/*------------------------------------------------------------------------- * * vacuumlazy.c * Concurrent ("lazy") vacuuming. * * * The major space usage for LAZY VACUUM is storage for the array of dead tuple * TIDs. 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 * tuples we will 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 tuples. 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 suspend the heap scan phase and perform a pass of index cleanup and page * compaction, then resume the heap scan with an empty TID array. * * If we're processing a table with no indexes, we can just vacuum each page * as we go; there's no need to save up multiple tuples to minimize the number * of index scans performed. So we don't use maintenance_work_mem memory for * the TID array, just enough to hold as many heap tuples as fit on one page. * * * Portions Copyright (c) 1996-2019, 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 #include "access/heapam.h" #include "access/heapam_xlog.h" #include "access/htup_details.h" #include "access/indexgenam.h" #include "access/multixact.h" #include "access/transam.h" #include "access/visibilitymap.h" #include "access/xlog.h" #include "catalog/storage.h" #include "commands/dbcommands.h" #include "commands/progress.h" #include "commands/vacuum.h" #include "miscadmin.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 "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 */ /* * 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)) /* * Guesstimation of number of dead tuples per page. This is used to * provide an upper limit to memory allocated when vacuuming small * tables. */ #define LAZY_ALLOC_TUPLES MaxHeapTuplesPerPage /* * 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) typedef struct LVRelStats { /* useindex = true means two-pass strategy; false means one-pass */ bool useindex; /* Overall statistics about rel */ BlockNumber old_rel_pages; /* previous value of pg_class.relpages */ BlockNumber rel_pages; /* total number of pages */ BlockNumber scanned_pages; /* number of pages we examined */ BlockNumber pinskipped_pages; /* # of pages we skipped due to a pin */ BlockNumber frozenskipped_pages; /* # of frozen pages we skipped */ BlockNumber tupcount_pages; /* pages whose tuples we counted */ double old_live_tuples; /* previous value of pg_class.reltuples */ double new_rel_tuples; /* new estimated total # of tuples */ double new_live_tuples; /* new estimated total # of live tuples */ double new_dead_tuples; /* new estimated total # of dead tuples */ BlockNumber pages_removed; double tuples_deleted; BlockNumber nonempty_pages; /* actually, last nonempty page + 1 */ /* List of TIDs of tuples we intend to delete */ /* NB: this list is ordered by TID address */ int num_dead_tuples; /* current # of entries */ int max_dead_tuples; /* # slots allocated in array */ ItemPointer dead_tuples; /* array of ItemPointerData */ int num_index_scans; TransactionId latestRemovedXid; bool lock_waiter_detected; } LVRelStats; /* A few variables that don't seem worth passing around as parameters */ static int elevel = -1; static TransactionId OldestXmin; static TransactionId FreezeLimit; static MultiXactId MultiXactCutoff; static BufferAccessStrategy vac_strategy; /* non-export function prototypes */ static void lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats, Relation *Irel, int nindexes, bool aggressive); static void lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats); static bool lazy_check_needs_freeze(Buffer buf, bool *hastup); static void lazy_vacuum_index(Relation indrel, IndexBulkDeleteResult **stats, LVRelStats *vacrelstats); static void lazy_vacuum_all_indexes(Relation onerel, LVRelStats *vacrelstats, Relation *Irel, int nindexes, IndexBulkDeleteResult **indstats); static void lazy_cleanup_index(Relation indrel, IndexBulkDeleteResult *stats, LVRelStats *vacrelstats); static int lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer, int tupindex, LVRelStats *vacrelstats, Buffer *vmbuffer); static bool should_attempt_truncation(VacuumParams *params, LVRelStats *vacrelstats); static void lazy_truncate_heap(Relation onerel, LVRelStats *vacrelstats); static BlockNumber count_nondeletable_pages(Relation onerel, LVRelStats *vacrelstats); static void lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks); static void lazy_record_dead_tuple(LVRelStats *vacrelstats, ItemPointer itemptr); static bool lazy_tid_reaped(ItemPointer itemptr, void *state); static int vac_cmp_itemptr(const void *left, const void *right); static bool heap_page_is_all_visible(Relation rel, Buffer buf, TransactionId *visibility_cutoff_xid, bool *all_frozen); /* * heap_vacuum_rel() -- perform VACUUM for one heap relation * * This routine vacuums a single heap, cleans out its indexes, and * updates its relpages and reltuples statistics. * * At entry, we have already established a transaction and opened * and locked the relation. */ void heap_vacuum_rel(Relation onerel, VacuumParams *params, BufferAccessStrategy bstrategy) { LVRelStats *vacrelstats; Relation *Irel; int nindexes; PGRUsage ru0; TimestampTz starttime = 0; long secs; int usecs; double read_rate, write_rate; bool aggressive; /* should we scan all unfrozen pages? */ bool scanned_all_unfrozen; /* actually scanned all such pages? */ TransactionId xidFullScanLimit; MultiXactId mxactFullScanLimit; BlockNumber new_rel_pages; BlockNumber new_rel_allvisible; double new_live_tuples; TransactionId new_frozen_xid; MultiXactId new_min_multi; Assert(params != NULL); Assert(params->index_cleanup != VACOPT_TERNARY_DEFAULT); Assert(params->truncate != VACOPT_TERNARY_DEFAULT); /* not every AM requires these to be valid, but heap does */ Assert(TransactionIdIsNormal(onerel->rd_rel->relfrozenxid)); Assert(MultiXactIdIsValid(onerel->rd_rel->relminmxid)); /* measure elapsed time iff autovacuum logging requires it */ if (IsAutoVacuumWorkerProcess() && params->log_min_duration >= 0) { pg_rusage_init(&ru0); starttime = GetCurrentTimestamp(); } if (params->options & VACOPT_VERBOSE) elevel = INFO; else elevel = DEBUG2; pgstat_progress_start_command(PROGRESS_COMMAND_VACUUM, RelationGetRelid(onerel)); vac_strategy = bstrategy; vacuum_set_xid_limits(onerel, params->freeze_min_age, params->freeze_table_age, params->multixact_freeze_min_age, params->multixact_freeze_table_age, &OldestXmin, &FreezeLimit, &xidFullScanLimit, &MultiXactCutoff, &mxactFullScanLimit); /* * We request an aggressive scan if the table's frozen Xid is now older * than or equal to the requested Xid full-table scan limit; or if the * table's minimum MultiXactId is older than or equal to the requested * mxid full-table scan limit; or if DISABLE_PAGE_SKIPPING was specified. */ aggressive = TransactionIdPrecedesOrEquals(onerel->rd_rel->relfrozenxid, xidFullScanLimit); aggressive |= MultiXactIdPrecedesOrEquals(onerel->rd_rel->relminmxid, mxactFullScanLimit); if (params->options & VACOPT_DISABLE_PAGE_SKIPPING) aggressive = true; /* * Normally the relfrozenxid for an anti-wraparound vacuum will be old * enough to force an aggressive vacuum. However, a concurrent vacuum * might have already done this work that the relfrozenxid in relcache has * been updated. If that happens this vacuum is redundant, so skip it. */ if (params->is_wraparound && !aggressive) { ereport(DEBUG1, (errmsg("skipping redundant vacuum to prevent wraparound of table \"%s.%s.%s\"", get_database_name(MyDatabaseId), get_namespace_name(RelationGetNamespace(onerel)), RelationGetRelationName(onerel)))); pgstat_progress_end_command(); return; } vacrelstats = (LVRelStats *) palloc0(sizeof(LVRelStats)); vacrelstats->old_rel_pages = onerel->rd_rel->relpages; vacrelstats->old_live_tuples = onerel->rd_rel->reltuples; vacrelstats->num_index_scans = 0; vacrelstats->pages_removed = 0; vacrelstats->lock_waiter_detected = false; /* Open all indexes of the relation */ vac_open_indexes(onerel, RowExclusiveLock, &nindexes, &Irel); vacrelstats->useindex = (nindexes > 0 && params->index_cleanup == VACOPT_TERNARY_ENABLED); /* Do the vacuuming */ lazy_scan_heap(onerel, params, vacrelstats, Irel, nindexes, aggressive); /* Done with indexes */ vac_close_indexes(nindexes, Irel, NoLock); /* * Compute whether we actually scanned the all unfrozen pages. If we did, * we can adjust relfrozenxid and relminmxid. * * NB: We need to check this before truncating the relation, because that * will change ->rel_pages. */ if ((vacrelstats->scanned_pages + vacrelstats->frozenskipped_pages) < vacrelstats->rel_pages) { Assert(!aggressive); scanned_all_unfrozen = false; } else scanned_all_unfrozen = true; /* * Optionally truncate the relation. */ if (should_attempt_truncation(params, vacrelstats)) lazy_truncate_heap(onerel, vacrelstats); /* Report that we are now doing final cleanup */ pgstat_progress_update_param(PROGRESS_VACUUM_PHASE, PROGRESS_VACUUM_PHASE_FINAL_CLEANUP); /* * Update statistics in pg_class. * * A corner case here is that if we scanned no pages at all because every * page is all-visible, we should not update relpages/reltuples, because * we have no new information to contribute. In particular this keeps us * from replacing relpages=reltuples=0 (which means "unknown tuple * density") with nonzero relpages and reltuples=0 (which means "zero * tuple density") unless there's some actual evidence for the latter. * * It's important that we use tupcount_pages and not scanned_pages for the * check described above; scanned_pages counts pages where we could not * get cleanup lock, and which were processed only for frozenxid purposes. * * We do update relallvisible even in the corner case, since if the table * is all-visible we'd definitely like to know that. But clamp the value * to be not more than what we're setting relpages to. * * Also, don't change relfrozenxid/relminmxid if we skipped any pages, * since then we don't know for certain that all tuples have a newer xmin. */ new_rel_pages = vacrelstats->rel_pages; new_live_tuples = vacrelstats->new_live_tuples; if (vacrelstats->tupcount_pages == 0 && new_rel_pages > 0) { new_rel_pages = vacrelstats->old_rel_pages; new_live_tuples = vacrelstats->old_live_tuples; } visibilitymap_count(onerel, &new_rel_allvisible, NULL); if (new_rel_allvisible > new_rel_pages) new_rel_allvisible = new_rel_pages; new_frozen_xid = scanned_all_unfrozen ? FreezeLimit : InvalidTransactionId; new_min_multi = scanned_all_unfrozen ? MultiXactCutoff : InvalidMultiXactId; vac_update_relstats(onerel, new_rel_pages, new_live_tuples, new_rel_allvisible, nindexes > 0, new_frozen_xid, new_min_multi, false); /* report results to the stats collector, too */ pgstat_report_vacuum(RelationGetRelid(onerel), onerel->rd_rel->relisshared, new_live_tuples, vacrelstats->new_dead_tuples); pgstat_progress_end_command(); /* and log the action if appropriate */ if (IsAutoVacuumWorkerProcess() && params->log_min_duration >= 0) { TimestampTz endtime = GetCurrentTimestamp(); if (params->log_min_duration == 0 || TimestampDifferenceExceeds(starttime, endtime, params->log_min_duration)) { StringInfoData buf; char *msgfmt; TimestampDifference(starttime, endtime, &secs, &usecs); read_rate = 0; write_rate = 0; if ((secs > 0) || (usecs > 0)) { read_rate = (double) BLCKSZ * VacuumPageMiss / (1024 * 1024) / (secs + usecs / 1000000.0); write_rate = (double) BLCKSZ * VacuumPageDirty / (1024 * 1024) / (secs + usecs / 1000000.0); } /* * This is pretty messy, but we split it up so that we can skip * emitting individual parts of the message when not applicable. */ initStringInfo(&buf); if (params->is_wraparound) { /* an anti-wraparound vacuum has to be aggressive */ Assert(aggressive); msgfmt = _("automatic aggressive 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), get_namespace_name(RelationGetNamespace(onerel)), RelationGetRelationName(onerel), vacrelstats->num_index_scans); appendStringInfo(&buf, _("pages: %u removed, %u remain, %u skipped due to pins, %u skipped frozen\n"), vacrelstats->pages_removed, vacrelstats->rel_pages, vacrelstats->pinskipped_pages, vacrelstats->frozenskipped_pages); appendStringInfo(&buf, _("tuples: %.0f removed, %.0f remain, %.0f are dead but not yet removable, oldest xmin: %u\n"), vacrelstats->tuples_deleted, vacrelstats->new_rel_tuples, vacrelstats->new_dead_tuples, OldestXmin); appendStringInfo(&buf, _("buffer usage: %d hits, %d misses, %d dirtied\n"), VacuumPageHit, VacuumPageMiss, VacuumPageDirty); appendStringInfo(&buf, _("avg read rate: %.3f MB/s, avg write rate: %.3f MB/s\n"), read_rate, write_rate); appendStringInfo(&buf, _("system usage: %s"), pg_rusage_show(&ru0)); ereport(LOG, (errmsg_internal("%s", buf.data))); pfree(buf.data); } } } /* * For Hot Standby we need to know the highest transaction id that will * be removed by any change. VACUUM proceeds in a number of passes so * we need to consider how each pass operates. The first phase runs * heap_page_prune(), which can issue XLOG_HEAP2_CLEAN records as it * progresses - these will have a latestRemovedXid on each record. * In some cases this removes all of the tuples to be removed, though * often we have dead tuples with index pointers so we must remember them * for removal in phase 3. Index records for those rows are removed * in phase 2 and index blocks do not have MVCC information attached. * So before we can allow removal of any index tuples we need to issue * a WAL record containing the latestRemovedXid of rows that will be * removed in phase three. This allows recovery queries to block at the * correct place, i.e. before phase two, rather than during phase three * which would be after the rows have become inaccessible. */ static void vacuum_log_cleanup_info(Relation rel, LVRelStats *vacrelstats) { /* * Skip this for relations for which no WAL is to be written, or if we're * not trying to support archive recovery. */ if (!RelationNeedsWAL(rel) || !XLogIsNeeded()) return; /* * No need to write the record at all unless it contains a valid value */ if (TransactionIdIsValid(vacrelstats->latestRemovedXid)) (void) log_heap_cleanup_info(rel->rd_node, vacrelstats->latestRemovedXid); } /* * lazy_scan_heap() -- scan an open heap relation * * This routine prunes each page in the heap, which will among other * things truncate dead tuples to dead line pointers, defragment the * page, and set commit status bits (see heap_page_prune). It also builds * lists of dead tuples and pages with free space, calculates statistics * on the number of live tuples in the heap, and marks pages as * all-visible if appropriate. When done, or when we run low on space for * dead-tuple TIDs, invoke vacuuming of indexes and call lazy_vacuum_heap * to reclaim dead line pointers. * * If there are no indexes then we can reclaim line pointers on the fly; * dead line pointers need only be retained until all index pointers that * reference them have been killed. */ static void lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats, Relation *Irel, int nindexes, bool aggressive) { BlockNumber nblocks, blkno; HeapTupleData tuple; char *relname; TransactionId relfrozenxid = onerel->rd_rel->relfrozenxid; TransactionId relminmxid = onerel->rd_rel->relminmxid; BlockNumber empty_pages, vacuumed_pages, next_fsm_block_to_vacuum; double num_tuples, /* total number of nonremovable tuples */ live_tuples, /* live tuples (reltuples estimate) */ tups_vacuumed, /* tuples cleaned up by vacuum */ nkeep, /* dead-but-not-removable tuples */ nunused; /* unused line pointers */ IndexBulkDeleteResult **indstats; int i; PGRUsage ru0; Buffer vmbuffer = InvalidBuffer; BlockNumber next_unskippable_block; bool skipping_blocks; xl_heap_freeze_tuple *frozen; StringInfoData buf; const int initprog_index[] = { PROGRESS_VACUUM_PHASE, PROGRESS_VACUUM_TOTAL_HEAP_BLKS, PROGRESS_VACUUM_MAX_DEAD_TUPLES }; int64 initprog_val[3]; pg_rusage_init(&ru0); relname = RelationGetRelationName(onerel); if (aggressive) ereport(elevel, (errmsg("aggressively vacuuming \"%s.%s\"", get_namespace_name(RelationGetNamespace(onerel)), relname))); else ereport(elevel, (errmsg("vacuuming \"%s.%s\"", get_namespace_name(RelationGetNamespace(onerel)), relname))); empty_pages = vacuumed_pages = 0; next_fsm_block_to_vacuum = (BlockNumber) 0; num_tuples = live_tuples = tups_vacuumed = nkeep = nunused = 0; indstats = (IndexBulkDeleteResult **) palloc0(nindexes * sizeof(IndexBulkDeleteResult *)); nblocks = RelationGetNumberOfBlocks(onerel); vacrelstats->rel_pages = nblocks; vacrelstats->scanned_pages = 0; vacrelstats->tupcount_pages = 0; vacrelstats->nonempty_pages = 0; vacrelstats->latestRemovedXid = InvalidTransactionId; lazy_space_alloc(vacrelstats, nblocks); frozen = palloc(sizeof(xl_heap_freeze_tuple) * MaxHeapTuplesPerPage); /* Report that we're scanning the heap, advertising total # of blocks */ initprog_val[0] = PROGRESS_VACUUM_PHASE_SCAN_HEAP; initprog_val[1] = nblocks; initprog_val[2] = vacrelstats->max_dead_tuples; pgstat_progress_update_multi_param(3, initprog_index, initprog_val); /* * Except when aggressive is set, we want to skip pages that are * all-visible according to the visibility map, but only when we can skip * 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; that's likely to disable * readahead and so be counterproductive. Also, skipping even a single * page means that we can't update relfrozenxid, so we only want to do it * if we can skip a goodly number of pages. * * When aggressive is set, we can't skip pages just because they are * all-visible, but we can still skip pages that are all-frozen, since * such pages do not need freezing and do not affect the value that we can * safely set for relfrozenxid or relminmxid. * * Before entering the main loop, establish the invariant that * next_unskippable_block is the next block number >= blkno that we can't * skip based on the visibility map, either all-visible for a regular scan * or all-frozen for an aggressive scan. We set it to nblocks if there's * no such block. We also set up the skipping_blocks flag correctly at * this stage. * * Note: The value returned by visibilitymap_get_status could be slightly * out-of-date, since we make this test before reading the corresponding * heap page or locking the buffer. This is OK. If we mistakenly think * that the page is all-visible or all-frozen when in fact the flag's just * been cleared, we might fail to vacuum the page. It's easy to see that * skipping a page when aggressive is not set is not a very big deal; we * might leave some dead tuples lying around, but the next vacuum will * find them. But even when aggressive *is* set, it's still OK if we miss * a page whose all-frozen marking has just been cleared. Any new XIDs * just added to that page are necessarily newer than the GlobalXmin we * computed, so they'll have no effect on the value to which we can safely * set relfrozenxid. A similar argument applies for MXIDs and relminmxid. * * We will scan the table's last page, at least to the extent of * determining whether it has tuples or not, even if it should be skipped * according to the above rules; except when we've already determined that * it's not worth trying to truncate the table. This avoids having * lazy_truncate_heap() take access-exclusive lock on the table to attempt * a truncation that just fails immediately because there are tuples in * the last page. This is worth avoiding mainly because such a lock must * be replayed on any hot standby, where it can be disruptive. */ next_unskippable_block = 0; if ((params->options & VACOPT_DISABLE_PAGE_SKIPPING) == 0) { while (next_unskippable_block < nblocks) { uint8 vmstatus; vmstatus = visibilitymap_get_status(onerel, next_unskippable_block, &vmbuffer); if (aggressive) { if ((vmstatus & VISIBILITYMAP_ALL_FROZEN) == 0) break; } else { if ((vmstatus & VISIBILITYMAP_ALL_VISIBLE) == 0) break; } vacuum_delay_point(); next_unskippable_block++; } } if (next_unskippable_block >= SKIP_PAGES_THRESHOLD) skipping_blocks = true; else skipping_blocks = false; for (blkno = 0; blkno < nblocks; blkno++) { Buffer buf; Page page; OffsetNumber offnum, maxoff; bool tupgone, hastup; int prev_dead_count; int nfrozen; Size freespace; bool all_visible_according_to_vm = false; bool all_visible; bool all_frozen = true; /* provided all_visible is also true */ bool has_dead_tuples; TransactionId visibility_cutoff_xid = InvalidTransactionId; /* see note above about forcing scanning of last page */ #define FORCE_CHECK_PAGE() \ (blkno == nblocks - 1 && should_attempt_truncation(params, vacrelstats)) pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_SCANNED, blkno); if (blkno == next_unskippable_block) { /* Time to advance next_unskippable_block */ next_unskippable_block++; if ((params->options & VACOPT_DISABLE_PAGE_SKIPPING) == 0) { while (next_unskippable_block < nblocks) { uint8 vmskipflags; vmskipflags = visibilitymap_get_status(onerel, next_unskippable_block, &vmbuffer); if (aggressive) { if ((vmskipflags & VISIBILITYMAP_ALL_FROZEN) == 0) break; } else { if ((vmskipflags & VISIBILITYMAP_ALL_VISIBLE) == 0) break; } vacuum_delay_point(); next_unskippable_block++; } } /* * We know we can't skip the current block. But set up * skipping_blocks to do the right thing at the following blocks. */ if (next_unskippable_block - blkno > SKIP_PAGES_THRESHOLD) skipping_blocks = true; else skipping_blocks = false; /* * Normally, the fact that we can't skip this block must mean that * it's not all-visible. But in an aggressive vacuum we know only * that it's not all-frozen, so it might still be all-visible. */ if (aggressive && VM_ALL_VISIBLE(onerel, blkno, &vmbuffer)) all_visible_according_to_vm = true; } else { /* * The current block is potentially skippable; if we've seen a * long enough run of skippable blocks to justify skipping it, and * we're not forced to check it, then go ahead and skip. * Otherwise, the page must be at least all-visible if not * all-frozen, so we can set all_visible_according_to_vm = true. */ if (skipping_blocks && !FORCE_CHECK_PAGE()) { /* * Tricky, tricky. If this is in aggressive vacuum, the page * must have been all-frozen at the time we checked whether it * was skippable, but it might not be any more. We must be * careful to count it as a skipped all-frozen page in that * case, or else we'll think we can't update relfrozenxid and * relminmxid. If it's not an aggressive vacuum, we don't * know whether it was all-frozen, so we have to recheck; but * in this case an approximate answer is OK. */ if (aggressive || VM_ALL_FROZEN(onerel, blkno, &vmbuffer)) vacrelstats->frozenskipped_pages++; continue; } all_visible_according_to_vm = true; } vacuum_delay_point(); /* * If we are close to overrunning the available space for dead-tuple * TIDs, pause and do a cycle of vacuuming before we tackle this page. */ if ((vacrelstats->max_dead_tuples - vacrelstats->num_dead_tuples) < MaxHeapTuplesPerPage && vacrelstats->num_dead_tuples > 0) { /* * 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; } /* Work on all the indexes, then the heap */ lazy_vacuum_all_indexes(onerel, vacrelstats, Irel, nindexes, indstats); /* Remove tuples from heap */ lazy_vacuum_heap(onerel, vacrelstats); /* * Forget the now-vacuumed tuples, and press on, but be careful * not to reset latestRemovedXid since we want that value to be * valid. */ vacrelstats->num_dead_tuples = 0; /* * Vacuum the Free Space Map to make newly-freed space visible on * upper-level FSM pages. Note we have not yet processed blkno. */ FreeSpaceMapVacuumRange(onerel, 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. However, it's * possible that (a) next_unskippable_block is covered by a different * VM page than the current block or (b) we released our pin and did a * cycle of index vacuuming. * */ visibilitymap_pin(onerel, blkno, &vmbuffer); buf = ReadBufferExtended(onerel, MAIN_FORKNUM, blkno, RBM_NORMAL, vac_strategy); /* We need buffer cleanup lock so that we can prune HOT chains. */ if (!ConditionalLockBufferForCleanup(buf)) { /* * If we're not performing an aggressive scan to guard against XID * wraparound, and we don't want to forcibly check the page, then * it's OK to skip vacuuming pages we get a lock conflict on. They * will be dealt with in some future vacuum. */ if (!aggressive && !FORCE_CHECK_PAGE()) { ReleaseBuffer(buf); vacrelstats->pinskipped_pages++; continue; } /* * Read the page with share lock to see if any xids on it need to * be frozen. If not we just skip the page, after updating our * scan statistics. If there are some, we wait for cleanup lock. * * We could defer the lock request further by remembering the page * and coming back to it later, or we could even register * ourselves for multiple buffers and then service whichever one * is received first. For now, this seems good enough. * * If we get here with aggressive false, then we're just forcibly * checking the page, and so we don't want to insist on getting * the lock; we only need to know if the page contains tuples, so * that we can update nonempty_pages correctly. It's convenient * to use lazy_check_needs_freeze() for both situations, though. */ LockBuffer(buf, BUFFER_LOCK_SHARE); if (!lazy_check_needs_freeze(buf, &hastup)) { UnlockReleaseBuffer(buf); vacrelstats->scanned_pages++; vacrelstats->pinskipped_pages++; if (hastup) vacrelstats->nonempty_pages = blkno + 1; continue; } if (!aggressive) { /* * Here, we must not advance scanned_pages; that would amount * to claiming that the page contains no freezable tuples. */ UnlockReleaseBuffer(buf); vacrelstats->pinskipped_pages++; if (hastup) vacrelstats->nonempty_pages = blkno + 1; continue; } LockBuffer(buf, BUFFER_LOCK_UNLOCK); LockBufferForCleanup(buf); /* drop through to normal processing */ } vacrelstats->scanned_pages++; vacrelstats->tupcount_pages++; page = BufferGetPage(buf); if (PageIsNew(page)) { bool still_new; /* * 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, but enters them into the FSM). * * 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. * * 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 not 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. */ /* * Perform checking of FSM after releasing lock, the fsm is * approximate, after all. */ still_new = PageIsNew(page); UnlockReleaseBuffer(buf); if (still_new) { empty_pages++; if (GetRecordedFreeSpace(onerel, blkno) == 0) { Size freespace; freespace = BufferGetPageSize(buf) - SizeOfPageHeaderData; RecordPageWithFreeSpace(onerel, blkno, freespace); } } continue; } if (PageIsEmpty(page)) { empty_pages++; freespace = PageGetHeapFreeSpace(page); /* * Empty pages are always all-visible and all-frozen (note that * the same is currently not true for new pages, see above). */ 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(onerel) && PageGetLSN(page) == InvalidXLogRecPtr) log_newpage_buffer(buf, true); PageSetAllVisible(page); visibilitymap_set(onerel, blkno, buf, InvalidXLogRecPtr, vmbuffer, InvalidTransactionId, VISIBILITYMAP_ALL_VISIBLE | VISIBILITYMAP_ALL_FROZEN); END_CRIT_SECTION(); } UnlockReleaseBuffer(buf); RecordPageWithFreeSpace(onerel, blkno, freespace); continue; } /* * Prune all HOT-update chains in this page. * * We count tuples removed by the pruning step as removed by VACUUM. */ tups_vacuumed += heap_page_prune(onerel, buf, OldestXmin, false, &vacrelstats->latestRemovedXid); /* * Now scan the page to collect vacuumable items and check for tuples * requiring freezing. */ all_visible = true; has_dead_tuples = false; nfrozen = 0; hastup = false; prev_dead_count = vacrelstats->num_dead_tuples; maxoff = PageGetMaxOffsetNumber(page); /* * Note: If you change anything in the loop below, also look at * heap_page_is_all_visible to see if that needs to be changed. */ for (offnum = FirstOffsetNumber; offnum <= maxoff; offnum = OffsetNumberNext(offnum)) { ItemId itemid; itemid = PageGetItemId(page, offnum); /* Unused items require no processing, but we count 'em */ if (!ItemIdIsUsed(itemid)) { nunused += 1; continue; } /* Redirect items mustn't be touched */ if (ItemIdIsRedirected(itemid)) { hastup = true; /* this page won't be truncatable */ continue; } ItemPointerSet(&(tuple.t_self), blkno, offnum); /* * DEAD line pointers are to be vacuumed normally; but we don't * count them in tups_vacuumed, else we'd be double-counting (at * least in the common case where heap_page_prune() just freed up * a non-HOT tuple). */ if (ItemIdIsDead(itemid)) { lazy_record_dead_tuple(vacrelstats, &(tuple.t_self)); all_visible = false; continue; } Assert(ItemIdIsNormal(itemid)); tuple.t_data = (HeapTupleHeader) PageGetItem(page, itemid); tuple.t_len = ItemIdGetLength(itemid); tuple.t_tableOid = RelationGetRelid(onerel); tupgone = false; /* * 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). */ switch (HeapTupleSatisfiesVacuum(&tuple, OldestXmin, buf)) { case HEAPTUPLE_DEAD: /* * Ordinarily, DEAD tuples would have been removed by * heap_page_prune(), but it's possible that the tuple * state changed since heap_page_prune() looked. In * particular an INSERT_IN_PROGRESS tuple could have * changed to DEAD if the inserter aborted. So this * cannot be considered an error condition. * * If the tuple is HOT-updated then it must only be * removed by a prune operation; so we keep it just as if * it were RECENTLY_DEAD. Also, if it's a heap-only * tuple, we choose to keep it, because it'll be a lot * cheaper to get rid of it in the next pruning pass than * to treat it like an indexed tuple. Finally, if index * cleanup is disabled, the second heap pass will not * execute, and the tuple will not get removed, so we must * treat it like any other dead tuple that we choose to * keep. * * If this were to happen for a tuple that actually needed * to be deleted, we'd be in trouble, because it'd * possibly leave a tuple below the relation's xmin * horizon alive. heap_prepare_freeze_tuple() is prepared * to detect that case and abort the transaction, * preventing corruption. */ if (HeapTupleIsHotUpdated(&tuple) || HeapTupleIsHeapOnly(&tuple) || params->index_cleanup == VACOPT_TERNARY_DISABLED) nkeep += 1; else tupgone = true; /* we can delete the tuple */ all_visible = false; break; case HEAPTUPLE_LIVE: /* * Count it as live. Not only is this natural, but it's * also what acquire_sample_rows() does. */ live_tuples += 1; /* * 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 (all_visible) { TransactionId xmin; if (!HeapTupleHeaderXminCommitted(tuple.t_data)) { 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, OldestXmin)) { all_visible = false; break; } /* Track newest xmin on page. */ if (TransactionIdFollows(xmin, visibility_cutoff_xid)) visibility_cutoff_xid = xmin; } break; case HEAPTUPLE_RECENTLY_DEAD: /* * If tuple is recently deleted then we must not remove it * from relation. */ nkeep += 1; all_visible = false; break; case HEAPTUPLE_INSERT_IN_PROGRESS: /* * This is an expected case during concurrent vacuum. * * 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. */ all_visible = false; break; case HEAPTUPLE_DELETE_IN_PROGRESS: /* This is an expected case during concurrent vacuum */ 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 += 1; break; default: elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result"); break; } if (tupgone) { lazy_record_dead_tuple(vacrelstats, &(tuple.t_self)); HeapTupleHeaderAdvanceLatestRemovedXid(tuple.t_data, &vacrelstats->latestRemovedXid); tups_vacuumed += 1; has_dead_tuples = true; } else { bool tuple_totally_frozen; num_tuples += 1; hastup = true; /* * Each non-removable tuple must be checked to see if it needs * freezing. Note we already have exclusive buffer lock. */ if (heap_prepare_freeze_tuple(tuple.t_data, relfrozenxid, relminmxid, FreezeLimit, MultiXactCutoff, &frozen[nfrozen], &tuple_totally_frozen)) frozen[nfrozen++].offset = offnum; if (!tuple_totally_frozen) all_frozen = false; } } /* scan along page */ /* * If we froze any tuples, 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. */ if (nfrozen > 0) { START_CRIT_SECTION(); MarkBufferDirty(buf); /* execute collected freezes */ for (i = 0; i < nfrozen; i++) { ItemId itemid; 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(onerel)) { XLogRecPtr recptr; recptr = log_heap_freeze(onerel, buf, FreezeLimit, frozen, nfrozen); PageSetLSN(page, recptr); } END_CRIT_SECTION(); } /* * If there are no indexes we can vacuum the page right now instead of * doing a second scan. Also we don't do that but forget dead tuples * when index cleanup is disabled. */ if (!vacrelstats->useindex && vacrelstats->num_dead_tuples > 0) { if (nindexes == 0) { /* Remove tuples from heap if the table has no index */ lazy_vacuum_page(onerel, blkno, buf, 0, vacrelstats, &vmbuffer); vacuumed_pages++; has_dead_tuples = false; } else { /* * Here, we have indexes but index cleanup is disabled. * Instead of vacuuming the dead tuples on the heap, we just * forget them. * * Note that vacrelstats->dead_tuples could have tuples which * became dead after HOT-pruning but are not marked dead yet. * We do not process them because it's a very rare condition, * and the next vacuum will process them anyway. */ Assert(params->index_cleanup == VACOPT_TERNARY_DISABLED); } /* * Forget the now-vacuumed tuples, and press on, but be careful * not to reset latestRemovedXid since we want that value to be * valid. */ vacrelstats->num_dead_tuples = 0; /* * Periodically do incremental FSM vacuuming to make newly-freed * space visible on upper FSM pages. Note: although we've cleaned * the current block, we haven't yet updated its FSM entry (that * happens further down), so passing end == blkno is correct. */ if (blkno - next_fsm_block_to_vacuum >= VACUUM_FSM_EVERY_PAGES) { FreeSpaceMapVacuumRange(onerel, next_fsm_block_to_vacuum, blkno); next_fsm_block_to_vacuum = blkno; } } freespace = PageGetHeapFreeSpace(page); /* mark page all-visible, if appropriate */ if (all_visible && !all_visible_according_to_vm) { uint8 flags = VISIBILITYMAP_ALL_VISIBLE; if (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 the 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(onerel, blkno, buf, InvalidXLogRecPtr, vmbuffer, 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 we checked it and before we took the buffer * content lock, so we must recheck before jumping to the conclusion * that something bad has happened. */ else if (all_visible_according_to_vm && !PageIsAllVisible(page) && VM_ALL_VISIBLE(onerel, blkno, &vmbuffer)) { elog(WARNING, "page is not marked all-visible but visibility map bit is set in relation \"%s\" page %u", relname, blkno); visibilitymap_clear(onerel, blkno, vmbuffer, VISIBILITYMAP_VALID_BITS); } /* * It's possible for the value returned by GetOldestXmin() 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 * GetOldestXmin() 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 dead tuples on a page with PD_ALL_VISIBLE * set, however. */ else if (PageIsAllVisible(page) && has_dead_tuples) { elog(WARNING, "page containing dead tuples is marked as all-visible in relation \"%s\" page %u", relname, blkno); PageClearAllVisible(page); MarkBufferDirty(buf); visibilitymap_clear(onerel, blkno, vmbuffer, VISIBILITYMAP_VALID_BITS); } /* * If the all-visible page is turned out to be all-frozen but not * marked, we should so mark it. Note that all_frozen is only valid * if all_visible is true, so we must check both. */ else if (all_visible_according_to_vm && all_visible && all_frozen && !VM_ALL_FROZEN(onerel, blkno, &vmbuffer)) { /* * We can pass InvalidTransactionId as the cutoff XID here, * because setting the all-frozen bit doesn't cause recovery * conflicts. */ visibilitymap_set(onerel, blkno, buf, InvalidXLogRecPtr, vmbuffer, InvalidTransactionId, VISIBILITYMAP_ALL_FROZEN); } UnlockReleaseBuffer(buf); /* Remember the location of the last page with nonremovable tuples */ if (hastup) vacrelstats->nonempty_pages = blkno + 1; /* * If we remembered any tuples for deletion, then the page will be * visited again by lazy_vacuum_heap, which will compute and record * its post-compaction free space. If not, then we're done with this * page, so remember its free space as-is. (This path will always be * taken if there are no indexes.) */ if (vacrelstats->num_dead_tuples == prev_dead_count) RecordPageWithFreeSpace(onerel, blkno, freespace); } /* report that everything is scanned and vacuumed */ pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_SCANNED, blkno); pfree(frozen); /* save stats for use later */ vacrelstats->tuples_deleted = tups_vacuumed; vacrelstats->new_dead_tuples = nkeep; /* now we can compute the new value for pg_class.reltuples */ vacrelstats->new_live_tuples = vac_estimate_reltuples(onerel, nblocks, vacrelstats->tupcount_pages, live_tuples); /* also compute total number of surviving heap entries */ vacrelstats->new_rel_tuples = vacrelstats->new_live_tuples + vacrelstats->new_dead_tuples; /* * Release any remaining pin on visibility map page. */ if (BufferIsValid(vmbuffer)) { ReleaseBuffer(vmbuffer); vmbuffer = InvalidBuffer; } /* If any tuples need to be deleted, perform final vacuum cycle */ /* XXX put a threshold on min number of tuples here? */ if (vacrelstats->num_dead_tuples > 0) { /* Work on all the indexes, and then the heap */ lazy_vacuum_all_indexes(onerel, vacrelstats, Irel, nindexes, indstats); /* Remove tuples from heap */ lazy_vacuum_heap(onerel, vacrelstats); } /* * Vacuum the remainder of the Free Space Map. We must do this whether or * not there were indexes. */ if (blkno > next_fsm_block_to_vacuum) FreeSpaceMapVacuumRange(onerel, next_fsm_block_to_vacuum, blkno); /* report all blocks vacuumed; and that we're cleaning up */ pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_VACUUMED, blkno); pgstat_progress_update_param(PROGRESS_VACUUM_PHASE, PROGRESS_VACUUM_PHASE_INDEX_CLEANUP); /* Do post-vacuum cleanup and statistics update for each index */ if (vacrelstats->useindex) { for (i = 0; i < nindexes; i++) lazy_cleanup_index(Irel[i], indstats[i], vacrelstats); } /* If no indexes, make log report that lazy_vacuum_heap would've made */ if (vacuumed_pages) ereport(elevel, (errmsg("\"%s\": removed %.0f row versions in %u pages", RelationGetRelationName(onerel), tups_vacuumed, vacuumed_pages))); /* * This is pretty messy, but we split it up so that we can skip emitting * individual parts of the message when not applicable. */ initStringInfo(&buf); appendStringInfo(&buf, _("%.0f dead row versions cannot be removed yet, oldest xmin: %u\n"), nkeep, OldestXmin); appendStringInfo(&buf, _("There were %.0f unused item identifiers.\n"), nunused); appendStringInfo(&buf, ngettext("Skipped %u page due to buffer pins, ", "Skipped %u pages due to buffer pins, ", vacrelstats->pinskipped_pages), vacrelstats->pinskipped_pages); appendStringInfo(&buf, ngettext("%u frozen page.\n", "%u frozen pages.\n", vacrelstats->frozenskipped_pages), vacrelstats->frozenskipped_pages); appendStringInfo(&buf, ngettext("%u page is entirely empty.\n", "%u pages are entirely empty.\n", empty_pages), empty_pages); appendStringInfo(&buf, _("%s."), pg_rusage_show(&ru0)); ereport(elevel, (errmsg("\"%s\": found %.0f removable, %.0f nonremovable row versions in %u out of %u pages", RelationGetRelationName(onerel), tups_vacuumed, num_tuples, vacrelstats->scanned_pages, nblocks), errdetail_internal("%s", buf.data))); pfree(buf.data); } /* * lazy_vacuum_all_indexes() -- vacuum all indexes of relation. * * This is a utility wrapper for lazy_vacuum_index(), able to do * progress reporting. */ static void lazy_vacuum_all_indexes(Relation onerel, LVRelStats *vacrelstats, Relation *Irel, int nindexes, IndexBulkDeleteResult **indstats) { int i; /* Log cleanup info before we touch indexes */ vacuum_log_cleanup_info(onerel, vacrelstats); /* Report that we are now vacuuming indexes */ pgstat_progress_update_param(PROGRESS_VACUUM_PHASE, PROGRESS_VACUUM_PHASE_VACUUM_INDEX); /* Remove index entries */ for (i = 0; i < nindexes; i++) lazy_vacuum_index(Irel[i], &indstats[i], vacrelstats); /* Increase and report the number of index scans */ vacrelstats->num_index_scans++; pgstat_progress_update_param(PROGRESS_VACUUM_NUM_INDEX_VACUUMS, vacrelstats->num_index_scans); } /* * lazy_vacuum_heap() -- second pass over the heap * * This routine marks dead tuples as unused and compacts out free * space on their pages. Pages not having dead tuples recorded from * lazy_scan_heap are not visited at all. * * 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(Relation onerel, LVRelStats *vacrelstats) { int tupindex; int npages; PGRUsage ru0; Buffer vmbuffer = InvalidBuffer; /* Report that we are now vacuuming the heap */ pgstat_progress_update_param(PROGRESS_VACUUM_PHASE, PROGRESS_VACUUM_PHASE_VACUUM_HEAP); pg_rusage_init(&ru0); npages = 0; tupindex = 0; while (tupindex < vacrelstats->num_dead_tuples) { BlockNumber tblk; Buffer buf; Page page; Size freespace; vacuum_delay_point(); tblk = ItemPointerGetBlockNumber(&vacrelstats->dead_tuples[tupindex]); buf = ReadBufferExtended(onerel, MAIN_FORKNUM, tblk, RBM_NORMAL, vac_strategy); if (!ConditionalLockBufferForCleanup(buf)) { ReleaseBuffer(buf); ++tupindex; continue; } tupindex = lazy_vacuum_page(onerel, tblk, buf, tupindex, vacrelstats, &vmbuffer); /* Now that we've compacted the page, record its available space */ page = BufferGetPage(buf); freespace = PageGetHeapFreeSpace(page); UnlockReleaseBuffer(buf); RecordPageWithFreeSpace(onerel, tblk, freespace); npages++; } if (BufferIsValid(vmbuffer)) { ReleaseBuffer(vmbuffer); vmbuffer = InvalidBuffer; } ereport(elevel, (errmsg("\"%s\": removed %d row versions in %d pages", RelationGetRelationName(onerel), tupindex, npages), errdetail_internal("%s", pg_rusage_show(&ru0)))); } /* * lazy_vacuum_page() -- free dead tuples on a page * and repair its fragmentation. * * Caller must hold pin and buffer cleanup lock on the buffer. * * tupindex is the index in vacrelstats->dead_tuples of the first dead * tuple for this page. We assume the rest follow sequentially. * The return value is the first tupindex after the tuples of this page. */ static int lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer, int tupindex, LVRelStats *vacrelstats, Buffer *vmbuffer) { Page page = BufferGetPage(buffer); OffsetNumber unused[MaxOffsetNumber]; int uncnt = 0; TransactionId visibility_cutoff_xid; bool all_frozen; pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_VACUUMED, blkno); START_CRIT_SECTION(); for (; tupindex < vacrelstats->num_dead_tuples; tupindex++) { BlockNumber tblk; OffsetNumber toff; ItemId itemid; tblk = ItemPointerGetBlockNumber(&vacrelstats->dead_tuples[tupindex]); if (tblk != blkno) break; /* past end of tuples for this block */ toff = ItemPointerGetOffsetNumber(&vacrelstats->dead_tuples[tupindex]); itemid = PageGetItemId(page, toff); ItemIdSetUnused(itemid); unused[uncnt++] = toff; } PageRepairFragmentation(page); /* * Mark buffer dirty before we write WAL. */ MarkBufferDirty(buffer); /* XLOG stuff */ if (RelationNeedsWAL(onerel)) { XLogRecPtr recptr; recptr = log_heap_clean(onerel, buffer, NULL, 0, NULL, 0, unused, uncnt, vacrelstats->latestRemovedXid); 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 dead tuples 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 in the log_heap_clean() above. */ if (heap_page_is_all_visible(onerel, 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 vm_status = visibilitymap_get_status(onerel, blkno, vmbuffer); uint8 flags = 0; /* 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(onerel, blkno, buffer, InvalidXLogRecPtr, *vmbuffer, visibility_cutoff_xid, flags); } return tupindex; } /* * lazy_check_needs_freeze() -- scan page to see if any tuples * need to be cleaned to avoid wraparound * * Returns true if the page needs to be vacuumed using cleanup lock. * Also returns a flag indicating whether page contains any tuples at all. */ static bool lazy_check_needs_freeze(Buffer buf, bool *hastup) { Page page = BufferGetPage(buf); OffsetNumber offnum, maxoff; HeapTupleHeader tupleheader; *hastup = false; /* * New and empty pages, obviously, don't contain tuples. We could make * sure that the page is registered in the FSM, but it doesn't seem worth * waiting for a cleanup lock just for that, especially because it's * likely that the pin holder will do so. */ if (PageIsNew(page) || PageIsEmpty(page)) return false; maxoff = PageGetMaxOffsetNumber(page); for (offnum = FirstOffsetNumber; offnum <= maxoff; offnum = OffsetNumberNext(offnum)) { ItemId itemid; itemid = PageGetItemId(page, offnum); /* this should match hastup test in count_nondeletable_pages() */ if (ItemIdIsUsed(itemid)) *hastup = true; /* dead and redirect items never need freezing */ if (!ItemIdIsNormal(itemid)) continue; tupleheader = (HeapTupleHeader) PageGetItem(page, itemid); if (heap_tuple_needs_freeze(tupleheader, FreezeLimit, MultiXactCutoff, buf)) return true; } /* scan along page */ return false; } /* * lazy_vacuum_index() -- vacuum one index relation. * * Delete all the index entries pointing to tuples listed in * vacrelstats->dead_tuples, and update running statistics. */ static void lazy_vacuum_index(Relation indrel, IndexBulkDeleteResult **stats, LVRelStats *vacrelstats) { IndexVacuumInfo ivinfo; PGRUsage ru0; pg_rusage_init(&ru0); ivinfo.index = indrel; ivinfo.analyze_only = false; ivinfo.report_progress = false; ivinfo.estimated_count = true; ivinfo.message_level = elevel; /* We can only provide an approximate value of num_heap_tuples here */ ivinfo.num_heap_tuples = vacrelstats->old_live_tuples; ivinfo.strategy = vac_strategy; /* Do bulk deletion */ *stats = index_bulk_delete(&ivinfo, *stats, lazy_tid_reaped, (void *) vacrelstats); ereport(elevel, (errmsg("scanned index \"%s\" to remove %d row versions", RelationGetRelationName(indrel), vacrelstats->num_dead_tuples), errdetail_internal("%s", pg_rusage_show(&ru0)))); } /* * lazy_cleanup_index() -- do post-vacuum cleanup for one index relation. */ static void lazy_cleanup_index(Relation indrel, IndexBulkDeleteResult *stats, LVRelStats *vacrelstats) { IndexVacuumInfo ivinfo; PGRUsage ru0; pg_rusage_init(&ru0); ivinfo.index = indrel; ivinfo.analyze_only = false; ivinfo.report_progress = false; ivinfo.estimated_count = (vacrelstats->tupcount_pages < vacrelstats->rel_pages); ivinfo.message_level = elevel; /* * Now we can provide a better estimate of total number of surviving * tuples (we assume indexes are more interested in that than in the * number of nominally live tuples). */ ivinfo.num_heap_tuples = vacrelstats->new_rel_tuples; ivinfo.strategy = vac_strategy; stats = index_vacuum_cleanup(&ivinfo, stats); if (!stats) return; /* * Now update statistics in pg_class, but only if the index says the count * is accurate. */ if (!stats->estimated_count) vac_update_relstats(indrel, stats->num_pages, stats->num_index_tuples, 0, false, InvalidTransactionId, InvalidMultiXactId, false); ereport(elevel, (errmsg("index \"%s\" now contains %.0f row versions in %u pages", RelationGetRelationName(indrel), stats->num_index_tuples, stats->num_pages), errdetail("%.0f index row versions were removed.\n" "%u index pages have been deleted, %u are currently reusable.\n" "%s.", stats->tuples_removed, stats->pages_deleted, stats->pages_free, pg_rusage_show(&ru0)))); pfree(stats); } /* * 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. * * 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. We might be able to get away with * truncating all except one of the pages, setting its LSN to (at least) the * maximum of the truncated range if we also treated an index leaf tuple * pointing to a missing heap page as something to trigger the "snapshot too * old" error, but that seems fragile and seems like it deserves its own patch * if we consider it. * * This is split out so that we can test whether truncation is going to be * called for before we actually do it. If you change the logic here, be * careful to depend only on fields that lazy_scan_heap updates on-the-fly. */ static bool should_attempt_truncation(VacuumParams *params, LVRelStats *vacrelstats) { BlockNumber possibly_freeable; if (params->truncate == VACOPT_TERNARY_DISABLED) return false; possibly_freeable = vacrelstats->rel_pages - vacrelstats->nonempty_pages; if (possibly_freeable > 0 && (possibly_freeable >= REL_TRUNCATE_MINIMUM || possibly_freeable >= vacrelstats->rel_pages / REL_TRUNCATE_FRACTION) && old_snapshot_threshold < 0) return true; else return false; } /* * lazy_truncate_heap - try to truncate off any empty pages at the end */ static void lazy_truncate_heap(Relation onerel, LVRelStats *vacrelstats) { BlockNumber old_rel_pages = vacrelstats->rel_pages; BlockNumber new_rel_pages; PGRUsage ru0; int lock_retry; pg_rusage_init(&ru0); /* Report that we are now truncating */ pgstat_progress_update_param(PROGRESS_VACUUM_PHASE, PROGRESS_VACUUM_PHASE_TRUNCATE); /* * 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). */ vacrelstats->lock_waiter_detected = false; lock_retry = 0; while (true) { if (ConditionalLockRelation(onerel, 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. */ vacrelstats->lock_waiter_detected = true; ereport(elevel, (errmsg("\"%s\": stopping truncate due to conflicting lock request", RelationGetRelationName(onerel)))); return; } pg_usleep(VACUUM_TRUNCATE_LOCK_WAIT_INTERVAL * 1000L); } /* * 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(onerel); if (new_rel_pages != old_rel_pages) { /* * Note: we intentionally don't update vacrelstats->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(onerel, 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(onerel, vacrelstats); if (new_rel_pages >= old_rel_pages) { /* can't do anything after all */ UnlockRelation(onerel, AccessExclusiveLock); return; } /* * Okay to truncate. */ RelationTruncate(onerel, 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(onerel, 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. */ vacrelstats->pages_removed += old_rel_pages - new_rel_pages; vacrelstats->rel_pages = new_rel_pages; ereport(elevel, (errmsg("\"%s\": truncated %u to %u pages", RelationGetRelationName(onerel), old_rel_pages, new_rel_pages), errdetail_internal("%s", pg_rusage_show(&ru0)))); old_rel_pages = new_rel_pages; } while (new_rel_pages > vacrelstats->nonempty_pages && vacrelstats->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(Relation onerel, LVRelStats *vacrelstats) { 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 = vacrelstats->rel_pages; StaticAssertStmt((PREFETCH_SIZE & (PREFETCH_SIZE - 1)) == 0, "prefetch size must be power of 2"); prefetchedUntil = InvalidBlockNumber; while (blkno > vacrelstats->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(onerel, AccessExclusiveLock)) { ereport(elevel, (errmsg("\"%s\": suspending truncate due to conflicting lock request", RelationGetRelationName(onerel)))); vacrelstats->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(onerel, MAIN_FORKNUM, pblkno); CHECK_FOR_INTERRUPTS(); } prefetchedUntil = prefetchStart; } buf = ReadBufferExtended(onerel, MAIN_FORKNUM, blkno, RBM_NORMAL, vac_strategy); /* 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. We formerly thought that DEAD tuples could be * thrown away, but that's not so, because we'd not have cleaned * out their 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 vacrelstats->nonempty_pages; } /* * lazy_space_alloc - space allocation decisions for lazy vacuum * * See the comments at the head of this file for rationale. */ static void lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks) { long maxtuples; int vac_work_mem = IsAutoVacuumWorkerProcess() && autovacuum_work_mem != -1 ? autovacuum_work_mem : maintenance_work_mem; if (vacrelstats->useindex) { maxtuples = (vac_work_mem * 1024L) / sizeof(ItemPointerData); maxtuples = Min(maxtuples, INT_MAX); maxtuples = Min(maxtuples, MaxAllocSize / sizeof(ItemPointerData)); /* curious coding here to ensure the multiplication can't overflow */ if ((BlockNumber) (maxtuples / LAZY_ALLOC_TUPLES) > relblocks) maxtuples = relblocks * LAZY_ALLOC_TUPLES; /* stay sane if small maintenance_work_mem */ maxtuples = Max(maxtuples, MaxHeapTuplesPerPage); } else { maxtuples = MaxHeapTuplesPerPage; } vacrelstats->num_dead_tuples = 0; vacrelstats->max_dead_tuples = (int) maxtuples; vacrelstats->dead_tuples = (ItemPointer) palloc(maxtuples * sizeof(ItemPointerData)); } /* * lazy_record_dead_tuple - remember one deletable tuple */ static void lazy_record_dead_tuple(LVRelStats *vacrelstats, ItemPointer itemptr) { /* * The array shouldn't overflow under normal behavior, but perhaps it * could if we are given a really small maintenance_work_mem. In that * case, just forget the last few tuples (we'll get 'em next time). */ if (vacrelstats->num_dead_tuples < vacrelstats->max_dead_tuples) { vacrelstats->dead_tuples[vacrelstats->num_dead_tuples] = *itemptr; vacrelstats->num_dead_tuples++; pgstat_progress_update_param(PROGRESS_VACUUM_NUM_DEAD_TUPLES, vacrelstats->num_dead_tuples); } } /* * lazy_tid_reaped() -- is a particular tid deletable? * * This has the right signature to be an IndexBulkDeleteCallback. * * Assumes dead_tuples array is in sorted order. */ static bool lazy_tid_reaped(ItemPointer itemptr, void *state) { LVRelStats *vacrelstats = (LVRelStats *) state; ItemPointer res; res = (ItemPointer) bsearch((void *) itemptr, (void *) vacrelstats->dead_tuples, vacrelstats->num_dead_tuples, sizeof(ItemPointerData), vac_cmp_itemptr); return (res != NULL); } /* * Comparator routines for use with qsort() and bsearch(). */ static int vac_cmp_itemptr(const void *left, const void *right) { BlockNumber lblk, rblk; OffsetNumber loff, roff; lblk = ItemPointerGetBlockNumber((ItemPointer) left); rblk = ItemPointerGetBlockNumber((ItemPointer) right); if (lblk < rblk) return -1; if (lblk > rblk) return 1; loff = ItemPointerGetOffsetNumber((ItemPointer) left); roff = ItemPointerGetOffsetNumber((ItemPointer) right); if (loff < roff) return -1; if (loff > roff) return 1; return 0; } /* * 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. */ static bool heap_page_is_all_visible(Relation rel, 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; /* * This is a stripped down version of the line pointer scan in * lazy_scan_heap(). So if you change anything here, also check that code. */ maxoff = PageGetMaxOffsetNumber(page); for (offnum = FirstOffsetNumber; offnum <= maxoff && all_visible; offnum = OffsetNumberNext(offnum)) { ItemId itemid; HeapTupleData tuple; 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(rel); switch (HeapTupleSatisfiesVacuum(&tuple, OldestXmin, buf)) { case HEAPTUPLE_LIVE: { TransactionId xmin; /* Check comments in lazy_scan_heap. */ 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, 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 */ return all_visible; }