) continue; /* somebody deleted the rel, forget it */ isshared = ((Form_pg_class) GETSTRUCT(classTup))->relisshared; ReleaseSysCache(classTup); /* * Hold schedule lock from here until we've claimed the table. We * also need the AutovacuumLock to walk the worker array, but that one * can just be a shared lock. */ LWLockAcquire(AutovacuumScheduleLock, LW_EXCLUSIVE); LWLockAcquire(AutovacuumLock, LW_SHARED); /* * Check whether the table is being vacuumed concurrently by another * worker. */ skipit = false; dlist_foreach(iter, &AutoVacuumShmem->av_runningWorkers) { WorkerInfo worker = dlist_container(WorkerInfoData, wi_links, iter.cur); /* ignore myself */ if (worker == MyWorkerInfo) continue; /* ignore workers in other databases (unless table is shared) */ if (!worker->wi_sharedrel && worker->wi_dboid != MyDatabaseId) continue; if (worker->wi_tableoid == relid) { skipit = true; found_concurrent_worker = true; break; } } LWLockRelease(AutovacuumLock); if (skipit) { LWLockRelease(AutovacuumScheduleLock); continue; } /* * Store the table's OID in shared memory before releasing the * schedule lock, so that other workers don't try to vacuum it * concurrently. (We claim it here so as not to hold * AutovacuumScheduleLock while rechecking the stats.) */ MyWorkerInfo->wi_tableoid = relid; MyWorkerInfo->wi_sharedrel = isshared; LWLockRelease(AutovacuumScheduleLock); /* * Check whether pgstat data still says we need to vacuum this table. * It could have changed if something else processed the table while * we weren't looking. This doesn't entirely close the race condition, * but it is very small. */ MemoryContextSwitchTo(AutovacMemCxt); tab = table_recheck_autovac(relid, table_toast_map, pg_class_desc, effective_multixact_freeze_max_age); if (tab == NULL) { /* someone else vacuumed the table, or it went away */ LWLockAcquire(AutovacuumScheduleLock, LW_EXCLUSIVE); MyWorkerInfo->wi_tableoid = InvalidOid; MyWorkerInfo->wi_sharedrel = false; LWLockRelease(AutovacuumScheduleLock); continue; } /* * Save the cost-related storage parameter values in global variables * for reference when updating vacuum_cost_delay and vacuum_cost_limit * during vacuuming this table. */ av_storage_param_cost_delay = tab->at_storage_param_vac_cost_delay; av_storage_param_cost_limit = tab->at_storage_param_vac_cost_limit; /* * We only expect this worker to ever set the flag, so don't bother * checking the return value. We shouldn't have to retry. */ if (tab->at_dobalance) pg_atomic_test_set_flag(&MyWorkerInfo->wi_dobalance); else pg_atomic_clear_flag(&MyWorkerInfo->wi_dobalance); LWLockAcquire(AutovacuumLock, LW_SHARED); autovac_recalculate_workers_for_balance(); LWLockRelease(AutovacuumLock); /* * We wait until this point to update cost delay and cost limit * values, even though we reloaded the configuration file above, so * that we can take into account the cost-related storage parameters. */ VacuumUpdateCosts(); /* clean up memory before each iteration */ MemoryContextReset(PortalContext); /* * Save the relation name for a possible error message, to avoid a * catalog lookup in case of an error. If any of these return NULL, * then the relation has been dropped since last we checked; skip it. * Note: they must live in a long-lived memory context because we call * vacuum and analyze in different transactions. */ tab->at_relname = get_rel_name(tab->at_relid); tab->at_nspname = get_namespace_name(get_rel_namespace(tab->at_relid)); tab->at_datname = get_database_name(MyDatabaseId); if (!tab->at_relname || !tab->at_nspname || !tab->at_datname) goto deleted; /* * We will abort vacuuming the current table if something errors out, * and continue with the next one in schedule; in particular, this * happens if we are interrupted with SIGINT. */ PG_TRY(); { /* Use PortalContext for any per-table allocations */ MemoryContextSwitchTo(PortalContext); /* have at it */ autovacuum_do_vac_analyze(tab, bstrategy); /* * Clear a possible query-cancel signal, to avoid a late reaction * to an automatically-sent signal because of vacuuming the * current table (we're done with it, so it would make no sense to * cancel at this point.) */ QueryCancelPending = false; } PG_CATCH(); { /* * Abort the transaction, start a new one, and proceed with the * next table in our list. */ HOLD_INTERRUPTS(); if (tab->at_params.options & VACOPT_VACUUM) errcontext("automatic vacuum of table \"%s.%s.%s\"", tab->at_datname, tab->at_nspname, tab->at_relname); else errcontext("automatic analyze of table \"%s.%s.%s\"", tab->at_datname, tab->at_nspname, tab->at_relname); EmitErrorReport(); /* this resets ProcGlobal->statusFlags[i] too */ AbortOutOfAnyTransaction(); FlushErrorState(); MemoryContextReset(PortalContext); /* restart our transaction for the following operations */ StartTransactionCommand(); RESUME_INTERRUPTS(); } PG_END_TRY(); /* Make sure we're back in AutovacMemCxt */ MemoryContextSwitchTo(AutovacMemCxt); did_vacuum = true; /* ProcGlobal->statusFlags[i] are reset at the next end of xact */ /* be tidy */ deleted: if (tab->at_datname != NULL) pfree(tab->at_datname); if (tab->at_nspname != NULL) pfree(tab->at_nspname); if (tab->at_relname != NULL) pfree(tab->at_relname); pfree(tab); /* * Remove my info from shared memory. We set wi_dobalance on the * assumption that we are more likely than not to vacuum a table with * no cost-related storage parameters next, so we want to claim our * share of I/O as soon as possible to avoid thrashing the global * balance. */ LWLockAcquire(AutovacuumScheduleLock, LW_EXCLUSIVE); MyWorkerInfo->wi_tableoid = InvalidOid; MyWorkerInfo->wi_sharedrel = false; LWLockRelease(AutovacuumScheduleLock); pg_atomic_test_set_flag(&MyWorkerInfo->wi_dobalance); } /* * Perform additional work items, as requested by backends. */ LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE); for (i = 0; i < NUM_WORKITEMS; i++) { AutoVacuumWorkItem *workitem = &AutoVacuumShmem->av_workItems[i]; if (!workitem->avw_used) continue; if (workitem->avw_active) continue; if (workitem->avw_database != MyDatabaseId) continue; /* claim this one, and release lock while performing it */ workitem->avw_active = true; LWLockRelease(AutovacuumLock); perform_work_item(workitem); /* * Check for config changes before acquiring lock for further jobs. */ CHECK_FOR_INTERRUPTS(); if (ConfigReloadPending) { ConfigReloadPending = false; ProcessConfigFile(PGC_SIGHUP); VacuumUpdateCosts(); } LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE); /* and mark it done */ workitem->avw_active = false; workitem->avw_used = false; } LWLockRelease(AutovacuumLock); /* * We leak table_toast_map here (among other things), but since we're * going away soon, it's not a problem. */ /* * Update pg_database.datfrozenxid, and truncate pg_xact if possible. We * only need to do this once, not after each table. * * Even if we didn't vacuum anything, it may still be important to do * this, because one indirect effect of vac_update_datfrozenxid() is to * update TransamVariables->xidVacLimit. That might need to be done even * if we haven't vacuumed anything, because relations with older * relfrozenxid values or other databases with older datfrozenxid values * might have been dropped, allowing xidVacLimit to advance. * * However, it's also important not to do this blindly in all cases, * because when autovacuum=off this will restart the autovacuum launcher. * If we're not careful, an infinite loop can result, where workers find * no work to do and restart the launcher, which starts another worker in * the same database that finds no work to do. To prevent that, we skip * this if (1) we found no work to do and (2) we skipped at least one * table due to concurrent autovacuum activity. In that case, the other * worker has already done it, or will do so when it finishes. */ if (did_vacuum || !found_concurrent_worker) vac_update_datfrozenxid(); /* Finally close out the last transaction. */ CommitTransactionCommand(); } /* * Execute a previously registered work item. */ static void perform_work_item(AutoVacuumWorkItem *workitem) { char *cur_datname = NULL; char *cur_nspname = NULL; char *cur_relname = NULL; /* * Note we do not store table info in MyWorkerInfo, since this is not * vacuuming proper. */ /* * Save the relation name for a possible error message, to avoid a catalog * lookup in case of an error. If any of these return NULL, then the * relation has been dropped since last we checked; skip it. */ Assert(CurrentMemoryContext == AutovacMemCxt); cur_relname = get_rel_name(workitem->avw_relation); cur_nspname = get_namespace_name(get_rel_namespace(workitem->avw_relation)); cur_datname = get_database_name(MyDatabaseId); if (!cur_relname || !cur_nspname || !cur_datname) goto deleted2; autovac_report_workitem(workitem, cur_nspname, cur_relname); /* clean up memory before each work item */ MemoryContextReset(PortalContext); /* * We will abort the current work item if something errors out, and * continue with the next one; in particular, this happens if we are * interrupted with SIGINT. Note that this means that the work item list * can be lossy. */ PG_TRY(); { /* Use PortalContext for any per-work-item allocations */ MemoryContextSwitchTo(PortalContext); /* * Have at it. Functions called here are responsible for any required * user switch and sandbox. */ switch (workitem->avw_type) { case AVW_BRINSummarizeRange: DirectFunctionCall2(brin_summarize_range, ObjectIdGetDatum(workitem->avw_relation), Int64GetDatum((int64) workitem->avw_blockNumber)); break; default: elog(WARNING, "unrecognized work item found: type %d", workitem->avw_type); break; } /* * Clear a possible query-cancel signal, to avoid a late reaction to * an automatically-sent signal because of vacuuming the current table * (we're done with it, so it would make no sense to cancel at this * point.) */ QueryCancelPending = false; } PG_CATCH(); { /* * Abort the transaction, start a new one, and proceed with the next * table in our list. */ HOLD_INTERRUPTS(); errcontext("processing work entry for relation \"%s.%s.%s\"", cur_datname, cur_nspname, cur_relname); EmitErrorReport(); /* this resets ProcGlobal->statusFlags[i] too */ AbortOutOfAnyTransaction(); FlushErrorState(); MemoryContextReset(PortalContext); /* restart our transaction for the following operations */ StartTransactionCommand(); RESUME_INTERRUPTS(); } PG_END_TRY(); /* Make sure we're back in AutovacMemCxt */ MemoryContextSwitchTo(AutovacMemCxt); /* We intentionally do not set did_vacuum here */ /* be tidy */ deleted2: if (cur_datname) pfree(cur_datname); if (cur_nspname) pfree(cur_nspname); if (cur_relname) pfree(cur_relname); } /* * extract_autovac_opts * * Given a relation's pg_class tuple, return the AutoVacOpts portion of * reloptions, if set; otherwise, return NULL. * * Note: callers do not have a relation lock on the table at this point, * so the table could have been dropped, and its catalog rows gone, after * we acquired the pg_class row. If pg_class had a TOAST table, this would * be a risk; fortunately, it doesn't. */ static AutoVacOpts * extract_autovac_opts(HeapTuple tup, TupleDesc pg_class_desc) { bytea *relopts; CommonRdOptions common; AutoVacOpts *av; Assert(((Form_pg_class) GETSTRUCT(tup))->relkind == RELKIND_RELATION || ((Form_pg_class) GETSTRUCT(tup))->relkind == RELKIND_MATVIEW || ((Form_pg_class) GETSTRUCT(tup))->relkind == RELKIND_TOASTVALUE); relopts = extractRelOptions(tup, pg_class_desc, GetTableAmRoutineByAmOid(((Form_pg_class) GETSTRUCT(tup))->relam), NULL, &common); if (relopts) pfree(relopts); av = palloc(sizeof(AutoVacOpts)); memcpy(av, &(common.autovacuum), sizeof(AutoVacOpts)); return av; } /* * table_recheck_autovac * * Recheck whether a table still needs vacuum or analyze. Return value is a * valid autovac_table pointer if it does, NULL otherwise. * * Note that the returned autovac_table does not have the name fields set. */ static autovac_table * table_recheck_autovac(Oid relid, HTAB *table_toast_map, TupleDesc pg_class_desc, int effective_multixact_freeze_max_age) { Form_pg_class classForm; HeapTuple classTup; bool dovacuum; bool doanalyze; autovac_table *tab = NULL; bool wraparound; AutoVacOpts *avopts; /* fetch the relation's relcache entry */ classTup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relid)); if (!HeapTupleIsValid(classTup)) return NULL; classForm = (Form_pg_class) GETSTRUCT(classTup); /* * Get the applicable reloptions. If it is a TOAST table, try to get the * main table reloptions if the toast table itself doesn't have. */ avopts = extract_autovac_opts(classTup, pg_class_desc); if (classForm->relkind == RELKIND_TOASTVALUE && avopts == NULL && table_toast_map != NULL) { av_relation *hentry; bool found; hentry = hash_search(table_toast_map, &relid, HASH_FIND, &found); if (found && hentry->ar_hasrelopts) avopts = &hentry->ar_reloptions; } recheck_relation_needs_vacanalyze(relid, avopts, classForm, effective_multixact_freeze_max_age, &dovacuum, &doanalyze, &wraparound); /* OK, it needs something done */ if (doanalyze || dovacuum) { int freeze_min_age; int freeze_table_age; int multixact_freeze_min_age; int multixact_freeze_table_age; int log_min_duration; /* * Calculate the vacuum cost parameters and the freeze ages. If there * are options set in pg_class.reloptions, use them; in the case of a * toast table, try the main table too. Otherwise use the GUC * defaults, autovacuum's own first and plain vacuum second. */ /* -1 in autovac setting means use log_autovacuum_min_duration */ log_min_duration = (avopts && avopts->log_min_duration >= 0) ? avopts->log_min_duration : Log_autovacuum_min_duration; /* these do not have autovacuum-specific settings */ freeze_min_age = (avopts && avopts->freeze_min_age >= 0) ? avopts->freeze_min_age : default_freeze_min_age; freeze_table_age = (avopts && avopts->freeze_table_age >= 0) ? avopts->freeze_table_age : default_freeze_table_age; multixact_freeze_min_age = (avopts && avopts->multixact_freeze_min_age >= 0) ? avopts->multixact_freeze_min_age : default_multixact_freeze_min_age; multixact_freeze_table_age = (avopts && avopts->multixact_freeze_table_age >= 0) ? avopts->multixact_freeze_table_age : default_multixact_freeze_table_age; tab = palloc(sizeof(autovac_table)); tab->at_relid = relid; tab->at_sharedrel = classForm->relisshared; /* * Select VACUUM options. Note we don't say VACOPT_PROCESS_TOAST, so * that vacuum() skips toast relations. Also note we tell vacuum() to * skip vac_update_datfrozenxid(); we'll do that separately. */ tab->at_params.options = (dovacuum ? (VACOPT_VACUUM | VACOPT_PROCESS_MAIN | VACOPT_SKIP_DATABASE_STATS) : 0) | (doanalyze ? VACOPT_ANALYZE : 0) | (!wraparound ? VACOPT_SKIP_LOCKED : 0); /* * index_cleanup and truncate are unspecified at first in autovacuum. * They will be filled in with usable values using their reloptions * (or reloption defaults) later. */ tab->at_params.index_cleanup = VACOPTVALUE_UNSPECIFIED; tab->at_params.truncate = VACOPTVALUE_UNSPECIFIED; /* As of now, we don't support parallel vacuum for autovacuum */ tab->at_params.nworkers = -1; tab->at_params.freeze_min_age = freeze_min_age; tab->at_params.freeze_table_age = freeze_table_age; tab->at_params.multixact_freeze_min_age = multixact_freeze_min_age; tab->at_params.multixact_freeze_table_age = multixact_freeze_table_age; tab->at_params.is_wraparound = wraparound; tab->at_params.log_min_duration = log_min_duration; tab->at_params.toast_parent = InvalidOid; tab->at_storage_param_vac_cost_limit = avopts ? avopts->vacuum_cost_limit : 0; tab->at_storage_param_vac_cost_delay = avopts ? avopts->vacuum_cost_delay : -1; tab->at_relname = NULL; tab->at_nspname = NULL; tab->at_datname = NULL; /* * If any of the cost delay parameters has been set individually for * this table, disable the balancing algorithm. */ tab->at_dobalance = !(avopts && (avopts->vacuum_cost_limit > 0 || avopts->vacuum_cost_delay >= 0)); } heap_freetuple(classTup); return tab; } /* * recheck_relation_needs_vacanalyze * * Subroutine for table_recheck_autovac. * * Fetch the pgstat of a relation and recheck whether a relation * needs to be vacuumed or analyzed. */ static void recheck_relation_needs_vacanalyze(Oid relid, AutoVacOpts *avopts, Form_pg_class classForm, int effective_multixact_freeze_max_age, bool *dovacuum, bool *doanalyze, bool *wraparound) { PgStat_StatTabEntry *tabentry; /* fetch the pgstat table entry */ tabentry = pgstat_fetch_stat_tabentry_ext(classForm->relisshared, relid); relation_needs_vacanalyze(relid, avopts, classForm, tabentry, effective_multixact_freeze_max_age, dovacuum, doanalyze, wraparound); /* ignore ANALYZE for toast tables */ if (classForm->relkind == RELKIND_TOASTVALUE) *doanalyze = false; } /* * relation_needs_vacanalyze * * Check whether a relation needs to be vacuumed or analyzed; return each into * "dovacuum" and "doanalyze", respectively. Also return whether the vacuum is * being forced because of Xid or multixact wraparound. * * relopts is a pointer to the AutoVacOpts options (either for itself in the * case of a plain table, or for either itself or its parent table in the case * of a TOAST table), NULL if none; tabentry is the pgstats entry, which can be * NULL. * * A table needs to be vacuumed if the number of dead tuples exceeds a * threshold. This threshold is calculated as * * threshold = vac_base_thresh + vac_scale_factor * reltuples * * For analyze, the analysis done is that the number of tuples inserted, * deleted and updated since the last analyze exceeds a threshold calculated * in the same fashion as above. Note that the cumulative stats system stores * the number of tuples (both live and dead) that there were as of the last * analyze. This is asymmetric to the VACUUM case. * * We also force vacuum if the table's relfrozenxid is more than freeze_max_age * transactions back, and if its relminmxid is more than * multixact_freeze_max_age multixacts back. * * A table whose autovacuum_enabled option is false is * automatically skipped (unless we have to vacuum it due to freeze_max_age). * Thus autovacuum can be disabled for specific tables. Also, when the cumulative * stats system does not have data about a table, it will be skipped. * * A table whose vac_base_thresh value is < 0 takes the base value from the * autovacuum_vacuum_threshold GUC variable. Similarly, a vac_scale_factor * value < 0 is substituted with the value of * autovacuum_vacuum_scale_factor GUC variable. Ditto for analyze. */ static void relation_needs_vacanalyze(Oid relid, AutoVacOpts *relopts, Form_pg_class classForm, PgStat_StatTabEntry *tabentry, int effective_multixact_freeze_max_age, /* output params below */ bool *dovacuum, bool *doanalyze, bool *wraparound) { bool force_vacuum; bool av_enabled; float4 reltuples; /* pg_class.reltuples */ /* constants from reloptions or GUC variables */ int vac_base_thresh, vac_ins_base_thresh, anl_base_thresh; float4 vac_scale_factor, vac_ins_scale_factor, anl_scale_factor; /* thresholds calculated from above constants */ float4 vacthresh, vacinsthresh, anlthresh; /* number of vacuum (resp. analyze) tuples at this time */ float4 vactuples, instuples, anltuples; /* freeze parameters */ int freeze_max_age; int multixact_freeze_max_age; TransactionId xidForceLimit; MultiXactId multiForceLimit; Assert(classForm != NULL); Assert(OidIsValid(relid)); /* * Determine vacuum/analyze equation parameters. We have two possible * sources: the passed reloptions (which could be a main table or a toast * table), or the autovacuum GUC variables. */ /* -1 in autovac setting means use plain vacuum_scale_factor */ vac_scale_factor = (relopts && relopts->vacuum_scale_factor >= 0) ? relopts->vacuum_scale_factor : autovacuum_vac_scale; vac_base_thresh = (relopts && relopts->vacuum_threshold >= 0) ? relopts->vacuum_threshold : autovacuum_vac_thresh; vac_ins_scale_factor = (relopts && relopts->vacuum_ins_scale_factor >= 0) ? relopts->vacuum_ins_scale_factor : autovacuum_vac_ins_scale; /* -1 is used to disable insert vacuums */ vac_ins_base_thresh = (relopts && relopts->vacuum_ins_threshold >= -1) ? relopts->vacuum_ins_threshold : autovacuum_vac_ins_thresh; anl_scale_factor = (relopts && relopts->analyze_scale_factor >= 0) ? relopts->analyze_scale_factor : autovacuum_anl_scale; anl_base_thresh = (relopts && relopts->analyze_threshold >= 0) ? relopts->analyze_threshold : autovacuum_anl_thresh; freeze_max_age = (relopts && relopts->freeze_max_age >= 0) ? Min(relopts->freeze_max_age, autovacuum_freeze_max_age) : autovacuum_freeze_max_age; multixact_freeze_max_age = (relopts && relopts->multixact_freeze_max_age >= 0) ? Min(relopts->multixact_freeze_max_age, effective_multixact_freeze_max_age) : effective_multixact_freeze_max_age; av_enabled = (relopts ? relopts->enabled : true); /* Force vacuum if table is at risk of wraparound */ xidForceLimit = recentXid - freeze_max_age; if (xidForceLimit < FirstNormalTransactionId) xidForceLimit -= FirstNormalTransactionId; force_vacuum = (TransactionIdIsNormal(classForm->relfrozenxid) && TransactionIdPrecedes(classForm->relfrozenxid, xidForceLimit)); if (!force_vacuum) { multiForceLimit = recentMulti - multixact_freeze_max_age; if (multiForceLimit < FirstMultiXactId) multiForceLimit -= FirstMultiXactId; force_vacuum = MultiXactIdIsValid(classForm->relminmxid) && MultiXactIdPrecedes(classForm->relminmxid, multiForceLimit); } *wraparound = force_vacuum; /* User disabled it in pg_class.reloptions? (But ignore if at risk) */ if (!av_enabled && !force_vacuum) { *doanalyze = false; *dovacuum = false; return; } /* * If we found stats for the table, and autovacuum is currently enabled, * make a threshold-based decision whether to vacuum and/or analyze. If * autovacuum is currently disabled, we must be here for anti-wraparound * vacuuming only, so don't vacuum (or analyze) anything that's not being * forced. */ if (PointerIsValid(tabentry) && AutoVacuumingActive()) { reltuples = classForm->reltuples; vactuples = tabentry->dead_tuples; instuples = tabentry->ins_since_vacuum; anltuples = tabentry->mod_since_analyze; /* If the table hasn't yet been vacuumed, take reltuples as zero */ if (reltuples < 0) reltuples = 0; vacthresh = (float4) vac_base_thresh + vac_scale_factor * reltuples; vacinsthresh = (float4) vac_ins_base_thresh + vac_ins_scale_factor * reltuples; anlthresh = (float4) anl_base_thresh + anl_scale_factor * reltuples; /* * Note that we don't need to take special consideration for stat * reset, because if that happens, the last vacuum and analyze counts * will be reset too. */ if (vac_ins_base_thresh >= 0) elog(DEBUG3, "%s: vac: %.0f (threshold %.0f), ins: %.0f (threshold %.0f), anl: %.0f (threshold %.0f)", NameStr(classForm->relname), vactuples, vacthresh, instuples, vacinsthresh, anltuples, anlthresh); else elog(DEBUG3, "%s: vac: %.0f (threshold %.0f), ins: (disabled), anl: %.0f (threshold %.0f)", NameStr(classForm->relname), vactuples, vacthresh, anltuples, anlthresh); /* Determine if this table needs vacuum or analyze. */ *dovacuum = force_vacuum || (vactuples > vacthresh) || (vac_ins_base_thresh >= 0 && instuples > vacinsthresh); *doanalyze = (anltuples > anlthresh); } else { /* * Skip a table not found in stat hash, unless we have to force vacuum * for anti-wrap purposes. If it's not acted upon, there's no need to * vacuum it. */ *dovacuum = force_vacuum; *doanalyze = false; } /* ANALYZE refuses to work with pg_statistic */ if (relid == StatisticRelationId) *doanalyze = false; } /* * autovacuum_do_vac_analyze * Vacuum and/or analyze the specified table * * We expect the caller to have switched into a memory context that won't * disappear at transaction commit. */ static void autovacuum_do_vac_analyze(autovac_table *tab, BufferAccessStrategy bstrategy) { RangeVar *rangevar; VacuumRelation *rel; List *rel_list; MemoryContext vac_context; /* Let pgstat know what we're doing */ autovac_report_activity(tab); /* Set up one VacuumRelation target, identified by OID, for vacuum() */ rangevar = makeRangeVar(tab->at_nspname, tab->at_relname, -1); rel = makeVacuumRelation(rangevar, tab->at_relid, NIL); rel_list = list_make1(rel); vac_context = AllocSetContextCreate(CurrentMemoryContext, "Vacuum", ALLOCSET_DEFAULT_SIZES); vacuum(rel_list, &tab->at_params, bstrategy, vac_context, true); MemoryContextDelete(vac_context); } /* * autovac_report_activity * Report to pgstat what autovacuum is doing * * We send a SQL string corresponding to what the user would see if the * equivalent command was to be issued manually. * * Note we assume that we are going to report the next command as soon as we're * done with the current one, and exit right after the last one, so we don't * bother to report "" or some such. */ static void autovac_report_activity(autovac_table *tab) { #define MAX_AUTOVAC_ACTIV_LEN (NAMEDATALEN * 2 + 56) char activity[MAX_AUTOVAC_ACTIV_LEN]; int len; /* Report the command and possible options */ if (tab->at_params.options & VACOPT_VACUUM) snprintf(activity, MAX_AUTOVAC_ACTIV_LEN, "autovacuum: VACUUM%s", tab->at_params.options & VACOPT_ANALYZE ? " ANALYZE" : ""); else snprintf(activity, MAX_AUTOVAC_ACTIV_LEN, "autovacuum: ANALYZE"); /* * Report the qualified name of the relation. */ len = strlen(activity); snprintf(activity + len, MAX_AUTOVAC_ACTIV_LEN - len, " %s.%s%s", tab->at_nspname, tab->at_relname, tab->at_params.is_wraparound ? " (to prevent wraparound)" : ""); /* Set statement_timestamp() to current time for pg_stat_activity */ SetCurrentStatementStartTimestamp(); pgstat_report_activity(STATE_RUNNING, activity); } /* * autovac_report_workitem * Report to pgstat that autovacuum is processing a work item */ static void autovac_report_workitem(AutoVacuumWorkItem *workitem, const char *nspname, const char *relname) { char activity[MAX_AUTOVAC_ACTIV_LEN + 12 + 2]; char blk[12 + 2]; int len; switch (workitem->avw_type) { case AVW_BRINSummarizeRange: snprintf(activity, MAX_AUTOVAC_ACTIV_LEN, "autovacuum: BRIN summarize"); break; } /* * Report the qualified name of the relation, and the block number if any */ len = strlen(activity); if (BlockNumberIsValid(workitem->avw_blockNumber)) snprintf(blk, sizeof(blk), " %u", workitem->avw_blockNumber); else blk[0] = '\0'; snprintf(activity + len, MAX_AUTOVAC_ACTIV_LEN - len, " %s.%s%s", nspname, relname, blk); /* Set statement_timestamp() to current time for pg_stat_activity */ SetCurrentStatementStartTimestamp(); pgstat_report_activity(STATE_RUNNING, activity); } /* * AutoVacuumingActive * Check GUC vars and report whether the autovacuum process should be * running. */ bool AutoVacuumingActive(void) { if (!autovacuum_start_daemon || !pgstat_track_counts) return false; return true; } /* * Request one work item to the next autovacuum run processing our database. * Return false if the request can't be recorded. */ bool AutoVacuumRequestWork(AutoVacuumWorkItemType type, Oid relationId, BlockNumber blkno) { int i; bool result = false; LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE); /* * Locate an unused work item and fill it with the given data. */ for (i = 0; i < NUM_WORKITEMS; i++) { AutoVacuumWorkItem *workitem = &AutoVacuumShmem->av_workItems[i]; if (workitem->avw_used) continue; workitem->avw_used = true; workitem->avw_active = false; workitem->avw_type = type; workitem->avw_database = MyDatabaseId; workitem->avw_relation = relationId; workitem->avw_blockNumber = blkno; result = true; /* done */ break; } LWLockRelease(AutovacuumLock); return result; } /* * autovac_init * This is called at postmaster initialization. * * All we do here is annoy the user if he got it wrong. */ void autovac_init(void) { if (autovacuum_start_daemon && !pgstat_track_counts) ereport(WARNING, (errmsg("autovacuum not started because of misconfiguration"), errhint("Enable the \"track_counts\" option."))); } /* * AutoVacuumShmemSize * Compute space needed for autovacuum-related shared memory */ Size AutoVacuumShmemSize(void) { Size size; /* * Need the fixed struct and the array of WorkerInfoData. */ size = sizeof(AutoVacuumShmemStruct); size = MAXALIGN(size); size = add_size(size, mul_size(autovacuum_max_workers, sizeof(WorkerInfoData))); return size; } /* * AutoVacuumShmemInit * Allocate and initialize autovacuum-related shared memory */ void AutoVacuumShmemInit(void) { bool found; AutoVacuumShmem = (AutoVacuumShmemStruct *) ShmemInitStruct("AutoVacuum Data", AutoVacuumShmemSize(), &found); if (!IsUnderPostmaster) { WorkerInfo worker; int i; Assert(!found); AutoVacuumShmem->av_launcherpid = 0; dlist_init(&AutoVacuumShmem->av_freeWorkers); dlist_init(&AutoVacuumShmem->av_runningWorkers); AutoVacuumShmem->av_startingWorker = NULL; memset(AutoVacuumShmem->av_workItems, 0, sizeof(AutoVacuumWorkItem) * NUM_WORKITEMS); worker = (WorkerInfo) ((char *) AutoVacuumShmem + MAXALIGN(sizeof(AutoVacuumShmemStruct))); /* initialize the WorkerInfo free list */ for (i = 0; i < autovacuum_max_workers; i++) { dlist_push_head(&AutoVacuumShmem->av_freeWorkers, &worker[i].wi_links); pg_atomic_init_flag(&worker[i].wi_dobalance); } pg_atomic_init_u32(&AutoVacuumShmem->av_nworkersForBalance, 0); } else Assert(found); } /* * GUC check_hook for autovacuum_work_mem */ bool check_autovacuum_work_mem(int *newval, void **extra, GucSource source) { /* * -1 indicates fallback. * * If we haven't yet changed the boot_val default of -1, just let it be. * Autovacuum will look to maintenance_work_mem instead. */ if (*newval == -1) return true; /* * We clamp manually-set values to at least 1MB. Since * maintenance_work_mem is always set to at least this value, do the same * here. */ if (*newval < 1024) *newval = 1024; return true; }