granicus.if.org Git - postgresql/blob - src/backend/access/index/indexam.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * indexam.c
   4  *        general index access method routines
   5  *
   6  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        src/backend/access/index/indexam.c
  12  *
  13  * INTERFACE ROUTINES
  14  *              index_open              - open an index relation by relation OID
  15  *              index_close             - close an index relation
  16  *              index_beginscan - start a scan of an index with amgettuple
  17  *              index_beginscan_bitmap - start a scan of an index with amgetbitmap
  18  *              index_rescan    - restart a scan of an index
  19  *              index_endscan   - end a scan
  20  *              index_insert    - insert an index tuple into a relation
  21  *              index_markpos   - mark a scan position
  22  *              index_restrpos  - restore a scan position
  23  *              index_getnext   - get the next tuple from a scan
  24  *              index_getbitmap - get all tuples from a scan
  25  *              index_bulk_delete       - bulk deletion of index tuples
  26  *              index_vacuum_cleanup    - post-deletion cleanup of an index
  27  *              index_getprocid - get a support procedure OID
  28  *              index_getprocinfo - get a support procedure's lookup info
  29  *
  30  * NOTES
  31  *              This file contains the index_ routines which used
  32  *              to be a scattered collection of stuff in access/genam.
  33  *
  34  *
  35  * old comments
  36  *              Scans are implemented as follows:
  37  *
  38  *              `0' represents an invalid item pointer.
  39  *              `-' represents an unknown item pointer.
  40  *              `X' represents a known item pointers.
  41  *              `+' represents known or invalid item pointers.
  42  *              `*' represents any item pointers.
  43  *
  44  *              State is represented by a triple of these symbols in the order of
  45  *              previous, current, next.  Note that the case of reverse scans works
  46  *              identically.
  47  *
  48  *                              State   Result
  49  *              (1)             + + -   + 0 0                   (if the next item pointer is invalid)
  50  *              (2)                             + X -                   (otherwise)
  51  *              (3)             * 0 0   * 0 0                   (no change)
  52  *              (4)             + X 0   X 0 0                   (shift)
  53  *              (5)             * + X   + X -                   (shift, add unknown)
  54  *
  55  *              All other states cannot occur.
  56  *
  57  *              Note: It would be possible to cache the status of the previous and
  58  *                        next item pointer using the flags.
  59  *
  60  *-------------------------------------------------------------------------
  61  */
  62
  63 #include "postgres.h"
  64
  65 #include "access/relscan.h"
  66 #include "access/transam.h"
  67 #include "pgstat.h"
  68 #include "storage/bufmgr.h"
  69 #include "storage/lmgr.h"
  70 #include "utils/relcache.h"
  71 #include "utils/snapmgr.h"
  72 #include "utils/tqual.h"
  73
  74
  75 /* ----------------------------------------------------------------
  76  *                                      macros used in index_ routines
  77  * ----------------------------------------------------------------
  78  */
  79 #define RELATION_CHECKS \
  80 ( \
  81         AssertMacro(RelationIsValid(indexRelation)), \
  82         AssertMacro(PointerIsValid(indexRelation->rd_am)) \
  83 )
  84
  85 #define SCAN_CHECKS \
  86 ( \
  87         AssertMacro(IndexScanIsValid(scan)), \
  88         AssertMacro(RelationIsValid(scan->indexRelation)), \
  89         AssertMacro(PointerIsValid(scan->indexRelation->rd_am)) \
  90 )
  91
  92 #define GET_REL_PROCEDURE(pname) \
  93 do { \
  94         procedure = &indexRelation->rd_aminfo->pname; \
  95         if (!OidIsValid(procedure->fn_oid)) \
  96         { \
  97                 RegProcedure    procOid = indexRelation->rd_am->pname; \
  98                 if (!RegProcedureIsValid(procOid)) \
  99                         elog(ERROR, "invalid %s regproc", CppAsString(pname)); \
 100                 fmgr_info_cxt(procOid, procedure, indexRelation->rd_indexcxt); \
 101         } \
 102 } while(0)
 103
 104 #define GET_SCAN_PROCEDURE(pname) \
 105 do { \
 106         procedure = &scan->indexRelation->rd_aminfo->pname; \
 107         if (!OidIsValid(procedure->fn_oid)) \
 108         { \
 109                 RegProcedure    procOid = scan->indexRelation->rd_am->pname; \
 110                 if (!RegProcedureIsValid(procOid)) \
 111                         elog(ERROR, "invalid %s regproc", CppAsString(pname)); \
 112                 fmgr_info_cxt(procOid, procedure, scan->indexRelation->rd_indexcxt); \
 113         } \
 114 } while(0)
 115
 116 static IndexScanDesc index_beginscan_internal(Relation indexRelation,
 117                                                  int nkeys, int norderbys);
 118
 119
 120 /* ----------------------------------------------------------------
 121  *                                 index_ interface functions
 122  * ----------------------------------------------------------------
 123  */
 124
 125 /* ----------------
 126  *              index_open - open an index relation by relation OID
 127  *
 128  *              If lockmode is not "NoLock", the specified kind of lock is
 129  *              obtained on the index.  (Generally, NoLock should only be
 130  *              used if the caller knows it has some appropriate lock on the
 131  *              index already.)
 132  *
 133  *              An error is raised if the index does not exist.
 134  *
 135  *              This is a convenience routine adapted for indexscan use.
 136  *              Some callers may prefer to use relation_open directly.
 137  * ----------------
 138  */
 139 Relation
 140 index_open(Oid relationId, LOCKMODE lockmode)
 141 {
 142         Relation        r;
 143
 144         r = relation_open(relationId, lockmode);
 145
 146         if (r->rd_rel->relkind != RELKIND_INDEX)
 147                 ereport(ERROR,
 148                                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 149                                  errmsg("\"%s\" is not an index",
 150                                                 RelationGetRelationName(r))));
 151
 152         return r;
 153 }
 154
 155 /* ----------------
 156  *              index_close - close an index relation
 157  *
 158  *              If lockmode is not "NoLock", we then release the specified lock.
 159  *
 160  *              Note that it is often sensible to hold a lock beyond index_close;
 161  *              in that case, the lock is released automatically at xact end.
 162  * ----------------
 163  */
 164 void
 165 index_close(Relation relation, LOCKMODE lockmode)
 166 {
 167         LockRelId       relid = relation->rd_lockInfo.lockRelId;
 168
 169         Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
 170
 171         /* The relcache does the real work... */
 172         RelationClose(relation);
 173
 174         if (lockmode != NoLock)
 175                 UnlockRelationId(&relid, lockmode);
 176 }
 177
 178 /* ----------------
 179  *              index_insert - insert an index tuple into a relation
 180  * ----------------
 181  */
 182 bool
 183 index_insert(Relation indexRelation,
 184                          Datum *values,
 185                          bool *isnull,
 186                          ItemPointer heap_t_ctid,
 187                          Relation heapRelation,
 188                          IndexUniqueCheck checkUnique)
 189 {
 190         FmgrInfo   *procedure;
 191
 192         RELATION_CHECKS;
 193         GET_REL_PROCEDURE(aminsert);
 194
 195         /*
 196          * have the am's insert proc do all the work.
 197          */
 198         return DatumGetBool(FunctionCall6(procedure,
 199                                                                           PointerGetDatum(indexRelation),
 200                                                                           PointerGetDatum(values),
 201                                                                           PointerGetDatum(isnull),
 202                                                                           PointerGetDatum(heap_t_ctid),
 203                                                                           PointerGetDatum(heapRelation),
 204                                                                           Int32GetDatum((int32) checkUnique)));
 205 }
 206
 207 /*
 208  * index_beginscan - start a scan of an index with amgettuple
 209  *
 210  * Caller must be holding suitable locks on the heap and the index.
 211  */
 212 IndexScanDesc
 213 index_beginscan(Relation heapRelation,
 214                                 Relation indexRelation,
 215                                 Snapshot snapshot,
 216                                 int nkeys, int norderbys)
 217 {
 218         IndexScanDesc scan;
 219
 220         scan = index_beginscan_internal(indexRelation, nkeys, norderbys);
 221
 222         /*
 223          * Save additional parameters into the scandesc.  Everything else was set
 224          * up by RelationGetIndexScan.
 225          */
 226         scan->heapRelation = heapRelation;
 227         scan->xs_snapshot = snapshot;
 228
 229         return scan;
 230 }
 231
 232 /*
 233  * index_beginscan_bitmap - start a scan of an index with amgetbitmap
 234  *
 235  * As above, caller had better be holding some lock on the parent heap
 236  * relation, even though it's not explicitly mentioned here.
 237  */
 238 IndexScanDesc
 239 index_beginscan_bitmap(Relation indexRelation,
 240                                            Snapshot snapshot,
 241                                            int nkeys)
 242 {
 243         IndexScanDesc scan;
 244
 245         scan = index_beginscan_internal(indexRelation, nkeys, 0);
 246
 247         /*
 248          * Save additional parameters into the scandesc.  Everything else was set
 249          * up by RelationGetIndexScan.
 250          */
 251         scan->xs_snapshot = snapshot;
 252
 253         return scan;
 254 }
 255
 256 /*
 257  * index_beginscan_internal --- common code for index_beginscan variants
 258  */
 259 static IndexScanDesc
 260 index_beginscan_internal(Relation indexRelation,
 261                                                  int nkeys, int norderbys)
 262 {
 263         IndexScanDesc scan;
 264         FmgrInfo   *procedure;
 265
 266         RELATION_CHECKS;
 267         GET_REL_PROCEDURE(ambeginscan);
 268
 269         /*
 270          * We hold a reference count to the relcache entry throughout the scan.
 271          */
 272         RelationIncrementReferenceCount(indexRelation);
 273
 274         /*
 275          * Tell the AM to open a scan.
 276          */
 277         scan = (IndexScanDesc)
 278                 DatumGetPointer(FunctionCall3(procedure,
 279                                                                           PointerGetDatum(indexRelation),
 280                                                                           Int32GetDatum(nkeys),
 281                                                                           Int32GetDatum(norderbys)));
 282
 283         return scan;
 284 }
 285
 286 /* ----------------
 287  *              index_rescan  - (re)start a scan of an index
 288  *
 289  * During a restart, the caller may specify a new set of scankeys and/or
 290  * orderbykeys; but the number of keys cannot differ from what index_beginscan
 291  * was told.  (Later we might relax that to "must not exceed", but currently
 292  * the index AMs tend to assume that scan->numberOfKeys is what to believe.)
 293  * To restart the scan without changing keys, pass NULL for the key arrays.
 294  * (Of course, keys *must* be passed on the first call, unless
 295  * scan->numberOfKeys is zero.)
 296  * ----------------
 297  */
 298 void
 299 index_rescan(IndexScanDesc scan,
 300                          ScanKey keys, int nkeys,
 301                          ScanKey orderbys, int norderbys)
 302 {
 303         FmgrInfo   *procedure;
 304
 305         SCAN_CHECKS;
 306         GET_SCAN_PROCEDURE(amrescan);
 307
 308         Assert(nkeys == scan->numberOfKeys);
 309         Assert(norderbys == scan->numberOfOrderBys);
 310
 311         /* Release any held pin on a heap page */
 312         if (BufferIsValid(scan->xs_cbuf))
 313         {
 314                 ReleaseBuffer(scan->xs_cbuf);
 315                 scan->xs_cbuf = InvalidBuffer;
 316         }
 317
 318         scan->xs_next_hot = InvalidOffsetNumber;
 319
 320         scan->kill_prior_tuple = false;         /* for safety */
 321
 322         FunctionCall5(procedure,
 323                                   PointerGetDatum(scan),
 324                                   PointerGetDatum(keys),
 325                                   Int32GetDatum(nkeys),
 326                                   PointerGetDatum(orderbys),
 327                                   Int32GetDatum(norderbys));
 328 }
 329
 330 /* ----------------
 331  *              index_endscan - end a scan
 332  * ----------------
 333  */
 334 void
 335 index_endscan(IndexScanDesc scan)
 336 {
 337         FmgrInfo   *procedure;
 338
 339         SCAN_CHECKS;
 340         GET_SCAN_PROCEDURE(amendscan);
 341
 342         /* Release any held pin on a heap page */
 343         if (BufferIsValid(scan->xs_cbuf))
 344         {
 345                 ReleaseBuffer(scan->xs_cbuf);
 346                 scan->xs_cbuf = InvalidBuffer;
 347         }
 348
 349         /* End the AM's scan */
 350         FunctionCall1(procedure, PointerGetDatum(scan));
 351
 352         /* Release index refcount acquired by index_beginscan */
 353         RelationDecrementReferenceCount(scan->indexRelation);
 354
 355         /* Release the scan data structure itself */
 356         IndexScanEnd(scan);
 357 }
 358
 359 /* ----------------
 360  *              index_markpos  - mark a scan position
 361  * ----------------
 362  */
 363 void
 364 index_markpos(IndexScanDesc scan)
 365 {
 366         FmgrInfo   *procedure;
 367
 368         SCAN_CHECKS;
 369         GET_SCAN_PROCEDURE(ammarkpos);
 370
 371         FunctionCall1(procedure, PointerGetDatum(scan));
 372 }
 373
 374 /* ----------------
 375  *              index_restrpos  - restore a scan position
 376  *
 377  * NOTE: this only restores the internal scan state of the index AM.
 378  * The current result tuple (scan->xs_ctup) doesn't change.  See comments
 379  * for ExecRestrPos().
 380  *
 381  * NOTE: in the presence of HOT chains, mark/restore only works correctly
 382  * if the scan's snapshot is MVCC-safe; that ensures that there's at most one
 383  * returnable tuple in each HOT chain, and so restoring the prior state at the
 384  * granularity of the index AM is sufficient.  Since the only current user
 385  * of mark/restore functionality is nodeMergejoin.c, this effectively means
 386  * that merge-join plans only work for MVCC snapshots.  This could be fixed
 387  * if necessary, but for now it seems unimportant.
 388  * ----------------
 389  */
 390 void
 391 index_restrpos(IndexScanDesc scan)
 392 {
 393         FmgrInfo   *procedure;
 394
 395         Assert(IsMVCCSnapshot(scan->xs_snapshot));
 396
 397         SCAN_CHECKS;
 398         GET_SCAN_PROCEDURE(amrestrpos);
 399
 400         scan->xs_next_hot = InvalidOffsetNumber;
 401
 402         scan->kill_prior_tuple = false;         /* for safety */
 403
 404         FunctionCall1(procedure, PointerGetDatum(scan));
 405 }
 406
 407 /* ----------------
 408  *              index_getnext - get the next heap tuple from a scan
 409  *
 410  * The result is the next heap tuple satisfying the scan keys and the
 411  * snapshot, or NULL if no more matching tuples exist.  On success,
 412  * the buffer containing the heap tuple is pinned (the pin will be dropped
 413  * at the next index_getnext or index_endscan).
 414  *
 415  * Note: caller must check scan->xs_recheck, and perform rechecking of the
 416  * scan keys if required.  We do not do that here because we don't have
 417  * enough information to do it efficiently in the general case.
 418  * ----------------
 419  */
 420 HeapTuple
 421 index_getnext(IndexScanDesc scan, ScanDirection direction)
 422 {
 423         HeapTuple       heapTuple = &scan->xs_ctup;
 424         ItemPointer tid = &heapTuple->t_self;
 425         FmgrInfo   *procedure;
 426
 427         SCAN_CHECKS;
 428         GET_SCAN_PROCEDURE(amgettuple);
 429
 430         Assert(TransactionIdIsValid(RecentGlobalXmin));
 431
 432         /*
 433          * We always reset xs_hot_dead; if we are here then either we are just
 434          * starting the scan, or we previously returned a visible tuple, and in
 435          * either case it's inappropriate to kill the prior index entry.
 436          */
 437         scan->xs_hot_dead = false;
 438
 439         for (;;)
 440         {
 441                 OffsetNumber offnum;
 442                 bool            at_chain_start;
 443                 Page            dp;
 444
 445                 if (scan->xs_next_hot != InvalidOffsetNumber)
 446                 {
 447                         /*
 448                          * We are resuming scan of a HOT chain after having returned an
 449                          * earlier member.      Must still hold pin on current heap page.
 450                          */
 451                         Assert(BufferIsValid(scan->xs_cbuf));
 452                         Assert(ItemPointerGetBlockNumber(tid) ==
 453                                    BufferGetBlockNumber(scan->xs_cbuf));
 454                         Assert(TransactionIdIsValid(scan->xs_prev_xmax));
 455                         offnum = scan->xs_next_hot;
 456                         at_chain_start = false;
 457                         scan->xs_next_hot = InvalidOffsetNumber;
 458                 }
 459                 else
 460                 {
 461                         bool            found;
 462                         Buffer          prev_buf;
 463
 464                         /*
 465                          * If we scanned a whole HOT chain and found only dead tuples,
 466                          * tell index AM to kill its entry for that TID. We do not do this
 467                          * when in recovery because it may violate MVCC to do so. see
 468                          * comments in RelationGetIndexScan().
 469                          */
 470                         if (!scan->xactStartedInRecovery)
 471                                 scan->kill_prior_tuple = scan->xs_hot_dead;
 472
 473                         /*
 474                          * The AM's gettuple proc finds the next index entry matching the
 475                          * scan keys, and puts the TID in xs_ctup.t_self (ie, *tid). It
 476                          * should also set scan->xs_recheck, though we pay no attention to
 477                          * that here.
 478                          */
 479                         found = DatumGetBool(FunctionCall2(procedure,
 480                                                                                            PointerGetDatum(scan),
 481                                                                                            Int32GetDatum(direction)));
 482
 483                         /* Reset kill flag immediately for safety */
 484                         scan->kill_prior_tuple = false;
 485
 486                         /* If we're out of index entries, break out of outer loop */
 487                         if (!found)
 488                                 break;
 489
 490                         pgstat_count_index_tuples(scan->indexRelation, 1);
 491
 492                         /* Switch to correct buffer if we don't have it already */
 493                         prev_buf = scan->xs_cbuf;
 494                         scan->xs_cbuf = ReleaseAndReadBuffer(scan->xs_cbuf,
 495                                                                                                  scan->heapRelation,
 496                                                                                          ItemPointerGetBlockNumber(tid));
 497
 498                         /*
 499                          * Prune page, but only if we weren't already on this page
 500                          */
 501                         if (prev_buf != scan->xs_cbuf)
 502                                 heap_page_prune_opt(scan->heapRelation, scan->xs_cbuf,
 503                                                                         RecentGlobalXmin);
 504
 505                         /* Prepare to scan HOT chain starting at index-referenced offnum */
 506                         offnum = ItemPointerGetOffsetNumber(tid);
 507                         at_chain_start = true;
 508
 509                         /* We don't know what the first tuple's xmin should be */
 510                         scan->xs_prev_xmax = InvalidTransactionId;
 511
 512                         /* Initialize flag to detect if all entries are dead */
 513                         scan->xs_hot_dead = true;
 514                 }
 515
 516                 /* Obtain share-lock on the buffer so we can examine visibility */
 517                 LockBuffer(scan->xs_cbuf, BUFFER_LOCK_SHARE);
 518
 519                 dp = (Page) BufferGetPage(scan->xs_cbuf);
 520
 521                 /* Scan through possible multiple members of HOT-chain */
 522                 for (;;)
 523                 {
 524                         ItemId          lp;
 525                         ItemPointer ctid;
 526
 527                         /* check for bogus TID */
 528                         if (offnum < FirstOffsetNumber ||
 529                                 offnum > PageGetMaxOffsetNumber(dp))
 530                                 break;
 531
 532                         lp = PageGetItemId(dp, offnum);
 533
 534                         /* check for unused, dead, or redirected items */
 535                         if (!ItemIdIsNormal(lp))
 536                         {
 537                                 /* We should only see a redirect at start of chain */
 538                                 if (ItemIdIsRedirected(lp) && at_chain_start)
 539                                 {
 540                                         /* Follow the redirect */
 541                                         offnum = ItemIdGetRedirect(lp);
 542                                         at_chain_start = false;
 543                                         continue;
 544                                 }
 545                                 /* else must be end of chain */
 546                                 break;
 547                         }
 548
 549                         /*
 550                          * We must initialize all of *heapTuple (ie, scan->xs_ctup) since
 551                          * it is returned to the executor on success.
 552                          */
 553                         heapTuple->t_data = (HeapTupleHeader) PageGetItem(dp, lp);
 554                         heapTuple->t_len = ItemIdGetLength(lp);
 555                         ItemPointerSetOffsetNumber(tid, offnum);
 556                         heapTuple->t_tableOid = RelationGetRelid(scan->heapRelation);
 557                         ctid = &heapTuple->t_data->t_ctid;
 558
 559                         /*
 560                          * Shouldn't see a HEAP_ONLY tuple at chain start.  (This test
 561                          * should be unnecessary, since the chain root can't be removed
 562                          * while we have pin on the index entry, but let's make it
 563                          * anyway.)
 564                          */
 565                         if (at_chain_start && HeapTupleIsHeapOnly(heapTuple))
 566                                 break;
 567
 568                         /*
 569                          * The xmin should match the previous xmax value, else chain is
 570                          * broken.      (Note: this test is not optional because it protects
 571                          * us against the case where the prior chain member's xmax aborted
 572                          * since we looked at it.)
 573                          */
 574                         if (TransactionIdIsValid(scan->xs_prev_xmax) &&
 575                                 !TransactionIdEquals(scan->xs_prev_xmax,
 576                                                                   HeapTupleHeaderGetXmin(heapTuple->t_data)))
 577                                 break;
 578
 579                         /* If it's visible per the snapshot, we must return it */
 580                         if (HeapTupleSatisfiesVisibility(heapTuple, scan->xs_snapshot,
 581                                                                                          scan->xs_cbuf))
 582                         {
 583                                 /*
 584                                  * If the snapshot is MVCC, we know that it could accept at
 585                                  * most one member of the HOT chain, so we can skip examining
 586                                  * any more members.  Otherwise, check for continuation of the
 587                                  * HOT-chain, and set state for next time.
 588                                  */
 589                                 if (IsMVCCSnapshot(scan->xs_snapshot))
 590                                         scan->xs_next_hot = InvalidOffsetNumber;
 591                                 else if (HeapTupleIsHotUpdated(heapTuple))
 592                                 {
 593                                         Assert(ItemPointerGetBlockNumber(ctid) ==
 594                                                    ItemPointerGetBlockNumber(tid));
 595                                         scan->xs_next_hot = ItemPointerGetOffsetNumber(ctid);
 596                                         scan->xs_prev_xmax = HeapTupleHeaderGetXmax(heapTuple->t_data);
 597                                 }
 598                                 else
 599                                         scan->xs_next_hot = InvalidOffsetNumber;
 600
 601                                 LockBuffer(scan->xs_cbuf, BUFFER_LOCK_UNLOCK);
 602
 603                                 pgstat_count_heap_fetch(scan->indexRelation);
 604
 605                                 return heapTuple;
 606                         }
 607
 608                         /*
 609                          * If we can't see it, maybe no one else can either.  Check to see
 610                          * if the tuple is dead to all transactions.  If we find that all
 611                          * the tuples in the HOT chain are dead, we'll signal the index AM
 612                          * to not return that TID on future indexscans.
 613                          */
 614                         if (scan->xs_hot_dead &&
 615                                 HeapTupleSatisfiesVacuum(heapTuple->t_data, RecentGlobalXmin,
 616                                                                                  scan->xs_cbuf) != HEAPTUPLE_DEAD)
 617                                 scan->xs_hot_dead = false;
 618
 619                         /*
 620                          * Check to see if HOT chain continues past this tuple; if so
 621                          * fetch the next offnum (we don't bother storing it into
 622                          * xs_next_hot, but must store xs_prev_xmax), and loop around.
 623                          */
 624                         if (HeapTupleIsHotUpdated(heapTuple))
 625                         {
 626                                 Assert(ItemPointerGetBlockNumber(ctid) ==
 627                                            ItemPointerGetBlockNumber(tid));
 628                                 offnum = ItemPointerGetOffsetNumber(ctid);
 629                                 at_chain_start = false;
 630                                 scan->xs_prev_xmax = HeapTupleHeaderGetXmax(heapTuple->t_data);
 631                         }
 632                         else
 633                                 break;                  /* end of chain */
 634                 }                                               /* loop over a single HOT chain */
 635
 636                 LockBuffer(scan->xs_cbuf, BUFFER_LOCK_UNLOCK);
 637
 638                 /* Loop around to ask index AM for another TID */
 639                 scan->xs_next_hot = InvalidOffsetNumber;
 640         }
 641
 642         /* Release any held pin on a heap page */
 643         if (BufferIsValid(scan->xs_cbuf))
 644         {
 645                 ReleaseBuffer(scan->xs_cbuf);
 646                 scan->xs_cbuf = InvalidBuffer;
 647         }
 648
 649         return NULL;                            /* failure exit */
 650 }
 651
 652 /* ----------------
 653  *              index_getbitmap - get all tuples at once from an index scan
 654  *
 655  * Adds the TIDs of all heap tuples satisfying the scan keys to a bitmap.
 656  * Since there's no interlock between the index scan and the eventual heap
 657  * access, this is only safe to use with MVCC-based snapshots: the heap
 658  * item slot could have been replaced by a newer tuple by the time we get
 659  * to it.
 660  *
 661  * Returns the number of matching tuples found.  (Note: this might be only
 662  * approximate, so it should only be used for statistical purposes.)
 663  * ----------------
 664  */
 665 int64
 666 index_getbitmap(IndexScanDesc scan, TIDBitmap *bitmap)
 667 {
 668         FmgrInfo   *procedure;
 669         int64           ntids;
 670         Datum           d;
 671
 672         SCAN_CHECKS;
 673         GET_SCAN_PROCEDURE(amgetbitmap);
 674
 675         /* just make sure this is false... */
 676         scan->kill_prior_tuple = false;
 677
 678         /*
 679          * have the am's getbitmap proc do all the work.
 680          */
 681         d = FunctionCall2(procedure,
 682                                           PointerGetDatum(scan),
 683                                           PointerGetDatum(bitmap));
 684
 685         ntids = DatumGetInt64(d);
 686
 687         /* If int8 is pass-by-ref, must free the result to avoid memory leak */
 688 #ifndef USE_FLOAT8_BYVAL
 689         pfree(DatumGetPointer(d));
 690 #endif
 691
 692         pgstat_count_index_tuples(scan->indexRelation, ntids);
 693
 694         return ntids;
 695 }
 696
 697 /* ----------------
 698  *              index_bulk_delete - do mass deletion of index entries
 699  *
 700  *              callback routine tells whether a given main-heap tuple is
 701  *              to be deleted
 702  *
 703  *              return value is an optional palloc'd struct of statistics
 704  * ----------------
 705  */
 706 IndexBulkDeleteResult *
 707 index_bulk_delete(IndexVacuumInfo *info,
 708                                   IndexBulkDeleteResult *stats,
 709                                   IndexBulkDeleteCallback callback,
 710                                   void *callback_state)
 711 {
 712         Relation        indexRelation = info->index;
 713         FmgrInfo   *procedure;
 714         IndexBulkDeleteResult *result;
 715
 716         RELATION_CHECKS;
 717         GET_REL_PROCEDURE(ambulkdelete);
 718
 719         result = (IndexBulkDeleteResult *)
 720                 DatumGetPointer(FunctionCall4(procedure,
 721                                                                           PointerGetDatum(info),
 722                                                                           PointerGetDatum(stats),
 723                                                                           PointerGetDatum((Pointer) callback),
 724                                                                           PointerGetDatum(callback_state)));
 725
 726         return result;
 727 }
 728
 729 /* ----------------
 730  *              index_vacuum_cleanup - do post-deletion cleanup of an index
 731  *
 732  *              return value is an optional palloc'd struct of statistics
 733  * ----------------
 734  */
 735 IndexBulkDeleteResult *
 736 index_vacuum_cleanup(IndexVacuumInfo *info,
 737                                          IndexBulkDeleteResult *stats)
 738 {
 739         Relation        indexRelation = info->index;
 740         FmgrInfo   *procedure;
 741         IndexBulkDeleteResult *result;
 742
 743         RELATION_CHECKS;
 744         GET_REL_PROCEDURE(amvacuumcleanup);
 745
 746         result = (IndexBulkDeleteResult *)
 747                 DatumGetPointer(FunctionCall2(procedure,
 748                                                                           PointerGetDatum(info),
 749                                                                           PointerGetDatum(stats)));
 750
 751         return result;
 752 }
 753
 754 /* ----------------
 755  *              index_getprocid
 756  *
 757  *              Index access methods typically require support routines that are
 758  *              not directly the implementation of any WHERE-clause query operator
 759  *              and so cannot be kept in pg_amop.  Instead, such routines are kept
 760  *              in pg_amproc.  These registered procedure OIDs are assigned numbers
 761  *              according to a convention established by the access method.
 762  *              The general index code doesn't know anything about the routines
 763  *              involved; it just builds an ordered list of them for
 764  *              each attribute on which an index is defined.
 765  *
 766  *              As of Postgres 8.3, support routines within an operator family
 767  *              are further subdivided by the "left type" and "right type" of the
 768  *              query operator(s) that they support.  The "default" functions for a
 769  *              particular indexed attribute are those with both types equal to
 770  *              the index opclass' opcintype (note that this is subtly different
 771  *              from the indexed attribute's own type: it may be a binary-compatible
 772  *              type instead).  Only the default functions are stored in relcache
 773  *              entries --- access methods can use the syscache to look up non-default
 774  *              functions.
 775  *
 776  *              This routine returns the requested default procedure OID for a
 777  *              particular indexed attribute.
 778  * ----------------
 779  */
 780 RegProcedure
 781 index_getprocid(Relation irel,
 782                                 AttrNumber attnum,
 783                                 uint16 procnum)
 784 {
 785         RegProcedure *loc;
 786         int                     nproc;
 787         int                     procindex;
 788
 789         nproc = irel->rd_am->amsupport;
 790
 791         Assert(procnum > 0 && procnum <= (uint16) nproc);
 792
 793         procindex = (nproc * (attnum - 1)) + (procnum - 1);
 794
 795         loc = irel->rd_support;
 796
 797         Assert(loc != NULL);
 798
 799         return loc[procindex];
 800 }
 801
 802 /* ----------------
 803  *              index_getprocinfo
 804  *
 805  *              This routine allows index AMs to keep fmgr lookup info for
 806  *              support procs in the relcache.  As above, only the "default"
 807  *              functions for any particular indexed attribute are cached.
 808  *
 809  * Note: the return value points into cached data that will be lost during
 810  * any relcache rebuild!  Therefore, either use the callinfo right away,
 811  * or save it only after having acquired some type of lock on the index rel.
 812  * ----------------
 813  */
 814 FmgrInfo *
 815 index_getprocinfo(Relation irel,
 816                                   AttrNumber attnum,
 817                                   uint16 procnum)
 818 {
 819         FmgrInfo   *locinfo;
 820         int                     nproc;
 821         int                     procindex;
 822
 823         nproc = irel->rd_am->amsupport;
 824
 825         Assert(procnum > 0 && procnum <= (uint16) nproc);
 826
 827         procindex = (nproc * (attnum - 1)) + (procnum - 1);
 828
 829         locinfo = irel->rd_supportinfo;
 830
 831         Assert(locinfo != NULL);
 832
 833         locinfo += procindex;
 834
 835         /* Initialize the lookup info if first time through */
 836         if (locinfo->fn_oid == InvalidOid)
 837         {
 838                 RegProcedure *loc = irel->rd_support;
 839                 RegProcedure procId;
 840
 841                 Assert(loc != NULL);
 842
 843                 procId = loc[procindex];
 844
 845                 /*
 846                  * Complain if function was not found during IndexSupportInitialize.
 847                  * This should not happen unless the system tables contain bogus
 848                  * entries for the index opclass.  (If an AM wants to allow a support
 849                  * function to be optional, it can use index_getprocid.)
 850                  */
 851                 if (!RegProcedureIsValid(procId))
 852                         elog(ERROR, "missing support function %d for attribute %d of index \"%s\"",
 853                                  procnum, attnum, RelationGetRelationName(irel));
 854
 855                 fmgr_info_cxt(procId, locinfo, irel->rd_indexcxt);
 856         }
 857
 858         return locinfo;
 859 }