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 1.48 2001/03/22 06:16:07 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         specificResult = (InsertIndexResult)
 197                 DatumGetPointer(OidFunctionCall5(procedure,
 198                                                                                  PointerGetDatum(relation),
 199                                                                                  PointerGetDatum(datum),
 200                                                                                  PointerGetDatum(nulls),
 201                                                                                  PointerGetDatum(heap_t_ctid),
 202                                                                                  PointerGetDatum(heapRel)));
 203
 204         /* must be pfree'ed */
 205         return specificResult;
 206 }
 207
 208 /* ----------------
 209  *              index_delete - delete an item from an index relation
 210  * ----------------
 211  */
 212 void
 213 index_delete(Relation relation, ItemPointer indexItem)
 214 {
 215         RegProcedure procedure;
 216
 217         RELATION_CHECKS;
 218         GET_REL_PROCEDURE(delete, amdelete);
 219
 220         OidFunctionCall2(procedure,
 221                                          PointerGetDatum(relation),
 222                                          PointerGetDatum(indexItem));
 223 }
 224
 225 /* ----------------
 226  *              index_beginscan - start a scan of an index
 227  * ----------------
 228  */
 229 IndexScanDesc
 230 index_beginscan(Relation relation,
 231                                 bool scanFromEnd,
 232                                 uint16 numberOfKeys,
 233                                 ScanKey key)
 234 {
 235         IndexScanDesc scandesc;
 236         RegProcedure procedure;
 237
 238         RELATION_CHECKS;
 239         GET_REL_PROCEDURE(beginscan, ambeginscan);
 240
 241         RelationIncrementReferenceCount(relation);
 242
 243         /*
 244          * Acquire AccessShareLock for the duration of the scan
 245          *
 246          * Note: we could get an SI inval message here and consequently have to
 247          * rebuild the relcache entry.  The refcount increment above ensures
 248          * that we will rebuild it and not just flush it...
 249          */
 250         LockRelation(relation, AccessShareLock);
 251
 252         scandesc = (IndexScanDesc)
 253                 DatumGetPointer(OidFunctionCall4(procedure,
 254                                                                                  PointerGetDatum(relation),
 255                                                                                  BoolGetDatum(scanFromEnd),
 256                                                                                  UInt16GetDatum(numberOfKeys),
 257                                                                                  PointerGetDatum(key)));
 258
 259         return scandesc;
 260 }
 261
 262 /* ----------------
 263  *              index_rescan  - restart a scan of an index
 264  * ----------------
 265  */
 266 void
 267 index_rescan(IndexScanDesc scan, bool scanFromEnd, ScanKey key)
 268 {
 269         RegProcedure procedure;
 270
 271         SCAN_CHECKS;
 272         GET_SCAN_PROCEDURE(rescan, amrescan);
 273
 274         OidFunctionCall3(procedure,
 275                                          PointerGetDatum(scan),
 276                                          BoolGetDatum(scanFromEnd),
 277                                          PointerGetDatum(key));
 278 }
 279
 280 /* ----------------
 281  *              index_endscan - end a scan
 282  * ----------------
 283  */
 284 void
 285 index_endscan(IndexScanDesc scan)
 286 {
 287         RegProcedure procedure;
 288
 289         SCAN_CHECKS;
 290         GET_SCAN_PROCEDURE(endscan, amendscan);
 291
 292         OidFunctionCall1(procedure, PointerGetDatum(scan));
 293
 294         /* Release lock and refcount acquired by index_beginscan */
 295
 296         UnlockRelation(scan->relation, AccessShareLock);
 297
 298         RelationDecrementReferenceCount(scan->relation);
 299
 300         /* Release the scan data structure itself */
 301         IndexScanEnd(scan);
 302 }
 303
 304 /* ----------------
 305  *              index_markpos  - mark a scan position
 306  * ----------------
 307  */
 308 void
 309 index_markpos(IndexScanDesc scan)
 310 {
 311         RegProcedure procedure;
 312
 313         SCAN_CHECKS;
 314         GET_SCAN_PROCEDURE(markpos, ammarkpos);
 315
 316         OidFunctionCall1(procedure, PointerGetDatum(scan));
 317 }
 318
 319 /* ----------------
 320  *              index_restrpos  - restore a scan position
 321  * ----------------
 322  */
 323 void
 324 index_restrpos(IndexScanDesc scan)
 325 {
 326         RegProcedure procedure;
 327
 328         SCAN_CHECKS;
 329         GET_SCAN_PROCEDURE(restrpos, amrestrpos);
 330
 331         OidFunctionCall1(procedure, PointerGetDatum(scan));
 332 }
 333
 334 /* ----------------
 335  *              index_getnext - get the next tuple from a scan
 336  *
 337  *              A RetrieveIndexResult is a index tuple/heap tuple pair
 338  * ----------------
 339  */
 340 RetrieveIndexResult
 341 index_getnext(IndexScanDesc scan,
 342                           ScanDirection direction)
 343 {
 344         RetrieveIndexResult result;
 345
 346         SCAN_CHECKS;
 347
 348         /*
 349          * Look up the access procedure only once per scan.
 350          */
 351         if (scan->fn_getnext.fn_oid == InvalidOid)
 352         {
 353                 RegProcedure procedure;
 354
 355                 GET_SCAN_PROCEDURE(getnext, amgettuple);
 356                 fmgr_info(procedure, &scan->fn_getnext);
 357         }
 358
 359         /*
 360          * have the am's gettuple proc do all the work.
 361          */
 362         result = (RetrieveIndexResult)
 363                 DatumGetPointer(FunctionCall2(&scan->fn_getnext,
 364                                                                           PointerGetDatum(scan),
 365                                                                           Int32GetDatum(direction)));
 366
 367         return result;
 368 }
 369
 370 /* ----------------
 371  *              index_cost_estimator
 372  *
 373  *              Fetch the amcostestimate procedure OID for an index.
 374  *
 375  *              We could combine fetching and calling the procedure,
 376  *              as index_insert does for example; but that would require
 377  *              importing a bunch of planner/optimizer stuff into this file.
 378  * ----------------
 379  */
 380 RegProcedure
 381 index_cost_estimator(Relation relation)
 382 {
 383         RegProcedure procedure;
 384
 385         RELATION_CHECKS;
 386         GET_REL_PROCEDURE(cost_estimator, amcostestimate);
 387
 388         return procedure;
 389 }
 390
 391 /* ----------------
 392  *              index_getprocid
 393  *
 394  *              Some indexed access methods may require support routines that are
 395  *              not in the operator class/operator model imposed by pg_am.      These
 396  *              access methods may store the OIDs of registered procedures they
 397  *              need in pg_amproc.      These registered procedure OIDs are ordered in
 398  *              a way that makes sense to the access method, and used only by the
 399  *              access method.  The general index code doesn't know anything about
 400  *              the routines involved; it just builds an ordered list of them for
 401  *              each attribute on which an index is defined.
 402  *
 403  *              This routine returns the requested procedure OID for a particular
 404  *              indexed attribute.
 405  * ----------------
 406  */
 407 RegProcedure
 408 index_getprocid(Relation irel,
 409                                 AttrNumber attnum,
 410                                 uint16 procnum)
 411 {
 412         RegProcedure *loc;
 413         int                     natts;
 414
 415         natts = irel->rd_rel->relnatts;
 416
 417         loc = irel->rd_support;
 418
 419         Assert(loc != NULL);
 420
 421         return loc[(natts * (procnum - 1)) + (attnum - 1)];
 422 }