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Diffstat (limited to 'src/backend/access/heap/vacuumlazy.c')
| -rw-r--r-- | src/backend/access/heap/vacuumlazy.c | 3462 |
1 files changed, 3462 insertions, 0 deletions
diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c new file mode 100644 index 0000000..b802ed2 --- /dev/null +++ b/src/backend/access/heap/vacuumlazy.c @@ -0,0 +1,3462 @@ +/*------------------------------------------------------------------------- + * + * vacuumlazy.c + * Concurrent ("lazy") vacuuming. + * + * The major space usage for vacuuming is storage for the array of dead TIDs + * that are to be removed from indexes. We want to ensure we can vacuum even + * the very largest relations with finite memory space usage. To do that, we + * set upper bounds on the number of TIDs we can keep track of at once. + * + * We are willing to use at most maintenance_work_mem (or perhaps + * autovacuum_work_mem) memory space to keep track of dead TIDs. We initially + * allocate an array of TIDs of that size, with an upper limit that depends on + * table size (this limit ensures we don't allocate a huge area uselessly for + * vacuuming small tables). If the array threatens to overflow, we must call + * lazy_vacuum to vacuum indexes (and to vacuum the pages that we've pruned). + * This frees up the memory space dedicated to storing dead TIDs. + * + * In practice VACUUM will often complete its initial pass over the target + * heap relation without ever running out of space to store TIDs. This means + * that there only needs to be one call to lazy_vacuum, after the initial pass + * completes. + * + * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * + * IDENTIFICATION + * src/backend/access/heap/vacuumlazy.c + * + *------------------------------------------------------------------------- + */ +#include "postgres.h" + +#include <math.h> + +#include "access/amapi.h" +#include "access/genam.h" +#include "access/heapam.h" +#include "access/heapam_xlog.h" +#include "access/htup_details.h" +#include "access/multixact.h" +#include "access/transam.h" +#include "access/visibilitymap.h" +#include "access/xact.h" +#include "access/xlog.h" +#include "access/xloginsert.h" +#include "catalog/index.h" +#include "catalog/storage.h" +#include "commands/dbcommands.h" +#include "commands/progress.h" +#include "commands/vacuum.h" +#include "executor/instrument.h" +#include "miscadmin.h" +#include "optimizer/paths.h" +#include "pgstat.h" +#include "portability/instr_time.h" +#include "postmaster/autovacuum.h" +#include "storage/bufmgr.h" +#include "storage/freespace.h" +#include "storage/lmgr.h" +#include "tcop/tcopprot.h" +#include "utils/lsyscache.h" +#include "utils/memutils.h" +#include "utils/pg_rusage.h" +#include "utils/timestamp.h" + + +/* + * Space/time tradeoff parameters: do these need to be user-tunable? + * + * To consider truncating the relation, we want there to be at least + * REL_TRUNCATE_MINIMUM or (relsize / REL_TRUNCATE_FRACTION) (whichever + * is less) potentially-freeable pages. + */ +#define REL_TRUNCATE_MINIMUM 1000 +#define REL_TRUNCATE_FRACTION 16 + +/* + * Timing parameters for truncate locking heuristics. + * + * These were not exposed as user tunable GUC values because it didn't seem + * that the potential for improvement was great enough to merit the cost of + * supporting them. + */ +#define VACUUM_TRUNCATE_LOCK_CHECK_INTERVAL 20 /* ms */ +#define VACUUM_TRUNCATE_LOCK_WAIT_INTERVAL 50 /* ms */ +#define VACUUM_TRUNCATE_LOCK_TIMEOUT 5000 /* ms */ + +/* + * Threshold that controls whether we bypass index vacuuming and heap + * vacuuming as an optimization + */ +#define BYPASS_THRESHOLD_PAGES 0.02 /* i.e. 2% of rel_pages */ + +/* + * Perform a failsafe check every 4GB during the heap scan, approximately + */ +#define FAILSAFE_EVERY_PAGES \ + ((BlockNumber) (((uint64) 4 * 1024 * 1024 * 1024) / BLCKSZ)) + +/* + * When a table has no indexes, vacuum the FSM after every 8GB, approximately + * (it won't be exact because we only vacuum FSM after processing a heap page + * that has some removable tuples). When there are indexes, this is ignored, + * and we vacuum FSM after each index/heap cleaning pass. + */ +#define VACUUM_FSM_EVERY_PAGES \ + ((BlockNumber) (((uint64) 8 * 1024 * 1024 * 1024) / BLCKSZ)) + +/* + * Before we consider skipping a page that's marked as clean in + * visibility map, we must've seen at least this many clean pages. + */ +#define SKIP_PAGES_THRESHOLD ((BlockNumber) 32) + +/* + * Size of the prefetch window for lazy vacuum backwards truncation scan. + * Needs to be a power of 2. + */ +#define PREFETCH_SIZE ((BlockNumber) 32) + +/* + * Macro to check if we are in a parallel vacuum. If true, we are in the + * parallel mode and the DSM segment is initialized. + */ +#define ParallelVacuumIsActive(vacrel) ((vacrel)->pvs != NULL) + +/* Phases of vacuum during which we report error context. */ +typedef enum +{ + VACUUM_ERRCB_PHASE_UNKNOWN, + VACUUM_ERRCB_PHASE_SCAN_HEAP, + VACUUM_ERRCB_PHASE_VACUUM_INDEX, + VACUUM_ERRCB_PHASE_VACUUM_HEAP, + VACUUM_ERRCB_PHASE_INDEX_CLEANUP, + VACUUM_ERRCB_PHASE_TRUNCATE +} VacErrPhase; + +typedef struct LVRelState +{ + /* Target heap relation and its indexes */ + Relation rel; + Relation *indrels; + int nindexes; + + /* Aggressive VACUUM? (must set relfrozenxid >= FreezeLimit) */ + bool aggressive; + /* Use visibility map to skip? (disabled by DISABLE_PAGE_SKIPPING) */ + bool skipwithvm; + /* Wraparound failsafe has been triggered? */ + bool failsafe_active; + /* Consider index vacuuming bypass optimization? */ + bool consider_bypass_optimization; + + /* Doing index vacuuming, index cleanup, rel truncation? */ + bool do_index_vacuuming; + bool do_index_cleanup; + bool do_rel_truncate; + + /* Buffer access strategy and parallel vacuum state */ + BufferAccessStrategy bstrategy; + ParallelVacuumState *pvs; + + /* rel's initial relfrozenxid and relminmxid */ + TransactionId relfrozenxid; + MultiXactId relminmxid; + double old_live_tuples; /* previous value of pg_class.reltuples */ + + /* VACUUM operation's cutoffs for freezing and pruning */ + TransactionId OldestXmin; + GlobalVisState *vistest; + /* VACUUM operation's target cutoffs for freezing XIDs and MultiXactIds */ + TransactionId FreezeLimit; + MultiXactId MultiXactCutoff; + /* Tracks oldest extant XID/MXID for setting relfrozenxid/relminmxid */ + TransactionId NewRelfrozenXid; + MultiXactId NewRelminMxid; + bool skippedallvis; + + /* Error reporting state */ + char *relnamespace; + char *relname; + char *indname; /* Current index name */ + BlockNumber blkno; /* used only for heap operations */ + OffsetNumber offnum; /* used only for heap operations */ + VacErrPhase phase; + bool verbose; /* VACUUM VERBOSE? */ + + /* + * dead_items stores TIDs whose index tuples are deleted by index + * vacuuming. Each TID points to an LP_DEAD line pointer from a heap page + * that has been processed by lazy_scan_prune. Also needed by + * lazy_vacuum_heap_rel, which marks the same LP_DEAD line pointers as + * LP_UNUSED during second heap pass. + */ + VacDeadItems *dead_items; /* TIDs whose index tuples we'll delete */ + BlockNumber rel_pages; /* total number of pages */ + BlockNumber scanned_pages; /* # pages examined (not skipped via VM) */ + BlockNumber removed_pages; /* # pages removed by relation truncation */ + BlockNumber lpdead_item_pages; /* # pages with LP_DEAD items */ + BlockNumber missed_dead_pages; /* # pages with missed dead tuples */ + BlockNumber nonempty_pages; /* actually, last nonempty page + 1 */ + + /* Statistics output by us, for table */ + double new_rel_tuples; /* new estimated total # of tuples */ + double new_live_tuples; /* new estimated total # of live tuples */ + /* Statistics output by index AMs */ + IndexBulkDeleteResult **indstats; + + /* Instrumentation counters */ + int num_index_scans; + /* Counters that follow are only for scanned_pages */ + int64 tuples_deleted; /* # deleted from table */ + int64 lpdead_items; /* # deleted from indexes */ + int64 live_tuples; /* # live tuples remaining */ + int64 recently_dead_tuples; /* # dead, but not yet removable */ + int64 missed_dead_tuples; /* # removable, but not removed */ +} LVRelState; + +/* + * State returned by lazy_scan_prune() + */ +typedef struct LVPagePruneState +{ + bool hastup; /* Page prevents rel truncation? */ + bool has_lpdead_items; /* includes existing LP_DEAD items */ + + /* + * State describes the proper VM bit states to set for the page following + * pruning and freezing. all_visible implies !has_lpdead_items, but don't + * trust all_frozen result unless all_visible is also set to true. + */ + bool all_visible; /* Every item visible to all? */ + bool all_frozen; /* provided all_visible is also true */ + TransactionId visibility_cutoff_xid; /* For recovery conflicts */ +} LVPagePruneState; + +/* Struct for saving and restoring vacuum error information. */ +typedef struct LVSavedErrInfo +{ + BlockNumber blkno; + OffsetNumber offnum; + VacErrPhase phase; +} LVSavedErrInfo; + + +/* non-export function prototypes */ +static void lazy_scan_heap(LVRelState *vacrel); +static BlockNumber lazy_scan_skip(LVRelState *vacrel, Buffer *vmbuffer, + BlockNumber next_block, + bool *next_unskippable_allvis, + bool *skipping_current_range); +static bool lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf, + BlockNumber blkno, Page page, + bool sharelock, Buffer vmbuffer); +static void lazy_scan_prune(LVRelState *vacrel, Buffer buf, + BlockNumber blkno, Page page, + LVPagePruneState *prunestate); +static bool lazy_scan_noprune(LVRelState *vacrel, Buffer buf, + BlockNumber blkno, Page page, + bool *hastup, bool *recordfreespace); +static void lazy_vacuum(LVRelState *vacrel); +static bool lazy_vacuum_all_indexes(LVRelState *vacrel); +static void lazy_vacuum_heap_rel(LVRelState *vacrel); +static int lazy_vacuum_heap_page(LVRelState *vacrel, BlockNumber blkno, + Buffer buffer, int index, Buffer *vmbuffer); +static bool lazy_check_wraparound_failsafe(LVRelState *vacrel); +static void lazy_cleanup_all_indexes(LVRelState *vacrel); +static IndexBulkDeleteResult *lazy_vacuum_one_index(Relation indrel, + IndexBulkDeleteResult *istat, + double reltuples, + LVRelState *vacrel); +static IndexBulkDeleteResult *lazy_cleanup_one_index(Relation indrel, + IndexBulkDeleteResult *istat, + double reltuples, + bool estimated_count, + LVRelState *vacrel); +static bool should_attempt_truncation(LVRelState *vacrel); +static void lazy_truncate_heap(LVRelState *vacrel); +static BlockNumber count_nondeletable_pages(LVRelState *vacrel, + bool *lock_waiter_detected); +static void dead_items_alloc(LVRelState *vacrel, int nworkers); +static void dead_items_cleanup(LVRelState *vacrel); +static bool heap_page_is_all_visible(LVRelState *vacrel, Buffer buf, + TransactionId *visibility_cutoff_xid, bool *all_frozen); +static void update_relstats_all_indexes(LVRelState *vacrel); +static void vacuum_error_callback(void *arg); +static void update_vacuum_error_info(LVRelState *vacrel, + LVSavedErrInfo *saved_vacrel, + int phase, BlockNumber blkno, + OffsetNumber offnum); +static void restore_vacuum_error_info(LVRelState *vacrel, + const LVSavedErrInfo *saved_vacrel); + + +/* + * heap_vacuum_rel() -- perform VACUUM for one heap relation + * + * This routine sets things up for and then calls lazy_scan_heap, where + * almost all work actually takes place. Finalizes everything after call + * returns by managing relation truncation and updating rel's pg_class + * entry. (Also updates pg_class entries for any indexes that need it.) + * + * At entry, we have already established a transaction and opened + * and locked the relation. + */ +void +heap_vacuum_rel(Relation rel, VacuumParams *params, + BufferAccessStrategy bstrategy) +{ + LVRelState *vacrel; + bool verbose, + instrument, + aggressive, + skipwithvm, + frozenxid_updated, + minmulti_updated; + TransactionId OldestXmin, + FreezeLimit; + MultiXactId OldestMxact, + MultiXactCutoff; + BlockNumber orig_rel_pages, + new_rel_pages, + new_rel_allvisible; + PGRUsage ru0; + TimestampTz starttime = 0; + PgStat_Counter startreadtime = 0, + startwritetime = 0; + WalUsage startwalusage = pgWalUsage; + int64 StartPageHit = VacuumPageHit, + StartPageMiss = VacuumPageMiss, + StartPageDirty = VacuumPageDirty; + ErrorContextCallback errcallback; + char **indnames = NULL; + + verbose = (params->options & VACOPT_VERBOSE) != 0; + instrument = (verbose || (IsAutoVacuumWorkerProcess() && + params->log_min_duration >= 0)); + if (instrument) + { + pg_rusage_init(&ru0); + starttime = GetCurrentTimestamp(); + if (track_io_timing) + { + startreadtime = pgStatBlockReadTime; + startwritetime = pgStatBlockWriteTime; + } + } + + pgstat_progress_start_command(PROGRESS_COMMAND_VACUUM, + RelationGetRelid(rel)); + + /* + * Get OldestXmin cutoff, which is used to determine which deleted tuples + * are considered DEAD, not just RECENTLY_DEAD. Also get related cutoffs + * used to determine which XIDs/MultiXactIds will be frozen. If this is + * an aggressive VACUUM then lazy_scan_heap cannot leave behind unfrozen + * XIDs < FreezeLimit (all MXIDs < MultiXactCutoff also need to go away). + */ + aggressive = vacuum_set_xid_limits(rel, + params->freeze_min_age, + params->freeze_table_age, + params->multixact_freeze_min_age, + params->multixact_freeze_table_age, + &OldestXmin, &OldestMxact, + &FreezeLimit, &MultiXactCutoff); + + skipwithvm = true; + if (params->options & VACOPT_DISABLE_PAGE_SKIPPING) + { + /* + * Force aggressive mode, and disable skipping blocks using the + * visibility map (even those set all-frozen) + */ + aggressive = true; + skipwithvm = false; + } + + /* + * Setup error traceback support for ereport() first. The idea is to set + * up an error context callback to display additional information on any + * error during a vacuum. During different phases of vacuum, we update + * the state so that the error context callback always display current + * information. + * + * Copy the names of heap rel into local memory for error reporting + * purposes, too. It isn't always safe to assume that we can get the name + * of each rel. It's convenient for code in lazy_scan_heap to always use + * these temp copies. + */ + vacrel = (LVRelState *) palloc0(sizeof(LVRelState)); + vacrel->relnamespace = get_namespace_name(RelationGetNamespace(rel)); + vacrel->relname = pstrdup(RelationGetRelationName(rel)); + vacrel->indname = NULL; + vacrel->phase = VACUUM_ERRCB_PHASE_UNKNOWN; + vacrel->verbose = verbose; + errcallback.callback = vacuum_error_callback; + errcallback.arg = vacrel; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + if (verbose) + { + Assert(!IsAutoVacuumWorkerProcess()); + if (aggressive) + ereport(INFO, + (errmsg("aggressively vacuuming \"%s.%s.%s\"", + get_database_name(MyDatabaseId), + vacrel->relnamespace, vacrel->relname))); + else + ereport(INFO, + (errmsg("vacuuming \"%s.%s.%s\"", + get_database_name(MyDatabaseId), + vacrel->relnamespace, vacrel->relname))); + } + + /* Set up high level stuff about rel and its indexes */ + vacrel->rel = rel; + vac_open_indexes(vacrel->rel, RowExclusiveLock, &vacrel->nindexes, + &vacrel->indrels); + if (instrument && vacrel->nindexes > 0) + { + /* Copy index names used by instrumentation (not error reporting) */ + indnames = palloc(sizeof(char *) * vacrel->nindexes); + for (int i = 0; i < vacrel->nindexes; i++) + indnames[i] = pstrdup(RelationGetRelationName(vacrel->indrels[i])); + } + + /* + * The index_cleanup param either disables index vacuuming and cleanup or + * forces it to go ahead when we would otherwise apply the index bypass + * optimization. The default is 'auto', which leaves the final decision + * up to lazy_vacuum(). + * + * The truncate param allows user to avoid attempting relation truncation, + * though it can't force truncation to happen. + */ + Assert(params->index_cleanup != VACOPTVALUE_UNSPECIFIED); + Assert(params->truncate != VACOPTVALUE_UNSPECIFIED && + params->truncate != VACOPTVALUE_AUTO); + vacrel->aggressive = aggressive; + vacrel->skipwithvm = skipwithvm; + vacrel->failsafe_active = false; + vacrel->consider_bypass_optimization = true; + vacrel->do_index_vacuuming = true; + vacrel->do_index_cleanup = true; + vacrel->do_rel_truncate = (params->truncate != VACOPTVALUE_DISABLED); + if (params->index_cleanup == VACOPTVALUE_DISABLED) + { + /* Force disable index vacuuming up-front */ + vacrel->do_index_vacuuming = false; + vacrel->do_index_cleanup = false; + } + else if (params->index_cleanup == VACOPTVALUE_ENABLED) + { + /* Force index vacuuming. Note that failsafe can still bypass. */ + vacrel->consider_bypass_optimization = false; + } + else + { + /* Default/auto, make all decisions dynamically */ + Assert(params->index_cleanup == VACOPTVALUE_AUTO); + } + + vacrel->bstrategy = bstrategy; + vacrel->relfrozenxid = rel->rd_rel->relfrozenxid; + vacrel->relminmxid = rel->rd_rel->relminmxid; + vacrel->old_live_tuples = rel->rd_rel->reltuples; + + /* Initialize page counters explicitly (be tidy) */ + vacrel->scanned_pages = 0; + vacrel->removed_pages = 0; + vacrel->lpdead_item_pages = 0; + vacrel->missed_dead_pages = 0; + vacrel->nonempty_pages = 0; + /* dead_items_alloc allocates vacrel->dead_items later on */ + + /* Allocate/initialize output statistics state */ + vacrel->new_rel_tuples = 0; + vacrel->new_live_tuples = 0; + vacrel->indstats = (IndexBulkDeleteResult **) + palloc0(vacrel->nindexes * sizeof(IndexBulkDeleteResult *)); + + /* Initialize remaining counters (be tidy) */ + vacrel->num_index_scans = 0; + vacrel->tuples_deleted = 0; + vacrel->lpdead_items = 0; + vacrel->live_tuples = 0; + vacrel->recently_dead_tuples = 0; + vacrel->missed_dead_tuples = 0; + + /* + * Determine the extent of the blocks that we'll scan in lazy_scan_heap, + * and finalize cutoffs used for freezing and pruning in lazy_scan_prune. + * + * We expect vistest will always make heap_page_prune remove any deleted + * tuple whose xmax is < OldestXmin. lazy_scan_prune must never become + * confused about whether a tuple should be frozen or removed. (In the + * future we might want to teach lazy_scan_prune to recompute vistest from + * time to time, to increase the number of dead tuples it can prune away.) + * + * We must determine rel_pages _after_ OldestXmin has been established. + * lazy_scan_heap's physical heap scan (scan of pages < rel_pages) is + * thereby guaranteed to not miss any tuples with XIDs < OldestXmin. These + * XIDs must at least be considered for freezing (though not necessarily + * frozen) during its scan. + */ + vacrel->rel_pages = orig_rel_pages = RelationGetNumberOfBlocks(rel); + vacrel->OldestXmin = OldestXmin; + vacrel->vistest = GlobalVisTestFor(rel); + /* FreezeLimit controls XID freezing (always <= OldestXmin) */ + vacrel->FreezeLimit = FreezeLimit; + /* MultiXactCutoff controls MXID freezing (always <= OldestMxact) */ + vacrel->MultiXactCutoff = MultiXactCutoff; + /* Initialize state used to track oldest extant XID/MXID */ + vacrel->NewRelfrozenXid = OldestXmin; + vacrel->NewRelminMxid = OldestMxact; + vacrel->skippedallvis = false; + + /* + * Allocate dead_items array memory using dead_items_alloc. This handles + * parallel VACUUM initialization as part of allocating shared memory + * space used for dead_items. (But do a failsafe precheck first, to + * ensure that parallel VACUUM won't be attempted at all when relfrozenxid + * is already dangerously old.) + */ + lazy_check_wraparound_failsafe(vacrel); + dead_items_alloc(vacrel, params->nworkers); + + /* + * Call lazy_scan_heap to perform all required heap pruning, index + * vacuuming, and heap vacuuming (plus related processing) + */ + lazy_scan_heap(vacrel); + + /* + * Free resources managed by dead_items_alloc. This ends parallel mode in + * passing when necessary. + */ + dead_items_cleanup(vacrel); + Assert(!IsInParallelMode()); + + /* + * Update pg_class entries for each of rel's indexes where appropriate. + * + * Unlike the later update to rel's pg_class entry, this is not critical. + * Maintains relpages/reltuples statistics used by the planner only. + */ + if (vacrel->do_index_cleanup) + update_relstats_all_indexes(vacrel); + + /* Done with rel's indexes */ + vac_close_indexes(vacrel->nindexes, vacrel->indrels, NoLock); + + /* Optionally truncate rel */ + if (should_attempt_truncation(vacrel)) + lazy_truncate_heap(vacrel); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; + + /* Report that we are now doing final cleanup */ + pgstat_progress_update_param(PROGRESS_VACUUM_PHASE, + PROGRESS_VACUUM_PHASE_FINAL_CLEANUP); + + /* + * Prepare to update rel's pg_class entry. + * + * Aggressive VACUUMs must always be able to advance relfrozenxid to a + * value >= FreezeLimit, and relminmxid to a value >= MultiXactCutoff. + * Non-aggressive VACUUMs may advance them by any amount, or not at all. + */ + Assert(vacrel->NewRelfrozenXid == OldestXmin || + TransactionIdPrecedesOrEquals(aggressive ? FreezeLimit : + vacrel->relfrozenxid, + vacrel->NewRelfrozenXid)); + Assert(vacrel->NewRelminMxid == OldestMxact || + MultiXactIdPrecedesOrEquals(aggressive ? MultiXactCutoff : + vacrel->relminmxid, + vacrel->NewRelminMxid)); + if (vacrel->skippedallvis) + { + /* + * Must keep original relfrozenxid in a non-aggressive VACUUM that + * chose to skip an all-visible page range. The state that tracks new + * values will have missed unfrozen XIDs from the pages we skipped. + */ + Assert(!aggressive); + vacrel->NewRelfrozenXid = InvalidTransactionId; + vacrel->NewRelminMxid = InvalidMultiXactId; + } + + /* + * For safety, clamp relallvisible to be not more than what we're setting + * pg_class.relpages to + */ + new_rel_pages = vacrel->rel_pages; /* After possible rel truncation */ + visibilitymap_count(rel, &new_rel_allvisible, NULL); + if (new_rel_allvisible > new_rel_pages) + new_rel_allvisible = new_rel_pages; + + /* + * Now actually update rel's pg_class entry. + * + * In principle new_live_tuples could be -1 indicating that we (still) + * don't know the tuple count. In practice that can't happen, since we + * scan every page that isn't skipped using the visibility map. + */ + vac_update_relstats(rel, new_rel_pages, vacrel->new_live_tuples, + new_rel_allvisible, vacrel->nindexes > 0, + vacrel->NewRelfrozenXid, vacrel->NewRelminMxid, + &frozenxid_updated, &minmulti_updated, false); + + /* + * Report results to the cumulative stats system, too. + * + * Deliberately avoid telling the stats system about LP_DEAD items that + * remain in the table due to VACUUM bypassing index and heap vacuuming. + * ANALYZE will consider the remaining LP_DEAD items to be dead "tuples". + * It seems like a good idea to err on the side of not vacuuming again too + * soon in cases where the failsafe prevented significant amounts of heap + * vacuuming. + */ + pgstat_report_vacuum(RelationGetRelid(rel), + rel->rd_rel->relisshared, + Max(vacrel->new_live_tuples, 0), + vacrel->recently_dead_tuples + + vacrel->missed_dead_tuples); + pgstat_progress_end_command(); + + if (instrument) + { + TimestampTz endtime = GetCurrentTimestamp(); + + if (verbose || params->log_min_duration == 0 || + TimestampDifferenceExceeds(starttime, endtime, + params->log_min_duration)) + { + long secs_dur; + int usecs_dur; + WalUsage walusage; + StringInfoData buf; + char *msgfmt; + int32 diff; + int64 PageHitOp = VacuumPageHit - StartPageHit, + PageMissOp = VacuumPageMiss - StartPageMiss, + PageDirtyOp = VacuumPageDirty - StartPageDirty; + double read_rate = 0, + write_rate = 0; + + TimestampDifference(starttime, endtime, &secs_dur, &usecs_dur); + memset(&walusage, 0, sizeof(WalUsage)); + WalUsageAccumDiff(&walusage, &pgWalUsage, &startwalusage); + + initStringInfo(&buf); + if (verbose) + { + /* + * Aggressiveness already reported earlier, in dedicated + * VACUUM VERBOSE ereport + */ + Assert(!params->is_wraparound); + msgfmt = _("finished vacuuming \"%s.%s.%s\": index scans: %d\n"); + } + else if (params->is_wraparound) + { + /* + * While it's possible for a VACUUM to be both is_wraparound + * and !aggressive, that's just a corner-case -- is_wraparound + * implies aggressive. Produce distinct output for the corner + * case all the same, just in case. + */ + if (aggressive) + msgfmt = _("automatic aggressive vacuum to prevent wraparound of table \"%s.%s.%s\": index scans: %d\n"); + else + msgfmt = _("automatic vacuum to prevent wraparound of table \"%s.%s.%s\": index scans: %d\n"); + } + else + { + if (aggressive) + msgfmt = _("automatic aggressive vacuum of table \"%s.%s.%s\": index scans: %d\n"); + else + msgfmt = _("automatic vacuum of table \"%s.%s.%s\": index scans: %d\n"); + } + appendStringInfo(&buf, msgfmt, + get_database_name(MyDatabaseId), + vacrel->relnamespace, + vacrel->relname, + vacrel->num_index_scans); + appendStringInfo(&buf, _("pages: %u removed, %u remain, %u scanned (%.2f%% of total)\n"), + vacrel->removed_pages, + new_rel_pages, + vacrel->scanned_pages, + orig_rel_pages == 0 ? 100.0 : + 100.0 * vacrel->scanned_pages / orig_rel_pages); + appendStringInfo(&buf, + _("tuples: %lld removed, %lld remain, %lld are dead but not yet removable\n"), + (long long) vacrel->tuples_deleted, + (long long) vacrel->new_rel_tuples, + (long long) vacrel->recently_dead_tuples); + if (vacrel->missed_dead_tuples > 0) + appendStringInfo(&buf, + _("tuples missed: %lld dead from %u pages not removed due to cleanup lock contention\n"), + (long long) vacrel->missed_dead_tuples, + vacrel->missed_dead_pages); + diff = (int32) (ReadNextTransactionId() - OldestXmin); + appendStringInfo(&buf, + _("removable cutoff: %u, which was %d XIDs old when operation ended\n"), + OldestXmin, diff); + if (frozenxid_updated) + { + diff = (int32) (vacrel->NewRelfrozenXid - vacrel->relfrozenxid); + appendStringInfo(&buf, + _("new relfrozenxid: %u, which is %d XIDs ahead of previous value\n"), + vacrel->NewRelfrozenXid, diff); + } + if (minmulti_updated) + { + diff = (int32) (vacrel->NewRelminMxid - vacrel->relminmxid); + appendStringInfo(&buf, + _("new relminmxid: %u, which is %d MXIDs ahead of previous value\n"), + vacrel->NewRelminMxid, diff); + } + if (vacrel->do_index_vacuuming) + { + if (vacrel->nindexes == 0 || vacrel->num_index_scans == 0) + appendStringInfoString(&buf, _("index scan not needed: ")); + else + appendStringInfoString(&buf, _("index scan needed: ")); + + msgfmt = _("%u pages from table (%.2f%% of total) had %lld dead item identifiers removed\n"); + } + else + { + if (!vacrel->failsafe_active) + appendStringInfoString(&buf, _("index scan bypassed: ")); + else + appendStringInfoString(&buf, _("index scan bypassed by failsafe: ")); + + msgfmt = _("%u pages from table (%.2f%% of total) have %lld dead item identifiers\n"); + } + appendStringInfo(&buf, msgfmt, + vacrel->lpdead_item_pages, + orig_rel_pages == 0 ? 100.0 : + 100.0 * vacrel->lpdead_item_pages / orig_rel_pages, + (long long) vacrel->lpdead_items); + for (int i = 0; i < vacrel->nindexes; i++) + { + IndexBulkDeleteResult *istat = vacrel->indstats[i]; + + if (!istat) + continue; + + appendStringInfo(&buf, + _("index \"%s\": pages: %u in total, %u newly deleted, %u currently deleted, %u reusable\n"), + indnames[i], + istat->num_pages, + istat->pages_newly_deleted, + istat->pages_deleted, + istat->pages_free); + } + if (track_io_timing) + { + double read_ms = (double) (pgStatBlockReadTime - startreadtime) / 1000; + double write_ms = (double) (pgStatBlockWriteTime - startwritetime) / 1000; + + appendStringInfo(&buf, _("I/O timings: read: %.3f ms, write: %.3f ms\n"), + read_ms, write_ms); + } + if (secs_dur > 0 || usecs_dur > 0) + { + read_rate = (double) BLCKSZ * PageMissOp / (1024 * 1024) / + (secs_dur + usecs_dur / 1000000.0); + write_rate = (double) BLCKSZ * PageDirtyOp / (1024 * 1024) / + (secs_dur + usecs_dur / 1000000.0); + } + appendStringInfo(&buf, _("avg read rate: %.3f MB/s, avg write rate: %.3f MB/s\n"), + read_rate, write_rate); + appendStringInfo(&buf, + _("buffer usage: %lld hits, %lld misses, %lld dirtied\n"), + (long long) PageHitOp, + (long long) PageMissOp, + (long long) PageDirtyOp); + appendStringInfo(&buf, + _("WAL usage: %lld records, %lld full page images, %llu bytes\n"), + (long long) walusage.wal_records, + (long long) walusage.wal_fpi, + (unsigned long long) walusage.wal_bytes); + appendStringInfo(&buf, _("system usage: %s"), pg_rusage_show(&ru0)); + + ereport(verbose ? INFO : LOG, + (errmsg_internal("%s", buf.data))); + pfree(buf.data); + } + } + + /* Cleanup index statistics and index names */ + for (int i = 0; i < vacrel->nindexes; i++) + { + if (vacrel->indstats[i]) + pfree(vacrel->indstats[i]); + + if (instrument) + pfree(indnames[i]); + } +} + +/* + * lazy_scan_heap() -- workhorse function for VACUUM + * + * This routine prunes each page in the heap, and considers the need to + * freeze remaining tuples with storage (not including pages that can be + * skipped using the visibility map). Also performs related maintenance + * of the FSM and visibility map. These steps all take place during an + * initial pass over the target heap relation. + * + * Also invokes lazy_vacuum_all_indexes to vacuum indexes, which largely + * consists of deleting index tuples that point to LP_DEAD items left in + * heap pages following pruning. Earlier initial pass over the heap will + * have collected the TIDs whose index tuples need to be removed. + * + * Finally, invokes lazy_vacuum_heap_rel to vacuum heap pages, which + * largely consists of marking LP_DEAD items (from collected TID array) + * as LP_UNUSED. This has to happen in a second, final pass over the + * heap, to preserve a basic invariant that all index AMs rely on: no + * extant index tuple can ever be allowed to contain a TID that points to + * an LP_UNUSED line pointer in the heap. We must disallow premature + * recycling of line pointers to avoid index scans that get confused + * about which TID points to which tuple immediately after recycling. + * (Actually, this isn't a concern when target heap relation happens to + * have no indexes, which allows us to safely apply the one-pass strategy + * as an optimization). + * + * In practice we often have enough space to fit all TIDs, and so won't + * need to call lazy_vacuum more than once, after our initial pass over + * the heap has totally finished. Otherwise things are slightly more + * complicated: our "initial pass" over the heap applies only to those + * pages that were pruned before we needed to call lazy_vacuum, and our + * "final pass" over the heap only vacuums these same heap pages. + * However, we process indexes in full every time lazy_vacuum is called, + * which makes index processing very inefficient when memory is in short + * supply. + */ +static void +lazy_scan_heap(LVRelState *vacrel) +{ + BlockNumber rel_pages = vacrel->rel_pages, + blkno, + next_unskippable_block, + next_failsafe_block = 0, + next_fsm_block_to_vacuum = 0; + VacDeadItems *dead_items = vacrel->dead_items; + Buffer vmbuffer = InvalidBuffer; + bool next_unskippable_allvis, + skipping_current_range; + const int initprog_index[] = { + PROGRESS_VACUUM_PHASE, + PROGRESS_VACUUM_TOTAL_HEAP_BLKS, + PROGRESS_VACUUM_MAX_DEAD_TUPLES + }; + int64 initprog_val[3]; + + /* Report that we're scanning the heap, advertising total # of blocks */ + initprog_val[0] = PROGRESS_VACUUM_PHASE_SCAN_HEAP; + initprog_val[1] = rel_pages; + initprog_val[2] = dead_items->max_items; + pgstat_progress_update_multi_param(3, initprog_index, initprog_val); + + /* Set up an initial range of skippable blocks using the visibility map */ + next_unskippable_block = lazy_scan_skip(vacrel, &vmbuffer, 0, + &next_unskippable_allvis, + &skipping_current_range); + for (blkno = 0; blkno < rel_pages; blkno++) + { + Buffer buf; + Page page; + bool all_visible_according_to_vm; + LVPagePruneState prunestate; + + if (blkno == next_unskippable_block) + { + /* + * Can't skip this page safely. Must scan the page. But + * determine the next skippable range after the page first. + */ + all_visible_according_to_vm = next_unskippable_allvis; + next_unskippable_block = lazy_scan_skip(vacrel, &vmbuffer, + blkno + 1, + &next_unskippable_allvis, + &skipping_current_range); + + Assert(next_unskippable_block >= blkno + 1); + } + else + { + /* Last page always scanned (may need to set nonempty_pages) */ + Assert(blkno < rel_pages - 1); + + if (skipping_current_range) + continue; + + /* Current range is too small to skip -- just scan the page */ + all_visible_according_to_vm = true; + } + + vacrel->scanned_pages++; + + /* Report as block scanned, update error traceback information */ + pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_SCANNED, blkno); + update_vacuum_error_info(vacrel, NULL, VACUUM_ERRCB_PHASE_SCAN_HEAP, + blkno, InvalidOffsetNumber); + + vacuum_delay_point(); + + /* + * Regularly check if wraparound failsafe should trigger. + * + * There is a similar check inside lazy_vacuum_all_indexes(), but + * relfrozenxid might start to look dangerously old before we reach + * that point. This check also provides failsafe coverage for the + * one-pass strategy, and the two-pass strategy with the index_cleanup + * param set to 'off'. + */ + if (blkno - next_failsafe_block >= FAILSAFE_EVERY_PAGES) + { + lazy_check_wraparound_failsafe(vacrel); + next_failsafe_block = blkno; + } + + /* + * Consider if we definitely have enough space to process TIDs on page + * already. If we are close to overrunning the available space for + * dead_items TIDs, pause and do a cycle of vacuuming before we tackle + * this page. + */ + Assert(dead_items->max_items >= MaxHeapTuplesPerPage); + if (dead_items->max_items - dead_items->num_items < MaxHeapTuplesPerPage) + { + /* + * Before beginning index vacuuming, we release any pin we may + * hold on the visibility map page. This isn't necessary for + * correctness, but we do it anyway to avoid holding the pin + * across a lengthy, unrelated operation. + */ + if (BufferIsValid(vmbuffer)) + { + ReleaseBuffer(vmbuffer); + vmbuffer = InvalidBuffer; + } + + /* Perform a round of index and heap vacuuming */ + vacrel->consider_bypass_optimization = false; + lazy_vacuum(vacrel); + + /* + * Vacuum the Free Space Map to make newly-freed space visible on + * upper-level FSM pages. Note we have not yet processed blkno. + */ + FreeSpaceMapVacuumRange(vacrel->rel, next_fsm_block_to_vacuum, + blkno); + next_fsm_block_to_vacuum = blkno; + + /* Report that we are once again scanning the heap */ + pgstat_progress_update_param(PROGRESS_VACUUM_PHASE, + PROGRESS_VACUUM_PHASE_SCAN_HEAP); + } + + /* + * Pin the visibility map page in case we need to mark the page + * all-visible. In most cases this will be very cheap, because we'll + * already have the correct page pinned anyway. + */ + visibilitymap_pin(vacrel->rel, blkno, &vmbuffer); + + /* Finished preparatory checks. Actually scan the page. */ + buf = ReadBufferExtended(vacrel->rel, MAIN_FORKNUM, blkno, + RBM_NORMAL, vacrel->bstrategy); + page = BufferGetPage(buf); + + /* + * We need a buffer cleanup lock to prune HOT chains and defragment + * the page in lazy_scan_prune. But when it's not possible to acquire + * a cleanup lock right away, we may be able to settle for reduced + * processing using lazy_scan_noprune. + */ + if (!ConditionalLockBufferForCleanup(buf)) + { + bool hastup, + recordfreespace; + + LockBuffer(buf, BUFFER_LOCK_SHARE); + + /* Check for new or empty pages before lazy_scan_noprune call */ + if (lazy_scan_new_or_empty(vacrel, buf, blkno, page, true, + vmbuffer)) + { + /* Processed as new/empty page (lock and pin released) */ + continue; + } + + /* Collect LP_DEAD items in dead_items array, count tuples */ + if (lazy_scan_noprune(vacrel, buf, blkno, page, &hastup, + &recordfreespace)) + { + Size freespace = 0; + + /* + * Processed page successfully (without cleanup lock) -- just + * need to perform rel truncation and FSM steps, much like the + * lazy_scan_prune case. Don't bother trying to match its + * visibility map setting steps, though. + */ + if (hastup) + vacrel->nonempty_pages = blkno + 1; + if (recordfreespace) + freespace = PageGetHeapFreeSpace(page); + UnlockReleaseBuffer(buf); + if (recordfreespace) + RecordPageWithFreeSpace(vacrel->rel, blkno, freespace); + continue; + } + + /* + * lazy_scan_noprune could not do all required processing. Wait + * for a cleanup lock, and call lazy_scan_prune in the usual way. + */ + Assert(vacrel->aggressive); + LockBuffer(buf, BUFFER_LOCK_UNLOCK); + LockBufferForCleanup(buf); + } + + /* Check for new or empty pages before lazy_scan_prune call */ + if (lazy_scan_new_or_empty(vacrel, buf, blkno, page, false, vmbuffer)) + { + /* Processed as new/empty page (lock and pin released) */ + continue; + } + + /* + * Prune, freeze, and count tuples. + * + * Accumulates details of remaining LP_DEAD line pointers on page in + * dead_items array. This includes LP_DEAD line pointers that we + * pruned ourselves, as well as existing LP_DEAD line pointers that + * were pruned some time earlier. Also considers freezing XIDs in the + * tuple headers of remaining items with storage. + */ + lazy_scan_prune(vacrel, buf, blkno, page, &prunestate); + + Assert(!prunestate.all_visible || !prunestate.has_lpdead_items); + + /* Remember the location of the last page with nonremovable tuples */ + if (prunestate.hastup) + vacrel->nonempty_pages = blkno + 1; + + if (vacrel->nindexes == 0) + { + /* + * Consider the need to do page-at-a-time heap vacuuming when + * using the one-pass strategy now. + * + * The one-pass strategy will never call lazy_vacuum(). The steps + * performed here can be thought of as the one-pass equivalent of + * a call to lazy_vacuum(). + */ + if (prunestate.has_lpdead_items) + { + Size freespace; + + lazy_vacuum_heap_page(vacrel, blkno, buf, 0, &vmbuffer); + + /* Forget the LP_DEAD items that we just vacuumed */ + dead_items->num_items = 0; + + /* + * Periodically perform FSM vacuuming to make newly-freed + * space visible on upper FSM pages. Note we have not yet + * performed FSM processing for blkno. + */ + if (blkno - next_fsm_block_to_vacuum >= VACUUM_FSM_EVERY_PAGES) + { + FreeSpaceMapVacuumRange(vacrel->rel, next_fsm_block_to_vacuum, + blkno); + next_fsm_block_to_vacuum = blkno; + } + + /* + * Now perform FSM processing for blkno, and move on to next + * page. + * + * Our call to lazy_vacuum_heap_page() will have considered if + * it's possible to set all_visible/all_frozen independently + * of lazy_scan_prune(). Note that prunestate was invalidated + * by lazy_vacuum_heap_page() call. + */ + freespace = PageGetHeapFreeSpace(page); + + UnlockReleaseBuffer(buf); + RecordPageWithFreeSpace(vacrel->rel, blkno, freespace); + continue; + } + + /* + * There was no call to lazy_vacuum_heap_page() because pruning + * didn't encounter/create any LP_DEAD items that needed to be + * vacuumed. Prune state has not been invalidated, so proceed + * with prunestate-driven visibility map and FSM steps (just like + * the two-pass strategy). + */ + Assert(dead_items->num_items == 0); + } + + /* + * Handle setting visibility map bit based on information from the VM + * (as of last lazy_scan_skip() call), and from prunestate + */ + if (!all_visible_according_to_vm && prunestate.all_visible) + { + uint8 flags = VISIBILITYMAP_ALL_VISIBLE; + + if (prunestate.all_frozen) + flags |= VISIBILITYMAP_ALL_FROZEN; + + /* + * It should never be the case that the visibility map page is set + * while the page-level bit is clear, but the reverse is allowed + * (if checksums are not enabled). Regardless, set both bits so + * that we get back in sync. + * + * NB: If the heap page is all-visible but the VM bit is not set, + * we don't need to dirty the heap page. However, if checksums + * are enabled, we do need to make sure that the heap page is + * dirtied before passing it to visibilitymap_set(), because it + * may be logged. Given that this situation should only happen in + * rare cases after a crash, it is not worth optimizing. + */ + PageSetAllVisible(page); + MarkBufferDirty(buf); + visibilitymap_set(vacrel->rel, blkno, buf, InvalidXLogRecPtr, + vmbuffer, prunestate.visibility_cutoff_xid, + flags); + } + + /* + * As of PostgreSQL 9.2, the visibility map bit should never be set if + * the page-level bit is clear. However, it's possible that the bit + * got cleared after lazy_scan_skip() was called, so we must recheck + * with buffer lock before concluding that the VM is corrupt. + */ + else if (all_visible_according_to_vm && !PageIsAllVisible(page) + && VM_ALL_VISIBLE(vacrel->rel, blkno, &vmbuffer)) + { + elog(WARNING, "page is not marked all-visible but visibility map bit is set in relation \"%s\" page %u", + vacrel->relname, blkno); + visibilitymap_clear(vacrel->rel, blkno, vmbuffer, + VISIBILITYMAP_VALID_BITS); + } + + /* + * It's possible for the value returned by + * GetOldestNonRemovableTransactionId() to move backwards, so it's not + * wrong for us to see tuples that appear to not be visible to + * everyone yet, while PD_ALL_VISIBLE is already set. The real safe + * xmin value never moves backwards, but + * GetOldestNonRemovableTransactionId() is conservative and sometimes + * returns a value that's unnecessarily small, so if we see that + * contradiction it just means that the tuples that we think are not + * visible to everyone yet actually are, and the PD_ALL_VISIBLE flag + * is correct. + * + * There should never be LP_DEAD items on a page with PD_ALL_VISIBLE + * set, however. + */ + else if (prunestate.has_lpdead_items && PageIsAllVisible(page)) + { + elog(WARNING, "page containing LP_DEAD items is marked as all-visible in relation \"%s\" page %u", + vacrel->relname, blkno); + PageClearAllVisible(page); + MarkBufferDirty(buf); + visibilitymap_clear(vacrel->rel, blkno, vmbuffer, + VISIBILITYMAP_VALID_BITS); + } + + /* + * If the all-visible page is all-frozen but not marked as such yet, + * mark it as all-frozen. Note that all_frozen is only valid if + * all_visible is true, so we must check both prunestate fields. + */ + else if (all_visible_according_to_vm && prunestate.all_visible && + prunestate.all_frozen && + !VM_ALL_FROZEN(vacrel->rel, blkno, &vmbuffer)) + { + /* + * We can pass InvalidTransactionId as the cutoff XID here, + * because setting the all-frozen bit doesn't cause recovery + * conflicts. + */ + visibilitymap_set(vacrel->rel, blkno, buf, InvalidXLogRecPtr, + vmbuffer, InvalidTransactionId, + VISIBILITYMAP_ALL_FROZEN); + } + + /* + * Final steps for block: drop cleanup lock, record free space in the + * FSM + */ + if (prunestate.has_lpdead_items && vacrel->do_index_vacuuming) + { + /* + * Wait until lazy_vacuum_heap_rel() to save free space. This + * doesn't just save us some cycles; it also allows us to record + * any additional free space that lazy_vacuum_heap_page() will + * make available in cases where it's possible to truncate the + * page's line pointer array. + * + * Note: It's not in fact 100% certain that we really will call + * lazy_vacuum_heap_rel() -- lazy_vacuum() might yet opt to skip + * index vacuuming (and so must skip heap vacuuming). This is + * deemed okay because it only happens in emergencies, or when + * there is very little free space anyway. (Besides, we start + * recording free space in the FSM once index vacuuming has been + * abandoned.) + * + * Note: The one-pass (no indexes) case is only supposed to make + * it this far when there were no LP_DEAD items during pruning. + */ + Assert(vacrel->nindexes > 0); + UnlockReleaseBuffer(buf); + } + else + { + Size freespace = PageGetHeapFreeSpace(page); + + UnlockReleaseBuffer(buf); + RecordPageWithFreeSpace(vacrel->rel, blkno, freespace); + } + } + + vacrel->blkno = InvalidBlockNumber; + if (BufferIsValid(vmbuffer)) + ReleaseBuffer(vmbuffer); + + /* report that everything is now scanned */ + pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_SCANNED, blkno); + + /* now we can compute the new value for pg_class.reltuples */ + vacrel->new_live_tuples = vac_estimate_reltuples(vacrel->rel, rel_pages, + vacrel->scanned_pages, + vacrel->live_tuples); + + /* + * Also compute the total number of surviving heap entries. In the + * (unlikely) scenario that new_live_tuples is -1, take it as zero. + */ + vacrel->new_rel_tuples = + Max(vacrel->new_live_tuples, 0) + vacrel->recently_dead_tuples + + vacrel->missed_dead_tuples; + + /* + * Do index vacuuming (call each index's ambulkdelete routine), then do + * related heap vacuuming + */ + if (dead_items->num_items > 0) + lazy_vacuum(vacrel); + + /* + * Vacuum the remainder of the Free Space Map. We must do this whether or + * not there were indexes, and whether or not we bypassed index vacuuming. + */ + if (blkno > next_fsm_block_to_vacuum) + FreeSpaceMapVacuumRange(vacrel->rel, next_fsm_block_to_vacuum, blkno); + + /* report all blocks vacuumed */ + pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_VACUUMED, blkno); + + /* Do final index cleanup (call each index's amvacuumcleanup routine) */ + if (vacrel->nindexes > 0 && vacrel->do_index_cleanup) + lazy_cleanup_all_indexes(vacrel); +} + +/* + * lazy_scan_skip() -- set up range of skippable blocks using visibility map. + * + * lazy_scan_heap() calls here every time it needs to set up a new range of + * blocks to skip via the visibility map. Caller passes the next block in + * line. We return a next_unskippable_block for this range. When there are + * no skippable blocks we just return caller's next_block. The all-visible + * status of the returned block is set in *next_unskippable_allvis for caller, + * too. Block usually won't be all-visible (since it's unskippable), but it + * can be during aggressive VACUUMs (as well as in certain edge cases). + * + * Sets *skipping_current_range to indicate if caller should skip this range. + * Costs and benefits drive our decision. Very small ranges won't be skipped. + * + * Note: our opinion of which blocks can be skipped can go stale immediately. + * It's okay if caller "misses" a page whose all-visible or all-frozen marking + * was concurrently cleared, though. All that matters is that caller scan all + * pages whose tuples might contain XIDs < OldestXmin, or MXIDs < OldestMxact. + * (Actually, non-aggressive VACUUMs can choose to skip all-visible pages with + * older XIDs/MXIDs. The vacrel->skippedallvis flag will be set here when the + * choice to skip such a range is actually made, making everything safe.) + */ +static BlockNumber +lazy_scan_skip(LVRelState *vacrel, Buffer *vmbuffer, BlockNumber next_block, + bool *next_unskippable_allvis, bool *skipping_current_range) +{ + BlockNumber rel_pages = vacrel->rel_pages, + next_unskippable_block = next_block, + nskippable_blocks = 0; + bool skipsallvis = false; + + *next_unskippable_allvis = true; + while (next_unskippable_block < rel_pages) + { + uint8 mapbits = visibilitymap_get_status(vacrel->rel, + next_unskippable_block, + vmbuffer); + + if ((mapbits & VISIBILITYMAP_ALL_VISIBLE) == 0) + { + Assert((mapbits & VISIBILITYMAP_ALL_FROZEN) == 0); + *next_unskippable_allvis = false; + break; + } + + /* + * Caller must scan the last page to determine whether it has tuples + * (caller must have the opportunity to set vacrel->nonempty_pages). + * This rule avoids having lazy_truncate_heap() take access-exclusive + * lock on rel to attempt a truncation that fails anyway, just because + * there are tuples on the last page (it is likely that there will be + * tuples on other nearby pages as well, but those can be skipped). + * + * Implement this by always treating the last block as unsafe to skip. + */ + if (next_unskippable_block == rel_pages - 1) + break; + + /* DISABLE_PAGE_SKIPPING makes all skipping unsafe */ + if (!vacrel->skipwithvm) + break; + + /* + * Aggressive VACUUM caller can't skip pages just because they are + * all-visible. They may still skip all-frozen pages, which can't + * contain XIDs < OldestXmin (XIDs that aren't already frozen by now). + */ + if ((mapbits & VISIBILITYMAP_ALL_FROZEN) == 0) + { + if (vacrel->aggressive) + break; + + /* + * All-visible block is safe to skip in non-aggressive case. But + * remember that the final range contains such a block for later. + */ + skipsallvis = true; + } + + vacuum_delay_point(); + next_unskippable_block++; + nskippable_blocks++; + } + + /* + * We only skip a range with at least SKIP_PAGES_THRESHOLD consecutive + * pages. Since we're reading sequentially, the OS should be doing + * readahead for us, so there's no gain in skipping a page now and then. + * Skipping such a range might even discourage sequential detection. + * + * This test also enables more frequent relfrozenxid advancement during + * non-aggressive VACUUMs. If the range has any all-visible pages then + * skipping makes updating relfrozenxid unsafe, which is a real downside. + */ + if (nskippable_blocks < SKIP_PAGES_THRESHOLD) + *skipping_current_range = false; + else + { + *skipping_current_range = true; + if (skipsallvis) + vacrel->skippedallvis = true; + } + + return next_unskippable_block; +} + +/* + * lazy_scan_new_or_empty() -- lazy_scan_heap() new/empty page handling. + * + * Must call here to handle both new and empty pages before calling + * lazy_scan_prune or lazy_scan_noprune, since they're not prepared to deal + * with new or empty pages. + * + * It's necessary to consider new pages as a special case, since the rules for + * maintaining the visibility map and FSM with empty pages are a little + * different (though new pages can be truncated away during rel truncation). + * + * Empty pages are not really a special case -- they're just heap pages that + * have no allocated tuples (including even LP_UNUSED items). You might + * wonder why we need to handle them here all the same. It's only necessary + * because of a corner-case involving a hard crash during heap relation + * extension. If we ever make relation-extension crash safe, then it should + * no longer be necessary to deal with empty pages here (or new pages, for + * that matter). + * + * Caller must hold at least a shared lock. We might need to escalate the + * lock in that case, so the type of lock caller holds needs to be specified + * using 'sharelock' argument. + * + * Returns false in common case where caller should go on to call + * lazy_scan_prune (or lazy_scan_noprune). Otherwise returns true, indicating + * that lazy_scan_heap is done processing the page, releasing lock on caller's + * behalf. + */ +static bool +lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf, BlockNumber blkno, + Page page, bool sharelock, Buffer vmbuffer) +{ + Size freespace; + + if (PageIsNew(page)) + { + /* + * All-zeroes pages can be left over if either a backend extends the + * relation by a single page, but crashes before the newly initialized + * page has been written out, or when bulk-extending the relation + * (which creates a number of empty pages at the tail end of the + * relation), and then enters them into the FSM. + * + * Note we do not enter the page into the visibilitymap. That has the + * downside that we repeatedly visit this page in subsequent vacuums, + * but otherwise we'll never discover the space on a promoted standby. + * The harm of repeated checking ought to normally not be too bad. The + * space usually should be used at some point, otherwise there + * wouldn't be any regular vacuums. + * + * Make sure these pages are in the FSM, to ensure they can be reused. + * Do that by testing if there's any space recorded for the page. If + * not, enter it. We do so after releasing the lock on the heap page, + * the FSM is approximate, after all. + */ + UnlockReleaseBuffer(buf); + + if (GetRecordedFreeSpace(vacrel->rel, blkno) == 0) + { + freespace = BLCKSZ - SizeOfPageHeaderData; + + RecordPageWithFreeSpace(vacrel->rel, blkno, freespace); + } + + return true; + } + + if (PageIsEmpty(page)) + { + /* + * It seems likely that caller will always be able to get a cleanup + * lock on an empty page. But don't take any chances -- escalate to + * an exclusive lock (still don't need a cleanup lock, though). + */ + if (sharelock) + { + LockBuffer(buf, BUFFER_LOCK_UNLOCK); + LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE); + + if (!PageIsEmpty(page)) + { + /* page isn't new or empty -- keep lock and pin for now */ + return false; + } + } + else + { + /* Already have a full cleanup lock (which is more than enough) */ + } + + /* + * Unlike new pages, empty pages are always set all-visible and + * all-frozen. + */ + if (!PageIsAllVisible(page)) + { + START_CRIT_SECTION(); + + /* mark buffer dirty before writing a WAL record */ + MarkBufferDirty(buf); + + /* + * It's possible that another backend has extended the heap, + * initialized the page, and then failed to WAL-log the page due + * to an ERROR. Since heap extension is not WAL-logged, recovery + * might try to replay our record setting the page all-visible and + * find that the page isn't initialized, which will cause a PANIC. + * To prevent that, check whether the page has been previously + * WAL-logged, and if not, do that now. + */ + if (RelationNeedsWAL(vacrel->rel) && + PageGetLSN(page) == InvalidXLogRecPtr) + log_newpage_buffer(buf, true); + + PageSetAllVisible(page); + visibilitymap_set(vacrel->rel, blkno, buf, InvalidXLogRecPtr, + vmbuffer, InvalidTransactionId, + VISIBILITYMAP_ALL_VISIBLE | VISIBILITYMAP_ALL_FROZEN); + END_CRIT_SECTION(); + } + + freespace = PageGetHeapFreeSpace(page); + UnlockReleaseBuffer(buf); + RecordPageWithFreeSpace(vacrel->rel, blkno, freespace); + return true; + } + + /* page isn't new or empty -- keep lock and pin */ + return false; +} + +/* + * lazy_scan_prune() -- lazy_scan_heap() pruning and freezing. + * + * Caller must hold pin and buffer cleanup lock on the buffer. + * + * Prior to PostgreSQL 14 there were very rare cases where heap_page_prune() + * was allowed to disagree with our HeapTupleSatisfiesVacuum() call about + * whether or not a tuple should be considered DEAD. This happened when an + * inserting transaction concurrently aborted (after our heap_page_prune() + * call, before our HeapTupleSatisfiesVacuum() call). There was rather a lot + * of complexity just so we could deal with tuples that were DEAD to VACUUM, + * but nevertheless were left with storage after pruning. + * + * The approach we take now is to restart pruning when the race condition is + * detected. This allows heap_page_prune() to prune the tuples inserted by + * the now-aborted transaction. This is a little crude, but it guarantees + * that any items that make it into the dead_items array are simple LP_DEAD + * line pointers, and that every remaining item with tuple storage is + * considered as a candidate for freezing. + */ +static void +lazy_scan_prune(LVRelState *vacrel, + Buffer buf, + BlockNumber blkno, + Page page, + LVPagePruneState *prunestate) +{ + Relation rel = vacrel->rel; + OffsetNumber offnum, + maxoff; + ItemId itemid; + HeapTupleData tuple; + HTSV_Result res; + int tuples_deleted, + lpdead_items, + live_tuples, + recently_dead_tuples; + int nnewlpdead; + int nfrozen; + TransactionId NewRelfrozenXid; + MultiXactId NewRelminMxid; + OffsetNumber deadoffsets[MaxHeapTuplesPerPage]; + xl_heap_freeze_tuple frozen[MaxHeapTuplesPerPage]; + + Assert(BufferGetBlockNumber(buf) == blkno); + + /* + * maxoff might be reduced following line pointer array truncation in + * heap_page_prune. That's safe for us to ignore, since the reclaimed + * space will continue to look like LP_UNUSED items below. + */ + maxoff = PageGetMaxOffsetNumber(page); + +retry: + + /* Initialize (or reset) page-level state */ + NewRelfrozenXid = vacrel->NewRelfrozenXid; + NewRelminMxid = vacrel->NewRelminMxid; + tuples_deleted = 0; + lpdead_items = 0; + live_tuples = 0; + recently_dead_tuples = 0; + + /* + * Prune all HOT-update chains in this page. + * + * We count tuples removed by the pruning step as tuples_deleted. Its + * final value can be thought of as the number of tuples that have been + * deleted from the table. It should not be confused with lpdead_items; + * lpdead_items's final value can be thought of as the number of tuples + * that were deleted from indexes. + */ + tuples_deleted = heap_page_prune(rel, buf, vacrel->vistest, + InvalidTransactionId, 0, &nnewlpdead, + &vacrel->offnum); + + /* + * Now scan the page to collect LP_DEAD items and check for tuples + * requiring freezing among remaining tuples with storage + */ + prunestate->hastup = false; + prunestate->has_lpdead_items = false; + prunestate->all_visible = true; + prunestate->all_frozen = true; + prunestate->visibility_cutoff_xid = InvalidTransactionId; + nfrozen = 0; + + for (offnum = FirstOffsetNumber; + offnum <= maxoff; + offnum = OffsetNumberNext(offnum)) + { + bool tuple_totally_frozen; + + /* + * Set the offset number so that we can display it along with any + * error that occurred while processing this tuple. + */ + vacrel->offnum = offnum; + itemid = PageGetItemId(page, offnum); + + if (!ItemIdIsUsed(itemid)) + continue; + + /* Redirect items mustn't be touched */ + if (ItemIdIsRedirected(itemid)) + { + prunestate->hastup = true; /* page won't be truncatable */ + continue; + } + + /* + * LP_DEAD items are processed outside of the loop. + * + * Note that we deliberately don't set hastup=true in the case of an + * LP_DEAD item here, which is not how count_nondeletable_pages() does + * it -- it only considers pages empty/truncatable when they have no + * items at all (except LP_UNUSED items). + * + * Our assumption is that any LP_DEAD items we encounter here will + * become LP_UNUSED inside lazy_vacuum_heap_page() before we actually + * call count_nondeletable_pages(). In any case our opinion of + * whether or not a page 'hastup' (which is how our caller sets its + * vacrel->nonempty_pages value) is inherently race-prone. It must be + * treated as advisory/unreliable, so we might as well be slightly + * optimistic. + */ + if (ItemIdIsDead(itemid)) + { + deadoffsets[lpdead_items++] = offnum; + prunestate->all_visible = false; + prunestate->has_lpdead_items = true; + continue; + } + + Assert(ItemIdIsNormal(itemid)); + + ItemPointerSet(&(tuple.t_self), blkno, offnum); + tuple.t_data = (HeapTupleHeader) PageGetItem(page, itemid); + tuple.t_len = ItemIdGetLength(itemid); + tuple.t_tableOid = RelationGetRelid(rel); + + /* + * DEAD tuples are almost always pruned into LP_DEAD line pointers by + * heap_page_prune(), but it's possible that the tuple state changed + * since heap_page_prune() looked. Handle that here by restarting. + * (See comments at the top of function for a full explanation.) + */ + res = HeapTupleSatisfiesVacuum(&tuple, vacrel->OldestXmin, buf); + + if (unlikely(res == HEAPTUPLE_DEAD)) + goto retry; + + /* + * The criteria for counting a tuple as live in this block need to + * match what analyze.c's acquire_sample_rows() does, otherwise VACUUM + * and ANALYZE may produce wildly different reltuples values, e.g. + * when there are many recently-dead tuples. + * + * The logic here is a bit simpler than acquire_sample_rows(), as + * VACUUM can't run inside a transaction block, which makes some cases + * impossible (e.g. in-progress insert from the same transaction). + * + * We treat LP_DEAD items (which are the closest thing to DEAD tuples + * that might be seen here) differently, too: we assume that they'll + * become LP_UNUSED before VACUUM finishes. This difference is only + * superficial. VACUUM effectively agrees with ANALYZE about DEAD + * items, in the end. VACUUM won't remember LP_DEAD items, but only + * because they're not supposed to be left behind when it is done. + * (Cases where we bypass index vacuuming will violate this optimistic + * assumption, but the overall impact of that should be negligible.) + */ + switch (res) + { + case HEAPTUPLE_LIVE: + + /* + * Count it as live. Not only is this natural, but it's also + * what acquire_sample_rows() does. + */ + live_tuples++; + + /* + * Is the tuple definitely visible to all transactions? + * + * NB: Like with per-tuple hint bits, we can't set the + * PD_ALL_VISIBLE flag if the inserter committed + * asynchronously. See SetHintBits for more info. Check that + * the tuple is hinted xmin-committed because of that. + */ + if (prunestate->all_visible) + { + TransactionId xmin; + + if (!HeapTupleHeaderXminCommitted(tuple.t_data)) + { + prunestate->all_visible = false; + break; + } + + /* + * The inserter definitely committed. But is it old enough + * that everyone sees it as committed? + */ + xmin = HeapTupleHeaderGetXmin(tuple.t_data); + if (!TransactionIdPrecedes(xmin, vacrel->OldestXmin)) + { + prunestate->all_visible = false; + break; + } + + /* Track newest xmin on page. */ + if (TransactionIdFollows(xmin, prunestate->visibility_cutoff_xid)) + prunestate->visibility_cutoff_xid = xmin; + } + break; + case HEAPTUPLE_RECENTLY_DEAD: + + /* + * If tuple is recently dead then we must not remove it from + * the relation. (We only remove items that are LP_DEAD from + * pruning.) + */ + recently_dead_tuples++; + prunestate->all_visible = false; + break; + case HEAPTUPLE_INSERT_IN_PROGRESS: + + /* + * We do not count these rows as live, because we expect the + * inserting transaction to update the counters at commit, and + * we assume that will happen only after we report our + * results. This assumption is a bit shaky, but it is what + * acquire_sample_rows() does, so be consistent. + */ + prunestate->all_visible = false; + break; + case HEAPTUPLE_DELETE_IN_PROGRESS: + /* This is an expected case during concurrent vacuum */ + prunestate->all_visible = false; + + /* + * Count such rows as live. As above, we assume the deleting + * transaction will commit and update the counters after we + * report. + */ + live_tuples++; + break; + default: + elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result"); + break; + } + + /* + * Non-removable tuple (i.e. tuple with storage). + * + * Check tuple left behind after pruning to see if needs to be frozen + * now. + */ + prunestate->hastup = true; /* page makes rel truncation unsafe */ + if (heap_prepare_freeze_tuple(tuple.t_data, + vacrel->relfrozenxid, + vacrel->relminmxid, + vacrel->FreezeLimit, + vacrel->MultiXactCutoff, + &frozen[nfrozen], &tuple_totally_frozen, + &NewRelfrozenXid, &NewRelminMxid)) + { + /* Will execute freeze below */ + frozen[nfrozen++].offset = offnum; + } + + /* + * If tuple is not frozen (and not about to become frozen) then caller + * had better not go on to set this page's VM bit + */ + if (!tuple_totally_frozen) + prunestate->all_frozen = false; + } + + vacrel->offnum = InvalidOffsetNumber; + + /* + * We have now divided every item on the page into either an LP_DEAD item + * that will need to be vacuumed in indexes later, or a LP_NORMAL tuple + * that remains and needs to be considered for freezing now (LP_UNUSED and + * LP_REDIRECT items also remain, but are of no further interest to us). + */ + vacrel->NewRelfrozenXid = NewRelfrozenXid; + vacrel->NewRelminMxid = NewRelminMxid; + + /* + * Consider the need to freeze any items with tuple storage from the page + * first (arbitrary) + */ + if (nfrozen > 0) + { + Assert(prunestate->hastup); + + /* + * At least one tuple with storage needs to be frozen -- execute that + * now. + * + * If we need to freeze any tuples we'll mark the buffer dirty, and + * write a WAL record recording the changes. We must log the changes + * to be crash-safe against future truncation of CLOG. + */ + START_CRIT_SECTION(); + + MarkBufferDirty(buf); + + /* execute collected freezes */ + for (int i = 0; i < nfrozen; i++) + { + HeapTupleHeader htup; + + itemid = PageGetItemId(page, frozen[i].offset); + htup = (HeapTupleHeader) PageGetItem(page, itemid); + + heap_execute_freeze_tuple(htup, &frozen[i]); + } + + /* Now WAL-log freezing if necessary */ + if (RelationNeedsWAL(vacrel->rel)) + { + XLogRecPtr recptr; + + recptr = log_heap_freeze(vacrel->rel, buf, vacrel->FreezeLimit, + frozen, nfrozen); + PageSetLSN(page, recptr); + } + + END_CRIT_SECTION(); + } + + /* + * The second pass over the heap can also set visibility map bits, using + * the same approach. This is important when the table frequently has a + * few old LP_DEAD items on each page by the time we get to it (typically + * because past opportunistic pruning operations freed some non-HOT + * tuples). + * + * VACUUM will call heap_page_is_all_visible() during the second pass over + * the heap to determine all_visible and all_frozen for the page -- this + * is a specialized version of the logic from this function. Now that + * we've finished pruning and freezing, make sure that we're in total + * agreement with heap_page_is_all_visible() using an assertion. + */ +#ifdef USE_ASSERT_CHECKING + /* Note that all_frozen value does not matter when !all_visible */ + if (prunestate->all_visible) + { + TransactionId cutoff; + bool all_frozen; + + if (!heap_page_is_all_visible(vacrel, buf, &cutoff, &all_frozen)) + Assert(false); + + Assert(lpdead_items == 0); + Assert(prunestate->all_frozen == all_frozen); + + /* + * It's possible that we froze tuples and made the page's XID cutoff + * (for recovery conflict purposes) FrozenTransactionId. This is okay + * because visibility_cutoff_xid will be logged by our caller in a + * moment. + */ + Assert(cutoff == FrozenTransactionId || + cutoff == prunestate->visibility_cutoff_xid); + } +#endif + + /* + * Now save details of the LP_DEAD items from the page in vacrel + */ + if (lpdead_items > 0) + { + VacDeadItems *dead_items = vacrel->dead_items; + ItemPointerData tmp; + + Assert(!prunestate->all_visible); + Assert(prunestate->has_lpdead_items); + + vacrel->lpdead_item_pages++; + + ItemPointerSetBlockNumber(&tmp, blkno); + + for (int i = 0; i < lpdead_items; i++) + { + ItemPointerSetOffsetNumber(&tmp, deadoffsets[i]); + dead_items->items[dead_items->num_items++] = tmp; + } + + Assert(dead_items->num_items <= dead_items->max_items); + pgstat_progress_update_param(PROGRESS_VACUUM_NUM_DEAD_TUPLES, + dead_items->num_items); + } + + /* Finally, add page-local counts to whole-VACUUM counts */ + vacrel->tuples_deleted += tuples_deleted; + vacrel->lpdead_items += lpdead_items; + vacrel->live_tuples += live_tuples; + vacrel->recently_dead_tuples += recently_dead_tuples; +} + +/* + * lazy_scan_noprune() -- lazy_scan_prune() without pruning or freezing + * + * Caller need only hold a pin and share lock on the buffer, unlike + * lazy_scan_prune, which requires a full cleanup lock. While pruning isn't + * performed here, it's quite possible that an earlier opportunistic pruning + * operation left LP_DEAD items behind. We'll at least collect any such items + * in the dead_items array for removal from indexes. + * + * For aggressive VACUUM callers, we may return false to indicate that a full + * cleanup lock is required for processing by lazy_scan_prune. This is only + * necessary when the aggressive VACUUM needs to freeze some tuple XIDs from + * one or more tuples on the page. We always return true for non-aggressive + * callers. + * + * See lazy_scan_prune for an explanation of hastup return flag. + * recordfreespace flag instructs caller on whether or not it should do + * generic FSM processing for page. + */ +static bool +lazy_scan_noprune(LVRelState *vacrel, + Buffer buf, + BlockNumber blkno, + Page page, + bool *hastup, + bool *recordfreespace) +{ + OffsetNumber offnum, + maxoff; + int lpdead_items, + live_tuples, + recently_dead_tuples, + missed_dead_tuples; + HeapTupleHeader tupleheader; + TransactionId NewRelfrozenXid = vacrel->NewRelfrozenXid; + MultiXactId NewRelminMxid = vacrel->NewRelminMxid; + OffsetNumber deadoffsets[MaxHeapTuplesPerPage]; + + Assert(BufferGetBlockNumber(buf) == blkno); + + *hastup = false; /* for now */ + *recordfreespace = false; /* for now */ + + lpdead_items = 0; + live_tuples = 0; + recently_dead_tuples = 0; + missed_dead_tuples = 0; + + maxoff = PageGetMaxOffsetNumber(page); + for (offnum = FirstOffsetNumber; + offnum <= maxoff; + offnum = OffsetNumberNext(offnum)) + { + ItemId itemid; + HeapTupleData tuple; + + vacrel->offnum = offnum; + itemid = PageGetItemId(page, offnum); + + if (!ItemIdIsUsed(itemid)) + continue; + + if (ItemIdIsRedirected(itemid)) + { + *hastup = true; + continue; + } + + if (ItemIdIsDead(itemid)) + { + /* + * Deliberately don't set hastup=true here. See same point in + * lazy_scan_prune for an explanation. + */ + deadoffsets[lpdead_items++] = offnum; + continue; + } + + *hastup = true; /* page prevents rel truncation */ + tupleheader = (HeapTupleHeader) PageGetItem(page, itemid); + if (heap_tuple_would_freeze(tupleheader, + vacrel->FreezeLimit, + vacrel->MultiXactCutoff, + &NewRelfrozenXid, &NewRelminMxid)) + { + /* Tuple with XID < FreezeLimit (or MXID < MultiXactCutoff) */ + if (vacrel->aggressive) + { + /* + * Aggressive VACUUMs must always be able to advance rel's + * relfrozenxid to a value >= FreezeLimit (and be able to + * advance rel's relminmxid to a value >= MultiXactCutoff). + * The ongoing aggressive VACUUM won't be able to do that + * unless it can freeze an XID (or MXID) from this tuple now. + * + * The only safe option is to have caller perform processing + * of this page using lazy_scan_prune. Caller might have to + * wait a while for a cleanup lock, but it can't be helped. + */ + vacrel->offnum = InvalidOffsetNumber; + return false; + } + + /* + * Non-aggressive VACUUMs are under no obligation to advance + * relfrozenxid (even by one XID). We can be much laxer here. + * + * Currently we always just accept an older final relfrozenxid + * and/or relminmxid value. We never make caller wait or work a + * little harder, even when it likely makes sense to do so. + */ + } + + ItemPointerSet(&(tuple.t_self), blkno, offnum); + tuple.t_data = (HeapTupleHeader) PageGetItem(page, itemid); + tuple.t_len = ItemIdGetLength(itemid); + tuple.t_tableOid = RelationGetRelid(vacrel->rel); + + switch (HeapTupleSatisfiesVacuum(&tuple, vacrel->OldestXmin, buf)) + { + case HEAPTUPLE_DELETE_IN_PROGRESS: + case HEAPTUPLE_LIVE: + + /* + * Count both cases as live, just like lazy_scan_prune + */ + live_tuples++; + + break; + case HEAPTUPLE_DEAD: + + /* + * There is some useful work for pruning to do, that won't be + * done due to failure to get a cleanup lock. + */ + missed_dead_tuples++; + break; + case HEAPTUPLE_RECENTLY_DEAD: + + /* + * Count in recently_dead_tuples, just like lazy_scan_prune + */ + recently_dead_tuples++; + break; + case HEAPTUPLE_INSERT_IN_PROGRESS: + + /* + * Do not count these rows as live, just like lazy_scan_prune + */ + break; + default: + elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result"); + break; + } + } + + vacrel->offnum = InvalidOffsetNumber; + + /* + * By here we know for sure that caller can put off freezing and pruning + * this particular page until the next VACUUM. Remember its details now. + * (lazy_scan_prune expects a clean slate, so we have to do this last.) + */ + vacrel->NewRelfrozenXid = NewRelfrozenXid; + vacrel->NewRelminMxid = NewRelminMxid; + + /* Save any LP_DEAD items found on the page in dead_items array */ + if (vacrel->nindexes == 0) + { + /* Using one-pass strategy (since table has no indexes) */ + if (lpdead_items > 0) + { + /* + * Perfunctory handling for the corner case where a single pass + * strategy VACUUM cannot get a cleanup lock, and it turns out + * that there is one or more LP_DEAD items: just count the LP_DEAD + * items as missed_dead_tuples instead. (This is a bit dishonest, + * but it beats having to maintain specialized heap vacuuming code + * forever, for vanishingly little benefit.) + */ + *hastup = true; + missed_dead_tuples += lpdead_items; + } + + *recordfreespace = true; + } + else if (lpdead_items == 0) + { + /* + * Won't be vacuuming this page later, so record page's freespace in + * the FSM now + */ + *recordfreespace = true; + } + else + { + VacDeadItems *dead_items = vacrel->dead_items; + ItemPointerData tmp; + + /* + * Page has LP_DEAD items, and so any references/TIDs that remain in + * indexes will be deleted during index vacuuming (and then marked + * LP_UNUSED in the heap) + */ + vacrel->lpdead_item_pages++; + + ItemPointerSetBlockNumber(&tmp, blkno); + + for (int i = 0; i < lpdead_items; i++) + { + ItemPointerSetOffsetNumber(&tmp, deadoffsets[i]); + dead_items->items[dead_items->num_items++] = tmp; + } + + Assert(dead_items->num_items <= dead_items->max_items); + pgstat_progress_update_param(PROGRESS_VACUUM_NUM_DEAD_TUPLES, + dead_items->num_items); + + vacrel->lpdead_items += lpdead_items; + + /* + * Assume that we'll go on to vacuum this heap page during final pass + * over the heap. Don't record free space until then. + */ + *recordfreespace = false; + } + + /* + * Finally, add relevant page-local counts to whole-VACUUM counts + */ + vacrel->live_tuples += live_tuples; + vacrel->recently_dead_tuples += recently_dead_tuples; + vacrel->missed_dead_tuples += missed_dead_tuples; + if (missed_dead_tuples > 0) + vacrel->missed_dead_pages++; + + /* Caller won't need to call lazy_scan_prune with same page */ + return true; +} + +/* + * Main entry point for index vacuuming and heap vacuuming. + * + * Removes items collected in dead_items from table's indexes, then marks the + * same items LP_UNUSED in the heap. See the comments above lazy_scan_heap + * for full details. + * + * Also empties dead_items, freeing up space for later TIDs. + * + * We may choose to bypass index vacuuming at this point, though only when the + * ongoing VACUUM operation will definitely only have one index scan/round of + * index vacuuming. + */ +static void +lazy_vacuum(LVRelState *vacrel) +{ + bool bypass; + + /* Should not end up here with no indexes */ + Assert(vacrel->nindexes > 0); + Assert(vacrel->lpdead_item_pages > 0); + + if (!vacrel->do_index_vacuuming) + { + Assert(!vacrel->do_index_cleanup); + vacrel->dead_items->num_items = 0; + return; + } + + /* + * Consider bypassing index vacuuming (and heap vacuuming) entirely. + * + * We currently only do this in cases where the number of LP_DEAD items + * for the entire VACUUM operation is close to zero. This avoids sharp + * discontinuities in the duration and overhead of successive VACUUM + * operations that run against the same table with a fixed workload. + * Ideally, successive VACUUM operations will behave as if there are + * exactly zero LP_DEAD items in cases where there are close to zero. + * + * This is likely to be helpful with a table that is continually affected + * by UPDATEs that can mostly apply the HOT optimization, but occasionally + * have small aberrations that lead to just a few heap pages retaining + * only one or two LP_DEAD items. This is pretty common; even when the + * DBA goes out of their way to make UPDATEs use HOT, it is practically + * impossible to predict whether HOT will be applied in 100% of cases. + * It's far easier to ensure that 99%+ of all UPDATEs against a table use + * HOT through careful tuning. + */ + bypass = false; + if (vacrel->consider_bypass_optimization && vacrel->rel_pages > 0) + { + BlockNumber threshold; + + Assert(vacrel->num_index_scans == 0); + Assert(vacrel->lpdead_items == vacrel->dead_items->num_items); + Assert(vacrel->do_index_vacuuming); + Assert(vacrel->do_index_cleanup); + + /* + * This crossover point at which we'll start to do index vacuuming is + * expressed as a percentage of the total number of heap pages in the + * table that are known to have at least one LP_DEAD item. This is + * much more important than the total number of LP_DEAD items, since + * it's a proxy for the number of heap pages whose visibility map bits + * cannot be set on account of bypassing index and heap vacuuming. + * + * We apply one further precautionary test: the space currently used + * to store the TIDs (TIDs that now all point to LP_DEAD items) must + * not exceed 32MB. This limits the risk that we will bypass index + * vacuuming again and again until eventually there is a VACUUM whose + * dead_items space is not CPU cache resident. + * + * We don't take any special steps to remember the LP_DEAD items (such + * as counting them in our final update to the stats system) when the + * optimization is applied. Though the accounting used in analyze.c's + * acquire_sample_rows() will recognize the same LP_DEAD items as dead + * rows in its own stats report, that's okay. The discrepancy should + * be negligible. If this optimization is ever expanded to cover more + * cases then this may need to be reconsidered. + */ + threshold = (double) vacrel->rel_pages * BYPASS_THRESHOLD_PAGES; + bypass = (vacrel->lpdead_item_pages < threshold && + vacrel->lpdead_items < MAXDEADITEMS(32L * 1024L * 1024L)); + } + + if (bypass) + { + /* + * There are almost zero TIDs. Behave as if there were precisely + * zero: bypass index vacuuming, but do index cleanup. + * + * We expect that the ongoing VACUUM operation will finish very + * quickly, so there is no point in considering speeding up as a + * failsafe against wraparound failure. (Index cleanup is expected to + * finish very quickly in cases where there were no ambulkdelete() + * calls.) + */ + vacrel->do_index_vacuuming = false; + } + else if (lazy_vacuum_all_indexes(vacrel)) + { + /* + * We successfully completed a round of index vacuuming. Do related + * heap vacuuming now. + */ + lazy_vacuum_heap_rel(vacrel); + } + else + { + /* + * Failsafe case. + * + * We attempted index vacuuming, but didn't finish a full round/full + * index scan. This happens when relfrozenxid or relminmxid is too + * far in the past. + * + * From this point on the VACUUM operation will do no further index + * vacuuming or heap vacuuming. This VACUUM operation won't end up + * back here again. + */ + Assert(vacrel->failsafe_active); + } + + /* + * Forget the LP_DEAD items that we just vacuumed (or just decided to not + * vacuum) + */ + vacrel->dead_items->num_items = 0; +} + +/* + * lazy_vacuum_all_indexes() -- Main entry for index vacuuming + * + * Returns true in the common case when all indexes were successfully + * vacuumed. Returns false in rare cases where we determined that the ongoing + * VACUUM operation is at risk of taking too long to finish, leading to + * wraparound failure. + */ +static bool +lazy_vacuum_all_indexes(LVRelState *vacrel) +{ + bool allindexes = true; + + Assert(vacrel->nindexes > 0); + Assert(vacrel->do_index_vacuuming); + Assert(vacrel->do_index_cleanup); + + /* Precheck for XID wraparound emergencies */ + if (lazy_check_wraparound_failsafe(vacrel)) + { + /* Wraparound emergency -- don't even start an index scan */ + return false; + } + + /* Report that we are now vacuuming indexes */ + pgstat_progress_update_param(PROGRESS_VACUUM_PHASE, + PROGRESS_VACUUM_PHASE_VACUUM_INDEX); + + if (!ParallelVacuumIsActive(vacrel)) + { + for (int idx = 0; idx < vacrel->nindexes; idx++) + { + Relation indrel = vacrel->indrels[idx]; + IndexBulkDeleteResult *istat = vacrel->indstats[idx]; + + vacrel->indstats[idx] = + lazy_vacuum_one_index(indrel, istat, vacrel->old_live_tuples, + vacrel); + + if (lazy_check_wraparound_failsafe(vacrel)) + { + /* Wraparound emergency -- end current index scan */ + allindexes = false; + break; + } + } + } + else + { + /* Outsource everything to parallel variant */ + parallel_vacuum_bulkdel_all_indexes(vacrel->pvs, vacrel->old_live_tuples, + vacrel->num_index_scans); + + /* + * Do a postcheck to consider applying wraparound failsafe now. Note + * that parallel VACUUM only gets the precheck and this postcheck. + */ + if (lazy_check_wraparound_failsafe(vacrel)) + allindexes = false; + } + + /* + * We delete all LP_DEAD items from the first heap pass in all indexes on + * each call here (except calls where we choose to do the failsafe). This + * makes the next call to lazy_vacuum_heap_rel() safe (except in the event + * of the failsafe triggering, which prevents the next call from taking + * place). + */ + Assert(vacrel->num_index_scans > 0 || + vacrel->dead_items->num_items == vacrel->lpdead_items); + Assert(allindexes || vacrel->failsafe_active); + + /* + * Increase and report the number of index scans. + * + * We deliberately include the case where we started a round of bulk + * deletes that we weren't able to finish due to the failsafe triggering. + */ + vacrel->num_index_scans++; + pgstat_progress_update_param(PROGRESS_VACUUM_NUM_INDEX_VACUUMS, + vacrel->num_index_scans); + + return allindexes; +} + +/* + * lazy_vacuum_heap_rel() -- second pass over the heap for two pass strategy + * + * This routine marks LP_DEAD items in vacrel->dead_items array as LP_UNUSED. + * Pages that never had lazy_scan_prune record LP_DEAD items are not visited + * at all. + * + * We may also be able to truncate the line pointer array of the heap pages we + * visit. If there is a contiguous group of LP_UNUSED items at the end of the + * array, it can be reclaimed as free space. These LP_UNUSED items usually + * start out as LP_DEAD items recorded by lazy_scan_prune (we set items from + * each page to LP_UNUSED, and then consider if it's possible to truncate the + * page's line pointer array). + * + * Note: the reason for doing this as a second pass is we cannot remove the + * tuples until we've removed their index entries, and we want to process + * index entry removal in batches as large as possible. + */ +static void +lazy_vacuum_heap_rel(LVRelState *vacrel) +{ + int index; + BlockNumber vacuumed_pages; + Buffer vmbuffer = InvalidBuffer; + LVSavedErrInfo saved_err_info; + + Assert(vacrel->do_index_vacuuming); + Assert(vacrel->do_index_cleanup); + Assert(vacrel->num_index_scans > 0); + + /* Report that we are now vacuuming the heap */ + pgstat_progress_update_param(PROGRESS_VACUUM_PHASE, + PROGRESS_VACUUM_PHASE_VACUUM_HEAP); + + /* Update error traceback information */ + update_vacuum_error_info(vacrel, &saved_err_info, + VACUUM_ERRCB_PHASE_VACUUM_HEAP, + InvalidBlockNumber, InvalidOffsetNumber); + + vacuumed_pages = 0; + + index = 0; + while (index < vacrel->dead_items->num_items) + { + BlockNumber tblk; + Buffer buf; + Page page; + Size freespace; + + vacuum_delay_point(); + + tblk = ItemPointerGetBlockNumber(&vacrel->dead_items->items[index]); + vacrel->blkno = tblk; + buf = ReadBufferExtended(vacrel->rel, MAIN_FORKNUM, tblk, RBM_NORMAL, + vacrel->bstrategy); + LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE); + index = lazy_vacuum_heap_page(vacrel, tblk, buf, index, &vmbuffer); + + /* Now that we've vacuumed the page, record its available space */ + page = BufferGetPage(buf); + freespace = PageGetHeapFreeSpace(page); + + UnlockReleaseBuffer(buf); + RecordPageWithFreeSpace(vacrel->rel, tblk, freespace); + vacuumed_pages++; + } + + /* Clear the block number information */ + vacrel->blkno = InvalidBlockNumber; + + if (BufferIsValid(vmbuffer)) + { + ReleaseBuffer(vmbuffer); + vmbuffer = InvalidBuffer; + } + + /* + * We set all LP_DEAD items from the first heap pass to LP_UNUSED during + * the second heap pass. No more, no less. + */ + Assert(index > 0); + Assert(vacrel->num_index_scans > 1 || + (index == vacrel->lpdead_items && + vacuumed_pages == vacrel->lpdead_item_pages)); + + ereport(DEBUG2, + (errmsg("table \"%s\": removed %lld dead item identifiers in %u pages", + vacrel->relname, (long long) index, vacuumed_pages))); + + /* Revert to the previous phase information for error traceback */ + restore_vacuum_error_info(vacrel, &saved_err_info); +} + +/* + * lazy_vacuum_heap_page() -- free page's LP_DEAD items listed in the + * vacrel->dead_items array. + * + * Caller must have an exclusive buffer lock on the buffer (though a full + * cleanup lock is also acceptable). + * + * index is an offset into the vacrel->dead_items array for the first listed + * LP_DEAD item on the page. The return value is the first index immediately + * after all LP_DEAD items for the same page in the array. + */ +static int +lazy_vacuum_heap_page(LVRelState *vacrel, BlockNumber blkno, Buffer buffer, + int index, Buffer *vmbuffer) +{ + VacDeadItems *dead_items = vacrel->dead_items; + Page page = BufferGetPage(buffer); + OffsetNumber unused[MaxHeapTuplesPerPage]; + int uncnt = 0; + TransactionId visibility_cutoff_xid; + bool all_frozen; + LVSavedErrInfo saved_err_info; + + Assert(vacrel->nindexes == 0 || vacrel->do_index_vacuuming); + + pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_VACUUMED, blkno); + + /* Update error traceback information */ + update_vacuum_error_info(vacrel, &saved_err_info, + VACUUM_ERRCB_PHASE_VACUUM_HEAP, blkno, + InvalidOffsetNumber); + + START_CRIT_SECTION(); + + for (; index < dead_items->num_items; index++) + { + BlockNumber tblk; + OffsetNumber toff; + ItemId itemid; + + tblk = ItemPointerGetBlockNumber(&dead_items->items[index]); + if (tblk != blkno) + break; /* past end of tuples for this block */ + toff = ItemPointerGetOffsetNumber(&dead_items->items[index]); + itemid = PageGetItemId(page, toff); + + Assert(ItemIdIsDead(itemid) && !ItemIdHasStorage(itemid)); + ItemIdSetUnused(itemid); + unused[uncnt++] = toff; + } + + Assert(uncnt > 0); + + /* Attempt to truncate line pointer array now */ + PageTruncateLinePointerArray(page); + + /* + * Mark buffer dirty before we write WAL. + */ + MarkBufferDirty(buffer); + + /* XLOG stuff */ + if (RelationNeedsWAL(vacrel->rel)) + { + xl_heap_vacuum xlrec; + XLogRecPtr recptr; + + xlrec.nunused = uncnt; + + XLogBeginInsert(); + XLogRegisterData((char *) &xlrec, SizeOfHeapVacuum); + + XLogRegisterBuffer(0, buffer, REGBUF_STANDARD); + XLogRegisterBufData(0, (char *) unused, uncnt * sizeof(OffsetNumber)); + + recptr = XLogInsert(RM_HEAP2_ID, XLOG_HEAP2_VACUUM); + + PageSetLSN(page, recptr); + } + + /* + * End critical section, so we safely can do visibility tests (which + * possibly need to perform IO and allocate memory!). If we crash now the + * page (including the corresponding vm bit) might not be marked all + * visible, but that's fine. A later vacuum will fix that. + */ + END_CRIT_SECTION(); + + /* + * Now that we have removed the LD_DEAD items from the page, once again + * check if the page has become all-visible. The page is already marked + * dirty, exclusively locked, and, if needed, a full page image has been + * emitted. + */ + if (heap_page_is_all_visible(vacrel, buffer, &visibility_cutoff_xid, + &all_frozen)) + PageSetAllVisible(page); + + /* + * All the changes to the heap page have been done. If the all-visible + * flag is now set, also set the VM all-visible bit (and, if possible, the + * all-frozen bit) unless this has already been done previously. + */ + if (PageIsAllVisible(page)) + { + uint8 flags = 0; + uint8 vm_status = visibilitymap_get_status(vacrel->rel, + blkno, vmbuffer); + + /* Set the VM all-frozen bit to flag, if needed */ + if ((vm_status & VISIBILITYMAP_ALL_VISIBLE) == 0) + flags |= VISIBILITYMAP_ALL_VISIBLE; + if ((vm_status & VISIBILITYMAP_ALL_FROZEN) == 0 && all_frozen) + flags |= VISIBILITYMAP_ALL_FROZEN; + + Assert(BufferIsValid(*vmbuffer)); + if (flags != 0) + visibilitymap_set(vacrel->rel, blkno, buffer, InvalidXLogRecPtr, + *vmbuffer, visibility_cutoff_xid, flags); + } + + /* Revert to the previous phase information for error traceback */ + restore_vacuum_error_info(vacrel, &saved_err_info); + return index; +} + +/* + * Trigger the failsafe to avoid wraparound failure when vacrel table has a + * relfrozenxid and/or relminmxid that is dangerously far in the past. + * Triggering the failsafe makes the ongoing VACUUM bypass any further index + * vacuuming and heap vacuuming. Truncating the heap is also bypassed. + * + * Any remaining work (work that VACUUM cannot just bypass) is typically sped + * up when the failsafe triggers. VACUUM stops applying any cost-based delay + * that it started out with. + * + * Returns true when failsafe has been triggered. + */ +static bool +lazy_check_wraparound_failsafe(LVRelState *vacrel) +{ + Assert(TransactionIdIsNormal(vacrel->relfrozenxid)); + Assert(MultiXactIdIsValid(vacrel->relminmxid)); + + /* Don't warn more than once per VACUUM */ + if (vacrel->failsafe_active) + return true; + + if (unlikely(vacuum_xid_failsafe_check(vacrel->relfrozenxid, + vacrel->relminmxid))) + { + vacrel->failsafe_active = true; + + /* Disable index vacuuming, index cleanup, and heap rel truncation */ + vacrel->do_index_vacuuming = false; + vacrel->do_index_cleanup = false; + vacrel->do_rel_truncate = false; + + ereport(WARNING, + (errmsg("bypassing nonessential maintenance of table \"%s.%s.%s\" as a failsafe after %d index scans", + get_database_name(MyDatabaseId), + vacrel->relnamespace, + vacrel->relname, + vacrel->num_index_scans), + errdetail("The table's relfrozenxid or relminmxid is too far in the past."), + errhint("Consider increasing configuration parameter \"maintenance_work_mem\" or \"autovacuum_work_mem\".\n" + "You might also need to consider other ways for VACUUM to keep up with the allocation of transaction IDs."))); + + /* Stop applying cost limits from this point on */ + VacuumCostActive = false; + VacuumCostBalance = 0; + + return true; + } + + return false; +} + +/* + * lazy_cleanup_all_indexes() -- cleanup all indexes of relation. + */ +static void +lazy_cleanup_all_indexes(LVRelState *vacrel) +{ + double reltuples = vacrel->new_rel_tuples; + bool estimated_count = vacrel->scanned_pages < vacrel->rel_pages; + + Assert(vacrel->do_index_cleanup); + Assert(vacrel->nindexes > 0); + + /* Report that we are now cleaning up indexes */ + pgstat_progress_update_param(PROGRESS_VACUUM_PHASE, + PROGRESS_VACUUM_PHASE_INDEX_CLEANUP); + + if (!ParallelVacuumIsActive(vacrel)) + { + for (int idx = 0; idx < vacrel->nindexes; idx++) + { + Relation indrel = vacrel->indrels[idx]; + IndexBulkDeleteResult *istat = vacrel->indstats[idx]; + + vacrel->indstats[idx] = + lazy_cleanup_one_index(indrel, istat, reltuples, + estimated_count, vacrel); + } + } + else + { + /* Outsource everything to parallel variant */ + parallel_vacuum_cleanup_all_indexes(vacrel->pvs, reltuples, + vacrel->num_index_scans, + estimated_count); + } +} + +/* + * lazy_vacuum_one_index() -- vacuum index relation. + * + * Delete all the index tuples containing a TID collected in + * vacrel->dead_items array. Also update running statistics. + * Exact details depend on index AM's ambulkdelete routine. + * + * reltuples is the number of heap tuples to be passed to the + * bulkdelete callback. It's always assumed to be estimated. + * See indexam.sgml for more info. + * + * Returns bulk delete stats derived from input stats + */ +static IndexBulkDeleteResult * +lazy_vacuum_one_index(Relation indrel, IndexBulkDeleteResult *istat, + double reltuples, LVRelState *vacrel) +{ + IndexVacuumInfo ivinfo; + LVSavedErrInfo saved_err_info; + + ivinfo.index = indrel; + ivinfo.analyze_only = false; + ivinfo.report_progress = false; + ivinfo.estimated_count = true; + ivinfo.message_level = DEBUG2; + ivinfo.num_heap_tuples = reltuples; + ivinfo.strategy = vacrel->bstrategy; + + /* + * Update error traceback information. + * + * The index name is saved during this phase and restored immediately + * after this phase. See vacuum_error_callback. + */ + Assert(vacrel->indname == NULL); + vacrel->indname = pstrdup(RelationGetRelationName(indrel)); + update_vacuum_error_info(vacrel, &saved_err_info, + VACUUM_ERRCB_PHASE_VACUUM_INDEX, + InvalidBlockNumber, InvalidOffsetNumber); + + /* Do bulk deletion */ + istat = vac_bulkdel_one_index(&ivinfo, istat, (void *) vacrel->dead_items); + + /* Revert to the previous phase information for error traceback */ + restore_vacuum_error_info(vacrel, &saved_err_info); + pfree(vacrel->indname); + vacrel->indname = NULL; + + return istat; +} + +/* + * lazy_cleanup_one_index() -- do post-vacuum cleanup for index relation. + * + * Calls index AM's amvacuumcleanup routine. reltuples is the number + * of heap tuples and estimated_count is true if reltuples is an + * estimated value. See indexam.sgml for more info. + * + * Returns bulk delete stats derived from input stats + */ +static IndexBulkDeleteResult * +lazy_cleanup_one_index(Relation indrel, IndexBulkDeleteResult *istat, + double reltuples, bool estimated_count, + LVRelState *vacrel) +{ + IndexVacuumInfo ivinfo; + LVSavedErrInfo saved_err_info; + + ivinfo.index = indrel; + ivinfo.analyze_only = false; + ivinfo.report_progress = false; + ivinfo.estimated_count = estimated_count; + ivinfo.message_level = DEBUG2; + + ivinfo.num_heap_tuples = reltuples; + ivinfo.strategy = vacrel->bstrategy; + + /* + * Update error traceback information. + * + * The index name is saved during this phase and restored immediately + * after this phase. See vacuum_error_callback. + */ + Assert(vacrel->indname == NULL); + vacrel->indname = pstrdup(RelationGetRelationName(indrel)); + update_vacuum_error_info(vacrel, &saved_err_info, + VACUUM_ERRCB_PHASE_INDEX_CLEANUP, + InvalidBlockNumber, InvalidOffsetNumber); + + istat = vac_cleanup_one_index(&ivinfo, istat); + + /* Revert to the previous phase information for error traceback */ + restore_vacuum_error_info(vacrel, &saved_err_info); + pfree(vacrel->indname); + vacrel->indname = NULL; + + return istat; +} + +/* + * should_attempt_truncation - should we attempt to truncate the heap? + * + * Don't even think about it unless we have a shot at releasing a goodly + * number of pages. Otherwise, the time taken isn't worth it, mainly because + * an AccessExclusive lock must be replayed on any hot standby, where it can + * be particularly disruptive. + * + * Also don't attempt it if wraparound failsafe is in effect. The entire + * system might be refusing to allocate new XIDs at this point. The system + * definitely won't return to normal unless and until VACUUM actually advances + * the oldest relfrozenxid -- which hasn't happened for target rel just yet. + * If lazy_truncate_heap attempted to acquire an AccessExclusiveLock to + * truncate the table under these circumstances, an XID exhaustion error might + * make it impossible for VACUUM to fix the underlying XID exhaustion problem. + * There is very little chance of truncation working out when the failsafe is + * in effect in any case. lazy_scan_prune makes the optimistic assumption + * that any LP_DEAD items it encounters will always be LP_UNUSED by the time + * we're called. + * + * Also don't attempt it if we are doing early pruning/vacuuming, because a + * scan which cannot find a truncated heap page cannot determine that the + * snapshot is too old to read that page. + */ +static bool +should_attempt_truncation(LVRelState *vacrel) +{ + BlockNumber possibly_freeable; + + if (!vacrel->do_rel_truncate || vacrel->failsafe_active || + old_snapshot_threshold >= 0) + return false; + + possibly_freeable = vacrel->rel_pages - vacrel->nonempty_pages; + if (possibly_freeable > 0 && + (possibly_freeable >= REL_TRUNCATE_MINIMUM || + possibly_freeable >= vacrel->rel_pages / REL_TRUNCATE_FRACTION)) + return true; + + return false; +} + +/* + * lazy_truncate_heap - try to truncate off any empty pages at the end + */ +static void +lazy_truncate_heap(LVRelState *vacrel) +{ + BlockNumber orig_rel_pages = vacrel->rel_pages; + BlockNumber new_rel_pages; + bool lock_waiter_detected; + int lock_retry; + + /* Report that we are now truncating */ + pgstat_progress_update_param(PROGRESS_VACUUM_PHASE, + PROGRESS_VACUUM_PHASE_TRUNCATE); + + /* Update error traceback information one last time */ + update_vacuum_error_info(vacrel, NULL, VACUUM_ERRCB_PHASE_TRUNCATE, + vacrel->nonempty_pages, InvalidOffsetNumber); + + /* + * Loop until no more truncating can be done. + */ + do + { + /* + * We need full exclusive lock on the relation in order to do + * truncation. If we can't get it, give up rather than waiting --- we + * don't want to block other backends, and we don't want to deadlock + * (which is quite possible considering we already hold a lower-grade + * lock). + */ + lock_waiter_detected = false; + lock_retry = 0; + while (true) + { + if (ConditionalLockRelation(vacrel->rel, AccessExclusiveLock)) + break; + + /* + * Check for interrupts while trying to (re-)acquire the exclusive + * lock. + */ + CHECK_FOR_INTERRUPTS(); + + if (++lock_retry > (VACUUM_TRUNCATE_LOCK_TIMEOUT / + VACUUM_TRUNCATE_LOCK_WAIT_INTERVAL)) + { + /* + * We failed to establish the lock in the specified number of + * retries. This means we give up truncating. + */ + ereport(vacrel->verbose ? INFO : DEBUG2, + (errmsg("\"%s\": stopping truncate due to conflicting lock request", + vacrel->relname))); + return; + } + + (void) WaitLatch(MyLatch, + WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH, + VACUUM_TRUNCATE_LOCK_WAIT_INTERVAL, + WAIT_EVENT_VACUUM_TRUNCATE); + ResetLatch(MyLatch); + } + + /* + * Now that we have exclusive lock, look to see if the rel has grown + * whilst we were vacuuming with non-exclusive lock. If so, give up; + * the newly added pages presumably contain non-deletable tuples. + */ + new_rel_pages = RelationGetNumberOfBlocks(vacrel->rel); + if (new_rel_pages != orig_rel_pages) + { + /* + * Note: we intentionally don't update vacrel->rel_pages with the + * new rel size here. If we did, it would amount to assuming that + * the new pages are empty, which is unlikely. Leaving the numbers + * alone amounts to assuming that the new pages have the same + * tuple density as existing ones, which is less unlikely. + */ + UnlockRelation(vacrel->rel, AccessExclusiveLock); + return; + } + + /* + * Scan backwards from the end to verify that the end pages actually + * contain no tuples. This is *necessary*, not optional, because + * other backends could have added tuples to these pages whilst we + * were vacuuming. + */ + new_rel_pages = count_nondeletable_pages(vacrel, &lock_waiter_detected); + vacrel->blkno = new_rel_pages; + + if (new_rel_pages >= orig_rel_pages) + { + /* can't do anything after all */ + UnlockRelation(vacrel->rel, AccessExclusiveLock); + return; + } + + /* + * Okay to truncate. + */ + RelationTruncate(vacrel->rel, new_rel_pages); + + /* + * We can release the exclusive lock as soon as we have truncated. + * Other backends can't safely access the relation until they have + * processed the smgr invalidation that smgrtruncate sent out ... but + * that should happen as part of standard invalidation processing once + * they acquire lock on the relation. + */ + UnlockRelation(vacrel->rel, AccessExclusiveLock); + + /* + * Update statistics. Here, it *is* correct to adjust rel_pages + * without also touching reltuples, since the tuple count wasn't + * changed by the truncation. + */ + vacrel->removed_pages += orig_rel_pages - new_rel_pages; + vacrel->rel_pages = new_rel_pages; + + ereport(vacrel->verbose ? INFO : DEBUG2, + (errmsg("table \"%s\": truncated %u to %u pages", + vacrel->relname, + orig_rel_pages, new_rel_pages))); + orig_rel_pages = new_rel_pages; + } while (new_rel_pages > vacrel->nonempty_pages && lock_waiter_detected); +} + +/* + * Rescan end pages to verify that they are (still) empty of tuples. + * + * Returns number of nondeletable pages (last nonempty page + 1). + */ +static BlockNumber +count_nondeletable_pages(LVRelState *vacrel, bool *lock_waiter_detected) +{ + BlockNumber blkno; + BlockNumber prefetchedUntil; + instr_time starttime; + + /* Initialize the starttime if we check for conflicting lock requests */ + INSTR_TIME_SET_CURRENT(starttime); + + /* + * Start checking blocks at what we believe relation end to be and move + * backwards. (Strange coding of loop control is needed because blkno is + * unsigned.) To make the scan faster, we prefetch a few blocks at a time + * in forward direction, so that OS-level readahead can kick in. + */ + blkno = vacrel->rel_pages; + StaticAssertStmt((PREFETCH_SIZE & (PREFETCH_SIZE - 1)) == 0, + "prefetch size must be power of 2"); + prefetchedUntil = InvalidBlockNumber; + while (blkno > vacrel->nonempty_pages) + { + Buffer buf; + Page page; + OffsetNumber offnum, + maxoff; + bool hastup; + + /* + * Check if another process requests a lock on our relation. We are + * holding an AccessExclusiveLock here, so they will be waiting. We + * only do this once per VACUUM_TRUNCATE_LOCK_CHECK_INTERVAL, and we + * only check if that interval has elapsed once every 32 blocks to + * keep the number of system calls and actual shared lock table + * lookups to a minimum. + */ + if ((blkno % 32) == 0) + { + instr_time currenttime; + instr_time elapsed; + + INSTR_TIME_SET_CURRENT(currenttime); + elapsed = currenttime; + INSTR_TIME_SUBTRACT(elapsed, starttime); + if ((INSTR_TIME_GET_MICROSEC(elapsed) / 1000) + >= VACUUM_TRUNCATE_LOCK_CHECK_INTERVAL) + { + if (LockHasWaitersRelation(vacrel->rel, AccessExclusiveLock)) + { + ereport(vacrel->verbose ? INFO : DEBUG2, + (errmsg("table \"%s\": suspending truncate due to conflicting lock request", + vacrel->relname))); + + *lock_waiter_detected = true; + return blkno; + } + starttime = currenttime; + } + } + + /* + * We don't insert a vacuum delay point here, because we have an + * exclusive lock on the table which we want to hold for as short a + * time as possible. We still need to check for interrupts however. + */ + CHECK_FOR_INTERRUPTS(); + + blkno--; + + /* If we haven't prefetched this lot yet, do so now. */ + if (prefetchedUntil > blkno) + { + BlockNumber prefetchStart; + BlockNumber pblkno; + + prefetchStart = blkno & ~(PREFETCH_SIZE - 1); + for (pblkno = prefetchStart; pblkno <= blkno; pblkno++) + { + PrefetchBuffer(vacrel->rel, MAIN_FORKNUM, pblkno); + CHECK_FOR_INTERRUPTS(); + } + prefetchedUntil = prefetchStart; + } + + buf = ReadBufferExtended(vacrel->rel, MAIN_FORKNUM, blkno, RBM_NORMAL, + vacrel->bstrategy); + + /* In this phase we only need shared access to the buffer */ + LockBuffer(buf, BUFFER_LOCK_SHARE); + + page = BufferGetPage(buf); + + if (PageIsNew(page) || PageIsEmpty(page)) + { + UnlockReleaseBuffer(buf); + continue; + } + + hastup = false; + maxoff = PageGetMaxOffsetNumber(page); + for (offnum = FirstOffsetNumber; + offnum <= maxoff; + offnum = OffsetNumberNext(offnum)) + { + ItemId itemid; + + itemid = PageGetItemId(page, offnum); + + /* + * Note: any non-unused item should be taken as a reason to keep + * this page. Even an LP_DEAD item makes truncation unsafe, since + * we must not have cleaned out its index entries. + */ + if (ItemIdIsUsed(itemid)) + { + hastup = true; + break; /* can stop scanning */ + } + } /* scan along page */ + + UnlockReleaseBuffer(buf); + + /* Done scanning if we found a tuple here */ + if (hastup) + return blkno + 1; + } + + /* + * If we fall out of the loop, all the previously-thought-to-be-empty + * pages still are; we need not bother to look at the last known-nonempty + * page. + */ + return vacrel->nonempty_pages; +} + +/* + * Returns the number of dead TIDs that VACUUM should allocate space to + * store, given a heap rel of size vacrel->rel_pages, and given current + * maintenance_work_mem setting (or current autovacuum_work_mem setting, + * when applicable). + * + * See the comments at the head of this file for rationale. + */ +static int +dead_items_max_items(LVRelState *vacrel) +{ + int64 max_items; + int vac_work_mem = IsAutoVacuumWorkerProcess() && + autovacuum_work_mem != -1 ? + autovacuum_work_mem : maintenance_work_mem; + + if (vacrel->nindexes > 0) + { + BlockNumber rel_pages = vacrel->rel_pages; + + max_items = MAXDEADITEMS(vac_work_mem * 1024L); + max_items = Min(max_items, INT_MAX); + max_items = Min(max_items, MAXDEADITEMS(MaxAllocSize)); + + /* curious coding here to ensure the multiplication can't overflow */ + if ((BlockNumber) (max_items / MaxHeapTuplesPerPage) > rel_pages) + max_items = rel_pages * MaxHeapTuplesPerPage; + + /* stay sane if small maintenance_work_mem */ + max_items = Max(max_items, MaxHeapTuplesPerPage); + } + else + { + /* One-pass case only stores a single heap page's TIDs at a time */ + max_items = MaxHeapTuplesPerPage; + } + + return (int) max_items; +} + +/* + * Allocate dead_items (either using palloc, or in dynamic shared memory). + * Sets dead_items in vacrel for caller. + * + * Also handles parallel initialization as part of allocating dead_items in + * DSM when required. + */ +static void +dead_items_alloc(LVRelState *vacrel, int nworkers) +{ + VacDeadItems *dead_items; + int max_items; + + max_items = dead_items_max_items(vacrel); + Assert(max_items >= MaxHeapTuplesPerPage); + + /* + * Initialize state for a parallel vacuum. As of now, only one worker can + * be used for an index, so we invoke parallelism only if there are at + * least two indexes on a table. + */ + if (nworkers >= 0 && vacrel->nindexes > 1 && vacrel->do_index_vacuuming) + { + /* + * Since parallel workers cannot access data in temporary tables, we + * can't perform parallel vacuum on them. + */ + if (RelationUsesLocalBuffers(vacrel->rel)) + { + /* + * Give warning only if the user explicitly tries to perform a + * parallel vacuum on the temporary table. + */ + if (nworkers > 0) + ereport(WARNING, + (errmsg("disabling parallel option of vacuum on \"%s\" --- cannot vacuum temporary tables in parallel", + vacrel->relname))); + } + else + vacrel->pvs = parallel_vacuum_init(vacrel->rel, vacrel->indrels, + vacrel->nindexes, nworkers, + max_items, + vacrel->verbose ? INFO : DEBUG2, + vacrel->bstrategy); + + /* If parallel mode started, dead_items space is allocated in DSM */ + if (ParallelVacuumIsActive(vacrel)) + { + vacrel->dead_items = parallel_vacuum_get_dead_items(vacrel->pvs); + return; + } + } + + /* Serial VACUUM case */ + dead_items = (VacDeadItems *) palloc(vac_max_items_to_alloc_size(max_items)); + dead_items->max_items = max_items; + dead_items->num_items = 0; + + vacrel->dead_items = dead_items; +} + +/* + * Perform cleanup for resources allocated in dead_items_alloc + */ +static void +dead_items_cleanup(LVRelState *vacrel) +{ + if (!ParallelVacuumIsActive(vacrel)) + { + /* Don't bother with pfree here */ + return; + } + + /* End parallel mode */ + parallel_vacuum_end(vacrel->pvs, vacrel->indstats); + vacrel->pvs = NULL; +} + +/* + * Check if every tuple in the given page is visible to all current and future + * transactions. Also return the visibility_cutoff_xid which is the highest + * xmin amongst the visible tuples. Set *all_frozen to true if every tuple + * on this page is frozen. + * + * This is a stripped down version of lazy_scan_prune(). If you change + * anything here, make sure that everything stays in sync. Note that an + * assertion calls us to verify that everybody still agrees. Be sure to avoid + * introducing new side-effects here. + */ +static bool +heap_page_is_all_visible(LVRelState *vacrel, Buffer buf, + TransactionId *visibility_cutoff_xid, + bool *all_frozen) +{ + Page page = BufferGetPage(buf); + BlockNumber blockno = BufferGetBlockNumber(buf); + OffsetNumber offnum, + maxoff; + bool all_visible = true; + + *visibility_cutoff_xid = InvalidTransactionId; + *all_frozen = true; + + maxoff = PageGetMaxOffsetNumber(page); + for (offnum = FirstOffsetNumber; + offnum <= maxoff && all_visible; + offnum = OffsetNumberNext(offnum)) + { + ItemId itemid; + HeapTupleData tuple; + + /* + * Set the offset number so that we can display it along with any + * error that occurred while processing this tuple. + */ + vacrel->offnum = offnum; + itemid = PageGetItemId(page, offnum); + + /* Unused or redirect line pointers are of no interest */ + if (!ItemIdIsUsed(itemid) || ItemIdIsRedirected(itemid)) + continue; + + ItemPointerSet(&(tuple.t_self), blockno, offnum); + + /* + * Dead line pointers can have index pointers pointing to them. So + * they can't be treated as visible + */ + if (ItemIdIsDead(itemid)) + { + all_visible = false; + *all_frozen = false; + break; + } + + Assert(ItemIdIsNormal(itemid)); + + tuple.t_data = (HeapTupleHeader) PageGetItem(page, itemid); + tuple.t_len = ItemIdGetLength(itemid); + tuple.t_tableOid = RelationGetRelid(vacrel->rel); + + switch (HeapTupleSatisfiesVacuum(&tuple, vacrel->OldestXmin, buf)) + { + case HEAPTUPLE_LIVE: + { + TransactionId xmin; + + /* Check comments in lazy_scan_prune. */ + if (!HeapTupleHeaderXminCommitted(tuple.t_data)) + { + all_visible = false; + *all_frozen = false; + break; + } + + /* + * The inserter definitely committed. But is it old enough + * that everyone sees it as committed? + */ + xmin = HeapTupleHeaderGetXmin(tuple.t_data); + if (!TransactionIdPrecedes(xmin, vacrel->OldestXmin)) + { + all_visible = false; + *all_frozen = false; + break; + } + + /* Track newest xmin on page. */ + if (TransactionIdFollows(xmin, *visibility_cutoff_xid)) + *visibility_cutoff_xid = xmin; + + /* Check whether this tuple is already frozen or not */ + if (all_visible && *all_frozen && + heap_tuple_needs_eventual_freeze(tuple.t_data)) + *all_frozen = false; + } + break; + + case HEAPTUPLE_DEAD: + case HEAPTUPLE_RECENTLY_DEAD: + case HEAPTUPLE_INSERT_IN_PROGRESS: + case HEAPTUPLE_DELETE_IN_PROGRESS: + { + all_visible = false; + *all_frozen = false; + break; + } + default: + elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result"); + break; + } + } /* scan along page */ + + /* Clear the offset information once we have processed the given page. */ + vacrel->offnum = InvalidOffsetNumber; + + return all_visible; +} + +/* + * Update index statistics in pg_class if the statistics are accurate. + */ +static void +update_relstats_all_indexes(LVRelState *vacrel) +{ + Relation *indrels = vacrel->indrels; + int nindexes = vacrel->nindexes; + IndexBulkDeleteResult **indstats = vacrel->indstats; + + Assert(vacrel->do_index_cleanup); + + for (int idx = 0; idx < nindexes; idx++) + { + Relation indrel = indrels[idx]; + IndexBulkDeleteResult *istat = indstats[idx]; + + if (istat == NULL || istat->estimated_count) + continue; + + /* Update index statistics */ + vac_update_relstats(indrel, + istat->num_pages, + istat->num_index_tuples, + 0, + false, + InvalidTransactionId, + InvalidMultiXactId, + NULL, NULL, false); + } +} + +/* + * Error context callback for errors occurring during vacuum. The error + * context messages for index phases should match the messages set in parallel + * vacuum. If you change this function for those phases, change + * parallel_vacuum_error_callback() as well. + */ +static void +vacuum_error_callback(void *arg) +{ + LVRelState *errinfo = arg; + + switch (errinfo->phase) + { + case VACUUM_ERRCB_PHASE_SCAN_HEAP: + if (BlockNumberIsValid(errinfo->blkno)) + { + if (OffsetNumberIsValid(errinfo->offnum)) + errcontext("while scanning block %u offset %u of relation \"%s.%s\"", + errinfo->blkno, errinfo->offnum, errinfo->relnamespace, errinfo->relname); + else + errcontext("while scanning block %u of relation \"%s.%s\"", + errinfo->blkno, errinfo->relnamespace, errinfo->relname); + } + else + errcontext("while scanning relation \"%s.%s\"", + errinfo->relnamespace, errinfo->relname); + break; + + case VACUUM_ERRCB_PHASE_VACUUM_HEAP: + if (BlockNumberIsValid(errinfo->blkno)) + { + if (OffsetNumberIsValid(errinfo->offnum)) + errcontext("while vacuuming block %u offset %u of relation \"%s.%s\"", + errinfo->blkno, errinfo->offnum, errinfo->relnamespace, errinfo->relname); + else + errcontext("while vacuuming block %u of relation \"%s.%s\"", + errinfo->blkno, errinfo->relnamespace, errinfo->relname); + } + else + errcontext("while vacuuming relation \"%s.%s\"", + errinfo->relnamespace, errinfo->relname); + break; + + case VACUUM_ERRCB_PHASE_VACUUM_INDEX: + errcontext("while vacuuming index \"%s\" of relation \"%s.%s\"", + errinfo->indname, errinfo->relnamespace, errinfo->relname); + break; + + case VACUUM_ERRCB_PHASE_INDEX_CLEANUP: + errcontext("while cleaning up index \"%s\" of relation \"%s.%s\"", + errinfo->indname, errinfo->relnamespace, errinfo->relname); + break; + + case VACUUM_ERRCB_PHASE_TRUNCATE: + if (BlockNumberIsValid(errinfo->blkno)) + errcontext("while truncating relation \"%s.%s\" to %u blocks", + errinfo->relnamespace, errinfo->relname, errinfo->blkno); + break; + + case VACUUM_ERRCB_PHASE_UNKNOWN: + default: + return; /* do nothing; the errinfo may not be + * initialized */ + } +} + +/* + * Updates the information required for vacuum error callback. This also saves + * the current information which can be later restored via restore_vacuum_error_info. + */ +static void +update_vacuum_error_info(LVRelState *vacrel, LVSavedErrInfo *saved_vacrel, + int phase, BlockNumber blkno, OffsetNumber offnum) +{ + if (saved_vacrel) + { + saved_vacrel->offnum = vacrel->offnum; + saved_vacrel->blkno = vacrel->blkno; + saved_vacrel->phase = vacrel->phase; + } + + vacrel->blkno = blkno; + vacrel->offnum = offnum; + vacrel->phase = phase; +} + +/* + * Restores the vacuum information saved via a prior call to update_vacuum_error_info. + */ +static void +restore_vacuum_error_info(LVRelState *vacrel, + const LVSavedErrInfo *saved_vacrel) +{ + vacrel->blkno = saved_vacrel->blkno; + vacrel->offnum = saved_vacrel->offnum; + vacrel->phase = saved_vacrel->phase; +} |