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) 1996-2002, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $Header: /cvsroot/pgsql/src/backend/access/index/indexam.c,v 1.67 2003/07/21 20:29:39 tgl Exp $
  12  *
  13  * INTERFACE ROUTINES
  14  *              index_open              - open an index relation by relation OID
  15  *              index_openrv    - open an index relation specified by a RangeVar
  16  *              index_openr             - open a system index relation by name
  17  *              index_close             - close an index relation
  18  *              index_beginscan - start a scan of an index
  19  *              index_rescan    - restart a scan of an index
  20  *              index_endscan   - end a scan
  21  *              index_insert    - insert an index tuple into a relation
  22  *              index_markpos   - mark a scan position
  23  *              index_restrpos  - restore a scan position
  24  *              index_getnext   - get the next tuple from a scan
  25  *              index_bulk_delete       - bulk deletion of index tuples
  26  *              index_vacuum_cleanup    - post-deletion cleanup of an index
  27  *              index_cost_estimator    - fetch amcostestimate procedure OID
  28  *              index_getprocid - get a support procedure OID
  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/genam.h"
  66 #include "access/heapam.h"
  67 #include "utils/relcache.h"
  68
  69 #include "pgstat.h"
  70
  71 /* ----------------------------------------------------------------
  72  *                                      macros used in index_ routines
  73  * ----------------------------------------------------------------
  74  */
  75 #define RELATION_CHECKS \
  76 ( \
  77         AssertMacro(RelationIsValid(indexRelation)), \
  78         AssertMacro(PointerIsValid(indexRelation->rd_am)) \
  79 )
  80
  81 #define SCAN_CHECKS \
  82 ( \
  83         AssertMacro(IndexScanIsValid(scan)), \
  84         AssertMacro(RelationIsValid(scan->indexRelation)), \
  85         AssertMacro(PointerIsValid(scan->indexRelation->rd_am)) \
  86 )
  87
  88 #define GET_REL_PROCEDURE(x,y) \
  89 ( \
  90         procedure = indexRelation->rd_am->y, \
  91         (!RegProcedureIsValid(procedure)) ? \
  92                 elog(ERROR, "index_%s: invalid %s regproc", \
  93                          CppAsString(x), CppAsString(y)) \
  94         : (void)NULL \
  95 )
  96
  97 #define GET_SCAN_PROCEDURE(x,y) \
  98 ( \
  99         procedure = scan->indexRelation->rd_am->y, \
 100         (!RegProcedureIsValid(procedure)) ? \
 101                 elog(ERROR, "index_%s: invalid %s regproc", \
 102                          CppAsString(x), CppAsString(y)) \
 103         : (void)NULL \
 104 )
 105
 106
 107 /* ----------------------------------------------------------------
 108  *                                 index_ interface functions
 109  * ----------------------------------------------------------------
 110  */
 111
 112 /* ----------------
 113  *              index_open - open an index relation by relation OID
 114  *
 115  *              Note: we acquire no lock on the index.  An AccessShareLock is
 116  *              acquired by index_beginscan (and released by index_endscan).
 117  *              Generally, the caller should already hold some type of lock on
 118  *              the parent relation to ensure that the index doesn't disappear.
 119  *
 120  *              This is a convenience routine adapted for indexscan use.
 121  *              Some callers may prefer to use relation_open directly.
 122  * ----------------
 123  */
 124 Relation
 125 index_open(Oid relationId)
 126 {
 127         Relation        r;
 128
 129         r = relation_open(relationId, NoLock);
 130
 131         if (r->rd_rel->relkind != RELKIND_INDEX)
 132                 ereport(ERROR,
 133                                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 134                                  errmsg("\"%s\" is not an index relation",
 135                                                 RelationGetRelationName(r))));
 136
 137         pgstat_initstats(&r->pgstat_info, r);
 138
 139         return r;
 140 }
 141
 142 /* ----------------
 143  *              index_openrv - open an index relation specified
 144  *              by a RangeVar node
 145  *
 146  *              As above, but relation is specified by a RangeVar.
 147  * ----------------
 148  */
 149 Relation
 150 index_openrv(const RangeVar *relation)
 151 {
 152         Relation        r;
 153
 154         r = relation_openrv(relation, NoLock);
 155
 156         if (r->rd_rel->relkind != RELKIND_INDEX)
 157                 ereport(ERROR,
 158                                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 159                                  errmsg("\"%s\" is not an index relation",
 160                                                 RelationGetRelationName(r))));
 161
 162         pgstat_initstats(&r->pgstat_info, r);
 163
 164         return r;
 165 }
 166
 167 /* ----------------
 168  *              index_openr - open a system index relation specified by name.
 169  *
 170  *              As above, but the relation is specified by an unqualified name;
 171  *              it is assumed to live in the system catalog namespace.
 172  * ----------------
 173  */
 174 Relation
 175 index_openr(const char *sysRelationName)
 176 {
 177         Relation        r;
 178
 179         r = relation_openr(sysRelationName, NoLock);
 180
 181         if (r->rd_rel->relkind != RELKIND_INDEX)
 182                 ereport(ERROR,
 183                                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 184                                  errmsg("\"%s\" is not an index relation",
 185                                                 RelationGetRelationName(r))));
 186
 187         pgstat_initstats(&r->pgstat_info, r);
 188
 189         return r;
 190 }
 191
 192 /* ----------------
 193  *              index_close - close a index relation
 194  *
 195  *              presently the relcache routines do all the work we need
 196  *              to open/close index relations.
 197  * ----------------
 198  */
 199 void
 200 index_close(Relation relation)
 201 {
 202         RelationClose(relation);
 203 }
 204
 205 /* ----------------
 206  *              index_insert - insert an index tuple into a relation
 207  * ----------------
 208  */
 209 InsertIndexResult
 210 index_insert(Relation indexRelation,
 211                          Datum *datums,
 212                          char *nulls,
 213                          ItemPointer heap_t_ctid,
 214                          Relation heapRelation,
 215                          bool check_uniqueness)
 216 {
 217         RegProcedure procedure;
 218         InsertIndexResult specificResult;
 219
 220         RELATION_CHECKS;
 221         GET_REL_PROCEDURE(insert, aminsert);
 222
 223         /*
 224          * have the am's insert proc do all the work.
 225          */
 226         specificResult = (InsertIndexResult)
 227                 DatumGetPointer(OidFunctionCall6(procedure,
 228                                                                                  PointerGetDatum(indexRelation),
 229                                                                                  PointerGetDatum(datums),
 230                                                                                  PointerGetDatum(nulls),
 231                                                                                  PointerGetDatum(heap_t_ctid),
 232                                                                                  PointerGetDatum(heapRelation),
 233                                                                                  BoolGetDatum(check_uniqueness)));
 234
 235         /* must be pfree'ed */
 236         return specificResult;
 237 }
 238
 239 /* ----------------
 240  *              index_beginscan - start a scan of an index
 241  *
 242  * Note: heapRelation may be NULL if there is no intention of calling
 243  * index_getnext on this scan; index_getnext_indexitem will not use the
 244  * heapRelation link (nor the snapshot).  However, the caller had better
 245  * be holding some kind of lock on the heap relation in any case, to ensure
 246  * no one deletes it (or the index) out from under us.
 247  * ----------------
 248  */
 249 IndexScanDesc
 250 index_beginscan(Relation heapRelation,
 251                                 Relation indexRelation,
 252                                 Snapshot snapshot,
 253                                 int nkeys, ScanKey key)
 254 {
 255         IndexScanDesc scan;
 256         RegProcedure procedure;
 257
 258         RELATION_CHECKS;
 259         GET_REL_PROCEDURE(beginscan, ambeginscan);
 260
 261         RelationIncrementReferenceCount(indexRelation);
 262
 263         /*
 264          * Acquire AccessShareLock for the duration of the scan
 265          *
 266          * Note: we could get an SI inval message here and consequently have to
 267          * rebuild the relcache entry.  The refcount increment above ensures
 268          * that we will rebuild it and not just flush it...
 269          */
 270         LockRelation(indexRelation, AccessShareLock);
 271
 272         /*
 273          * Tell the AM to open a scan.
 274          */
 275         scan = (IndexScanDesc)
 276                 DatumGetPointer(OidFunctionCall3(procedure,
 277                                                                                  PointerGetDatum(indexRelation),
 278                                                                                  Int32GetDatum(nkeys),
 279                                                                                  PointerGetDatum(key)));
 280
 281         /*
 282          * Save additional parameters into the scandesc.  Everything else was
 283          * set up by RelationGetIndexScan.
 284          */
 285         scan->heapRelation = heapRelation;
 286         scan->xs_snapshot = snapshot;
 287
 288         /*
 289          * We want to look up the amgettuple procedure just once per scan, not
 290          * once per index_getnext call.  So do it here and save the fmgr info
 291          * result in the scan descriptor.
 292          */
 293         GET_SCAN_PROCEDURE(beginscan, amgettuple);
 294         fmgr_info(procedure, &scan->fn_getnext);
 295
 296         return scan;
 297 }
 298
 299 /* ----------------
 300  *              index_rescan  - (re)start a scan of an index
 301  *
 302  * The caller may specify a new set of scankeys (but the number of keys
 303  * cannot change).  To restart the scan without changing keys, pass NULL
 304  * for the key array.
 305  *
 306  * Note that this is also called when first starting an indexscan;
 307  * see RelationGetIndexScan.  Keys *must* be passed in that case,
 308  * unless scan->numberOfKeys is zero.
 309  * ----------------
 310  */
 311 void
 312 index_rescan(IndexScanDesc scan, ScanKey key)
 313 {
 314         RegProcedure procedure;
 315
 316         SCAN_CHECKS;
 317         GET_SCAN_PROCEDURE(rescan, amrescan);
 318
 319         scan->kill_prior_tuple = false;         /* for safety */
 320         scan->keys_are_unique = false;          /* may be set by index AM */
 321         scan->got_tuple = false;
 322         scan->unique_tuple_pos = 0;
 323         scan->unique_tuple_mark = 0;
 324
 325         OidFunctionCall2(procedure,
 326                                          PointerGetDatum(scan),
 327                                          PointerGetDatum(key));
 328
 329         pgstat_reset_index_scan(&scan->xs_pgstat_info);
 330 }
 331
 332 /* ----------------
 333  *              index_endscan - end a scan
 334  * ----------------
 335  */
 336 void
 337 index_endscan(IndexScanDesc scan)
 338 {
 339         RegProcedure procedure;
 340
 341         SCAN_CHECKS;
 342         GET_SCAN_PROCEDURE(endscan, amendscan);
 343
 344         /* Release any held pin on a heap page */
 345         if (BufferIsValid(scan->xs_cbuf))
 346         {
 347                 ReleaseBuffer(scan->xs_cbuf);
 348                 scan->xs_cbuf = InvalidBuffer;
 349         }
 350
 351         /* End the AM's scan */
 352         OidFunctionCall1(procedure, PointerGetDatum(scan));
 353
 354         /* Release index lock and refcount acquired by index_beginscan */
 355
 356         UnlockRelation(scan->indexRelation, AccessShareLock);
 357
 358         RelationDecrementReferenceCount(scan->indexRelation);
 359
 360         /* Release the scan data structure itself */
 361         IndexScanEnd(scan);
 362 }
 363
 364 /* ----------------
 365  *              index_markpos  - mark a scan position
 366  * ----------------
 367  */
 368 void
 369 index_markpos(IndexScanDesc scan)
 370 {
 371         RegProcedure procedure;
 372
 373         SCAN_CHECKS;
 374         GET_SCAN_PROCEDURE(markpos, ammarkpos);
 375
 376         scan->unique_tuple_mark = scan->unique_tuple_pos;
 377
 378         OidFunctionCall1(procedure, PointerGetDatum(scan));
 379 }
 380
 381 /* ----------------
 382  *              index_restrpos  - restore a scan position
 383  * ----------------
 384  */
 385 void
 386 index_restrpos(IndexScanDesc scan)
 387 {
 388         RegProcedure procedure;
 389
 390         SCAN_CHECKS;
 391         GET_SCAN_PROCEDURE(restrpos, amrestrpos);
 392
 393         scan->kill_prior_tuple = false;         /* for safety */
 394
 395         /*
 396          * We do not reset got_tuple; so if the scan is actually being
 397          * short-circuited by index_getnext, the effective position restoration
 398          * is done by restoring unique_tuple_pos.
 399          */
 400         scan->unique_tuple_pos = scan->unique_tuple_mark;
 401
 402         OidFunctionCall1(procedure, PointerGetDatum(scan));
 403 }
 404
 405 /* ----------------
 406  *              index_getnext - get the next heap tuple from a scan
 407  *
 408  * The result is the next heap tuple satisfying the scan keys and the
 409  * snapshot, or NULL if no more matching tuples exist.  On success,
 410  * the buffer containing the heap tuple is pinned (the pin will be dropped
 411  * at the next index_getnext or index_endscan).  The index TID corresponding
 412  * to the heap tuple can be obtained if needed from scan->currentItemData.
 413  * ----------------
 414  */
 415 HeapTuple
 416 index_getnext(IndexScanDesc scan, ScanDirection direction)
 417 {
 418         HeapTuple       heapTuple = &scan->xs_ctup;
 419
 420         SCAN_CHECKS;
 421
 422         /* Release any previously held pin */
 423         if (BufferIsValid(scan->xs_cbuf))
 424         {
 425                 ReleaseBuffer(scan->xs_cbuf);
 426                 scan->xs_cbuf = InvalidBuffer;
 427         }
 428
 429         /*
 430          * If we already got a tuple and it must be unique, there's no need
 431          * to make the index AM look through any additional tuples.  (This can
 432          * save a useful amount of work in scenarios where there are many dead
 433          * tuples due to heavy update activity.)
 434          *
 435          * To do this we must keep track of the logical scan position
 436          * (before/on/after tuple).  Also, we have to be sure to release scan
 437          * resources before returning NULL; if we fail to do so then a multi-index
 438          * scan can easily run the system out of free buffers.  We can release
 439          * index-level resources fairly cheaply by calling index_rescan.  This
 440          * means there are two persistent states as far as the index AM is
 441          * concerned: on-tuple and rescanned.  If we are actually asked to
 442          * re-fetch the single tuple, we have to go through a fresh indexscan
 443          * startup, which penalizes that (infrequent) case.
 444          */
 445         if (scan->keys_are_unique && scan->got_tuple)
 446         {
 447                 int             new_tuple_pos = scan->unique_tuple_pos;
 448
 449                 if (ScanDirectionIsForward(direction))
 450                 {
 451                         if (new_tuple_pos <= 0)
 452                                 new_tuple_pos++;
 453                 }
 454                 else
 455                 {
 456                         if (new_tuple_pos >= 0)
 457                                 new_tuple_pos--;
 458                 }
 459                 if (new_tuple_pos == 0)
 460                 {
 461                         /*
 462                          * We are moving onto the unique tuple from having been off it.
 463                          * We just fall through and let the index AM do the work.  Note
 464                          * we should get the right answer regardless of scan direction.
 465                          */
 466                         scan->unique_tuple_pos = 0;     /* need to update position */
 467                 }
 468                 else
 469                 {
 470                         /*
 471                          * Moving off the tuple; must do amrescan to release index-level
 472                          * pins before we return NULL.  Since index_rescan will reset
 473                          * my state, must save and restore...
 474                          */
 475                         int             unique_tuple_mark = scan->unique_tuple_mark;
 476
 477                         index_rescan(scan, NULL /* no change to key */);
 478
 479                         scan->keys_are_unique = true;
 480                         scan->got_tuple = true;
 481                         scan->unique_tuple_pos = new_tuple_pos;
 482                         scan->unique_tuple_mark = unique_tuple_mark;
 483
 484                         return NULL;
 485                 }
 486         }
 487
 488         /* just make sure this is false... */
 489         scan->kill_prior_tuple = false;
 490
 491         for (;;)
 492         {
 493                 bool            found;
 494                 uint16          sv_infomask;
 495
 496                 pgstat_count_index_scan(&scan->xs_pgstat_info);
 497
 498                 /*
 499                  * The AM's gettuple proc finds the next tuple matching the scan
 500                  * keys.  index_beginscan already set up fn_getnext.
 501                  */
 502                 found = DatumGetBool(FunctionCall2(&scan->fn_getnext,
 503                                                                                    PointerGetDatum(scan),
 504                                                                                    Int32GetDatum(direction)));
 505
 506                 /* Reset kill flag immediately for safety */
 507                 scan->kill_prior_tuple = false;
 508
 509                 if (!found)
 510                         return NULL;            /* failure exit */
 511
 512                 /*
 513                  * Fetch the heap tuple and see if it matches the snapshot.
 514                  */
 515                 if (heap_fetch(scan->heapRelation, scan->xs_snapshot,
 516                                            heapTuple, &scan->xs_cbuf, true,
 517                                            &scan->xs_pgstat_info))
 518                         break;
 519
 520                 /* Skip if no tuple at this location */
 521                 if (heapTuple->t_data == NULL)
 522                         continue;                       /* should we raise an error instead? */
 523
 524                 /*
 525                  * If we can't see it, maybe no one else can either.  Check to see
 526                  * if the tuple is dead to all transactions.  If so, signal the
 527                  * index AM to not return it on future indexscans.
 528                  *
 529                  * We told heap_fetch to keep a pin on the buffer, so we can
 530                  * re-access the tuple here.  But we must re-lock the buffer
 531                  * first. Also, it's just barely possible for an update of hint
 532                  * bits to occur here.
 533                  */
 534                 LockBuffer(scan->xs_cbuf, BUFFER_LOCK_SHARE);
 535                 sv_infomask = heapTuple->t_data->t_infomask;
 536
 537                 if (HeapTupleSatisfiesVacuum(heapTuple->t_data, RecentGlobalXmin) ==
 538                         HEAPTUPLE_DEAD)
 539                         scan->kill_prior_tuple = true;
 540
 541                 if (sv_infomask != heapTuple->t_data->t_infomask)
 542                         SetBufferCommitInfoNeedsSave(scan->xs_cbuf);
 543                 LockBuffer(scan->xs_cbuf, BUFFER_LOCK_UNLOCK);
 544                 ReleaseBuffer(scan->xs_cbuf);
 545                 scan->xs_cbuf = InvalidBuffer;
 546         }
 547
 548         /* Success exit */
 549         scan->got_tuple = true;
 550
 551         /*
 552          * If we just fetched a known-unique tuple, then subsequent calls will
 553          * go through the short-circuit code above.  unique_tuple_pos has been
 554          * initialized to 0, which is the correct state ("on row").
 555          */
 556
 557         pgstat_count_index_getnext(&scan->xs_pgstat_info);
 558
 559         return heapTuple;
 560 }
 561
 562 /* ----------------
 563  *              index_getnext_indexitem - get the next index tuple from a scan
 564  *
 565  * Finds the next index tuple satisfying the scan keys.  Note that the
 566  * corresponding heap tuple is not accessed, and thus no time qual (snapshot)
 567  * check is done, other than the index AM's internal check for killed tuples
 568  * (which most callers of this routine will probably want to suppress by
 569  * setting scan->ignore_killed_tuples = false).
 570  *
 571  * On success (TRUE return), the found index TID is in scan->currentItemData,
 572  * and its heap TID is in scan->xs_ctup.t_self.  scan->xs_cbuf is untouched.
 573  * ----------------
 574  */
 575 bool
 576 index_getnext_indexitem(IndexScanDesc scan,
 577                                                 ScanDirection direction)
 578 {
 579         bool            found;
 580
 581         SCAN_CHECKS;
 582
 583         /* just make sure this is false... */
 584         scan->kill_prior_tuple = false;
 585
 586         /*
 587          * have the am's gettuple proc do all the work. index_beginscan
 588          * already set up fn_getnext.
 589          */
 590         found = DatumGetBool(FunctionCall2(&scan->fn_getnext,
 591                                                                            PointerGetDatum(scan),
 592                                                                            Int32GetDatum(direction)));
 593
 594         return found;
 595 }
 596
 597 /* ----------------
 598  *              index_bulk_delete - do mass deletion of index entries
 599  *
 600  *              callback routine tells whether a given main-heap tuple is
 601  *              to be deleted
 602  *
 603  *              return value is an optional palloc'd struct of statistics
 604  * ----------------
 605  */
 606 IndexBulkDeleteResult *
 607 index_bulk_delete(Relation indexRelation,
 608                                   IndexBulkDeleteCallback callback,
 609                                   void *callback_state)
 610 {
 611         RegProcedure procedure;
 612         IndexBulkDeleteResult *result;
 613
 614         RELATION_CHECKS;
 615         GET_REL_PROCEDURE(bulk_delete, ambulkdelete);
 616
 617         result = (IndexBulkDeleteResult *)
 618                 DatumGetPointer(OidFunctionCall3(procedure,
 619                                                                                  PointerGetDatum(indexRelation),
 620                                                                          PointerGetDatum((Pointer) callback),
 621                                                                            PointerGetDatum(callback_state)));
 622
 623         return result;
 624 }
 625
 626 /* ----------------
 627  *              index_vacuum_cleanup - do post-deletion cleanup of an index
 628  *
 629  *              return value is an optional palloc'd struct of statistics
 630  * ----------------
 631  */
 632 IndexBulkDeleteResult *
 633 index_vacuum_cleanup(Relation indexRelation,
 634                                          IndexVacuumCleanupInfo *info,
 635                                          IndexBulkDeleteResult *stats)
 636 {
 637         RegProcedure procedure;
 638         IndexBulkDeleteResult *result;
 639
 640         RELATION_CHECKS;
 641
 642         /* It's okay for an index AM not to have a vacuumcleanup procedure */
 643         if (!RegProcedureIsValid(indexRelation->rd_am->amvacuumcleanup))
 644                 return stats;
 645
 646         GET_REL_PROCEDURE(vacuum_cleanup, amvacuumcleanup);
 647
 648         result = (IndexBulkDeleteResult *)
 649                 DatumGetPointer(OidFunctionCall3(procedure,
 650                                                                                  PointerGetDatum(indexRelation),
 651                                                                                  PointerGetDatum((Pointer) info),
 652                                                                                  PointerGetDatum((Pointer) stats)));
 653
 654         return result;
 655 }
 656
 657 /* ----------------
 658  *              index_cost_estimator
 659  *
 660  *              Fetch the amcostestimate procedure OID for an index.
 661  *
 662  *              We could combine fetching and calling the procedure,
 663  *              as index_insert does for example; but that would require
 664  *              importing a bunch of planner/optimizer stuff into this file.
 665  * ----------------
 666  */
 667 RegProcedure
 668 index_cost_estimator(Relation indexRelation)
 669 {
 670         RegProcedure procedure;
 671
 672         RELATION_CHECKS;
 673         GET_REL_PROCEDURE(cost_estimator, amcostestimate);
 674
 675         return procedure;
 676 }
 677
 678 /* ----------------
 679  *              index_getprocid
 680  *
 681  *              Some indexed access methods may require support routines that are
 682  *              not in the operator class/operator model imposed by pg_am.      These
 683  *              access methods may store the OIDs of registered procedures they
 684  *              need in pg_amproc.      These registered procedure OIDs are ordered in
 685  *              a way that makes sense to the access method, and used only by the
 686  *              access method.  The general index code doesn't know anything about
 687  *              the routines involved; it just builds an ordered list of them for
 688  *              each attribute on which an index is defined.
 689  *
 690  *              This routine returns the requested procedure OID for a particular
 691  *              indexed attribute.
 692  * ----------------
 693  */
 694 RegProcedure
 695 index_getprocid(Relation irel,
 696                                 AttrNumber attnum,
 697                                 uint16 procnum)
 698 {
 699         RegProcedure *loc;
 700         int                     nproc;
 701         int                     procindex;
 702
 703         nproc = irel->rd_am->amsupport;
 704
 705         Assert(procnum > 0 && procnum <= (uint16) nproc);
 706
 707         procindex = (nproc * (attnum - 1)) + (procnum - 1);
 708
 709         loc = irel->rd_support;
 710
 711         Assert(loc != NULL);
 712
 713         return loc[procindex];
 714 }
 715
 716 /* ----------------
 717  *              index_getprocinfo
 718  *
 719  *              This routine allows index AMs to keep fmgr lookup info for
 720  *              support procs in the relcache.
 721  * ----------------
 722  */
 723 struct FmgrInfo *
 724 index_getprocinfo(Relation irel,
 725                                   AttrNumber attnum,
 726                                   uint16 procnum)
 727 {
 728         FmgrInfo   *locinfo;
 729         int                     nproc;
 730         int                     procindex;
 731
 732         nproc = irel->rd_am->amsupport;
 733
 734         Assert(procnum > 0 && procnum <= (uint16) nproc);
 735
 736         procindex = (nproc * (attnum - 1)) + (procnum - 1);
 737
 738         locinfo = irel->rd_supportinfo;
 739
 740         Assert(locinfo != NULL);
 741
 742         locinfo += procindex;
 743
 744         /* Initialize the lookup info if first time through */
 745         if (locinfo->fn_oid == InvalidOid)
 746         {
 747                 RegProcedure *loc = irel->rd_support;
 748                 RegProcedure procId;
 749
 750                 Assert(loc != NULL);
 751
 752                 procId = loc[procindex];
 753
 754                 /*
 755                  * Complain if function was not found during
 756                  * IndexSupportInitialize. This should not happen unless the
 757                  * system tables contain bogus entries for the index opclass.  (If
 758                  * an AM wants to allow a support function to be optional, it can
 759                  * use index_getprocid.)
 760                  */
 761                 if (!RegProcedureIsValid(procId))
 762                         elog(ERROR, "missing support function %d for attribute %d of index \"%s\"",
 763                                  procnum, attnum, RelationGetRelationName(irel));
 764
 765                 fmgr_info_cxt(procId, locinfo, irel->rd_indexcxt);
 766         }
 767
 768         return locinfo;
 769 }