granicus.if.org Git - postgresql/blob - src/backend/executor/nodeSubplan.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * nodeSubplan.c
   4  *        routines to support subselects
   5  *
   6  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  * IDENTIFICATION
  10  *        $PostgreSQL: pgsql/src/backend/executor/nodeSubplan.c,v 1.92 2008/01/01 19:45:49 momjian Exp $
  11  *
  12  *-------------------------------------------------------------------------
  13  */
  14 /*
  15  *       INTERFACE ROUTINES
  16  *              ExecSubPlan  - process a subselect
  17  *              ExecInitSubPlan - initialize a subselect
  18  */
  19 #include "postgres.h"
  20
  21 #include <math.h>
  22
  23 #include "access/heapam.h"
  24 #include "executor/executor.h"
  25 #include "executor/nodeSubplan.h"
  26 #include "nodes/makefuncs.h"
  27 #include "optimizer/clauses.h"
  28 #include "utils/array.h"
  29 #include "utils/lsyscache.h"
  30 #include "utils/memutils.h"
  31
  32
  33 static Datum ExecHashSubPlan(SubPlanState *node,
  34                                 ExprContext *econtext,
  35                                 bool *isNull);
  36 static Datum ExecScanSubPlan(SubPlanState *node,
  37                                 ExprContext *econtext,
  38                                 bool *isNull);
  39 static void buildSubPlanHash(SubPlanState *node, ExprContext *econtext);
  40 static bool findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot);
  41 static bool slotAllNulls(TupleTableSlot *slot);
  42 static bool slotNoNulls(TupleTableSlot *slot);
  43
  44
  45 /* ----------------------------------------------------------------
  46  *              ExecSubPlan
  47  * ----------------------------------------------------------------
  48  */
  49 Datum
  50 ExecSubPlan(SubPlanState *node,
  51                         ExprContext *econtext,
  52                         bool *isNull,
  53                         ExprDoneCond *isDone)
  54 {
  55         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  56
  57         /* Set default values for result flags: non-null, not a set result */
  58         *isNull = false;
  59         if (isDone)
  60                 *isDone = ExprSingleResult;
  61
  62         if (subplan->setParam != NIL)
  63                 elog(ERROR, "cannot set parent params from subquery");
  64
  65         if (subplan->useHashTable)
  66                 return ExecHashSubPlan(node, econtext, isNull);
  67         else
  68                 return ExecScanSubPlan(node, econtext, isNull);
  69 }
  70
  71 /*
  72  * ExecHashSubPlan: store subselect result in an in-memory hash table
  73  */
  74 static Datum
  75 ExecHashSubPlan(SubPlanState *node,
  76                                 ExprContext *econtext,
  77                                 bool *isNull)
  78 {
  79         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  80         PlanState  *planstate = node->planstate;
  81         ExprContext *innerecontext = node->innerecontext;
  82         TupleTableSlot *slot;
  83
  84         /* Shouldn't have any direct correlation Vars */
  85         if (subplan->parParam != NIL || node->args != NIL)
  86                 elog(ERROR, "hashed subplan with direct correlation not supported");
  87
  88         /*
  89          * If first time through or we need to rescan the subplan, build the hash
  90          * table.
  91          */
  92         if (node->hashtable == NULL || planstate->chgParam != NULL)
  93                 buildSubPlanHash(node, econtext);
  94
  95         /*
  96          * The result for an empty subplan is always FALSE; no need to evaluate
  97          * lefthand side.
  98          */
  99         *isNull = false;
 100         if (!node->havehashrows && !node->havenullrows)
 101                 return BoolGetDatum(false);
 102
 103         /*
 104          * Evaluate lefthand expressions and form a projection tuple. First we
 105          * have to set the econtext to use (hack alert!).
 106          */
 107         node->projLeft->pi_exprContext = econtext;
 108         slot = ExecProject(node->projLeft, NULL);
 109
 110         /*
 111          * Note: because we are typically called in a per-tuple context, we have
 112          * to explicitly clear the projected tuple before returning. Otherwise,
 113          * we'll have a double-free situation: the per-tuple context will probably
 114          * be reset before we're called again, and then the tuple slot will think
 115          * it still needs to free the tuple.
 116          */
 117
 118         /*
 119          * Since the hashtable routines will use innerecontext's per-tuple memory
 120          * as working memory, be sure to reset it for each tuple.
 121          */
 122         ResetExprContext(innerecontext);
 123
 124         /*
 125          * If the LHS is all non-null, probe for an exact match in the main hash
 126          * table.  If we find one, the result is TRUE. Otherwise, scan the
 127          * partly-null table to see if there are any rows that aren't provably
 128          * unequal to the LHS; if so, the result is UNKNOWN.  (We skip that part
 129          * if we don't care about UNKNOWN.) Otherwise, the result is FALSE.
 130          *
 131          * Note: the reason we can avoid a full scan of the main hash table is
 132          * that the combining operators are assumed never to yield NULL when both
 133          * inputs are non-null.  If they were to do so, we might need to produce
 134          * UNKNOWN instead of FALSE because of an UNKNOWN result in comparing the
 135          * LHS to some main-table entry --- which is a comparison we will not even
 136          * make, unless there's a chance match of hash keys.
 137          */
 138         if (slotNoNulls(slot))
 139         {
 140                 if (node->havehashrows &&
 141                         FindTupleHashEntry(node->hashtable,
 142                                                            slot,
 143                                                            node->cur_eq_funcs,
 144                                                            node->lhs_hash_funcs) != NULL)
 145                 {
 146                         ExecClearTuple(slot);
 147                         return BoolGetDatum(true);
 148                 }
 149                 if (node->havenullrows &&
 150                         findPartialMatch(node->hashnulls, slot))
 151                 {
 152                         ExecClearTuple(slot);
 153                         *isNull = true;
 154                         return BoolGetDatum(false);
 155                 }
 156                 ExecClearTuple(slot);
 157                 return BoolGetDatum(false);
 158         }
 159
 160         /*
 161          * When the LHS is partly or wholly NULL, we can never return TRUE. If we
 162          * don't care about UNKNOWN, just return FALSE.  Otherwise, if the LHS is
 163          * wholly NULL, immediately return UNKNOWN.  (Since the combining
 164          * operators are strict, the result could only be FALSE if the sub-select
 165          * were empty, but we already handled that case.) Otherwise, we must scan
 166          * both the main and partly-null tables to see if there are any rows that
 167          * aren't provably unequal to the LHS; if so, the result is UNKNOWN.
 168          * Otherwise, the result is FALSE.
 169          */
 170         if (node->hashnulls == NULL)
 171         {
 172                 ExecClearTuple(slot);
 173                 return BoolGetDatum(false);
 174         }
 175         if (slotAllNulls(slot))
 176         {
 177                 ExecClearTuple(slot);
 178                 *isNull = true;
 179                 return BoolGetDatum(false);
 180         }
 181         /* Scan partly-null table first, since more likely to get a match */
 182         if (node->havenullrows &&
 183                 findPartialMatch(node->hashnulls, slot))
 184         {
 185                 ExecClearTuple(slot);
 186                 *isNull = true;
 187                 return BoolGetDatum(false);
 188         }
 189         if (node->havehashrows &&
 190                 findPartialMatch(node->hashtable, slot))
 191         {
 192                 ExecClearTuple(slot);
 193                 *isNull = true;
 194                 return BoolGetDatum(false);
 195         }
 196         ExecClearTuple(slot);
 197         return BoolGetDatum(false);
 198 }
 199
 200 /*
 201  * ExecScanSubPlan: default case where we have to rescan subplan each time
 202  */
 203 static Datum
 204 ExecScanSubPlan(SubPlanState *node,
 205                                 ExprContext *econtext,
 206                                 bool *isNull)
 207 {
 208         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 209         PlanState  *planstate = node->planstate;
 210         SubLinkType subLinkType = subplan->subLinkType;
 211         MemoryContext oldcontext;
 212         TupleTableSlot *slot;
 213         Datum           result;
 214         bool            found = false;  /* TRUE if got at least one subplan tuple */
 215         ListCell   *pvar;
 216         ListCell   *l;
 217         ArrayBuildState *astate = NULL;
 218
 219         /*
 220          * We are probably in a short-lived expression-evaluation context. Switch
 221          * to the per-query context for manipulating the child plan's chgParam,
 222          * calling ExecProcNode on it, etc.
 223          */
 224         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 225
 226         /*
 227          * Set Params of this plan from parent plan correlation values. (Any
 228          * calculation we have to do is done in the parent econtext, since the
 229          * Param values don't need to have per-query lifetime.)
 230          */
 231         Assert(list_length(subplan->parParam) == list_length(node->args));
 232
 233         forboth(l, subplan->parParam, pvar, node->args)
 234         {
 235                 int                     paramid = lfirst_int(l);
 236                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 237
 238                 prm->value = ExecEvalExprSwitchContext((ExprState *) lfirst(pvar),
 239                                                                                            econtext,
 240                                                                                            &(prm->isnull),
 241                                                                                            NULL);
 242                 planstate->chgParam = bms_add_member(planstate->chgParam, paramid);
 243         }
 244
 245         /*
 246          * Now that we've set up its parameters, we can reset the subplan.
 247          */
 248         ExecReScan(planstate, NULL);
 249
 250         /*
 251          * For all sublink types except EXPR_SUBLINK and ARRAY_SUBLINK, the result
 252          * is boolean as are the results of the combining operators. We combine
 253          * results across tuples (if the subplan produces more than one) using OR
 254          * semantics for ANY_SUBLINK or AND semantics for ALL_SUBLINK.
 255          * (ROWCOMPARE_SUBLINK doesn't allow multiple tuples from the subplan.)
 256          * NULL results from the combining operators are handled according to the
 257          * usual SQL semantics for OR and AND.  The result for no input tuples is
 258          * FALSE for ANY_SUBLINK, TRUE for ALL_SUBLINK, NULL for
 259          * ROWCOMPARE_SUBLINK.
 260          *
 261          * For EXPR_SUBLINK we require the subplan to produce no more than one
 262          * tuple, else an error is raised.      If zero tuples are produced, we return
 263          * NULL.  Assuming we get a tuple, we just use its first column (there can
 264          * be only one non-junk column in this case).
 265          *
 266          * For ARRAY_SUBLINK we allow the subplan to produce any number of tuples,
 267          * and form an array of the first column's values.  Note in particular
 268          * that we produce a zero-element array if no tuples are produced (this is
 269          * a change from pre-8.3 behavior of returning NULL).
 270          */
 271         result = BoolGetDatum(subLinkType == ALL_SUBLINK);
 272         *isNull = false;
 273
 274         for (slot = ExecProcNode(planstate);
 275                  !TupIsNull(slot);
 276                  slot = ExecProcNode(planstate))
 277         {
 278                 TupleDesc       tdesc = slot->tts_tupleDescriptor;
 279                 Datum           rowresult;
 280                 bool            rownull;
 281                 int                     col;
 282                 ListCell   *plst;
 283
 284                 if (subLinkType == EXISTS_SUBLINK)
 285                 {
 286                         found = true;
 287                         result = BoolGetDatum(true);
 288                         break;
 289                 }
 290
 291                 if (subLinkType == EXPR_SUBLINK)
 292                 {
 293                         /* cannot allow multiple input tuples for EXPR sublink */
 294                         if (found)
 295                                 ereport(ERROR,
 296                                                 (errcode(ERRCODE_CARDINALITY_VIOLATION),
 297                                                  errmsg("more than one row returned by a subquery used as an expression")));
 298                         found = true;
 299
 300                         /*
 301                          * We need to copy the subplan's tuple in case the result is of
 302                          * pass-by-ref type --- our return value will point into this
 303                          * copied tuple!  Can't use the subplan's instance of the tuple
 304                          * since it won't still be valid after next ExecProcNode() call.
 305                          * node->curTuple keeps track of the copied tuple for eventual
 306                          * freeing.
 307                          */
 308                         if (node->curTuple)
 309                                 heap_freetuple(node->curTuple);
 310                         node->curTuple = ExecCopySlotTuple(slot);
 311
 312                         result = heap_getattr(node->curTuple, 1, tdesc, isNull);
 313                         /* keep scanning subplan to make sure there's only one tuple */
 314                         continue;
 315                 }
 316
 317                 if (subLinkType == ARRAY_SUBLINK)
 318                 {
 319                         Datum           dvalue;
 320                         bool            disnull;
 321
 322                         found = true;
 323                         /* stash away current value */
 324                         Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
 325                         dvalue = slot_getattr(slot, 1, &disnull);
 326                         astate = accumArrayResult(astate, dvalue, disnull,
 327                                                                           subplan->firstColType, oldcontext);
 328                         /* keep scanning subplan to collect all values */
 329                         continue;
 330                 }
 331
 332                 /* cannot allow multiple input tuples for ROWCOMPARE sublink either */
 333                 if (subLinkType == ROWCOMPARE_SUBLINK && found)
 334                         ereport(ERROR,
 335                                         (errcode(ERRCODE_CARDINALITY_VIOLATION),
 336                                          errmsg("more than one row returned by a subquery used as an expression")));
 337
 338                 found = true;
 339
 340                 /*
 341                  * For ALL, ANY, and ROWCOMPARE sublinks, load up the Params
 342                  * representing the columns of the sub-select, and then evaluate the
 343                  * combining expression.
 344                  */
 345                 col = 1;
 346                 foreach(plst, subplan->paramIds)
 347                 {
 348                         int                     paramid = lfirst_int(plst);
 349                         ParamExecData *prmdata;
 350
 351                         prmdata = &(econtext->ecxt_param_exec_vals[paramid]);
 352                         Assert(prmdata->execPlan == NULL);
 353                         prmdata->value = slot_getattr(slot, col, &(prmdata->isnull));
 354                         col++;
 355                 }
 356
 357                 rowresult = ExecEvalExprSwitchContext(node->testexpr, econtext,
 358                                                                                           &rownull, NULL);
 359
 360                 if (subLinkType == ANY_SUBLINK)
 361                 {
 362                         /* combine across rows per OR semantics */
 363                         if (rownull)
 364                                 *isNull = true;
 365                         else if (DatumGetBool(rowresult))
 366                         {
 367                                 result = BoolGetDatum(true);
 368                                 *isNull = false;
 369                                 break;                  /* needn't look at any more rows */
 370                         }
 371                 }
 372                 else if (subLinkType == ALL_SUBLINK)
 373                 {
 374                         /* combine across rows per AND semantics */
 375                         if (rownull)
 376                                 *isNull = true;
 377                         else if (!DatumGetBool(rowresult))
 378                         {
 379                                 result = BoolGetDatum(false);
 380                                 *isNull = false;
 381                                 break;                  /* needn't look at any more rows */
 382                         }
 383                 }
 384                 else
 385                 {
 386                         /* must be ROWCOMPARE_SUBLINK */
 387                         result = rowresult;
 388                         *isNull = rownull;
 389                 }
 390         }
 391
 392         MemoryContextSwitchTo(oldcontext);
 393
 394         if (subLinkType == ARRAY_SUBLINK)
 395         {
 396                 /* We return the result in the caller's context */
 397                 if (astate != NULL)
 398                         result = makeArrayResult(astate, oldcontext);
 399                 else
 400                         result = PointerGetDatum(construct_empty_array(subplan->firstColType));
 401         }
 402         else if (!found)
 403         {
 404                 /*
 405                  * deal with empty subplan result.      result/isNull were previously
 406                  * initialized correctly for all sublink types except EXPR and
 407                  * ROWCOMPARE; for those, return NULL.
 408                  */
 409                 if (subLinkType == EXPR_SUBLINK ||
 410                         subLinkType == ROWCOMPARE_SUBLINK)
 411                 {
 412                         result = (Datum) 0;
 413                         *isNull = true;
 414                 }
 415         }
 416
 417         return result;
 418 }
 419
 420 /*
 421  * buildSubPlanHash: load hash table by scanning subplan output.
 422  */
 423 static void
 424 buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
 425 {
 426         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 427         PlanState  *planstate = node->planstate;
 428         int                     ncols = list_length(subplan->paramIds);
 429         ExprContext *innerecontext = node->innerecontext;
 430         MemoryContext tempcxt = innerecontext->ecxt_per_tuple_memory;
 431         MemoryContext oldcontext;
 432         int                     nbuckets;
 433         TupleTableSlot *slot;
 434
 435         Assert(subplan->subLinkType == ANY_SUBLINK);
 436
 437         /*
 438          * If we already had any hash tables, destroy 'em; then create empty hash
 439          * table(s).
 440          *
 441          * If we need to distinguish accurately between FALSE and UNKNOWN (i.e.,
 442          * NULL) results of the IN operation, then we have to store subplan output
 443          * rows that are partly or wholly NULL.  We store such rows in a separate
 444          * hash table that we expect will be much smaller than the main table. (We
 445          * can use hashing to eliminate partly-null rows that are not distinct. We
 446          * keep them separate to minimize the cost of the inevitable full-table
 447          * searches; see findPartialMatch.)
 448          *
 449          * If it's not necessary to distinguish FALSE and UNKNOWN, then we don't
 450          * need to store subplan output rows that contain NULL.
 451          */
 452         MemoryContextReset(node->tablecxt);
 453         node->hashtable = NULL;
 454         node->hashnulls = NULL;
 455         node->havehashrows = false;
 456         node->havenullrows = false;
 457
 458         nbuckets = (int) ceil(planstate->plan->plan_rows);
 459         if (nbuckets < 1)
 460                 nbuckets = 1;
 461
 462         node->hashtable = BuildTupleHashTable(ncols,
 463                                                                                   node->keyColIdx,
 464                                                                                   node->tab_eq_funcs,
 465                                                                                   node->tab_hash_funcs,
 466                                                                                   nbuckets,
 467                                                                                   sizeof(TupleHashEntryData),
 468                                                                                   node->tablecxt,
 469                                                                                   tempcxt);
 470
 471         if (!subplan->unknownEqFalse)
 472         {
 473                 if (ncols == 1)
 474                         nbuckets = 1;           /* there can only be one entry */
 475                 else
 476                 {
 477                         nbuckets /= 16;
 478                         if (nbuckets < 1)
 479                                 nbuckets = 1;
 480                 }
 481                 node->hashnulls = BuildTupleHashTable(ncols,
 482                                                                                           node->keyColIdx,
 483                                                                                           node->tab_eq_funcs,
 484                                                                                           node->tab_hash_funcs,
 485                                                                                           nbuckets,
 486                                                                                           sizeof(TupleHashEntryData),
 487                                                                                           node->tablecxt,
 488                                                                                           tempcxt);
 489         }
 490
 491         /*
 492          * We are probably in a short-lived expression-evaluation context. Switch
 493          * to the per-query context for manipulating the child plan.
 494          */
 495         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 496
 497         /*
 498          * Reset subplan to start.
 499          */
 500         ExecReScan(planstate, NULL);
 501
 502         /*
 503          * Scan the subplan and load the hash table(s).  Note that when there are
 504          * duplicate rows coming out of the sub-select, only one copy is stored.
 505          */
 506         for (slot = ExecProcNode(planstate);
 507                  !TupIsNull(slot);
 508                  slot = ExecProcNode(planstate))
 509         {
 510                 int                     col = 1;
 511                 ListCell   *plst;
 512                 bool            isnew;
 513
 514                 /*
 515                  * Load up the Params representing the raw sub-select outputs, then
 516                  * form the projection tuple to store in the hashtable.
 517                  */
 518                 foreach(plst, subplan->paramIds)
 519                 {
 520                         int                     paramid = lfirst_int(plst);
 521                         ParamExecData *prmdata;
 522
 523                         prmdata = &(innerecontext->ecxt_param_exec_vals[paramid]);
 524                         Assert(prmdata->execPlan == NULL);
 525                         prmdata->value = slot_getattr(slot, col,
 526                                                                                   &(prmdata->isnull));
 527                         col++;
 528                 }
 529                 slot = ExecProject(node->projRight, NULL);
 530
 531                 /*
 532                  * If result contains any nulls, store separately or not at all.
 533                  */
 534                 if (slotNoNulls(slot))
 535                 {
 536                         (void) LookupTupleHashEntry(node->hashtable, slot, &isnew);
 537                         node->havehashrows = true;
 538                 }
 539                 else if (node->hashnulls)
 540                 {
 541                         (void) LookupTupleHashEntry(node->hashnulls, slot, &isnew);
 542                         node->havenullrows = true;
 543                 }
 544
 545                 /*
 546                  * Reset innerecontext after each inner tuple to free any memory used
 547                  * in hash computation or comparison routines.
 548                  */
 549                 ResetExprContext(innerecontext);
 550         }
 551
 552         /*
 553          * Since the projected tuples are in the sub-query's context and not the
 554          * main context, we'd better clear the tuple slot before there's any
 555          * chance of a reset of the sub-query's context.  Else we will have the
 556          * potential for a double free attempt.  (XXX possibly no longer needed,
 557          * but can't hurt.)
 558          */
 559         ExecClearTuple(node->projRight->pi_slot);
 560
 561         MemoryContextSwitchTo(oldcontext);
 562 }
 563
 564 /*
 565  * findPartialMatch: does the hashtable contain an entry that is not
 566  * provably distinct from the tuple?
 567  *
 568  * We have to scan the whole hashtable; we can't usefully use hashkeys
 569  * to guide probing, since we might get partial matches on tuples with
 570  * hashkeys quite unrelated to what we'd get from the given tuple.
 571  */
 572 static bool
 573 findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot)
 574 {
 575         int                     numCols = hashtable->numCols;
 576         AttrNumber *keyColIdx = hashtable->keyColIdx;
 577         TupleHashIterator hashiter;
 578         TupleHashEntry entry;
 579
 580         InitTupleHashIterator(hashtable, &hashiter);
 581         while ((entry = ScanTupleHashTable(&hashiter)) != NULL)
 582         {
 583                 ExecStoreMinimalTuple(entry->firstTuple, hashtable->tableslot, false);
 584                 if (!execTuplesUnequal(slot, hashtable->tableslot,
 585                                                            numCols, keyColIdx,
 586                                                            hashtable->cur_eq_funcs,
 587                                                            hashtable->tempcxt))
 588                 {
 589                         TermTupleHashIterator(&hashiter);
 590                         return true;
 591                 }
 592         }
 593         /* No TermTupleHashIterator call needed here */
 594         return false;
 595 }
 596
 597 /*
 598  * slotAllNulls: is the slot completely NULL?
 599  *
 600  * This does not test for dropped columns, which is OK because we only
 601  * use it on projected tuples.
 602  */
 603 static bool
 604 slotAllNulls(TupleTableSlot *slot)
 605 {
 606         int                     ncols = slot->tts_tupleDescriptor->natts;
 607         int                     i;
 608
 609         for (i = 1; i <= ncols; i++)
 610         {
 611                 if (!slot_attisnull(slot, i))
 612                         return false;
 613         }
 614         return true;
 615 }
 616
 617 /*
 618  * slotNoNulls: is the slot entirely not NULL?
 619  *
 620  * This does not test for dropped columns, which is OK because we only
 621  * use it on projected tuples.
 622  */
 623 static bool
 624 slotNoNulls(TupleTableSlot *slot)
 625 {
 626         int                     ncols = slot->tts_tupleDescriptor->natts;
 627         int                     i;
 628
 629         for (i = 1; i <= ncols; i++)
 630         {
 631                 if (slot_attisnull(slot, i))
 632                         return false;
 633         }
 634         return true;
 635 }
 636
 637 /* ----------------------------------------------------------------
 638  *              ExecInitSubPlan
 639  *
 640  * Create a SubPlanState for a SubPlan; this is the SubPlan-specific part
 641  * of ExecInitExpr().  We split it out so that it can be used for InitPlans
 642  * as well as regular SubPlans.  Note that we don't link the SubPlan into
 643  * the parent's subPlan list, because that shouldn't happen for InitPlans.
 644  * Instead, ExecInitExpr() does that one part.
 645  * ----------------------------------------------------------------
 646  */
 647 SubPlanState *
 648 ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
 649 {
 650         SubPlanState *sstate = makeNode(SubPlanState);
 651         EState     *estate = parent->state;
 652
 653         sstate->xprstate.evalfunc = (ExprStateEvalFunc) ExecSubPlan;
 654         sstate->xprstate.expr = (Expr *) subplan;
 655
 656         /* Link the SubPlanState to already-initialized subplan */
 657         sstate->planstate = (PlanState *) list_nth(estate->es_subplanstates,
 658                                                                                            subplan->plan_id - 1);
 659
 660         /* Initialize subexpressions */
 661         sstate->testexpr = ExecInitExpr((Expr *) subplan->testexpr, parent);
 662         sstate->args = (List *) ExecInitExpr((Expr *) subplan->args, parent);
 663
 664         /*
 665          * initialize my state
 666          */
 667         sstate->curTuple = NULL;
 668         sstate->projLeft = NULL;
 669         sstate->projRight = NULL;
 670         sstate->hashtable = NULL;
 671         sstate->hashnulls = NULL;
 672         sstate->tablecxt = NULL;
 673         sstate->innerecontext = NULL;
 674         sstate->keyColIdx = NULL;
 675         sstate->tab_hash_funcs = NULL;
 676         sstate->tab_eq_funcs = NULL;
 677         sstate->lhs_hash_funcs = NULL;
 678         sstate->cur_eq_funcs = NULL;
 679
 680         /*
 681          * If this plan is un-correlated or undirect correlated one and want to
 682          * set params for parent plan then mark parameters as needing evaluation.
 683          *
 684          * Note that in the case of un-correlated subqueries we don't care about
 685          * setting parent->chgParam here: indices take care about it, for others -
 686          * it doesn't matter...
 687          */
 688         if (subplan->setParam != NIL)
 689         {
 690                 ListCell   *lst;
 691
 692                 foreach(lst, subplan->setParam)
 693                 {
 694                         int                     paramid = lfirst_int(lst);
 695                         ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
 696
 697                         prm->execPlan = sstate;
 698                 }
 699         }
 700
 701         /*
 702          * If we are going to hash the subquery output, initialize relevant stuff.
 703          * (We don't create the hashtable until needed, though.)
 704          */
 705         if (subplan->useHashTable)
 706         {
 707                 int                     ncols,
 708                                         i;
 709                 TupleDesc       tupDesc;
 710                 TupleTable      tupTable;
 711                 TupleTableSlot *slot;
 712                 List       *oplist,
 713                                    *lefttlist,
 714                                    *righttlist,
 715                                    *leftptlist,
 716                                    *rightptlist;
 717                 ListCell   *l;
 718
 719                 /* We need a memory context to hold the hash table(s) */
 720                 sstate->tablecxt =
 721                         AllocSetContextCreate(CurrentMemoryContext,
 722                                                                   "Subplan HashTable Context",
 723                                                                   ALLOCSET_DEFAULT_MINSIZE,
 724                                                                   ALLOCSET_DEFAULT_INITSIZE,
 725                                                                   ALLOCSET_DEFAULT_MAXSIZE);
 726                 /* and a short-lived exprcontext for function evaluation */
 727                 sstate->innerecontext = CreateExprContext(estate);
 728                 /* Silly little array of column numbers 1..n */
 729                 ncols = list_length(subplan->paramIds);
 730                 sstate->keyColIdx = (AttrNumber *) palloc(ncols * sizeof(AttrNumber));
 731                 for (i = 0; i < ncols; i++)
 732                         sstate->keyColIdx[i] = i + 1;
 733
 734                 /*
 735                  * We use ExecProject to evaluate the lefthand and righthand
 736                  * expression lists and form tuples.  (You might think that we could
 737                  * use the sub-select's output tuples directly, but that is not the
 738                  * case if we had to insert any run-time coercions of the sub-select's
 739                  * output datatypes; anyway this avoids storing any resjunk columns
 740                  * that might be in the sub-select's output.) Run through the
 741                  * combining expressions to build tlists for the lefthand and
 742                  * righthand sides.  We need both the ExprState list (for ExecProject)
 743                  * and the underlying parse Exprs (for ExecTypeFromTL).
 744                  *
 745                  * We also extract the combining operators themselves to initialize
 746                  * the equality and hashing functions for the hash tables.
 747                  */
 748                 if (IsA(sstate->testexpr->expr, OpExpr))
 749                 {
 750                         /* single combining operator */
 751                         oplist = list_make1(sstate->testexpr);
 752                 }
 753                 else if (and_clause((Node *) sstate->testexpr->expr))
 754                 {
 755                         /* multiple combining operators */
 756                         Assert(IsA(sstate->testexpr, BoolExprState));
 757                         oplist = ((BoolExprState *) sstate->testexpr)->args;
 758                 }
 759                 else
 760                 {
 761                         /* shouldn't see anything else in a hashable subplan */
 762                         elog(ERROR, "unrecognized testexpr type: %d",
 763                                  (int) nodeTag(sstate->testexpr->expr));
 764                         oplist = NIL;           /* keep compiler quiet */
 765                 }
 766                 Assert(list_length(oplist) == ncols);
 767
 768                 lefttlist = righttlist = NIL;
 769                 leftptlist = rightptlist = NIL;
 770                 sstate->tab_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 771                 sstate->tab_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 772                 sstate->lhs_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 773                 sstate->cur_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 774                 i = 1;
 775                 foreach(l, oplist)
 776                 {
 777                         FuncExprState *fstate = (FuncExprState *) lfirst(l);
 778                         OpExpr     *opexpr = (OpExpr *) fstate->xprstate.expr;
 779                         ExprState  *exstate;
 780                         Expr       *expr;
 781                         TargetEntry *tle;
 782                         GenericExprState *tlestate;
 783                         Oid                     rhs_eq_oper;
 784                         Oid                     left_hashfn;
 785                         Oid                     right_hashfn;
 786
 787                         Assert(IsA(fstate, FuncExprState));
 788                         Assert(IsA(opexpr, OpExpr));
 789                         Assert(list_length(fstate->args) == 2);
 790
 791                         /* Process lefthand argument */
 792                         exstate = (ExprState *) linitial(fstate->args);
 793                         expr = exstate->expr;
 794                         tle = makeTargetEntry(expr,
 795                                                                   i,
 796                                                                   NULL,
 797                                                                   false);
 798                         tlestate = makeNode(GenericExprState);
 799                         tlestate->xprstate.expr = (Expr *) tle;
 800                         tlestate->xprstate.evalfunc = NULL;
 801                         tlestate->arg = exstate;
 802                         lefttlist = lappend(lefttlist, tlestate);
 803                         leftptlist = lappend(leftptlist, tle);
 804
 805                         /* Process righthand argument */
 806                         exstate = (ExprState *) lsecond(fstate->args);
 807                         expr = exstate->expr;
 808                         tle = makeTargetEntry(expr,
 809                                                                   i,
 810                                                                   NULL,
 811                                                                   false);
 812                         tlestate = makeNode(GenericExprState);
 813                         tlestate->xprstate.expr = (Expr *) tle;
 814                         tlestate->xprstate.evalfunc = NULL;
 815                         tlestate->arg = exstate;
 816                         righttlist = lappend(righttlist, tlestate);
 817                         rightptlist = lappend(rightptlist, tle);
 818
 819                         /* Lookup the equality function (potentially cross-type) */
 820                         fmgr_info(opexpr->opfuncid, &sstate->cur_eq_funcs[i - 1]);
 821                         sstate->cur_eq_funcs[i - 1].fn_expr = (Node *) opexpr;
 822
 823                         /* Look up the equality function for the RHS type */
 824                         if (!get_compatible_hash_operators(opexpr->opno,
 825                                                                                            NULL, &rhs_eq_oper))
 826                                 elog(ERROR, "could not find compatible hash operator for operator %u",
 827                                          opexpr->opno);
 828                         fmgr_info(get_opcode(rhs_eq_oper), &sstate->tab_eq_funcs[i - 1]);
 829
 830                         /* Lookup the associated hash functions */
 831                         if (!get_op_hash_functions(opexpr->opno,
 832                                                                            &left_hashfn, &right_hashfn))
 833                                 elog(ERROR, "could not find hash function for hash operator %u",
 834                                          opexpr->opno);
 835                         fmgr_info(left_hashfn, &sstate->lhs_hash_funcs[i - 1]);
 836                         fmgr_info(right_hashfn, &sstate->tab_hash_funcs[i - 1]);
 837
 838                         i++;
 839                 }
 840
 841                 /*
 842                  * Create a tupletable to hold these tuples.  (Note: we never bother
 843                  * to free the tupletable explicitly; that's okay because it will
 844                  * never store raw disk tuples that might have associated buffer pins.
 845                  * The only resource involved is memory, which will be cleaned up by
 846                  * freeing the query context.)
 847                  */
 848                 tupTable = ExecCreateTupleTable(2);
 849
 850                 /*
 851                  * Construct tupdescs, slots and projection nodes for left and right
 852                  * sides.  The lefthand expressions will be evaluated in the parent
 853                  * plan node's exprcontext, which we don't have access to here.
 854                  * Fortunately we can just pass NULL for now and fill it in later
 855                  * (hack alert!).  The righthand expressions will be evaluated in our
 856                  * own innerecontext.
 857                  */
 858                 tupDesc = ExecTypeFromTL(leftptlist, false);
 859                 slot = ExecAllocTableSlot(tupTable);
 860                 ExecSetSlotDescriptor(slot, tupDesc);
 861                 sstate->projLeft = ExecBuildProjectionInfo(lefttlist,
 862                                                                                                    NULL,
 863                                                                                                    slot,
 864                                                                                                    NULL);
 865
 866                 tupDesc = ExecTypeFromTL(rightptlist, false);
 867                 slot = ExecAllocTableSlot(tupTable);
 868                 ExecSetSlotDescriptor(slot, tupDesc);
 869                 sstate->projRight = ExecBuildProjectionInfo(righttlist,
 870                                                                                                         sstate->innerecontext,
 871                                                                                                         slot,
 872                                                                                                         NULL);
 873         }
 874
 875         return sstate;
 876 }
 877
 878 /* ----------------------------------------------------------------
 879  *              ExecSetParamPlan
 880  *
 881  *              Executes an InitPlan subplan and sets its output parameters.
 882  *
 883  * This is called from ExecEvalParam() when the value of a PARAM_EXEC
 884  * parameter is requested and the param's execPlan field is set (indicating
 885  * that the param has not yet been evaluated).  This allows lazy evaluation
 886  * of initplans: we don't run the subplan until/unless we need its output.
 887  * Note that this routine MUST clear the execPlan fields of the plan's
 888  * output parameters after evaluating them!
 889  * ----------------------------------------------------------------
 890  */
 891 void
 892 ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
 893 {
 894         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 895         PlanState  *planstate = node->planstate;
 896         SubLinkType subLinkType = subplan->subLinkType;
 897         MemoryContext oldcontext;
 898         TupleTableSlot *slot;
 899         ListCell   *l;
 900         bool            found = false;
 901         ArrayBuildState *astate = NULL;
 902
 903         /*
 904          * Must switch to per-query memory context.
 905          */
 906         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 907
 908         if (subLinkType == ANY_SUBLINK ||
 909                 subLinkType == ALL_SUBLINK)
 910                 elog(ERROR, "ANY/ALL subselect unsupported as initplan");
 911
 912         /*
 913          * By definition, an initplan has no parameters from our query level, but
 914          * it could have some from an outer level.      Rescan it if needed.
 915          */
 916         if (planstate->chgParam != NULL)
 917                 ExecReScan(planstate, NULL);
 918
 919         for (slot = ExecProcNode(planstate);
 920                  !TupIsNull(slot);
 921                  slot = ExecProcNode(planstate))
 922         {
 923                 TupleDesc       tdesc = slot->tts_tupleDescriptor;
 924                 int                     i = 1;
 925
 926                 if (subLinkType == EXISTS_SUBLINK)
 927                 {
 928                         /* There can be only one param... */
 929                         int                     paramid = linitial_int(subplan->setParam);
 930                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 931
 932                         prm->execPlan = NULL;
 933                         prm->value = BoolGetDatum(true);
 934                         prm->isnull = false;
 935                         found = true;
 936                         break;
 937                 }
 938
 939                 if (subLinkType == ARRAY_SUBLINK)
 940                 {
 941                         Datum           dvalue;
 942                         bool            disnull;
 943
 944                         found = true;
 945                         /* stash away current value */
 946                         Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
 947                         dvalue = slot_getattr(slot, 1, &disnull);
 948                         astate = accumArrayResult(astate, dvalue, disnull,
 949                                                                           subplan->firstColType, oldcontext);
 950                         /* keep scanning subplan to collect all values */
 951                         continue;
 952                 }
 953
 954                 if (found &&
 955                         (subLinkType == EXPR_SUBLINK ||
 956                          subLinkType == ROWCOMPARE_SUBLINK))
 957                         ereport(ERROR,
 958                                         (errcode(ERRCODE_CARDINALITY_VIOLATION),
 959                                          errmsg("more than one row returned by a subquery used as an expression")));
 960
 961                 found = true;
 962
 963                 /*
 964                  * We need to copy the subplan's tuple into our own context, in case
 965                  * any of the params are pass-by-ref type --- the pointers stored in
 966                  * the param structs will point at this copied tuple! node->curTuple
 967                  * keeps track of the copied tuple for eventual freeing.
 968                  */
 969                 if (node->curTuple)
 970                         heap_freetuple(node->curTuple);
 971                 node->curTuple = ExecCopySlotTuple(slot);
 972
 973                 /*
 974                  * Now set all the setParam params from the columns of the tuple
 975                  */
 976                 foreach(l, subplan->setParam)
 977                 {
 978                         int                     paramid = lfirst_int(l);
 979                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 980
 981                         prm->execPlan = NULL;
 982                         prm->value = heap_getattr(node->curTuple, i, tdesc,
 983                                                                           &(prm->isnull));
 984                         i++;
 985                 }
 986         }
 987
 988         if (subLinkType == ARRAY_SUBLINK)
 989         {
 990                 /* There can be only one param... */
 991                 int                     paramid = linitial_int(subplan->setParam);
 992                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 993
 994                 prm->execPlan = NULL;
 995                 /* We build the result in query context so it won't disappear */
 996                 if (astate != NULL)
 997                         prm->value = makeArrayResult(astate,
 998                                                                                  econtext->ecxt_per_query_memory);
 999                 else
1000                 {
1001                         MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
1002                         prm->value = PointerGetDatum(construct_empty_array(subplan->firstColType));
1003                 }
1004                 prm->isnull = false;
1005         }
1006         else if (!found)
1007         {
1008                 if (subLinkType == EXISTS_SUBLINK)
1009                 {
1010                         /* There can be only one param... */
1011                         int                     paramid = linitial_int(subplan->setParam);
1012                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1013
1014                         prm->execPlan = NULL;
1015                         prm->value = BoolGetDatum(false);
1016                         prm->isnull = false;
1017                 }
1018                 else
1019                 {
1020                         foreach(l, subplan->setParam)
1021                         {
1022                                 int                     paramid = lfirst_int(l);
1023                                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1024
1025                                 prm->execPlan = NULL;
1026                                 prm->value = (Datum) 0;
1027                                 prm->isnull = true;
1028                         }
1029                 }
1030         }
1031
1032         MemoryContextSwitchTo(oldcontext);
1033 }
1034
1035 /*
1036  * Mark an initplan as needing recalculation
1037  */
1038 void
1039 ExecReScanSetParamPlan(SubPlanState *node, PlanState *parent)
1040 {
1041         PlanState  *planstate = node->planstate;
1042         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
1043         EState     *estate = parent->state;
1044         ListCell   *l;
1045
1046         /* sanity checks */
1047         if (subplan->parParam != NIL)
1048                 elog(ERROR, "direct correlated subquery unsupported as initplan");
1049         if (subplan->setParam == NIL)
1050                 elog(ERROR, "setParam list of initplan is empty");
1051         if (bms_is_empty(planstate->plan->extParam))
1052                 elog(ERROR, "extParam set of initplan is empty");
1053
1054         /*
1055          * Don't actually re-scan: ExecSetParamPlan does it if needed.
1056          */
1057
1058         /*
1059          * Mark this subplan's output parameters as needing recalculation
1060          */
1061         foreach(l, subplan->setParam)
1062         {
1063                 int                     paramid = lfirst_int(l);
1064                 ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
1065
1066                 prm->execPlan = node;
1067                 parent->chgParam = bms_add_member(parent->chgParam, paramid);
1068         }
1069 }