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) 1996-2011, 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 "access/xact.h"
  68 #include "pgstat.h"
  69 #include "storage/bufmgr.h"
  70 #include "storage/lmgr.h"
  71 #include "storage/predicate.h"
  72 #include "utils/relcache.h"
  73 #include "utils/snapmgr.h"
  74 #include "utils/tqual.h"
  75
  76
  77 /* ----------------------------------------------------------------
  78  *                                      macros used in index_ routines
  79  * ----------------------------------------------------------------
  80  */
  81 #define RELATION_CHECKS \
  82 ( \
  83         AssertMacro(RelationIsValid(indexRelation)), \
  84         AssertMacro(PointerIsValid(indexRelation->rd_am)) \
  85 )
  86
  87 #define SCAN_CHECKS \
  88 ( \
  89         AssertMacro(IndexScanIsValid(scan)), \
  90         AssertMacro(RelationIsValid(scan->indexRelation)), \
  91         AssertMacro(PointerIsValid(scan->indexRelation->rd_am)) \
  92 )
  93
  94 #define GET_REL_PROCEDURE(pname) \
  95 do { \
  96         procedure = &indexRelation->rd_aminfo->pname; \
  97         if (!OidIsValid(procedure->fn_oid)) \
  98         { \
  99                 RegProcedure    procOid = indexRelation->rd_am->pname; \
 100                 if (!RegProcedureIsValid(procOid)) \
 101                         elog(ERROR, "invalid %s regproc", CppAsString(pname)); \
 102                 fmgr_info_cxt(procOid, procedure, indexRelation->rd_indexcxt); \
 103         } \
 104 } while(0)
 105
 106 #define GET_SCAN_PROCEDURE(pname) \
 107 do { \
 108         procedure = &scan->indexRelation->rd_aminfo->pname; \
 109         if (!OidIsValid(procedure->fn_oid)) \
 110         { \
 111                 RegProcedure    procOid = scan->indexRelation->rd_am->pname; \
 112                 if (!RegProcedureIsValid(procOid)) \
 113                         elog(ERROR, "invalid %s regproc", CppAsString(pname)); \
 114                 fmgr_info_cxt(procOid, procedure, scan->indexRelation->rd_indexcxt); \
 115         } \
 116 } while(0)
 117
 118 static IndexScanDesc index_beginscan_internal(Relation indexRelation,
 119                                                  int nkeys, int norderbys);
 120
 121
 122 /* ----------------------------------------------------------------
 123  *                                 index_ interface functions
 124  * ----------------------------------------------------------------
 125  */
 126
 127 /* ----------------
 128  *              index_open - open an index relation by relation OID
 129  *
 130  *              If lockmode is not "NoLock", the specified kind of lock is
 131  *              obtained on the index.  (Generally, NoLock should only be
 132  *              used if the caller knows it has some appropriate lock on the
 133  *              index already.)
 134  *
 135  *              An error is raised if the index does not exist.
 136  *
 137  *              This is a convenience routine adapted for indexscan use.
 138  *              Some callers may prefer to use relation_open directly.
 139  * ----------------
 140  */
 141 Relation
 142 index_open(Oid relationId, LOCKMODE lockmode)
 143 {
 144         Relation        r;
 145
 146         r = relation_open(relationId, lockmode);
 147
 148         if (r->rd_rel->relkind != RELKIND_INDEX)
 149                 ereport(ERROR,
 150                                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 151                                  errmsg("\"%s\" is not an index",
 152                                                 RelationGetRelationName(r))));
 153
 154         return r;
 155 }
 156
 157 /* ----------------
 158  *              index_close - close an index relation
 159  *
 160  *              If lockmode is not "NoLock", we then release the specified lock.
 161  *
 162  *              Note that it is often sensible to hold a lock beyond index_close;
 163  *              in that case, the lock is released automatically at xact end.
 164  * ----------------
 165  */
 166 void
 167 index_close(Relation relation, LOCKMODE lockmode)
 168 {
 169         LockRelId       relid = relation->rd_lockInfo.lockRelId;
 170
 171         Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
 172
 173         /* The relcache does the real work... */
 174         RelationClose(relation);
 175
 176         if (lockmode != NoLock)
 177                 UnlockRelationId(&relid, lockmode);
 178 }
 179
 180 /* ----------------
 181  *              index_insert - insert an index tuple into a relation
 182  * ----------------
 183  */
 184 bool
 185 index_insert(Relation indexRelation,
 186                          Datum *values,
 187                          bool *isnull,
 188                          ItemPointer heap_t_ctid,
 189                          Relation heapRelation,
 190                          IndexUniqueCheck checkUnique)
 191 {
 192         FmgrInfo   *procedure;
 193
 194         RELATION_CHECKS;
 195         GET_REL_PROCEDURE(aminsert);
 196
 197         if (!(indexRelation->rd_am->ampredlocks))
 198                 CheckForSerializableConflictIn(indexRelation,
 199                                                                            (HeapTuple) NULL,
 200                                                                            InvalidBuffer);
 201
 202         /*
 203          * have the am's insert proc do all the work.
 204          */
 205         return DatumGetBool(FunctionCall6(procedure,
 206                                                                           PointerGetDatum(indexRelation),
 207                                                                           PointerGetDatum(values),
 208                                                                           PointerGetDatum(isnull),
 209                                                                           PointerGetDatum(heap_t_ctid),
 210                                                                           PointerGetDatum(heapRelation),
 211                                                                           Int32GetDatum((int32) checkUnique)));
 212 }
 213
 214 /*
 215  * index_beginscan - start a scan of an index with amgettuple
 216  *
 217  * Caller must be holding suitable locks on the heap and the index.
 218  */
 219 IndexScanDesc
 220 index_beginscan(Relation heapRelation,
 221                                 Relation indexRelation,
 222                                 Snapshot snapshot,
 223                                 int nkeys, int norderbys)
 224 {
 225         IndexScanDesc scan;
 226
 227         scan = index_beginscan_internal(indexRelation, nkeys, norderbys);
 228
 229         /*
 230          * Save additional parameters into the scandesc.  Everything else was set
 231          * up by RelationGetIndexScan.
 232          */
 233         scan->heapRelation = heapRelation;
 234         scan->xs_snapshot = snapshot;
 235
 236         return scan;
 237 }
 238
 239 /*
 240  * index_beginscan_bitmap - start a scan of an index with amgetbitmap
 241  *
 242  * As above, caller had better be holding some lock on the parent heap
 243  * relation, even though it's not explicitly mentioned here.
 244  */
 245 IndexScanDesc
 246 index_beginscan_bitmap(Relation indexRelation,
 247                                            Snapshot snapshot,
 248                                            int nkeys)
 249 {
 250         IndexScanDesc scan;
 251
 252         scan = index_beginscan_internal(indexRelation, nkeys, 0);
 253
 254         /*
 255          * Save additional parameters into the scandesc.  Everything else was set
 256          * up by RelationGetIndexScan.
 257          */
 258         scan->xs_snapshot = snapshot;
 259
 260         return scan;
 261 }
 262
 263 /*
 264  * index_beginscan_internal --- common code for index_beginscan variants
 265  */
 266 static IndexScanDesc
 267 index_beginscan_internal(Relation indexRelation,
 268                                                  int nkeys, int norderbys)
 269 {
 270         IndexScanDesc scan;
 271         FmgrInfo   *procedure;
 272
 273         RELATION_CHECKS;
 274         GET_REL_PROCEDURE(ambeginscan);
 275
 276         if (!(indexRelation->rd_am->ampredlocks))
 277                 PredicateLockRelation(indexRelation);
 278
 279         /*
 280          * We hold a reference count to the relcache entry throughout the scan.
 281          */
 282         RelationIncrementReferenceCount(indexRelation);
 283
 284         /*
 285          * Tell the AM to open a scan.
 286          */
 287         scan = (IndexScanDesc)
 288                 DatumGetPointer(FunctionCall3(procedure,
 289                                                                           PointerGetDatum(indexRelation),
 290                                                                           Int32GetDatum(nkeys),
 291                                                                           Int32GetDatum(norderbys)));
 292
 293         return scan;
 294 }
 295
 296 /* ----------------
 297  *              index_rescan  - (re)start a scan of an index
 298  *
 299  * During a restart, the caller may specify a new set of scankeys and/or
 300  * orderbykeys; but the number of keys cannot differ from what index_beginscan
 301  * was told.  (Later we might relax that to "must not exceed", but currently
 302  * the index AMs tend to assume that scan->numberOfKeys is what to believe.)
 303  * To restart the scan without changing keys, pass NULL for the key arrays.
 304  * (Of course, keys *must* be passed on the first call, unless
 305  * scan->numberOfKeys is zero.)
 306  * ----------------
 307  */
 308 void
 309 index_rescan(IndexScanDesc scan,
 310                          ScanKey keys, int nkeys,
 311                          ScanKey orderbys, int norderbys)
 312 {
 313         FmgrInfo   *procedure;
 314
 315         SCAN_CHECKS;
 316         GET_SCAN_PROCEDURE(amrescan);
 317
 318         Assert(nkeys == scan->numberOfKeys);
 319         Assert(norderbys == scan->numberOfOrderBys);
 320
 321         /* Release any held pin on a heap page */
 322         if (BufferIsValid(scan->xs_cbuf))
 323         {
 324                 ReleaseBuffer(scan->xs_cbuf);
 325                 scan->xs_cbuf = InvalidBuffer;
 326         }
 327
 328         scan->xs_next_hot = InvalidOffsetNumber;
 329
 330         scan->kill_prior_tuple = false;         /* for safety */
 331
 332         FunctionCall5(procedure,
 333                                   PointerGetDatum(scan),
 334                                   PointerGetDatum(keys),
 335                                   Int32GetDatum(nkeys),
 336                                   PointerGetDatum(orderbys),
 337                                   Int32GetDatum(norderbys));
 338 }
 339
 340 /* ----------------
 341  *              index_endscan - end a scan
 342  * ----------------
 343  */
 344 void
 345 index_endscan(IndexScanDesc scan)
 346 {
 347         FmgrInfo   *procedure;
 348
 349         SCAN_CHECKS;
 350         GET_SCAN_PROCEDURE(amendscan);
 351
 352         /* Release any held pin on a heap page */
 353         if (BufferIsValid(scan->xs_cbuf))
 354         {
 355                 ReleaseBuffer(scan->xs_cbuf);
 356                 scan->xs_cbuf = InvalidBuffer;
 357         }
 358
 359         /* End the AM's scan */
 360         FunctionCall1(procedure, PointerGetDatum(scan));
 361
 362         /* Release index refcount acquired by index_beginscan */
 363         RelationDecrementReferenceCount(scan->indexRelation);
 364
 365         /* Release the scan data structure itself */
 366         IndexScanEnd(scan);
 367 }
 368
 369 /* ----------------
 370  *              index_markpos  - mark a scan position
 371  * ----------------
 372  */
 373 void
 374 index_markpos(IndexScanDesc scan)
 375 {
 376         FmgrInfo   *procedure;
 377
 378         SCAN_CHECKS;
 379         GET_SCAN_PROCEDURE(ammarkpos);
 380
 381         FunctionCall1(procedure, PointerGetDatum(scan));
 382 }
 383
 384 /* ----------------
 385  *              index_restrpos  - restore a scan position
 386  *
 387  * NOTE: this only restores the internal scan state of the index AM.
 388  * The current result tuple (scan->xs_ctup) doesn't change.  See comments
 389  * for ExecRestrPos().
 390  *
 391  * NOTE: in the presence of HOT chains, mark/restore only works correctly
 392  * if the scan's snapshot is MVCC-safe; that ensures that there's at most one
 393  * returnable tuple in each HOT chain, and so restoring the prior state at the
 394  * granularity of the index AM is sufficient.  Since the only current user
 395  * of mark/restore functionality is nodeMergejoin.c, this effectively means
 396  * that merge-join plans only work for MVCC snapshots.  This could be fixed
 397  * if necessary, but for now it seems unimportant.
 398  * ----------------
 399  */
 400 void
 401 index_restrpos(IndexScanDesc scan)
 402 {
 403         FmgrInfo   *procedure;
 404
 405         Assert(IsMVCCSnapshot(scan->xs_snapshot));
 406
 407         SCAN_CHECKS;
 408         GET_SCAN_PROCEDURE(amrestrpos);
 409
 410         scan->xs_next_hot = InvalidOffsetNumber;
 411
 412         scan->kill_prior_tuple = false;         /* for safety */
 413
 414         FunctionCall1(procedure, PointerGetDatum(scan));
 415 }
 416
 417 /* ----------------
 418  *              index_getnext - get the next heap tuple from a scan
 419  *
 420  * The result is the next heap tuple satisfying the scan keys and the
 421  * snapshot, or NULL if no more matching tuples exist.  On success,
 422  * the buffer containing the heap tuple is pinned (the pin will be dropped
 423  * at the next index_getnext or index_endscan).
 424  *
 425  * Note: caller must check scan->xs_recheck, and perform rechecking of the
 426  * scan keys if required.  We do not do that here because we don't have
 427  * enough information to do it efficiently in the general case.
 428  * ----------------
 429  */
 430 HeapTuple
 431 index_getnext(IndexScanDesc scan, ScanDirection direction)
 432 {
 433         HeapTuple       heapTuple = &scan->xs_ctup;
 434         ItemPointer tid = &heapTuple->t_self;
 435         FmgrInfo   *procedure;
 436
 437         SCAN_CHECKS;
 438         GET_SCAN_PROCEDURE(amgettuple);
 439
 440         Assert(TransactionIdIsValid(RecentGlobalXmin));
 441
 442         /*
 443          * We always reset xs_hot_dead; if we are here then either we are just
 444          * starting the scan, or we previously returned a visible tuple, and in
 445          * either case it's inappropriate to kill the prior index entry.
 446          */
 447         scan->xs_hot_dead = false;
 448
 449         for (;;)
 450         {
 451                 OffsetNumber offnum;
 452                 bool            at_chain_start;
 453                 Page            dp;
 454
 455                 if (scan->xs_next_hot != InvalidOffsetNumber)
 456                 {
 457                         /*
 458                          * We are resuming scan of a HOT chain after having returned an
 459                          * earlier member.      Must still hold pin on current heap page.
 460                          */
 461                         Assert(BufferIsValid(scan->xs_cbuf));
 462                         Assert(ItemPointerGetBlockNumber(tid) ==
 463                                    BufferGetBlockNumber(scan->xs_cbuf));
 464                         Assert(TransactionIdIsValid(scan->xs_prev_xmax));
 465                         offnum = scan->xs_next_hot;
 466                         at_chain_start = false;
 467                         scan->xs_next_hot = InvalidOffsetNumber;
 468                 }
 469                 else
 470                 {
 471                         bool            found;
 472                         Buffer          prev_buf;
 473
 474                         /*
 475                          * If we scanned a whole HOT chain and found only dead tuples,
 476                          * tell index AM to kill its entry for that TID. We do not do this
 477                          * when in recovery because it may violate MVCC to do so. see
 478                          * comments in RelationGetIndexScan().
 479                          */
 480                         if (!scan->xactStartedInRecovery)
 481                                 scan->kill_prior_tuple = scan->xs_hot_dead;
 482
 483                         /*
 484                          * The AM's gettuple proc finds the next index entry matching the
 485                          * scan keys, and puts the TID in xs_ctup.t_self (ie, *tid). It
 486                          * should also set scan->xs_recheck, though we pay no attention to
 487                          * that here.
 488                          */
 489                         found = DatumGetBool(FunctionCall2(procedure,
 490                                                                                            PointerGetDatum(scan),
 491                                                                                            Int32GetDatum(direction)));
 492
 493                         /* Reset kill flag immediately for safety */
 494                         scan->kill_prior_tuple = false;
 495
 496                         /* If we're out of index entries, break out of outer loop */
 497                         if (!found)
 498                                 break;
 499
 500                         pgstat_count_index_tuples(scan->indexRelation, 1);
 501
 502                         /* Switch to correct buffer if we don't have it already */
 503                         prev_buf = scan->xs_cbuf;
 504                         scan->xs_cbuf = ReleaseAndReadBuffer(scan->xs_cbuf,
 505                                                                                                  scan->heapRelation,
 506                                                                                          ItemPointerGetBlockNumber(tid));
 507
 508                         /*
 509                          * Prune page, but only if we weren't already on this page
 510                          */
 511                         if (prev_buf != scan->xs_cbuf)
 512                                 heap_page_prune_opt(scan->heapRelation, scan->xs_cbuf,
 513                                                                         RecentGlobalXmin);
 514
 515                         /* Prepare to scan HOT chain starting at index-referenced offnum */
 516                         offnum = ItemPointerGetOffsetNumber(tid);
 517                         at_chain_start = true;
 518
 519                         /* We don't know what the first tuple's xmin should be */
 520                         scan->xs_prev_xmax = InvalidTransactionId;
 521
 522                         /* Initialize flag to detect if all entries are dead */
 523                         scan->xs_hot_dead = true;
 524                 }
 525
 526                 /* Obtain share-lock on the buffer so we can examine visibility */
 527                 LockBuffer(scan->xs_cbuf, BUFFER_LOCK_SHARE);
 528
 529                 dp = (Page) BufferGetPage(scan->xs_cbuf);
 530
 531                 /* Scan through possible multiple members of HOT-chain */
 532                 for (;;)
 533                 {
 534                         ItemId          lp;
 535                         ItemPointer ctid;
 536                         bool            valid;
 537
 538                         /* check for bogus TID */
 539                         if (offnum < FirstOffsetNumber ||
 540                                 offnum > PageGetMaxOffsetNumber(dp))
 541                                 break;
 542
 543                         lp = PageGetItemId(dp, offnum);
 544
 545                         /* check for unused, dead, or redirected items */
 546                         if (!ItemIdIsNormal(lp))
 547                         {
 548                                 /* We should only see a redirect at start of chain */
 549                                 if (ItemIdIsRedirected(lp) && at_chain_start)
 550                                 {
 551                                         /* Follow the redirect */
 552                                         offnum = ItemIdGetRedirect(lp);
 553                                         at_chain_start = false;
 554                                         continue;
 555                                 }
 556                                 /* else must be end of chain */
 557                                 break;
 558                         }
 559
 560                         /*
 561                          * We must initialize all of *heapTuple (ie, scan->xs_ctup) since
 562                          * it is returned to the executor on success.
 563                          */
 564                         heapTuple->t_data = (HeapTupleHeader) PageGetItem(dp, lp);
 565                         heapTuple->t_len = ItemIdGetLength(lp);
 566                         ItemPointerSetOffsetNumber(tid, offnum);
 567                         heapTuple->t_tableOid = RelationGetRelid(scan->heapRelation);
 568                         ctid = &heapTuple->t_data->t_ctid;
 569
 570                         /*
 571                          * Shouldn't see a HEAP_ONLY tuple at chain start.  (This test
 572                          * should be unnecessary, since the chain root can't be removed
 573                          * while we have pin on the index entry, but let's make it
 574                          * anyway.)
 575                          */
 576                         if (at_chain_start && HeapTupleIsHeapOnly(heapTuple))
 577                                 break;
 578
 579                         /*
 580                          * The xmin should match the previous xmax value, else chain is
 581                          * broken.      (Note: this test is not optional because it protects
 582                          * us against the case where the prior chain member's xmax aborted
 583                          * since we looked at it.)
 584                          */
 585                         if (TransactionIdIsValid(scan->xs_prev_xmax) &&
 586                                 !TransactionIdEquals(scan->xs_prev_xmax,
 587                                                                   HeapTupleHeaderGetXmin(heapTuple->t_data)))
 588                                 break;
 589
 590                         /* If it's visible per the snapshot, we must return it */
 591                         valid = HeapTupleSatisfiesVisibility(heapTuple, scan->xs_snapshot,
 592                                                                                                  scan->xs_cbuf);
 593
 594                         CheckForSerializableConflictOut(valid, scan->heapRelation,
 595                                                                                         heapTuple, scan->xs_cbuf);
 596
 597                         if (valid)
 598                         {
 599                                 /*
 600                                  * If the snapshot is MVCC, we know that it could accept at
 601                                  * most one member of the HOT chain, so we can skip examining
 602                                  * any more members.  Otherwise, check for continuation of the
 603                                  * HOT-chain, and set state for next time.
 604                                  */
 605                                 if (IsMVCCSnapshot(scan->xs_snapshot)
 606                                         && !IsolationIsSerializable())
 607                                         scan->xs_next_hot = InvalidOffsetNumber;
 608                                 else if (HeapTupleIsHotUpdated(heapTuple))
 609                                 {
 610                                         Assert(ItemPointerGetBlockNumber(ctid) ==
 611                                                    ItemPointerGetBlockNumber(tid));
 612                                         scan->xs_next_hot = ItemPointerGetOffsetNumber(ctid);
 613                                         scan->xs_prev_xmax = HeapTupleHeaderGetXmax(heapTuple->t_data);
 614                                 }
 615                                 else
 616                                         scan->xs_next_hot = InvalidOffsetNumber;
 617
 618                                 PredicateLockTuple(scan->heapRelation, heapTuple);
 619
 620                                 LockBuffer(scan->xs_cbuf, BUFFER_LOCK_UNLOCK);
 621
 622                                 pgstat_count_heap_fetch(scan->indexRelation);
 623
 624                                 return heapTuple;
 625                         }
 626
 627                         /*
 628                          * If we can't see it, maybe no one else can either.  Check to see
 629                          * if the tuple is dead to all transactions.  If we find that all
 630                          * the tuples in the HOT chain are dead, we'll signal the index AM
 631                          * to not return that TID on future indexscans.
 632                          */
 633                         if (scan->xs_hot_dead &&
 634                                 HeapTupleSatisfiesVacuum(heapTuple->t_data, RecentGlobalXmin,
 635                                                                                  scan->xs_cbuf) != HEAPTUPLE_DEAD)
 636                                 scan->xs_hot_dead = false;
 637
 638                         /*
 639                          * Check to see if HOT chain continues past this tuple; if so
 640                          * fetch the next offnum (we don't bother storing it into
 641                          * xs_next_hot, but must store xs_prev_xmax), and loop around.
 642                          */
 643                         if (HeapTupleIsHotUpdated(heapTuple))
 644                         {
 645                                 Assert(ItemPointerGetBlockNumber(ctid) ==
 646                                            ItemPointerGetBlockNumber(tid));
 647                                 offnum = ItemPointerGetOffsetNumber(ctid);
 648                                 at_chain_start = false;
 649                                 scan->xs_prev_xmax = HeapTupleHeaderGetXmax(heapTuple->t_data);
 650                         }
 651                         else
 652                                 break;                  /* end of chain */
 653                 }                                               /* loop over a single HOT chain */
 654
 655                 LockBuffer(scan->xs_cbuf, BUFFER_LOCK_UNLOCK);
 656
 657                 /* Loop around to ask index AM for another TID */
 658                 scan->xs_next_hot = InvalidOffsetNumber;
 659         }
 660
 661         /* Release any held pin on a heap page */
 662         if (BufferIsValid(scan->xs_cbuf))
 663         {
 664                 ReleaseBuffer(scan->xs_cbuf);
 665                 scan->xs_cbuf = InvalidBuffer;
 666         }
 667
 668         return NULL;                            /* failure exit */
 669 }
 670
 671 /* ----------------
 672  *              index_getbitmap - get all tuples at once from an index scan
 673  *
 674  * Adds the TIDs of all heap tuples satisfying the scan keys to a bitmap.
 675  * Since there's no interlock between the index scan and the eventual heap
 676  * access, this is only safe to use with MVCC-based snapshots: the heap
 677  * item slot could have been replaced by a newer tuple by the time we get
 678  * to it.
 679  *
 680  * Returns the number of matching tuples found.  (Note: this might be only
 681  * approximate, so it should only be used for statistical purposes.)
 682  * ----------------
 683  */
 684 int64
 685 index_getbitmap(IndexScanDesc scan, TIDBitmap *bitmap)
 686 {
 687         FmgrInfo   *procedure;
 688         int64           ntids;
 689         Datum           d;
 690
 691         SCAN_CHECKS;
 692         GET_SCAN_PROCEDURE(amgetbitmap);
 693
 694         /* just make sure this is false... */
 695         scan->kill_prior_tuple = false;
 696
 697         /*
 698          * have the am's getbitmap proc do all the work.
 699          */
 700         d = FunctionCall2(procedure,
 701                                           PointerGetDatum(scan),
 702                                           PointerGetDatum(bitmap));
 703
 704         ntids = DatumGetInt64(d);
 705
 706         /* If int8 is pass-by-ref, must free the result to avoid memory leak */
 707 #ifndef USE_FLOAT8_BYVAL
 708         pfree(DatumGetPointer(d));
 709 #endif
 710
 711         pgstat_count_index_tuples(scan->indexRelation, ntids);
 712
 713         return ntids;
 714 }
 715
 716 /* ----------------
 717  *              index_bulk_delete - do mass deletion of index entries
 718  *
 719  *              callback routine tells whether a given main-heap tuple is
 720  *              to be deleted
 721  *
 722  *              return value is an optional palloc'd struct of statistics
 723  * ----------------
 724  */
 725 IndexBulkDeleteResult *
 726 index_bulk_delete(IndexVacuumInfo *info,
 727                                   IndexBulkDeleteResult *stats,
 728                                   IndexBulkDeleteCallback callback,
 729                                   void *callback_state)
 730 {
 731         Relation        indexRelation = info->index;
 732         FmgrInfo   *procedure;
 733         IndexBulkDeleteResult *result;
 734
 735         RELATION_CHECKS;
 736         GET_REL_PROCEDURE(ambulkdelete);
 737
 738         result = (IndexBulkDeleteResult *)
 739                 DatumGetPointer(FunctionCall4(procedure,
 740                                                                           PointerGetDatum(info),
 741                                                                           PointerGetDatum(stats),
 742                                                                           PointerGetDatum((Pointer) callback),
 743                                                                           PointerGetDatum(callback_state)));
 744
 745         return result;
 746 }
 747
 748 /* ----------------
 749  *              index_vacuum_cleanup - do post-deletion cleanup of an index
 750  *
 751  *              return value is an optional palloc'd struct of statistics
 752  * ----------------
 753  */
 754 IndexBulkDeleteResult *
 755 index_vacuum_cleanup(IndexVacuumInfo *info,
 756                                          IndexBulkDeleteResult *stats)
 757 {
 758         Relation        indexRelation = info->index;
 759         FmgrInfo   *procedure;
 760         IndexBulkDeleteResult *result;
 761
 762         RELATION_CHECKS;
 763         GET_REL_PROCEDURE(amvacuumcleanup);
 764
 765         result = (IndexBulkDeleteResult *)
 766                 DatumGetPointer(FunctionCall2(procedure,
 767                                                                           PointerGetDatum(info),
 768                                                                           PointerGetDatum(stats)));
 769
 770         return result;
 771 }
 772
 773 /* ----------------
 774  *              index_getprocid
 775  *
 776  *              Index access methods typically require support routines that are
 777  *              not directly the implementation of any WHERE-clause query operator
 778  *              and so cannot be kept in pg_amop.  Instead, such routines are kept
 779  *              in pg_amproc.  These registered procedure OIDs are assigned numbers
 780  *              according to a convention established by the access method.
 781  *              The general index code doesn't know anything about the routines
 782  *              involved; it just builds an ordered list of them for
 783  *              each attribute on which an index is defined.
 784  *
 785  *              As of Postgres 8.3, support routines within an operator family
 786  *              are further subdivided by the "left type" and "right type" of the
 787  *              query operator(s) that they support.  The "default" functions for a
 788  *              particular indexed attribute are those with both types equal to
 789  *              the index opclass' opcintype (note that this is subtly different
 790  *              from the indexed attribute's own type: it may be a binary-compatible
 791  *              type instead).  Only the default functions are stored in relcache
 792  *              entries --- access methods can use the syscache to look up non-default
 793  *              functions.
 794  *
 795  *              This routine returns the requested default procedure OID for a
 796  *              particular indexed attribute.
 797  * ----------------
 798  */
 799 RegProcedure
 800 index_getprocid(Relation irel,
 801                                 AttrNumber attnum,
 802                                 uint16 procnum)
 803 {
 804         RegProcedure *loc;
 805         int                     nproc;
 806         int                     procindex;
 807
 808         nproc = irel->rd_am->amsupport;
 809
 810         Assert(procnum > 0 && procnum <= (uint16) nproc);
 811
 812         procindex = (nproc * (attnum - 1)) + (procnum - 1);
 813
 814         loc = irel->rd_support;
 815
 816         Assert(loc != NULL);
 817
 818         return loc[procindex];
 819 }
 820
 821 /* ----------------
 822  *              index_getprocinfo
 823  *
 824  *              This routine allows index AMs to keep fmgr lookup info for
 825  *              support procs in the relcache.  As above, only the "default"
 826  *              functions for any particular indexed attribute are cached.
 827  *
 828  * Note: the return value points into cached data that will be lost during
 829  * any relcache rebuild!  Therefore, either use the callinfo right away,
 830  * or save it only after having acquired some type of lock on the index rel.
 831  * ----------------
 832  */
 833 FmgrInfo *
 834 index_getprocinfo(Relation irel,
 835                                   AttrNumber attnum,
 836                                   uint16 procnum)
 837 {
 838         FmgrInfo   *locinfo;
 839         int                     nproc;
 840         int                     procindex;
 841
 842         nproc = irel->rd_am->amsupport;
 843
 844         Assert(procnum > 0 && procnum <= (uint16) nproc);
 845
 846         procindex = (nproc * (attnum - 1)) + (procnum - 1);
 847
 848         locinfo = irel->rd_supportinfo;
 849
 850         Assert(locinfo != NULL);
 851
 852         locinfo += procindex;
 853
 854         /* Initialize the lookup info if first time through */
 855         if (locinfo->fn_oid == InvalidOid)
 856         {
 857                 RegProcedure *loc = irel->rd_support;
 858                 RegProcedure procId;
 859
 860                 Assert(loc != NULL);
 861
 862                 procId = loc[procindex];
 863
 864                 /*
 865                  * Complain if function was not found during IndexSupportInitialize.
 866                  * This should not happen unless the system tables contain bogus
 867                  * entries for the index opclass.  (If an AM wants to allow a support
 868                  * function to be optional, it can use index_getprocid.)
 869                  */
 870                 if (!RegProcedureIsValid(procId))
 871                         elog(ERROR, "missing support function %d for attribute %d of index \"%s\"",
 872                                  procnum, attnum, RelationGetRelationName(irel));
 873
 874                 fmgr_info_cxt(procId, locinfo, irel->rd_indexcxt);
 875                 fmgr_info_set_collation(irel->rd_indcollation[attnum-1], locinfo);
 876         }
 877
 878         return locinfo;
 879 }