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) 1996-2001, 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 1.47 2001/01/24 19:42:48 momjian Exp $
  12  *
  13  * INTERFACE ROUTINES
  14  *              index_open              - open an index relation by relationId
  15  *              index_openr             - open a index relation by name
  16  *              index_close             - close a index relation
  17  *              index_beginscan - start a scan of an index
  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_delete    - delete an item from an index 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_fetch             - retrieve tuple with tid
  26  * **   index_replace   - replace a tuple
  27  * **   index_getattr   - get an attribute from an index tuple
  28  *              index_getprocid - get a support procedure id from the rel tuple
  29  *
  30  *              IndexScanIsValid - check index scan
  31  *
  32  * NOTES
  33  *              This file contains the index_ routines which used
  34  *              to be a scattered collection of stuff in access/genam.
  35  *
  36  *              The ** routines: index_fetch, index_replace, and index_getattr
  37  *              have not yet been implemented.  They may not be needed.
  38  *
  39  * old comments
  40  *              Scans are implemented as follows:
  41  *
  42  *              `0' represents an invalid item pointer.
  43  *              `-' represents an unknown item pointer.
  44  *              `X' represents a known item pointers.
  45  *              `+' represents known or invalid item pointers.
  46  *              `*' represents any item pointers.
  47  *
  48  *              State is represented by a triple of these symbols in the order of
  49  *              previous, current, next.  Note that the case of reverse scans works
  50  *              identically.
  51  *
  52  *                              State   Result
  53  *              (1)             + + -   + 0 0                   (if the next item pointer is invalid)
  54  *              (2)                             + X -                   (otherwise)
  55  *              (3)             * 0 0   * 0 0                   (no change)
  56  *              (4)             + X 0   X 0 0                   (shift)
  57  *              (5)             * + X   + X -                   (shift, add unknown)
  58  *
  59  *              All other states cannot occur.
  60  *
  61  *              Note: It would be possible to cache the status of the previous and
  62  *                        next item pointer using the flags.
  63  *
  64  *-------------------------------------------------------------------------
  65  */
  66
  67 #include "postgres.h"
  68
  69 #include "access/genam.h"
  70 #include "access/heapam.h"
  71 #include "utils/relcache.h"
  72
  73
  74 /* ----------------------------------------------------------------
  75  *                                      macros used in index_ routines
  76  * ----------------------------------------------------------------
  77  */
  78 #define RELATION_CHECKS \
  79 ( \
  80         AssertMacro(RelationIsValid(relation)), \
  81         AssertMacro(PointerIsValid(relation->rd_am)) \
  82 )
  83
  84 #define SCAN_CHECKS \
  85 ( \
  86         AssertMacro(IndexScanIsValid(scan)), \
  87         AssertMacro(RelationIsValid(scan->relation)), \
  88         AssertMacro(PointerIsValid(scan->relation->rd_am)) \
  89 )
  90
  91 #define GET_REL_PROCEDURE(x,y) \
  92 ( \
  93         procedure = relation->rd_am->y, \
  94         (!RegProcedureIsValid(procedure)) ? \
  95                 elog(ERROR, "index_%s: invalid %s regproc", \
  96                         CppAsString(x), CppAsString(y)) \
  97         : (void)NULL \
  98 )
  99
 100 #define GET_SCAN_PROCEDURE(x,y) \
 101 ( \
 102         procedure = scan->relation->rd_am->y, \
 103         (!RegProcedureIsValid(procedure)) ? \
 104                 elog(ERROR, "index_%s: invalid %s regproc", \
 105                         CppAsString(x), CppAsString(y)) \
 106         : (void)NULL \
 107 )
 108
 109
 110 /* ----------------------------------------------------------------
 111  *                                 index_ interface functions
 112  * ----------------------------------------------------------------
 113  */
 114 /* ----------------
 115  *              index_open - open an index relation by relationId
 116  *
 117  *              presently the relcache routines do all the work we need
 118  *              to open/close index relations.  However, callers of index_open
 119  *              expect it to succeed, so we need to check for a failure return.
 120  *
 121  *              Note: we acquire no lock on the index.  An AccessShareLock is
 122  *              acquired by index_beginscan (and released by index_endscan).
 123  * ----------------
 124  */
 125 Relation
 126 index_open(Oid relationId)
 127 {
 128         Relation        r;
 129
 130         r = RelationIdGetRelation(relationId);
 131
 132         if (!RelationIsValid(r))
 133                 elog(ERROR, "Index %u does not exist", relationId);
 134
 135         if (r->rd_rel->relkind != RELKIND_INDEX)
 136                 elog(ERROR, "%s is not an index relation", RelationGetRelationName(r));
 137
 138         return r;
 139 }
 140
 141 /* ----------------
 142  *              index_openr - open a index relation by name
 143  *
 144  *              As above, but lookup by name instead of OID.
 145  * ----------------
 146  */
 147 Relation
 148 index_openr(char *relationName)
 149 {
 150         Relation        r;
 151
 152         r = RelationNameGetRelation(relationName);
 153
 154         if (!RelationIsValid(r))
 155                 elog(ERROR, "Index '%s' does not exist", relationName);
 156
 157         if (r->rd_rel->relkind != RELKIND_INDEX)
 158                 elog(ERROR, "%s is not an index relation", RelationGetRelationName(r));
 159
 160         return r;
 161 }
 162
 163 /* ----------------
 164  *              index_close - close a index relation
 165  *
 166  *              presently the relcache routines do all the work we need
 167  *              to open/close index relations.
 168  * ----------------
 169  */
 170 void
 171 index_close(Relation relation)
 172 {
 173         RelationClose(relation);
 174 }
 175
 176 /* ----------------
 177  *              index_insert - insert an index tuple into a relation
 178  * ----------------
 179  */
 180 InsertIndexResult
 181 index_insert(Relation relation,
 182                          Datum *datum,
 183                          char *nulls,
 184                          ItemPointer heap_t_ctid,
 185                          Relation heapRel)
 186 {
 187         RegProcedure procedure;
 188         InsertIndexResult specificResult;
 189
 190         RELATION_CHECKS;
 191         GET_REL_PROCEDURE(insert, aminsert);
 192
 193         /* ----------------
 194          *      have the am's insert proc do all the work.
 195          * ----------------
 196          */
 197         specificResult = (InsertIndexResult)
 198                 DatumGetPointer(OidFunctionCall5(procedure,
 199                                                                                  PointerGetDatum(relation),
 200                                                                                  PointerGetDatum(datum),
 201                                                                                  PointerGetDatum(nulls),
 202                                                                                  PointerGetDatum(heap_t_ctid),
 203                                                                                  PointerGetDatum(heapRel)));
 204
 205         /* must be pfree'ed */
 206         return specificResult;
 207 }
 208
 209 /* ----------------
 210  *              index_delete - delete an item from an index relation
 211  * ----------------
 212  */
 213 void
 214 index_delete(Relation relation, ItemPointer indexItem)
 215 {
 216         RegProcedure procedure;
 217
 218         RELATION_CHECKS;
 219         GET_REL_PROCEDURE(delete, amdelete);
 220
 221         OidFunctionCall2(procedure,
 222                                          PointerGetDatum(relation),
 223                                          PointerGetDatum(indexItem));
 224 }
 225
 226 /* ----------------
 227  *              index_beginscan - start a scan of an index
 228  * ----------------
 229  */
 230 IndexScanDesc
 231 index_beginscan(Relation relation,
 232                                 bool scanFromEnd,
 233                                 uint16 numberOfKeys,
 234                                 ScanKey key)
 235 {
 236         IndexScanDesc scandesc;
 237         RegProcedure procedure;
 238
 239         RELATION_CHECKS;
 240         GET_REL_PROCEDURE(beginscan, ambeginscan);
 241
 242         RelationIncrementReferenceCount(relation);
 243
 244         /* ----------------
 245          *      Acquire AccessShareLock for the duration of the scan
 246          *
 247          *      Note: we could get an SI inval message here and consequently have
 248          *      to rebuild the relcache entry.  The refcount increment above
 249          *      ensures that we will rebuild it and not just flush it...
 250          * ----------------
 251          */
 252         LockRelation(relation, AccessShareLock);
 253
 254         scandesc = (IndexScanDesc)
 255                 DatumGetPointer(OidFunctionCall4(procedure,
 256                                                                                  PointerGetDatum(relation),
 257                                                                                  BoolGetDatum(scanFromEnd),
 258                                                                                  UInt16GetDatum(numberOfKeys),
 259                                                                                  PointerGetDatum(key)));
 260
 261         return scandesc;
 262 }
 263
 264 /* ----------------
 265  *              index_rescan  - restart a scan of an index
 266  * ----------------
 267  */
 268 void
 269 index_rescan(IndexScanDesc scan, bool scanFromEnd, ScanKey key)
 270 {
 271         RegProcedure procedure;
 272
 273         SCAN_CHECKS;
 274         GET_SCAN_PROCEDURE(rescan, amrescan);
 275
 276         OidFunctionCall3(procedure,
 277                                          PointerGetDatum(scan),
 278                                          BoolGetDatum(scanFromEnd),
 279                                          PointerGetDatum(key));
 280 }
 281
 282 /* ----------------
 283  *              index_endscan - end a scan
 284  * ----------------
 285  */
 286 void
 287 index_endscan(IndexScanDesc scan)
 288 {
 289         RegProcedure procedure;
 290
 291         SCAN_CHECKS;
 292         GET_SCAN_PROCEDURE(endscan, amendscan);
 293
 294         OidFunctionCall1(procedure, PointerGetDatum(scan));
 295
 296         /* Release lock and refcount acquired by index_beginscan */
 297
 298         UnlockRelation(scan->relation, AccessShareLock);
 299
 300         RelationDecrementReferenceCount(scan->relation);
 301
 302         /* Release the scan data structure itself */
 303         IndexScanEnd(scan);
 304 }
 305
 306 /* ----------------
 307  *              index_markpos  - mark a scan position
 308  * ----------------
 309  */
 310 void
 311 index_markpos(IndexScanDesc scan)
 312 {
 313         RegProcedure procedure;
 314
 315         SCAN_CHECKS;
 316         GET_SCAN_PROCEDURE(markpos, ammarkpos);
 317
 318         OidFunctionCall1(procedure, PointerGetDatum(scan));
 319 }
 320
 321 /* ----------------
 322  *              index_restrpos  - restore a scan position
 323  * ----------------
 324  */
 325 void
 326 index_restrpos(IndexScanDesc scan)
 327 {
 328         RegProcedure procedure;
 329
 330         SCAN_CHECKS;
 331         GET_SCAN_PROCEDURE(restrpos, amrestrpos);
 332
 333         OidFunctionCall1(procedure, PointerGetDatum(scan));
 334 }
 335
 336 /* ----------------
 337  *              index_getnext - get the next tuple from a scan
 338  *
 339  *              A RetrieveIndexResult is a index tuple/heap tuple pair
 340  * ----------------
 341  */
 342 RetrieveIndexResult
 343 index_getnext(IndexScanDesc scan,
 344                           ScanDirection direction)
 345 {
 346         RetrieveIndexResult result;
 347
 348         SCAN_CHECKS;
 349
 350         /* ----------------
 351          *      Look up the access procedure only once per scan.
 352          * ----------------
 353          */
 354         if (scan->fn_getnext.fn_oid == InvalidOid)
 355         {
 356                 RegProcedure procedure;
 357
 358                 GET_SCAN_PROCEDURE(getnext, amgettuple);
 359                 fmgr_info(procedure, &scan->fn_getnext);
 360         }
 361
 362         /* ----------------
 363          *      have the am's gettuple proc do all the work.
 364          * ----------------
 365          */
 366         result = (RetrieveIndexResult)
 367                 DatumGetPointer(FunctionCall2(&scan->fn_getnext,
 368                                                                           PointerGetDatum(scan),
 369                                                                           Int32GetDatum(direction)));
 370
 371         return result;
 372 }
 373
 374 /* ----------------
 375  *              index_cost_estimator
 376  *
 377  *              Fetch the amcostestimate procedure OID for an index.
 378  *
 379  *              We could combine fetching and calling the procedure,
 380  *              as index_insert does for example; but that would require
 381  *              importing a bunch of planner/optimizer stuff into this file.
 382  * ----------------
 383  */
 384 RegProcedure
 385 index_cost_estimator(Relation relation)
 386 {
 387         RegProcedure procedure;
 388
 389         RELATION_CHECKS;
 390         GET_REL_PROCEDURE(cost_estimator, amcostestimate);
 391
 392         return procedure;
 393 }
 394
 395 /* ----------------
 396  *              index_getprocid
 397  *
 398  *              Some indexed access methods may require support routines that are
 399  *              not in the operator class/operator model imposed by pg_am.      These
 400  *              access methods may store the OIDs of registered procedures they
 401  *              need in pg_amproc.      These registered procedure OIDs are ordered in
 402  *              a way that makes sense to the access method, and used only by the
 403  *              access method.  The general index code doesn't know anything about
 404  *              the routines involved; it just builds an ordered list of them for
 405  *              each attribute on which an index is defined.
 406  *
 407  *              This routine returns the requested procedure OID for a particular
 408  *              indexed attribute.
 409  * ----------------
 410  */
 411 RegProcedure
 412 index_getprocid(Relation irel,
 413                                 AttrNumber attnum,
 414                                 uint16 procnum)
 415 {
 416         RegProcedure *loc;
 417         int                     natts;
 418
 419         natts = irel->rd_rel->relnatts;
 420
 421         loc = irel->rd_support;
 422
 423         Assert(loc != NULL);
 424
 425         return loc[(natts * (procnum - 1)) + (attnum - 1)];
 426 }