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1131 lines
33 KiB
C
1131 lines
33 KiB
C
/*-------------------------------------------------------------------------
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*
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* nbtree.c
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* Implementation of Lehman and Yao's btree management algorithm for
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* Postgres.
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*
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* NOTES
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* This file contains only the public interface routines.
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*
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*
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* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* src/backend/access/nbtree/nbtree.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/nbtree.h"
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#include "access/relscan.h"
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#include "access/xlog.h"
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#include "catalog/index.h"
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#include "commands/vacuum.h"
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#include "storage/indexfsm.h"
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#include "storage/ipc.h"
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#include "storage/lmgr.h"
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#include "storage/smgr.h"
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#include "tcop/tcopprot.h" /* pgrminclude ignore */
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#include "utils/index_selfuncs.h"
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#include "utils/memutils.h"
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/* Working state for btbuild and its callback */
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typedef struct
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{
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bool isUnique;
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bool haveDead;
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Relation heapRel;
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BTSpool *spool;
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/*
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* spool2 is needed only when the index is a unique index. Dead tuples are
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* put into spool2 instead of spool in order to avoid uniqueness check.
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*/
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BTSpool *spool2;
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double indtuples;
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} BTBuildState;
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/* Working state needed by btvacuumpage */
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typedef struct
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{
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IndexVacuumInfo *info;
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IndexBulkDeleteResult *stats;
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IndexBulkDeleteCallback callback;
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void *callback_state;
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BTCycleId cycleid;
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BlockNumber lastBlockVacuumed; /* highest blkno actually vacuumed */
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BlockNumber lastBlockLocked; /* highest blkno we've cleanup-locked */
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BlockNumber totFreePages; /* true total # of free pages */
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MemoryContext pagedelcontext;
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} BTVacState;
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static void btbuildCallback(Relation index,
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HeapTuple htup,
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Datum *values,
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bool *isnull,
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bool tupleIsAlive,
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void *state);
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static void btvacuumscan(IndexVacuumInfo *info, IndexBulkDeleteResult *stats,
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IndexBulkDeleteCallback callback, void *callback_state,
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BTCycleId cycleid);
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static void btvacuumpage(BTVacState *vstate, BlockNumber blkno,
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BlockNumber orig_blkno);
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/*
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* Btree handler function: return IndexAmRoutine with access method parameters
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* and callbacks.
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*/
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Datum
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bthandler(PG_FUNCTION_ARGS)
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{
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IndexAmRoutine *amroutine = makeNode(IndexAmRoutine);
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amroutine->amstrategies = BTMaxStrategyNumber;
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amroutine->amsupport = BTNProcs;
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amroutine->amcanorder = true;
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amroutine->amcanorderbyop = false;
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amroutine->amcanbackward = true;
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amroutine->amcanunique = true;
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amroutine->amcanmulticol = true;
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amroutine->amoptionalkey = true;
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amroutine->amsearcharray = true;
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amroutine->amsearchnulls = true;
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amroutine->amstorage = false;
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amroutine->amclusterable = true;
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amroutine->ampredlocks = true;
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amroutine->amkeytype = InvalidOid;
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amroutine->ambuild = btbuild;
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amroutine->ambuildempty = btbuildempty;
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amroutine->aminsert = btinsert;
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amroutine->ambulkdelete = btbulkdelete;
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amroutine->amvacuumcleanup = btvacuumcleanup;
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amroutine->amcanreturn = btcanreturn;
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amroutine->amcostestimate = btcostestimate;
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amroutine->amoptions = btoptions;
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amroutine->amvalidate = btvalidate;
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amroutine->ambeginscan = btbeginscan;
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amroutine->amrescan = btrescan;
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amroutine->amgettuple = btgettuple;
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amroutine->amgetbitmap = btgetbitmap;
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amroutine->amendscan = btendscan;
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amroutine->ammarkpos = btmarkpos;
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amroutine->amrestrpos = btrestrpos;
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PG_RETURN_POINTER(amroutine);
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}
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/*
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* btbuild() -- build a new btree index.
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*/
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IndexBuildResult *
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btbuild(Relation heap, Relation index, IndexInfo *indexInfo)
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{
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IndexBuildResult *result;
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double reltuples;
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BTBuildState buildstate;
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buildstate.isUnique = indexInfo->ii_Unique;
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buildstate.haveDead = false;
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buildstate.heapRel = heap;
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buildstate.spool = NULL;
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buildstate.spool2 = NULL;
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buildstate.indtuples = 0;
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#ifdef BTREE_BUILD_STATS
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if (log_btree_build_stats)
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ResetUsage();
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#endif /* BTREE_BUILD_STATS */
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/*
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* We expect to be called exactly once for any index relation. If that's
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* not the case, big trouble's what we have.
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*/
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if (RelationGetNumberOfBlocks(index) != 0)
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elog(ERROR, "index \"%s\" already contains data",
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RelationGetRelationName(index));
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buildstate.spool = _bt_spoolinit(heap, index, indexInfo->ii_Unique, false);
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/*
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* If building a unique index, put dead tuples in a second spool to keep
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* them out of the uniqueness check.
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*/
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if (indexInfo->ii_Unique)
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buildstate.spool2 = _bt_spoolinit(heap, index, false, true);
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/* do the heap scan */
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reltuples = IndexBuildHeapScan(heap, index, indexInfo, true,
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btbuildCallback, (void *) &buildstate);
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/* okay, all heap tuples are indexed */
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if (buildstate.spool2 && !buildstate.haveDead)
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{
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/* spool2 turns out to be unnecessary */
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_bt_spooldestroy(buildstate.spool2);
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buildstate.spool2 = NULL;
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}
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/*
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* Finish the build by (1) completing the sort of the spool file, (2)
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* inserting the sorted tuples into btree pages and (3) building the upper
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* levels.
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*/
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_bt_leafbuild(buildstate.spool, buildstate.spool2);
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_bt_spooldestroy(buildstate.spool);
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if (buildstate.spool2)
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_bt_spooldestroy(buildstate.spool2);
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#ifdef BTREE_BUILD_STATS
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if (log_btree_build_stats)
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{
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ShowUsage("BTREE BUILD STATS");
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ResetUsage();
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}
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#endif /* BTREE_BUILD_STATS */
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/*
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* Return statistics
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*/
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result = (IndexBuildResult *) palloc(sizeof(IndexBuildResult));
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result->heap_tuples = reltuples;
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result->index_tuples = buildstate.indtuples;
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return result;
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}
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/*
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* Per-tuple callback from IndexBuildHeapScan
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*/
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static void
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btbuildCallback(Relation index,
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HeapTuple htup,
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Datum *values,
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bool *isnull,
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bool tupleIsAlive,
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void *state)
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{
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BTBuildState *buildstate = (BTBuildState *) state;
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/*
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* insert the index tuple into the appropriate spool file for subsequent
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* processing
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*/
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if (tupleIsAlive || buildstate->spool2 == NULL)
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_bt_spool(buildstate->spool, &htup->t_self, values, isnull);
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else
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{
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/* dead tuples are put into spool2 */
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buildstate->haveDead = true;
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_bt_spool(buildstate->spool2, &htup->t_self, values, isnull);
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}
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buildstate->indtuples += 1;
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}
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/*
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* btbuildempty() -- build an empty btree index in the initialization fork
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*/
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void
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btbuildempty(Relation index)
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{
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Page metapage;
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/* Construct metapage. */
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metapage = (Page) palloc(BLCKSZ);
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_bt_initmetapage(metapage, P_NONE, 0);
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/* Write the page. If archiving/streaming, XLOG it. */
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PageSetChecksumInplace(metapage, BTREE_METAPAGE);
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smgrwrite(index->rd_smgr, INIT_FORKNUM, BTREE_METAPAGE,
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(char *) metapage, true);
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if (XLogIsNeeded())
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log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
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BTREE_METAPAGE, metapage, false);
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/*
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* An immediate sync is required even if we xlog'd the page, because the
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* write did not go through shared_buffers and therefore a concurrent
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* checkpoint may have moved the redo pointer past our xlog record.
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*/
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smgrimmedsync(index->rd_smgr, INIT_FORKNUM);
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}
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/*
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* btinsert() -- insert an index tuple into a btree.
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*
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* Descend the tree recursively, find the appropriate location for our
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* new tuple, and put it there.
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*/
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bool
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btinsert(Relation rel, Datum *values, bool *isnull,
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ItemPointer ht_ctid, Relation heapRel,
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IndexUniqueCheck checkUnique)
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{
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bool result;
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IndexTuple itup;
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/* generate an index tuple */
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itup = index_form_tuple(RelationGetDescr(rel), values, isnull);
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itup->t_tid = *ht_ctid;
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result = _bt_doinsert(rel, itup, checkUnique, heapRel);
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pfree(itup);
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return result;
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}
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/*
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* btgettuple() -- Get the next tuple in the scan.
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*/
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bool
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btgettuple(IndexScanDesc scan, ScanDirection dir)
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{
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BTScanOpaque so = (BTScanOpaque) scan->opaque;
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bool res;
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/* btree indexes are never lossy */
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scan->xs_recheck = false;
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/*
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* If we have any array keys, initialize them during first call for a
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* scan. We can't do this in btrescan because we don't know the scan
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* direction at that time.
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*/
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if (so->numArrayKeys && !BTScanPosIsValid(so->currPos))
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{
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/* punt if we have any unsatisfiable array keys */
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if (so->numArrayKeys < 0)
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return false;
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_bt_start_array_keys(scan, dir);
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}
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/* This loop handles advancing to the next array elements, if any */
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do
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{
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/*
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* If we've already initialized this scan, we can just advance it in
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* the appropriate direction. If we haven't done so yet, we call
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* _bt_first() to get the first item in the scan.
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*/
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if (!BTScanPosIsValid(so->currPos))
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res = _bt_first(scan, dir);
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else
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{
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/*
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* Check to see if we should kill the previously-fetched tuple.
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*/
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if (scan->kill_prior_tuple)
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{
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/*
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* Yes, remember it for later. (We'll deal with all such
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* tuples at once right before leaving the index page.) The
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* test for numKilled overrun is not just paranoia: if the
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* caller reverses direction in the indexscan then the same
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* item might get entered multiple times. It's not worth
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* trying to optimize that, so we don't detect it, but instead
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* just forget any excess entries.
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*/
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if (so->killedItems == NULL)
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so->killedItems = (int *)
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palloc(MaxIndexTuplesPerPage * sizeof(int));
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if (so->numKilled < MaxIndexTuplesPerPage)
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so->killedItems[so->numKilled++] = so->currPos.itemIndex;
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}
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/*
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* Now continue the scan.
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*/
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res = _bt_next(scan, dir);
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}
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/* If we have a tuple, return it ... */
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if (res)
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break;
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/* ... otherwise see if we have more array keys to deal with */
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} while (so->numArrayKeys && _bt_advance_array_keys(scan, dir));
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return res;
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}
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/*
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* btgetbitmap() -- gets all matching tuples, and adds them to a bitmap
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*/
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int64
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btgetbitmap(IndexScanDesc scan, TIDBitmap *tbm)
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{
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BTScanOpaque so = (BTScanOpaque) scan->opaque;
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int64 ntids = 0;
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ItemPointer heapTid;
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/*
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* If we have any array keys, initialize them.
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*/
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if (so->numArrayKeys)
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{
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/* punt if we have any unsatisfiable array keys */
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if (so->numArrayKeys < 0)
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return ntids;
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_bt_start_array_keys(scan, ForwardScanDirection);
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}
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/* This loop handles advancing to the next array elements, if any */
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do
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{
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/* Fetch the first page & tuple */
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if (_bt_first(scan, ForwardScanDirection))
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{
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/* Save tuple ID, and continue scanning */
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heapTid = &scan->xs_ctup.t_self;
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tbm_add_tuples(tbm, heapTid, 1, false);
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ntids++;
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for (;;)
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{
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/*
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* Advance to next tuple within page. This is the same as the
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* easy case in _bt_next().
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*/
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if (++so->currPos.itemIndex > so->currPos.lastItem)
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{
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/* let _bt_next do the heavy lifting */
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if (!_bt_next(scan, ForwardScanDirection))
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break;
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}
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/* Save tuple ID, and continue scanning */
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heapTid = &so->currPos.items[so->currPos.itemIndex].heapTid;
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tbm_add_tuples(tbm, heapTid, 1, false);
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ntids++;
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}
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}
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/* Now see if we have more array keys to deal with */
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} while (so->numArrayKeys && _bt_advance_array_keys(scan, ForwardScanDirection));
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return ntids;
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}
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/*
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* btbeginscan() -- start a scan on a btree index
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*/
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IndexScanDesc
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btbeginscan(Relation rel, int nkeys, int norderbys)
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{
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IndexScanDesc scan;
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BTScanOpaque so;
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/* no order by operators allowed */
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Assert(norderbys == 0);
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/* get the scan */
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scan = RelationGetIndexScan(rel, nkeys, norderbys);
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/* allocate private workspace */
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so = (BTScanOpaque) palloc(sizeof(BTScanOpaqueData));
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BTScanPosInvalidate(so->currPos);
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BTScanPosInvalidate(so->markPos);
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if (scan->numberOfKeys > 0)
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so->keyData = (ScanKey) palloc(scan->numberOfKeys * sizeof(ScanKeyData));
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else
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so->keyData = NULL;
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so->arrayKeyData = NULL; /* assume no array keys for now */
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so->numArrayKeys = 0;
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so->arrayKeys = NULL;
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so->arrayContext = NULL;
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so->killedItems = NULL; /* until needed */
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so->numKilled = 0;
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/*
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* We don't know yet whether the scan will be index-only, so we do not
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* allocate the tuple workspace arrays until btrescan. However, we set up
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* scan->xs_itupdesc whether we'll need it or not, since that's so cheap.
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*/
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so->currTuples = so->markTuples = NULL;
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scan->xs_itupdesc = RelationGetDescr(rel);
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scan->opaque = so;
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return scan;
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}
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/*
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* btrescan() -- rescan an index relation
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*/
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void
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btrescan(IndexScanDesc scan, ScanKey scankey, int nscankeys,
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ScanKey orderbys, int norderbys)
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{
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BTScanOpaque so = (BTScanOpaque) scan->opaque;
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/* we aren't holding any read locks, but gotta drop the pins */
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if (BTScanPosIsValid(so->currPos))
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{
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/* Before leaving current page, deal with any killed items */
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if (so->numKilled > 0)
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_bt_killitems(scan);
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BTScanPosUnpinIfPinned(so->currPos);
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BTScanPosInvalidate(so->currPos);
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}
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so->markItemIndex = -1;
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BTScanPosUnpinIfPinned(so->markPos);
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BTScanPosInvalidate(so->markPos);
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/*
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* Allocate tuple workspace arrays, if needed for an index-only scan and
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* not already done in a previous rescan call. To save on palloc
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* overhead, both workspaces are allocated as one palloc block; only this
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* function and btendscan know that.
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*
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* NOTE: this data structure also makes it safe to return data from a
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* "name" column, even though btree name_ops uses an underlying storage
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* datatype of cstring. The risk there is that "name" is supposed to be
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* padded to NAMEDATALEN, but the actual index tuple is probably shorter.
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* However, since we only return data out of tuples sitting in the
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* currTuples array, a fetch of NAMEDATALEN bytes can at worst pull some
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* data out of the markTuples array --- running off the end of memory for
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* a SIGSEGV is not possible. Yeah, this is ugly as sin, but it beats
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* adding special-case treatment for name_ops elsewhere.
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*/
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if (scan->xs_want_itup && so->currTuples == NULL)
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{
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so->currTuples = (char *) palloc(BLCKSZ * 2);
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so->markTuples = so->currTuples + BLCKSZ;
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}
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/*
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* Reset the scan keys. Note that keys ordering stuff moved to _bt_first.
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* - vadim 05/05/97
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*/
|
|
if (scankey && scan->numberOfKeys > 0)
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memmove(scan->keyData,
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scankey,
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scan->numberOfKeys * sizeof(ScanKeyData));
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so->numberOfKeys = 0; /* until _bt_preprocess_keys sets it */
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/* If any keys are SK_SEARCHARRAY type, set up array-key info */
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_bt_preprocess_array_keys(scan);
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}
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|
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/*
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* btendscan() -- close down a scan
|
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*/
|
|
void
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btendscan(IndexScanDesc scan)
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{
|
|
BTScanOpaque so = (BTScanOpaque) scan->opaque;
|
|
|
|
/* we aren't holding any read locks, but gotta drop the pins */
|
|
if (BTScanPosIsValid(so->currPos))
|
|
{
|
|
/* Before leaving current page, deal with any killed items */
|
|
if (so->numKilled > 0)
|
|
_bt_killitems(scan);
|
|
BTScanPosUnpinIfPinned(so->currPos);
|
|
}
|
|
|
|
so->markItemIndex = -1;
|
|
BTScanPosUnpinIfPinned(so->markPos);
|
|
|
|
/* No need to invalidate positions, the RAM is about to be freed. */
|
|
|
|
/* Release storage */
|
|
if (so->keyData != NULL)
|
|
pfree(so->keyData);
|
|
/* so->arrayKeyData and so->arrayKeys are in arrayContext */
|
|
if (so->arrayContext != NULL)
|
|
MemoryContextDelete(so->arrayContext);
|
|
if (so->killedItems != NULL)
|
|
pfree(so->killedItems);
|
|
if (so->currTuples != NULL)
|
|
pfree(so->currTuples);
|
|
/* so->markTuples should not be pfree'd, see btrescan */
|
|
pfree(so);
|
|
}
|
|
|
|
/*
|
|
* btmarkpos() -- save current scan position
|
|
*/
|
|
void
|
|
btmarkpos(IndexScanDesc scan)
|
|
{
|
|
BTScanOpaque so = (BTScanOpaque) scan->opaque;
|
|
|
|
/* There may be an old mark with a pin (but no lock). */
|
|
BTScanPosUnpinIfPinned(so->markPos);
|
|
|
|
/*
|
|
* Just record the current itemIndex. If we later step to next page
|
|
* before releasing the marked position, _bt_steppage makes a full copy of
|
|
* the currPos struct in markPos. If (as often happens) the mark is moved
|
|
* before we leave the page, we don't have to do that work.
|
|
*/
|
|
if (BTScanPosIsValid(so->currPos))
|
|
so->markItemIndex = so->currPos.itemIndex;
|
|
else
|
|
{
|
|
BTScanPosInvalidate(so->markPos);
|
|
so->markItemIndex = -1;
|
|
}
|
|
|
|
/* Also record the current positions of any array keys */
|
|
if (so->numArrayKeys)
|
|
_bt_mark_array_keys(scan);
|
|
}
|
|
|
|
/*
|
|
* btrestrpos() -- restore scan to last saved position
|
|
*/
|
|
void
|
|
btrestrpos(IndexScanDesc scan)
|
|
{
|
|
BTScanOpaque so = (BTScanOpaque) scan->opaque;
|
|
|
|
/* Restore the marked positions of any array keys */
|
|
if (so->numArrayKeys)
|
|
_bt_restore_array_keys(scan);
|
|
|
|
if (so->markItemIndex >= 0)
|
|
{
|
|
/*
|
|
* The scan has never moved to a new page since the last mark. Just
|
|
* restore the itemIndex.
|
|
*
|
|
* NB: In this case we can't count on anything in so->markPos to be
|
|
* accurate.
|
|
*/
|
|
so->currPos.itemIndex = so->markItemIndex;
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* The scan moved to a new page after last mark or restore, and we are
|
|
* now restoring to the marked page. We aren't holding any read
|
|
* locks, but if we're still holding the pin for the current position,
|
|
* we must drop it.
|
|
*/
|
|
if (BTScanPosIsValid(so->currPos))
|
|
{
|
|
/* Before leaving current page, deal with any killed items */
|
|
if (so->numKilled > 0)
|
|
_bt_killitems(scan);
|
|
BTScanPosUnpinIfPinned(so->currPos);
|
|
}
|
|
|
|
if (BTScanPosIsValid(so->markPos))
|
|
{
|
|
/* bump pin on mark buffer for assignment to current buffer */
|
|
if (BTScanPosIsPinned(so->markPos))
|
|
IncrBufferRefCount(so->markPos.buf);
|
|
memcpy(&so->currPos, &so->markPos,
|
|
offsetof(BTScanPosData, items[1]) +
|
|
so->markPos.lastItem * sizeof(BTScanPosItem));
|
|
if (so->currTuples)
|
|
memcpy(so->currTuples, so->markTuples,
|
|
so->markPos.nextTupleOffset);
|
|
}
|
|
else
|
|
BTScanPosInvalidate(so->currPos);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Bulk deletion of all index entries pointing to a set of heap tuples.
|
|
* The set of target tuples is specified via a callback routine that tells
|
|
* whether any given heap tuple (identified by ItemPointer) is being deleted.
|
|
*
|
|
* Result: a palloc'd struct containing statistical info for VACUUM displays.
|
|
*/
|
|
IndexBulkDeleteResult *
|
|
btbulkdelete(IndexVacuumInfo *info, IndexBulkDeleteResult *stats,
|
|
IndexBulkDeleteCallback callback, void *callback_state)
|
|
{
|
|
Relation rel = info->index;
|
|
BTCycleId cycleid;
|
|
|
|
/* allocate stats if first time through, else re-use existing struct */
|
|
if (stats == NULL)
|
|
stats = (IndexBulkDeleteResult *) palloc0(sizeof(IndexBulkDeleteResult));
|
|
|
|
/* Establish the vacuum cycle ID to use for this scan */
|
|
/* The ENSURE stuff ensures we clean up shared memory on failure */
|
|
PG_ENSURE_ERROR_CLEANUP(_bt_end_vacuum_callback, PointerGetDatum(rel));
|
|
{
|
|
cycleid = _bt_start_vacuum(rel);
|
|
|
|
btvacuumscan(info, stats, callback, callback_state, cycleid);
|
|
}
|
|
PG_END_ENSURE_ERROR_CLEANUP(_bt_end_vacuum_callback, PointerGetDatum(rel));
|
|
_bt_end_vacuum(rel);
|
|
|
|
return stats;
|
|
}
|
|
|
|
/*
|
|
* Post-VACUUM cleanup.
|
|
*
|
|
* Result: a palloc'd struct containing statistical info for VACUUM displays.
|
|
*/
|
|
IndexBulkDeleteResult *
|
|
btvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
|
|
{
|
|
/* No-op in ANALYZE ONLY mode */
|
|
if (info->analyze_only)
|
|
return stats;
|
|
|
|
/*
|
|
* If btbulkdelete was called, we need not do anything, just return the
|
|
* stats from the latest btbulkdelete call. If it wasn't called, we must
|
|
* still do a pass over the index, to recycle any newly-recyclable pages
|
|
* and to obtain index statistics.
|
|
*
|
|
* Since we aren't going to actually delete any leaf items, there's no
|
|
* need to go through all the vacuum-cycle-ID pushups.
|
|
*/
|
|
if (stats == NULL)
|
|
{
|
|
stats = (IndexBulkDeleteResult *) palloc0(sizeof(IndexBulkDeleteResult));
|
|
btvacuumscan(info, stats, NULL, NULL, 0);
|
|
}
|
|
|
|
/* Finally, vacuum the FSM */
|
|
IndexFreeSpaceMapVacuum(info->index);
|
|
|
|
/*
|
|
* It's quite possible for us to be fooled by concurrent page splits into
|
|
* double-counting some index tuples, so disbelieve any total that exceeds
|
|
* the underlying heap's count ... if we know that accurately. Otherwise
|
|
* this might just make matters worse.
|
|
*/
|
|
if (!info->estimated_count)
|
|
{
|
|
if (stats->num_index_tuples > info->num_heap_tuples)
|
|
stats->num_index_tuples = info->num_heap_tuples;
|
|
}
|
|
|
|
return stats;
|
|
}
|
|
|
|
/*
|
|
* btvacuumscan --- scan the index for VACUUMing purposes
|
|
*
|
|
* This combines the functions of looking for leaf tuples that are deletable
|
|
* according to the vacuum callback, looking for empty pages that can be
|
|
* deleted, and looking for old deleted pages that can be recycled. Both
|
|
* btbulkdelete and btvacuumcleanup invoke this (the latter only if no
|
|
* btbulkdelete call occurred).
|
|
*
|
|
* The caller is responsible for initially allocating/zeroing a stats struct
|
|
* and for obtaining a vacuum cycle ID if necessary.
|
|
*/
|
|
static void
|
|
btvacuumscan(IndexVacuumInfo *info, IndexBulkDeleteResult *stats,
|
|
IndexBulkDeleteCallback callback, void *callback_state,
|
|
BTCycleId cycleid)
|
|
{
|
|
Relation rel = info->index;
|
|
BTVacState vstate;
|
|
BlockNumber num_pages;
|
|
BlockNumber blkno;
|
|
bool needLock;
|
|
|
|
/*
|
|
* Reset counts that will be incremented during the scan; needed in case
|
|
* of multiple scans during a single VACUUM command
|
|
*/
|
|
stats->estimated_count = false;
|
|
stats->num_index_tuples = 0;
|
|
stats->pages_deleted = 0;
|
|
|
|
/* Set up info to pass down to btvacuumpage */
|
|
vstate.info = info;
|
|
vstate.stats = stats;
|
|
vstate.callback = callback;
|
|
vstate.callback_state = callback_state;
|
|
vstate.cycleid = cycleid;
|
|
vstate.lastBlockVacuumed = BTREE_METAPAGE; /* Initialise at first block */
|
|
vstate.lastBlockLocked = BTREE_METAPAGE;
|
|
vstate.totFreePages = 0;
|
|
|
|
/* Create a temporary memory context to run _bt_pagedel in */
|
|
vstate.pagedelcontext = AllocSetContextCreate(CurrentMemoryContext,
|
|
"_bt_pagedel",
|
|
ALLOCSET_DEFAULT_MINSIZE,
|
|
ALLOCSET_DEFAULT_INITSIZE,
|
|
ALLOCSET_DEFAULT_MAXSIZE);
|
|
|
|
/*
|
|
* The outer loop iterates over all index pages except the metapage, in
|
|
* physical order (we hope the kernel will cooperate in providing
|
|
* read-ahead for speed). It is critical that we visit all leaf pages,
|
|
* including ones added after we start the scan, else we might fail to
|
|
* delete some deletable tuples. Hence, we must repeatedly check the
|
|
* relation length. We must acquire the relation-extension lock while
|
|
* doing so to avoid a race condition: if someone else is extending the
|
|
* relation, there is a window where bufmgr/smgr have created a new
|
|
* all-zero page but it hasn't yet been write-locked by _bt_getbuf(). If
|
|
* we manage to scan such a page here, we'll improperly assume it can be
|
|
* recycled. Taking the lock synchronizes things enough to prevent a
|
|
* problem: either num_pages won't include the new page, or _bt_getbuf
|
|
* already has write lock on the buffer and it will be fully initialized
|
|
* before we can examine it. (See also vacuumlazy.c, which has the same
|
|
* issue.) Also, we need not worry if a page is added immediately after
|
|
* we look; the page splitting code already has write-lock on the left
|
|
* page before it adds a right page, so we must already have processed any
|
|
* tuples due to be moved into such a page.
|
|
*
|
|
* We can skip locking for new or temp relations, however, since no one
|
|
* else could be accessing them.
|
|
*/
|
|
needLock = !RELATION_IS_LOCAL(rel);
|
|
|
|
blkno = BTREE_METAPAGE + 1;
|
|
for (;;)
|
|
{
|
|
/* Get the current relation length */
|
|
if (needLock)
|
|
LockRelationForExtension(rel, ExclusiveLock);
|
|
num_pages = RelationGetNumberOfBlocks(rel);
|
|
if (needLock)
|
|
UnlockRelationForExtension(rel, ExclusiveLock);
|
|
|
|
/* Quit if we've scanned the whole relation */
|
|
if (blkno >= num_pages)
|
|
break;
|
|
/* Iterate over pages, then loop back to recheck length */
|
|
for (; blkno < num_pages; blkno++)
|
|
{
|
|
btvacuumpage(&vstate, blkno, blkno);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Check to see if we need to issue one final WAL record for this index,
|
|
* which may be needed for correctness on a hot standby node when non-MVCC
|
|
* index scans could take place.
|
|
*
|
|
* If the WAL is replayed in hot standby, the replay process needs to get
|
|
* cleanup locks on all index leaf pages, just as we've been doing here.
|
|
* However, we won't issue any WAL records about pages that have no items
|
|
* to be deleted. For pages between pages we've vacuumed, the replay code
|
|
* will take locks under the direction of the lastBlockVacuumed fields in
|
|
* the XLOG_BTREE_VACUUM WAL records. To cover pages after the last one
|
|
* we vacuum, we need to issue a dummy XLOG_BTREE_VACUUM WAL record
|
|
* against the last leaf page in the index, if that one wasn't vacuumed.
|
|
*/
|
|
if (XLogStandbyInfoActive() &&
|
|
vstate.lastBlockVacuumed < vstate.lastBlockLocked)
|
|
{
|
|
Buffer buf;
|
|
|
|
/*
|
|
* The page should be valid, but we can't use _bt_getbuf() because we
|
|
* want to use a nondefault buffer access strategy. Since we aren't
|
|
* going to delete any items, getting cleanup lock again is probably
|
|
* overkill, but for consistency do that anyway.
|
|
*/
|
|
buf = ReadBufferExtended(rel, MAIN_FORKNUM, vstate.lastBlockLocked,
|
|
RBM_NORMAL, info->strategy);
|
|
LockBufferForCleanup(buf);
|
|
_bt_checkpage(rel, buf);
|
|
_bt_delitems_vacuum(rel, buf, NULL, 0, vstate.lastBlockVacuumed);
|
|
_bt_relbuf(rel, buf);
|
|
}
|
|
|
|
MemoryContextDelete(vstate.pagedelcontext);
|
|
|
|
/* update statistics */
|
|
stats->num_pages = num_pages;
|
|
stats->pages_free = vstate.totFreePages;
|
|
}
|
|
|
|
/*
|
|
* btvacuumpage --- VACUUM one page
|
|
*
|
|
* This processes a single page for btvacuumscan(). In some cases we
|
|
* must go back and re-examine previously-scanned pages; this routine
|
|
* recurses when necessary to handle that case.
|
|
*
|
|
* blkno is the page to process. orig_blkno is the highest block number
|
|
* reached by the outer btvacuumscan loop (the same as blkno, unless we
|
|
* are recursing to re-examine a previous page).
|
|
*/
|
|
static void
|
|
btvacuumpage(BTVacState *vstate, BlockNumber blkno, BlockNumber orig_blkno)
|
|
{
|
|
IndexVacuumInfo *info = vstate->info;
|
|
IndexBulkDeleteResult *stats = vstate->stats;
|
|
IndexBulkDeleteCallback callback = vstate->callback;
|
|
void *callback_state = vstate->callback_state;
|
|
Relation rel = info->index;
|
|
bool delete_now;
|
|
BlockNumber recurse_to;
|
|
Buffer buf;
|
|
Page page;
|
|
BTPageOpaque opaque = NULL;
|
|
|
|
restart:
|
|
delete_now = false;
|
|
recurse_to = P_NONE;
|
|
|
|
/* call vacuum_delay_point while not holding any buffer lock */
|
|
vacuum_delay_point();
|
|
|
|
/*
|
|
* We can't use _bt_getbuf() here because it always applies
|
|
* _bt_checkpage(), which will barf on an all-zero page. We want to
|
|
* recycle all-zero pages, not fail. Also, we want to use a nondefault
|
|
* buffer access strategy.
|
|
*/
|
|
buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL,
|
|
info->strategy);
|
|
LockBuffer(buf, BT_READ);
|
|
page = BufferGetPage(buf);
|
|
if (!PageIsNew(page))
|
|
{
|
|
_bt_checkpage(rel, buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
}
|
|
|
|
/*
|
|
* If we are recursing, the only case we want to do anything with is a
|
|
* live leaf page having the current vacuum cycle ID. Any other state
|
|
* implies we already saw the page (eg, deleted it as being empty).
|
|
*/
|
|
if (blkno != orig_blkno)
|
|
{
|
|
if (_bt_page_recyclable(page) ||
|
|
P_IGNORE(opaque) ||
|
|
!P_ISLEAF(opaque) ||
|
|
opaque->btpo_cycleid != vstate->cycleid)
|
|
{
|
|
_bt_relbuf(rel, buf);
|
|
return;
|
|
}
|
|
}
|
|
|
|
/* Page is valid, see what to do with it */
|
|
if (_bt_page_recyclable(page))
|
|
{
|
|
/* Okay to recycle this page */
|
|
RecordFreeIndexPage(rel, blkno);
|
|
vstate->totFreePages++;
|
|
stats->pages_deleted++;
|
|
}
|
|
else if (P_ISDELETED(opaque))
|
|
{
|
|
/* Already deleted, but can't recycle yet */
|
|
stats->pages_deleted++;
|
|
}
|
|
else if (P_ISHALFDEAD(opaque))
|
|
{
|
|
/* Half-dead, try to delete */
|
|
delete_now = true;
|
|
}
|
|
else if (P_ISLEAF(opaque))
|
|
{
|
|
OffsetNumber deletable[MaxOffsetNumber];
|
|
int ndeletable;
|
|
OffsetNumber offnum,
|
|
minoff,
|
|
maxoff;
|
|
|
|
/*
|
|
* Trade in the initial read lock for a super-exclusive write lock on
|
|
* this page. We must get such a lock on every leaf page over the
|
|
* course of the vacuum scan, whether or not it actually contains any
|
|
* deletable tuples --- see nbtree/README.
|
|
*/
|
|
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
|
|
LockBufferForCleanup(buf);
|
|
|
|
/*
|
|
* Remember highest leaf page number we've taken cleanup lock on; see
|
|
* notes in btvacuumscan
|
|
*/
|
|
if (blkno > vstate->lastBlockLocked)
|
|
vstate->lastBlockLocked = blkno;
|
|
|
|
/*
|
|
* Check whether we need to recurse back to earlier pages. What we
|
|
* are concerned about is a page split that happened since we started
|
|
* the vacuum scan. If the split moved some tuples to a lower page
|
|
* then we might have missed 'em. If so, set up for tail recursion.
|
|
* (Must do this before possibly clearing btpo_cycleid below!)
|
|
*/
|
|
if (vstate->cycleid != 0 &&
|
|
opaque->btpo_cycleid == vstate->cycleid &&
|
|
!(opaque->btpo_flags & BTP_SPLIT_END) &&
|
|
!P_RIGHTMOST(opaque) &&
|
|
opaque->btpo_next < orig_blkno)
|
|
recurse_to = opaque->btpo_next;
|
|
|
|
/*
|
|
* Scan over all items to see which ones need deleted according to the
|
|
* callback function.
|
|
*/
|
|
ndeletable = 0;
|
|
minoff = P_FIRSTDATAKEY(opaque);
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
if (callback)
|
|
{
|
|
for (offnum = minoff;
|
|
offnum <= maxoff;
|
|
offnum = OffsetNumberNext(offnum))
|
|
{
|
|
IndexTuple itup;
|
|
ItemPointer htup;
|
|
|
|
itup = (IndexTuple) PageGetItem(page,
|
|
PageGetItemId(page, offnum));
|
|
htup = &(itup->t_tid);
|
|
|
|
/*
|
|
* During Hot Standby we currently assume that
|
|
* XLOG_BTREE_VACUUM records do not produce conflicts. That is
|
|
* only true as long as the callback function depends only
|
|
* upon whether the index tuple refers to heap tuples removed
|
|
* in the initial heap scan. When vacuum starts it derives a
|
|
* value of OldestXmin. Backends taking later snapshots could
|
|
* have a RecentGlobalXmin with a later xid than the vacuum's
|
|
* OldestXmin, so it is possible that row versions deleted
|
|
* after OldestXmin could be marked as killed by other
|
|
* backends. The callback function *could* look at the index
|
|
* tuple state in isolation and decide to delete the index
|
|
* tuple, though currently it does not. If it ever did, we
|
|
* would need to reconsider whether XLOG_BTREE_VACUUM records
|
|
* should cause conflicts. If they did cause conflicts they
|
|
* would be fairly harsh conflicts, since we haven't yet
|
|
* worked out a way to pass a useful value for
|
|
* latestRemovedXid on the XLOG_BTREE_VACUUM records. This
|
|
* applies to *any* type of index that marks index tuples as
|
|
* killed.
|
|
*/
|
|
if (callback(htup, callback_state))
|
|
deletable[ndeletable++] = offnum;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Apply any needed deletes. We issue just one _bt_delitems_vacuum()
|
|
* call per page, so as to minimize WAL traffic.
|
|
*/
|
|
if (ndeletable > 0)
|
|
{
|
|
/*
|
|
* Notice that the issued XLOG_BTREE_VACUUM WAL record includes
|
|
* all information to the replay code to allow it to get a cleanup
|
|
* lock on all pages between the previous lastBlockVacuumed and
|
|
* this page. This ensures that WAL replay locks all leaf pages at
|
|
* some point, which is important should non-MVCC scans be
|
|
* requested. This is currently unused on standby, but we record
|
|
* it anyway, so that the WAL contains the required information.
|
|
*
|
|
* Since we can visit leaf pages out-of-order when recursing,
|
|
* replay might end up locking such pages an extra time, but it
|
|
* doesn't seem worth the amount of bookkeeping it'd take to avoid
|
|
* that.
|
|
*/
|
|
_bt_delitems_vacuum(rel, buf, deletable, ndeletable,
|
|
vstate->lastBlockVacuumed);
|
|
|
|
/*
|
|
* Remember highest leaf page number we've issued a
|
|
* XLOG_BTREE_VACUUM WAL record for.
|
|
*/
|
|
if (blkno > vstate->lastBlockVacuumed)
|
|
vstate->lastBlockVacuumed = blkno;
|
|
|
|
stats->tuples_removed += ndeletable;
|
|
/* must recompute maxoff */
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* If the page has been split during this vacuum cycle, it seems
|
|
* worth expending a write to clear btpo_cycleid even if we don't
|
|
* have any deletions to do. (If we do, _bt_delitems_vacuum takes
|
|
* care of this.) This ensures we won't process the page again.
|
|
*
|
|
* We treat this like a hint-bit update because there's no need to
|
|
* WAL-log it.
|
|
*/
|
|
if (vstate->cycleid != 0 &&
|
|
opaque->btpo_cycleid == vstate->cycleid)
|
|
{
|
|
opaque->btpo_cycleid = 0;
|
|
MarkBufferDirtyHint(buf, true);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If it's now empty, try to delete; else count the live tuples. We
|
|
* don't delete when recursing, though, to avoid putting entries into
|
|
* freePages out-of-order (doesn't seem worth any extra code to handle
|
|
* the case).
|
|
*/
|
|
if (minoff > maxoff)
|
|
delete_now = (blkno == orig_blkno);
|
|
else
|
|
stats->num_index_tuples += maxoff - minoff + 1;
|
|
}
|
|
|
|
if (delete_now)
|
|
{
|
|
MemoryContext oldcontext;
|
|
int ndel;
|
|
|
|
/* Run pagedel in a temp context to avoid memory leakage */
|
|
MemoryContextReset(vstate->pagedelcontext);
|
|
oldcontext = MemoryContextSwitchTo(vstate->pagedelcontext);
|
|
|
|
ndel = _bt_pagedel(rel, buf);
|
|
|
|
/* count only this page, else may double-count parent */
|
|
if (ndel)
|
|
stats->pages_deleted++;
|
|
|
|
MemoryContextSwitchTo(oldcontext);
|
|
/* pagedel released buffer, so we shouldn't */
|
|
}
|
|
else
|
|
_bt_relbuf(rel, buf);
|
|
|
|
/*
|
|
* This is really tail recursion, but if the compiler is too stupid to
|
|
* optimize it as such, we'd eat an uncomfortably large amount of stack
|
|
* space per recursion level (due to the deletable[] array). A failure is
|
|
* improbable since the number of levels isn't likely to be large ... but
|
|
* just in case, let's hand-optimize into a loop.
|
|
*/
|
|
if (recurse_to != P_NONE)
|
|
{
|
|
blkno = recurse_to;
|
|
goto restart;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* btcanreturn() -- Check whether btree indexes support index-only scans.
|
|
*
|
|
* btrees always do, so this is trivial.
|
|
*/
|
|
bool
|
|
btcanreturn(Relation index, int attno)
|
|
{
|
|
return true;
|
|
}
|