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) 1996-2014, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  * IDENTIFICATION
  10  *        src/backend/executor/nodeSubplan.c
  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 <limits.h>
  22 #include <math.h>
  23
  24 #include "access/htup_details.h"
  25 #include "executor/executor.h"
  26 #include "executor/nodeSubplan.h"
  27 #include "nodes/makefuncs.h"
  28 #include "optimizer/clauses.h"
  29 #include "utils/array.h"
  30 #include "utils/lsyscache.h"
  31 #include "utils/memutils.h"
  32
  33
  34 static Datum ExecSubPlan(SubPlanState *node,
  35                         ExprContext *econtext,
  36                         bool *isNull,
  37                         ExprDoneCond *isDone);
  38 static Datum ExecAlternativeSubPlan(AlternativeSubPlanState *node,
  39                                            ExprContext *econtext,
  40                                            bool *isNull,
  41                                            ExprDoneCond *isDone);
  42 static Datum ExecHashSubPlan(SubPlanState *node,
  43                                 ExprContext *econtext,
  44                                 bool *isNull);
  45 static Datum ExecScanSubPlan(SubPlanState *node,
  46                                 ExprContext *econtext,
  47                                 bool *isNull);
  48 static void buildSubPlanHash(SubPlanState *node, ExprContext *econtext);
  49 static bool findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot,
  50                                  FmgrInfo *eqfunctions);
  51 static bool slotAllNulls(TupleTableSlot *slot);
  52 static bool slotNoNulls(TupleTableSlot *slot);
  53
  54
  55 /* ----------------------------------------------------------------
  56  *              ExecSubPlan
  57  * ----------------------------------------------------------------
  58  */
  59 static Datum
  60 ExecSubPlan(SubPlanState *node,
  61                         ExprContext *econtext,
  62                         bool *isNull,
  63                         ExprDoneCond *isDone)
  64 {
  65         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  66
  67         /* Set default values for result flags: non-null, not a set result */
  68         *isNull = false;
  69         if (isDone)
  70                 *isDone = ExprSingleResult;
  71
  72         /* Sanity checks */
  73         if (subplan->subLinkType == CTE_SUBLINK)
  74                 elog(ERROR, "CTE subplans should not be executed via ExecSubPlan");
  75         if (subplan->setParam != NIL)
  76                 elog(ERROR, "cannot set parent params from subquery");
  77
  78         /* Select appropriate evaluation strategy */
  79         if (subplan->useHashTable)
  80                 return ExecHashSubPlan(node, econtext, isNull);
  81         else
  82                 return ExecScanSubPlan(node, econtext, isNull);
  83 }
  84
  85 /*
  86  * ExecHashSubPlan: store subselect result in an in-memory hash table
  87  */
  88 static Datum
  89 ExecHashSubPlan(SubPlanState *node,
  90                                 ExprContext *econtext,
  91                                 bool *isNull)
  92 {
  93         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  94         PlanState  *planstate = node->planstate;
  95         TupleTableSlot *slot;
  96
  97         /* Shouldn't have any direct correlation Vars */
  98         if (subplan->parParam != NIL || node->args != NIL)
  99                 elog(ERROR, "hashed subplan with direct correlation not supported");
 100
 101         /*
 102          * If first time through or we need to rescan the subplan, build the hash
 103          * table.
 104          */
 105         if (node->hashtable == NULL || planstate->chgParam != NULL)
 106                 buildSubPlanHash(node, econtext);
 107
 108         /*
 109          * The result for an empty subplan is always FALSE; no need to evaluate
 110          * lefthand side.
 111          */
 112         *isNull = false;
 113         if (!node->havehashrows && !node->havenullrows)
 114                 return BoolGetDatum(false);
 115
 116         /*
 117          * Evaluate lefthand expressions and form a projection tuple. First we
 118          * have to set the econtext to use (hack alert!).
 119          */
 120         node->projLeft->pi_exprContext = econtext;
 121         slot = ExecProject(node->projLeft, NULL);
 122
 123         /*
 124          * Note: because we are typically called in a per-tuple context, we have
 125          * to explicitly clear the projected tuple before returning. Otherwise,
 126          * we'll have a double-free situation: the per-tuple context will probably
 127          * be reset before we're called again, and then the tuple slot will think
 128          * it still needs to free the tuple.
 129          */
 130
 131         /*
 132          * If the LHS is all non-null, probe for an exact match in the main hash
 133          * table.  If we find one, the result is TRUE. Otherwise, scan the
 134          * partly-null table to see if there are any rows that aren't provably
 135          * unequal to the LHS; if so, the result is UNKNOWN.  (We skip that part
 136          * if we don't care about UNKNOWN.) Otherwise, the result is FALSE.
 137          *
 138          * Note: the reason we can avoid a full scan of the main hash table is
 139          * that the combining operators are assumed never to yield NULL when both
 140          * inputs are non-null.  If they were to do so, we might need to produce
 141          * UNKNOWN instead of FALSE because of an UNKNOWN result in comparing the
 142          * LHS to some main-table entry --- which is a comparison we will not even
 143          * make, unless there's a chance match of hash keys.
 144          */
 145         if (slotNoNulls(slot))
 146         {
 147                 if (node->havehashrows &&
 148                         FindTupleHashEntry(node->hashtable,
 149                                                            slot,
 150                                                            node->cur_eq_funcs,
 151                                                            node->lhs_hash_funcs) != NULL)
 152                 {
 153                         ExecClearTuple(slot);
 154                         return BoolGetDatum(true);
 155                 }
 156                 if (node->havenullrows &&
 157                         findPartialMatch(node->hashnulls, slot, node->cur_eq_funcs))
 158                 {
 159                         ExecClearTuple(slot);
 160                         *isNull = true;
 161                         return BoolGetDatum(false);
 162                 }
 163                 ExecClearTuple(slot);
 164                 return BoolGetDatum(false);
 165         }
 166
 167         /*
 168          * When the LHS is partly or wholly NULL, we can never return TRUE. If we
 169          * don't care about UNKNOWN, just return FALSE.  Otherwise, if the LHS is
 170          * wholly NULL, immediately return UNKNOWN.  (Since the combining
 171          * operators are strict, the result could only be FALSE if the sub-select
 172          * were empty, but we already handled that case.) Otherwise, we must scan
 173          * both the main and partly-null tables to see if there are any rows that
 174          * aren't provably unequal to the LHS; if so, the result is UNKNOWN.
 175          * Otherwise, the result is FALSE.
 176          */
 177         if (node->hashnulls == NULL)
 178         {
 179                 ExecClearTuple(slot);
 180                 return BoolGetDatum(false);
 181         }
 182         if (slotAllNulls(slot))
 183         {
 184                 ExecClearTuple(slot);
 185                 *isNull = true;
 186                 return BoolGetDatum(false);
 187         }
 188         /* Scan partly-null table first, since more likely to get a match */
 189         if (node->havenullrows &&
 190                 findPartialMatch(node->hashnulls, slot, node->cur_eq_funcs))
 191         {
 192                 ExecClearTuple(slot);
 193                 *isNull = true;
 194                 return BoolGetDatum(false);
 195         }
 196         if (node->havehashrows &&
 197                 findPartialMatch(node->hashtable, slot, node->cur_eq_funcs))
 198         {
 199                 ExecClearTuple(slot);
 200                 *isNull = true;
 201                 return BoolGetDatum(false);
 202         }
 203         ExecClearTuple(slot);
 204         return BoolGetDatum(false);
 205 }
 206
 207 /*
 208  * ExecScanSubPlan: default case where we have to rescan subplan each time
 209  */
 210 static Datum
 211 ExecScanSubPlan(SubPlanState *node,
 212                                 ExprContext *econtext,
 213                                 bool *isNull)
 214 {
 215         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 216         PlanState  *planstate = node->planstate;
 217         SubLinkType subLinkType = subplan->subLinkType;
 218         MemoryContext oldcontext;
 219         TupleTableSlot *slot;
 220         Datum           result;
 221         bool            found = false;  /* TRUE if got at least one subplan tuple */
 222         ListCell   *pvar;
 223         ListCell   *l;
 224         ArrayBuildState *astate = NULL;
 225
 226         /*
 227          * We are probably in a short-lived expression-evaluation context. Switch
 228          * to the per-query context for manipulating the child plan's chgParam,
 229          * calling ExecProcNode on it, etc.
 230          */
 231         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 232
 233         /*
 234          * Set Params of this plan from parent plan correlation values. (Any
 235          * calculation we have to do is done in the parent econtext, since the
 236          * Param values don't need to have per-query lifetime.)
 237          */
 238         Assert(list_length(subplan->parParam) == list_length(node->args));
 239
 240         forboth(l, subplan->parParam, pvar, node->args)
 241         {
 242                 int                     paramid = lfirst_int(l);
 243                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 244
 245                 prm->value = ExecEvalExprSwitchContext((ExprState *) lfirst(pvar),
 246                                                                                            econtext,
 247                                                                                            &(prm->isnull),
 248                                                                                            NULL);
 249                 planstate->chgParam = bms_add_member(planstate->chgParam, paramid);
 250         }
 251
 252         /*
 253          * Now that we've set up its parameters, we can reset the subplan.
 254          */
 255         ExecReScan(planstate);
 256
 257         /*
 258          * For all sublink types except EXPR_SUBLINK and ARRAY_SUBLINK, the result
 259          * is boolean as are the results of the combining operators. We combine
 260          * results across tuples (if the subplan produces more than one) using OR
 261          * semantics for ANY_SUBLINK or AND semantics for ALL_SUBLINK.
 262          * (ROWCOMPARE_SUBLINK doesn't allow multiple tuples from the subplan.)
 263          * NULL results from the combining operators are handled according to the
 264          * usual SQL semantics for OR and AND.  The result for no input tuples is
 265          * FALSE for ANY_SUBLINK, TRUE for ALL_SUBLINK, NULL for
 266          * ROWCOMPARE_SUBLINK.
 267          *
 268          * For EXPR_SUBLINK we require the subplan to produce no more than one
 269          * tuple, else an error is raised.  If zero tuples are produced, we return
 270          * NULL.  Assuming we get a tuple, we just use its first column (there can
 271          * be only one non-junk column in this case).
 272          *
 273          * For ARRAY_SUBLINK we allow the subplan to produce any number of tuples,
 274          * and form an array of the first column's values.  Note in particular
 275          * that we produce a zero-element array if no tuples are produced (this is
 276          * a change from pre-8.3 behavior of returning NULL).
 277          */
 278         result = BoolGetDatum(subLinkType == ALL_SUBLINK);
 279         *isNull = false;
 280
 281         for (slot = ExecProcNode(planstate);
 282                  !TupIsNull(slot);
 283                  slot = ExecProcNode(planstate))
 284         {
 285                 TupleDesc       tdesc = slot->tts_tupleDescriptor;
 286                 Datum           rowresult;
 287                 bool            rownull;
 288                 int                     col;
 289                 ListCell   *plst;
 290
 291                 if (subLinkType == EXISTS_SUBLINK)
 292                 {
 293                         found = true;
 294                         result = BoolGetDatum(true);
 295                         break;
 296                 }
 297
 298                 if (subLinkType == EXPR_SUBLINK)
 299                 {
 300                         /* cannot allow multiple input tuples for EXPR sublink */
 301                         if (found)
 302                                 ereport(ERROR,
 303                                                 (errcode(ERRCODE_CARDINALITY_VIOLATION),
 304                                                  errmsg("more than one row returned by a subquery used as an expression")));
 305                         found = true;
 306
 307                         /*
 308                          * We need to copy the subplan's tuple in case the result is of
 309                          * pass-by-ref type --- our return value will point into this
 310                          * copied tuple!  Can't use the subplan's instance of the tuple
 311                          * since it won't still be valid after next ExecProcNode() call.
 312                          * node->curTuple keeps track of the copied tuple for eventual
 313                          * freeing.
 314                          */
 315                         if (node->curTuple)
 316                                 heap_freetuple(node->curTuple);
 317                         node->curTuple = ExecCopySlotTuple(slot);
 318
 319                         result = heap_getattr(node->curTuple, 1, tdesc, isNull);
 320                         /* keep scanning subplan to make sure there's only one tuple */
 321                         continue;
 322                 }
 323
 324                 if (subLinkType == ARRAY_SUBLINK)
 325                 {
 326                         Datum           dvalue;
 327                         bool            disnull;
 328
 329                         found = true;
 330                         /* stash away current value */
 331                         Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
 332                         dvalue = slot_getattr(slot, 1, &disnull);
 333                         astate = accumArrayResult(astate, dvalue, disnull,
 334                                                                           subplan->firstColType, oldcontext);
 335                         /* keep scanning subplan to collect all values */
 336                         continue;
 337                 }
 338
 339                 /* cannot allow multiple input tuples for ROWCOMPARE sublink either */
 340                 if (subLinkType == ROWCOMPARE_SUBLINK && found)
 341                         ereport(ERROR,
 342                                         (errcode(ERRCODE_CARDINALITY_VIOLATION),
 343                                          errmsg("more than one row returned by a subquery used as an expression")));
 344
 345                 found = true;
 346
 347                 /*
 348                  * For ALL, ANY, and ROWCOMPARE sublinks, load up the Params
 349                  * representing the columns of the sub-select, and then evaluate the
 350                  * combining expression.
 351                  */
 352                 col = 1;
 353                 foreach(plst, subplan->paramIds)
 354                 {
 355                         int                     paramid = lfirst_int(plst);
 356                         ParamExecData *prmdata;
 357
 358                         prmdata = &(econtext->ecxt_param_exec_vals[paramid]);
 359                         Assert(prmdata->execPlan == NULL);
 360                         prmdata->value = slot_getattr(slot, col, &(prmdata->isnull));
 361                         col++;
 362                 }
 363
 364                 rowresult = ExecEvalExprSwitchContext(node->testexpr, econtext,
 365                                                                                           &rownull, NULL);
 366
 367                 if (subLinkType == ANY_SUBLINK)
 368                 {
 369                         /* combine across rows per OR semantics */
 370                         if (rownull)
 371                                 *isNull = true;
 372                         else if (DatumGetBool(rowresult))
 373                         {
 374                                 result = BoolGetDatum(true);
 375                                 *isNull = false;
 376                                 break;                  /* needn't look at any more rows */
 377                         }
 378                 }
 379                 else if (subLinkType == ALL_SUBLINK)
 380                 {
 381                         /* combine across rows per AND semantics */
 382                         if (rownull)
 383                                 *isNull = true;
 384                         else if (!DatumGetBool(rowresult))
 385                         {
 386                                 result = BoolGetDatum(false);
 387                                 *isNull = false;
 388                                 break;                  /* needn't look at any more rows */
 389                         }
 390                 }
 391                 else
 392                 {
 393                         /* must be ROWCOMPARE_SUBLINK */
 394                         result = rowresult;
 395                         *isNull = rownull;
 396                 }
 397         }
 398
 399         MemoryContextSwitchTo(oldcontext);
 400
 401         if (subLinkType == ARRAY_SUBLINK)
 402         {
 403                 /* We return the result in the caller's context */
 404                 if (astate != NULL)
 405                         result = makeArrayResult(astate, oldcontext);
 406                 else
 407                         result = PointerGetDatum(construct_empty_array(subplan->firstColType));
 408         }
 409         else if (!found)
 410         {
 411                 /*
 412                  * deal with empty subplan result.  result/isNull were previously
 413                  * initialized correctly for all sublink types except EXPR and
 414                  * ROWCOMPARE; for those, return NULL.
 415                  */
 416                 if (subLinkType == EXPR_SUBLINK ||
 417                         subLinkType == ROWCOMPARE_SUBLINK)
 418                 {
 419                         result = (Datum) 0;
 420                         *isNull = true;
 421                 }
 422         }
 423
 424         return result;
 425 }
 426
 427 /*
 428  * buildSubPlanHash: load hash table by scanning subplan output.
 429  */
 430 static void
 431 buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
 432 {
 433         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 434         PlanState  *planstate = node->planstate;
 435         int                     ncols = list_length(subplan->paramIds);
 436         ExprContext *innerecontext = node->innerecontext;
 437         MemoryContext oldcontext;
 438         long            nbuckets;
 439         TupleTableSlot *slot;
 440
 441         Assert(subplan->subLinkType == ANY_SUBLINK);
 442
 443         /*
 444          * If we already had any hash tables, destroy 'em; then create empty hash
 445          * table(s).
 446          *
 447          * If we need to distinguish accurately between FALSE and UNKNOWN (i.e.,
 448          * NULL) results of the IN operation, then we have to store subplan output
 449          * rows that are partly or wholly NULL.  We store such rows in a separate
 450          * hash table that we expect will be much smaller than the main table. (We
 451          * can use hashing to eliminate partly-null rows that are not distinct. We
 452          * keep them separate to minimize the cost of the inevitable full-table
 453          * searches; see findPartialMatch.)
 454          *
 455          * If it's not necessary to distinguish FALSE and UNKNOWN, then we don't
 456          * need to store subplan output rows that contain NULL.
 457          */
 458         MemoryContextReset(node->hashtablecxt);
 459         node->hashtable = NULL;
 460         node->hashnulls = NULL;
 461         node->havehashrows = false;
 462         node->havenullrows = false;
 463
 464         nbuckets = (long) Min(planstate->plan->plan_rows, (double) LONG_MAX);
 465         if (nbuckets < 1)
 466                 nbuckets = 1;
 467
 468         node->hashtable = BuildTupleHashTable(ncols,
 469                                                                                   node->keyColIdx,
 470                                                                                   node->tab_eq_funcs,
 471                                                                                   node->tab_hash_funcs,
 472                                                                                   nbuckets,
 473                                                                                   sizeof(TupleHashEntryData),
 474                                                                                   node->hashtablecxt,
 475                                                                                   node->hashtempcxt);
 476
 477         if (!subplan->unknownEqFalse)
 478         {
 479                 if (ncols == 1)
 480                         nbuckets = 1;           /* there can only be one entry */
 481                 else
 482                 {
 483                         nbuckets /= 16;
 484                         if (nbuckets < 1)
 485                                 nbuckets = 1;
 486                 }
 487                 node->hashnulls = BuildTupleHashTable(ncols,
 488                                                                                           node->keyColIdx,
 489                                                                                           node->tab_eq_funcs,
 490                                                                                           node->tab_hash_funcs,
 491                                                                                           nbuckets,
 492                                                                                           sizeof(TupleHashEntryData),
 493                                                                                           node->hashtablecxt,
 494                                                                                           node->hashtempcxt);
 495         }
 496
 497         /*
 498          * We are probably in a short-lived expression-evaluation context. Switch
 499          * to the per-query context for manipulating the child plan.
 500          */
 501         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 502
 503         /*
 504          * Reset subplan to start.
 505          */
 506         ExecReScan(planstate);
 507
 508         /*
 509          * Scan the subplan and load the hash table(s).  Note that when there are
 510          * duplicate rows coming out of the sub-select, only one copy is stored.
 511          */
 512         for (slot = ExecProcNode(planstate);
 513                  !TupIsNull(slot);
 514                  slot = ExecProcNode(planstate))
 515         {
 516                 int                     col = 1;
 517                 ListCell   *plst;
 518                 bool            isnew;
 519
 520                 /*
 521                  * Load up the Params representing the raw sub-select outputs, then
 522                  * form the projection tuple to store in the hashtable.
 523                  */
 524                 foreach(plst, subplan->paramIds)
 525                 {
 526                         int                     paramid = lfirst_int(plst);
 527                         ParamExecData *prmdata;
 528
 529                         prmdata = &(innerecontext->ecxt_param_exec_vals[paramid]);
 530                         Assert(prmdata->execPlan == NULL);
 531                         prmdata->value = slot_getattr(slot, col,
 532                                                                                   &(prmdata->isnull));
 533                         col++;
 534                 }
 535                 slot = ExecProject(node->projRight, NULL);
 536
 537                 /*
 538                  * If result contains any nulls, store separately or not at all.
 539                  */
 540                 if (slotNoNulls(slot))
 541                 {
 542                         (void) LookupTupleHashEntry(node->hashtable, slot, &isnew);
 543                         node->havehashrows = true;
 544                 }
 545                 else if (node->hashnulls)
 546                 {
 547                         (void) LookupTupleHashEntry(node->hashnulls, slot, &isnew);
 548                         node->havenullrows = true;
 549                 }
 550
 551                 /*
 552                  * Reset innerecontext after each inner tuple to free any memory used
 553                  * during ExecProject.
 554                  */
 555                 ResetExprContext(innerecontext);
 556         }
 557
 558         /*
 559          * Since the projected tuples are in the sub-query's context and not the
 560          * main context, we'd better clear the tuple slot before there's any
 561          * chance of a reset of the sub-query's context.  Else we will have the
 562          * potential for a double free attempt.  (XXX possibly no longer needed,
 563          * but can't hurt.)
 564          */
 565         ExecClearTuple(node->projRight->pi_slot);
 566
 567         MemoryContextSwitchTo(oldcontext);
 568 }
 569
 570 /*
 571  * findPartialMatch: does the hashtable contain an entry that is not
 572  * provably distinct from the tuple?
 573  *
 574  * We have to scan the whole hashtable; we can't usefully use hashkeys
 575  * to guide probing, since we might get partial matches on tuples with
 576  * hashkeys quite unrelated to what we'd get from the given tuple.
 577  *
 578  * Caller must provide the equality functions to use, since in cross-type
 579  * cases these are different from the hashtable's internal functions.
 580  */
 581 static bool
 582 findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot,
 583                                  FmgrInfo *eqfunctions)
 584 {
 585         int                     numCols = hashtable->numCols;
 586         AttrNumber *keyColIdx = hashtable->keyColIdx;
 587         TupleHashIterator hashiter;
 588         TupleHashEntry entry;
 589
 590         InitTupleHashIterator(hashtable, &hashiter);
 591         while ((entry = ScanTupleHashTable(&hashiter)) != NULL)
 592         {
 593                 ExecStoreMinimalTuple(entry->firstTuple, hashtable->tableslot, false);
 594                 if (!execTuplesUnequal(slot, hashtable->tableslot,
 595                                                            numCols, keyColIdx,
 596                                                            eqfunctions,
 597                                                            hashtable->tempcxt))
 598                 {
 599                         TermTupleHashIterator(&hashiter);
 600                         return true;
 601                 }
 602         }
 603         /* No TermTupleHashIterator call needed here */
 604         return false;
 605 }
 606
 607 /*
 608  * slotAllNulls: is the slot completely NULL?
 609  *
 610  * This does not test for dropped columns, which is OK because we only
 611  * use it on projected tuples.
 612  */
 613 static bool
 614 slotAllNulls(TupleTableSlot *slot)
 615 {
 616         int                     ncols = slot->tts_tupleDescriptor->natts;
 617         int                     i;
 618
 619         for (i = 1; i <= ncols; i++)
 620         {
 621                 if (!slot_attisnull(slot, i))
 622                         return false;
 623         }
 624         return true;
 625 }
 626
 627 /*
 628  * slotNoNulls: is the slot entirely not NULL?
 629  *
 630  * This does not test for dropped columns, which is OK because we only
 631  * use it on projected tuples.
 632  */
 633 static bool
 634 slotNoNulls(TupleTableSlot *slot)
 635 {
 636         int                     ncols = slot->tts_tupleDescriptor->natts;
 637         int                     i;
 638
 639         for (i = 1; i <= ncols; i++)
 640         {
 641                 if (slot_attisnull(slot, i))
 642                         return false;
 643         }
 644         return true;
 645 }
 646
 647 /* ----------------------------------------------------------------
 648  *              ExecInitSubPlan
 649  *
 650  * Create a SubPlanState for a SubPlan; this is the SubPlan-specific part
 651  * of ExecInitExpr().  We split it out so that it can be used for InitPlans
 652  * as well as regular SubPlans.  Note that we don't link the SubPlan into
 653  * the parent's subPlan list, because that shouldn't happen for InitPlans.
 654  * Instead, ExecInitExpr() does that one part.
 655  * ----------------------------------------------------------------
 656  */
 657 SubPlanState *
 658 ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
 659 {
 660         SubPlanState *sstate = makeNode(SubPlanState);
 661         EState     *estate = parent->state;
 662
 663         sstate->xprstate.evalfunc = (ExprStateEvalFunc) ExecSubPlan;
 664         sstate->xprstate.expr = (Expr *) subplan;
 665
 666         /* Link the SubPlanState to already-initialized subplan */
 667         sstate->planstate = (PlanState *) list_nth(estate->es_subplanstates,
 668                                                                                            subplan->plan_id - 1);
 669
 670         /* Initialize subexpressions */
 671         sstate->testexpr = ExecInitExpr((Expr *) subplan->testexpr, parent);
 672         sstate->args = (List *) ExecInitExpr((Expr *) subplan->args, parent);
 673
 674         /*
 675          * initialize my state
 676          */
 677         sstate->curTuple = NULL;
 678         sstate->curArray = PointerGetDatum(NULL);
 679         sstate->projLeft = NULL;
 680         sstate->projRight = NULL;
 681         sstate->hashtable = NULL;
 682         sstate->hashnulls = NULL;
 683         sstate->hashtablecxt = NULL;
 684         sstate->hashtempcxt = NULL;
 685         sstate->innerecontext = NULL;
 686         sstate->keyColIdx = NULL;
 687         sstate->tab_hash_funcs = NULL;
 688         sstate->tab_eq_funcs = NULL;
 689         sstate->lhs_hash_funcs = NULL;
 690         sstate->cur_eq_funcs = NULL;
 691
 692         /*
 693          * If this plan is un-correlated or undirect correlated one and want to
 694          * set params for parent plan then mark parameters as needing evaluation.
 695          *
 696          * A CTE subplan's output parameter is never to be evaluated in the normal
 697          * way, so skip this in that case.
 698          *
 699          * Note that in the case of un-correlated subqueries we don't care about
 700          * setting parent->chgParam here: indices take care about it, for others -
 701          * it doesn't matter...
 702          */
 703         if (subplan->setParam != NIL && subplan->subLinkType != CTE_SUBLINK)
 704         {
 705                 ListCell   *lst;
 706
 707                 foreach(lst, subplan->setParam)
 708                 {
 709                         int                     paramid = lfirst_int(lst);
 710                         ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
 711
 712                         prm->execPlan = sstate;
 713                 }
 714         }
 715
 716         /*
 717          * If we are going to hash the subquery output, initialize relevant stuff.
 718          * (We don't create the hashtable until needed, though.)
 719          */
 720         if (subplan->useHashTable)
 721         {
 722                 int                     ncols,
 723                                         i;
 724                 TupleDesc       tupDesc;
 725                 TupleTableSlot *slot;
 726                 List       *oplist,
 727                                    *lefttlist,
 728                                    *righttlist,
 729                                    *leftptlist,
 730                                    *rightptlist;
 731                 ListCell   *l;
 732
 733                 /* We need a memory context to hold the hash table(s) */
 734                 sstate->hashtablecxt =
 735                         AllocSetContextCreate(CurrentMemoryContext,
 736                                                                   "Subplan HashTable Context",
 737                                                                   ALLOCSET_DEFAULT_MINSIZE,
 738                                                                   ALLOCSET_DEFAULT_INITSIZE,
 739                                                                   ALLOCSET_DEFAULT_MAXSIZE);
 740                 /* and a small one for the hash tables to use as temp storage */
 741                 sstate->hashtempcxt =
 742                         AllocSetContextCreate(CurrentMemoryContext,
 743                                                                   "Subplan HashTable Temp Context",
 744                                                                   ALLOCSET_SMALL_MINSIZE,
 745                                                                   ALLOCSET_SMALL_INITSIZE,
 746                                                                   ALLOCSET_SMALL_MAXSIZE);
 747                 /* and a short-lived exprcontext for function evaluation */
 748                 sstate->innerecontext = CreateExprContext(estate);
 749                 /* Silly little array of column numbers 1..n */
 750                 ncols = list_length(subplan->paramIds);
 751                 sstate->keyColIdx = (AttrNumber *) palloc(ncols * sizeof(AttrNumber));
 752                 for (i = 0; i < ncols; i++)
 753                         sstate->keyColIdx[i] = i + 1;
 754
 755                 /*
 756                  * We use ExecProject to evaluate the lefthand and righthand
 757                  * expression lists and form tuples.  (You might think that we could
 758                  * use the sub-select's output tuples directly, but that is not the
 759                  * case if we had to insert any run-time coercions of the sub-select's
 760                  * output datatypes; anyway this avoids storing any resjunk columns
 761                  * that might be in the sub-select's output.) Run through the
 762                  * combining expressions to build tlists for the lefthand and
 763                  * righthand sides.  We need both the ExprState list (for ExecProject)
 764                  * and the underlying parse Exprs (for ExecTypeFromTL).
 765                  *
 766                  * We also extract the combining operators themselves to initialize
 767                  * the equality and hashing functions for the hash tables.
 768                  */
 769                 if (IsA(sstate->testexpr->expr, OpExpr))
 770                 {
 771                         /* single combining operator */
 772                         oplist = list_make1(sstate->testexpr);
 773                 }
 774                 else if (and_clause((Node *) sstate->testexpr->expr))
 775                 {
 776                         /* multiple combining operators */
 777                         Assert(IsA(sstate->testexpr, BoolExprState));
 778                         oplist = ((BoolExprState *) sstate->testexpr)->args;
 779                 }
 780                 else
 781                 {
 782                         /* shouldn't see anything else in a hashable subplan */
 783                         elog(ERROR, "unrecognized testexpr type: %d",
 784                                  (int) nodeTag(sstate->testexpr->expr));
 785                         oplist = NIL;           /* keep compiler quiet */
 786                 }
 787                 Assert(list_length(oplist) == ncols);
 788
 789                 lefttlist = righttlist = NIL;
 790                 leftptlist = rightptlist = NIL;
 791                 sstate->tab_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 792                 sstate->tab_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 793                 sstate->lhs_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 794                 sstate->cur_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 795                 i = 1;
 796                 foreach(l, oplist)
 797                 {
 798                         FuncExprState *fstate = (FuncExprState *) lfirst(l);
 799                         OpExpr     *opexpr = (OpExpr *) fstate->xprstate.expr;
 800                         ExprState  *exstate;
 801                         Expr       *expr;
 802                         TargetEntry *tle;
 803                         GenericExprState *tlestate;
 804                         Oid                     rhs_eq_oper;
 805                         Oid                     left_hashfn;
 806                         Oid                     right_hashfn;
 807
 808                         Assert(IsA(fstate, FuncExprState));
 809                         Assert(IsA(opexpr, OpExpr));
 810                         Assert(list_length(fstate->args) == 2);
 811
 812                         /* Process lefthand argument */
 813                         exstate = (ExprState *) linitial(fstate->args);
 814                         expr = exstate->expr;
 815                         tle = makeTargetEntry(expr,
 816                                                                   i,
 817                                                                   NULL,
 818                                                                   false);
 819                         tlestate = makeNode(GenericExprState);
 820                         tlestate->xprstate.expr = (Expr *) tle;
 821                         tlestate->xprstate.evalfunc = NULL;
 822                         tlestate->arg = exstate;
 823                         lefttlist = lappend(lefttlist, tlestate);
 824                         leftptlist = lappend(leftptlist, tle);
 825
 826                         /* Process righthand argument */
 827                         exstate = (ExprState *) lsecond(fstate->args);
 828                         expr = exstate->expr;
 829                         tle = makeTargetEntry(expr,
 830                                                                   i,
 831                                                                   NULL,
 832                                                                   false);
 833                         tlestate = makeNode(GenericExprState);
 834                         tlestate->xprstate.expr = (Expr *) tle;
 835                         tlestate->xprstate.evalfunc = NULL;
 836                         tlestate->arg = exstate;
 837                         righttlist = lappend(righttlist, tlestate);
 838                         rightptlist = lappend(rightptlist, tle);
 839
 840                         /* Lookup the equality function (potentially cross-type) */
 841                         fmgr_info(opexpr->opfuncid, &sstate->cur_eq_funcs[i - 1]);
 842                         fmgr_info_set_expr((Node *) opexpr, &sstate->cur_eq_funcs[i - 1]);
 843
 844                         /* Look up the equality function for the RHS type */
 845                         if (!get_compatible_hash_operators(opexpr->opno,
 846                                                                                            NULL, &rhs_eq_oper))
 847                                 elog(ERROR, "could not find compatible hash operator for operator %u",
 848                                          opexpr->opno);
 849                         fmgr_info(get_opcode(rhs_eq_oper), &sstate->tab_eq_funcs[i - 1]);
 850
 851                         /* Lookup the associated hash functions */
 852                         if (!get_op_hash_functions(opexpr->opno,
 853                                                                            &left_hashfn, &right_hashfn))
 854                                 elog(ERROR, "could not find hash function for hash operator %u",
 855                                          opexpr->opno);
 856                         fmgr_info(left_hashfn, &sstate->lhs_hash_funcs[i - 1]);
 857                         fmgr_info(right_hashfn, &sstate->tab_hash_funcs[i - 1]);
 858
 859                         i++;
 860                 }
 861
 862                 /*
 863                  * Construct tupdescs, slots and projection nodes for left and right
 864                  * sides.  The lefthand expressions will be evaluated in the parent
 865                  * plan node's exprcontext, which we don't have access to here.
 866                  * Fortunately we can just pass NULL for now and fill it in later
 867                  * (hack alert!).  The righthand expressions will be evaluated in our
 868                  * own innerecontext.
 869                  */
 870                 tupDesc = ExecTypeFromTL(leftptlist, false);
 871                 slot = ExecInitExtraTupleSlot(estate);
 872                 ExecSetSlotDescriptor(slot, tupDesc);
 873                 sstate->projLeft = ExecBuildProjectionInfo(lefttlist,
 874                                                                                                    NULL,
 875                                                                                                    slot,
 876                                                                                                    NULL);
 877
 878                 tupDesc = ExecTypeFromTL(rightptlist, false);
 879                 slot = ExecInitExtraTupleSlot(estate);
 880                 ExecSetSlotDescriptor(slot, tupDesc);
 881                 sstate->projRight = ExecBuildProjectionInfo(righttlist,
 882                                                                                                         sstate->innerecontext,
 883                                                                                                         slot,
 884                                                                                                         NULL);
 885         }
 886
 887         return sstate;
 888 }
 889
 890 /* ----------------------------------------------------------------
 891  *              ExecSetParamPlan
 892  *
 893  *              Executes an InitPlan subplan and sets its output parameters.
 894  *
 895  * This is called from ExecEvalParamExec() when the value of a PARAM_EXEC
 896  * parameter is requested and the param's execPlan field is set (indicating
 897  * that the param has not yet been evaluated).  This allows lazy evaluation
 898  * of initplans: we don't run the subplan until/unless we need its output.
 899  * Note that this routine MUST clear the execPlan fields of the plan's
 900  * output parameters after evaluating them!
 901  * ----------------------------------------------------------------
 902  */
 903 void
 904 ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
 905 {
 906         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 907         PlanState  *planstate = node->planstate;
 908         SubLinkType subLinkType = subplan->subLinkType;
 909         MemoryContext oldcontext;
 910         TupleTableSlot *slot;
 911         ListCell   *l;
 912         bool            found = false;
 913         ArrayBuildState *astate = NULL;
 914
 915         if (subLinkType == ANY_SUBLINK ||
 916                 subLinkType == ALL_SUBLINK)
 917                 elog(ERROR, "ANY/ALL subselect unsupported as initplan");
 918         if (subLinkType == CTE_SUBLINK)
 919                 elog(ERROR, "CTE subplans should not be executed via ExecSetParamPlan");
 920
 921         /*
 922          * Must switch to per-query memory context.
 923          */
 924         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 925
 926         /*
 927          * Run the plan.  (If it needs to be rescanned, the first ExecProcNode
 928          * call will take care of that.)
 929          */
 930         for (slot = ExecProcNode(planstate);
 931                  !TupIsNull(slot);
 932                  slot = ExecProcNode(planstate))
 933         {
 934                 TupleDesc       tdesc = slot->tts_tupleDescriptor;
 935                 int                     i = 1;
 936
 937                 if (subLinkType == EXISTS_SUBLINK)
 938                 {
 939                         /* There can be only one setParam... */
 940                         int                     paramid = linitial_int(subplan->setParam);
 941                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 942
 943                         prm->execPlan = NULL;
 944                         prm->value = BoolGetDatum(true);
 945                         prm->isnull = false;
 946                         found = true;
 947                         break;
 948                 }
 949
 950                 if (subLinkType == ARRAY_SUBLINK)
 951                 {
 952                         Datum           dvalue;
 953                         bool            disnull;
 954
 955                         found = true;
 956                         /* stash away current value */
 957                         Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
 958                         dvalue = slot_getattr(slot, 1, &disnull);
 959                         astate = accumArrayResult(astate, dvalue, disnull,
 960                                                                           subplan->firstColType, oldcontext);
 961                         /* keep scanning subplan to collect all values */
 962                         continue;
 963                 }
 964
 965                 if (found &&
 966                         (subLinkType == EXPR_SUBLINK ||
 967                          subLinkType == ROWCOMPARE_SUBLINK))
 968                         ereport(ERROR,
 969                                         (errcode(ERRCODE_CARDINALITY_VIOLATION),
 970                                          errmsg("more than one row returned by a subquery used as an expression")));
 971
 972                 found = true;
 973
 974                 /*
 975                  * We need to copy the subplan's tuple into our own context, in case
 976                  * any of the params are pass-by-ref type --- the pointers stored in
 977                  * the param structs will point at this copied tuple! node->curTuple
 978                  * keeps track of the copied tuple for eventual freeing.
 979                  */
 980                 if (node->curTuple)
 981                         heap_freetuple(node->curTuple);
 982                 node->curTuple = ExecCopySlotTuple(slot);
 983
 984                 /*
 985                  * Now set all the setParam params from the columns of the tuple
 986                  */
 987                 foreach(l, subplan->setParam)
 988                 {
 989                         int                     paramid = lfirst_int(l);
 990                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 991
 992                         prm->execPlan = NULL;
 993                         prm->value = heap_getattr(node->curTuple, i, tdesc,
 994                                                                           &(prm->isnull));
 995                         i++;
 996                 }
 997         }
 998
 999         if (subLinkType == ARRAY_SUBLINK)
1000         {
1001                 /* There can be only one setParam... */
1002                 int                     paramid = linitial_int(subplan->setParam);
1003                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1004
1005                 /*
1006                  * We build the result array in query context so it won't disappear;
1007                  * to avoid leaking memory across repeated calls, we have to remember
1008                  * the latest value, much as for curTuple above.
1009                  */
1010                 if (node->curArray != PointerGetDatum(NULL))
1011                         pfree(DatumGetPointer(node->curArray));
1012                 if (astate != NULL)
1013                         node->curArray = makeArrayResult(astate,
1014                                                                                          econtext->ecxt_per_query_memory);
1015                 else
1016                 {
1017                         MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
1018                         node->curArray = PointerGetDatum(construct_empty_array(subplan->firstColType));
1019                 }
1020                 prm->execPlan = NULL;
1021                 prm->value = node->curArray;
1022                 prm->isnull = false;
1023         }
1024         else if (!found)
1025         {
1026                 if (subLinkType == EXISTS_SUBLINK)
1027                 {
1028                         /* There can be only one setParam... */
1029                         int                     paramid = linitial_int(subplan->setParam);
1030                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1031
1032                         prm->execPlan = NULL;
1033                         prm->value = BoolGetDatum(false);
1034                         prm->isnull = false;
1035                 }
1036                 else
1037                 {
1038                         foreach(l, subplan->setParam)
1039                         {
1040                                 int                     paramid = lfirst_int(l);
1041                                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1042
1043                                 prm->execPlan = NULL;
1044                                 prm->value = (Datum) 0;
1045                                 prm->isnull = true;
1046                         }
1047                 }
1048         }
1049
1050         MemoryContextSwitchTo(oldcontext);
1051 }
1052
1053 /*
1054  * Mark an initplan as needing recalculation
1055  */
1056 void
1057 ExecReScanSetParamPlan(SubPlanState *node, PlanState *parent)
1058 {
1059         PlanState  *planstate = node->planstate;
1060         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
1061         EState     *estate = parent->state;
1062         ListCell   *l;
1063
1064         /* sanity checks */
1065         if (subplan->parParam != NIL)
1066                 elog(ERROR, "direct correlated subquery unsupported as initplan");
1067         if (subplan->setParam == NIL)
1068                 elog(ERROR, "setParam list of initplan is empty");
1069         if (bms_is_empty(planstate->plan->extParam))
1070                 elog(ERROR, "extParam set of initplan is empty");
1071
1072         /*
1073          * Don't actually re-scan: it'll happen inside ExecSetParamPlan if needed.
1074          */
1075
1076         /*
1077          * Mark this subplan's output parameters as needing recalculation.
1078          *
1079          * CTE subplans are never executed via parameter recalculation; instead
1080          * they get run when called by nodeCtescan.c.  So don't mark the output
1081          * parameter of a CTE subplan as dirty, but do set the chgParam bit for it
1082          * so that dependent plan nodes will get told to rescan.
1083          */
1084         foreach(l, subplan->setParam)
1085         {
1086                 int                     paramid = lfirst_int(l);
1087                 ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
1088
1089                 if (subplan->subLinkType != CTE_SUBLINK)
1090                         prm->execPlan = node;
1091
1092                 parent->chgParam = bms_add_member(parent->chgParam, paramid);
1093         }
1094 }
1095
1096
1097 /*
1098  * ExecInitAlternativeSubPlan
1099  *
1100  * Initialize for execution of one of a set of alternative subplans.
1101  */
1102 AlternativeSubPlanState *
1103 ExecInitAlternativeSubPlan(AlternativeSubPlan *asplan, PlanState *parent)
1104 {
1105         AlternativeSubPlanState *asstate = makeNode(AlternativeSubPlanState);
1106         double          num_calls;
1107         SubPlan    *subplan1;
1108         SubPlan    *subplan2;
1109         Cost            cost1;
1110         Cost            cost2;
1111
1112         asstate->xprstate.evalfunc = (ExprStateEvalFunc) ExecAlternativeSubPlan;
1113         asstate->xprstate.expr = (Expr *) asplan;
1114
1115         /*
1116          * Initialize subplans.  (Can we get away with only initializing the one
1117          * we're going to use?)
1118          */
1119         asstate->subplans = (List *) ExecInitExpr((Expr *) asplan->subplans,
1120                                                                                           parent);
1121
1122         /*
1123          * Select the one to be used.  For this, we need an estimate of the number
1124          * of executions of the subplan.  We use the number of output rows
1125          * expected from the parent plan node.  This is a good estimate if we are
1126          * in the parent's targetlist, and an underestimate (but probably not by
1127          * more than a factor of 2) if we are in the qual.
1128          */
1129         num_calls = parent->plan->plan_rows;
1130
1131         /*
1132          * The planner saved enough info so that we don't have to work very hard
1133          * to estimate the total cost, given the number-of-calls estimate.
1134          */
1135         Assert(list_length(asplan->subplans) == 2);
1136         subplan1 = (SubPlan *) linitial(asplan->subplans);
1137         subplan2 = (SubPlan *) lsecond(asplan->subplans);
1138
1139         cost1 = subplan1->startup_cost + num_calls * subplan1->per_call_cost;
1140         cost2 = subplan2->startup_cost + num_calls * subplan2->per_call_cost;
1141
1142         if (cost1 < cost2)
1143                 asstate->active = 0;
1144         else
1145                 asstate->active = 1;
1146
1147         return asstate;
1148 }
1149
1150 /*
1151  * ExecAlternativeSubPlan
1152  *
1153  * Execute one of a set of alternative subplans.
1154  *
1155  * Note: in future we might consider changing to different subplans on the
1156  * fly, in case the original rowcount estimate turns out to be way off.
1157  */
1158 static Datum
1159 ExecAlternativeSubPlan(AlternativeSubPlanState *node,
1160                                            ExprContext *econtext,
1161                                            bool *isNull,
1162                                            ExprDoneCond *isDone)
1163 {
1164         /* Just pass control to the active subplan */
1165         SubPlanState *activesp = (SubPlanState *) list_nth(node->subplans,
1166                                                                                                            node->active);
1167
1168         Assert(IsA(activesp, SubPlanState));
1169
1170         return ExecSubPlan(activesp,
1171                                            econtext,
1172                                            isNull,
1173                                            isDone);
1174 }