src/backend/executor/nodeSubplan.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * nodeSubplan.c
   4  *        routines to support subselects
   5  *
   6  * Portions Copyright (c) 1996-2011, 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 <math.h>
  22
  23 #include "executor/executor.h"
  24 #include "executor/nodeSubplan.h"
  25 #include "nodes/makefuncs.h"
  26 #include "optimizer/clauses.h"
  27 #include "utils/array.h"
  28 #include "utils/lsyscache.h"
  29 #include "utils/memutils.h"
  30
  31
  32 static Datum ExecSubPlan(SubPlanState *node,
  33                         ExprContext *econtext,
  34                         bool *isNull,
  35                         ExprDoneCond *isDone);
  36 static Datum ExecAlternativeSubPlan(AlternativeSubPlanState *node,
  37                                            ExprContext *econtext,
  38                                            bool *isNull,
  39                                            ExprDoneCond *isDone);
  40 static Datum ExecHashSubPlan(SubPlanState *node,
  41                                 ExprContext *econtext,
  42                                 bool *isNull);
  43 static Datum ExecScanSubPlan(SubPlanState *node,
  44                                 ExprContext *econtext,
  45                                 bool *isNull);
  46 static void buildSubPlanHash(SubPlanState *node, ExprContext *econtext);
  47 static bool findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot);
  48 static bool slotAllNulls(TupleTableSlot *slot);
  49 static bool slotNoNulls(TupleTableSlot *slot);
  50
  51
  52 /* ----------------------------------------------------------------
  53  *              ExecSubPlan
  54  * ----------------------------------------------------------------
  55  */
  56 static Datum
  57 ExecSubPlan(SubPlanState *node,
  58                         ExprContext *econtext,
  59                         bool *isNull,
  60                         ExprDoneCond *isDone)
  61 {
  62         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  63
  64         /* Set default values for result flags: non-null, not a set result */
  65         *isNull = false;
  66         if (isDone)
  67                 *isDone = ExprSingleResult;
  68
  69         /* Sanity checks */
  70         if (subplan->subLinkType == CTE_SUBLINK)
  71                 elog(ERROR, "CTE subplans should not be executed via ExecSubPlan");
  72         if (subplan->setParam != NIL)
  73                 elog(ERROR, "cannot set parent params from subquery");
  74
  75         /* Select appropriate evaluation strategy */
  76         if (subplan->useHashTable)
  77                 return ExecHashSubPlan(node, econtext, isNull);
  78         else
  79                 return ExecScanSubPlan(node, econtext, isNull);
  80 }
  81
  82 /*
  83  * ExecHashSubPlan: store subselect result in an in-memory hash table
  84  */
  85 static Datum
  86 ExecHashSubPlan(SubPlanState *node,
  87                                 ExprContext *econtext,
  88                                 bool *isNull)
  89 {
  90         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  91         PlanState  *planstate = node->planstate;
  92         TupleTableSlot *slot;
  93
  94         /* Shouldn't have any direct correlation Vars */
  95         if (subplan->parParam != NIL || node->args != NIL)
  96                 elog(ERROR, "hashed subplan with direct correlation not supported");
  97
  98         /*
  99          * If first time through or we need to rescan the subplan, build the hash
 100          * table.
 101          */
 102         if (node->hashtable == NULL || planstate->chgParam != NULL)
 103                 buildSubPlanHash(node, econtext);
 104
 105         /*
 106          * The result for an empty subplan is always FALSE; no need to evaluate
 107          * lefthand side.
 108          */
 109         *isNull = false;
 110         if (!node->havehashrows && !node->havenullrows)
 111                 return BoolGetDatum(false);
 112
 113         /*
 114          * Evaluate lefthand expressions and form a projection tuple. First we
 115          * have to set the econtext to use (hack alert!).
 116          */
 117         node->projLeft->pi_exprContext = econtext;
 118         slot = ExecProject(node->projLeft, NULL);
 119
 120         /*
 121          * Note: because we are typically called in a per-tuple context, we have
 122          * to explicitly clear the projected tuple before returning. Otherwise,
 123          * we'll have a double-free situation: the per-tuple context will probably
 124          * be reset before we're called again, and then the tuple slot will think
 125          * it still needs to free the tuple.
 126          */
 127
 128         /*
 129          * If the LHS is all non-null, probe for an exact match in the main hash
 130          * table.  If we find one, the result is TRUE. Otherwise, scan the
 131          * partly-null table to see if there are any rows that aren't provably
 132          * unequal to the LHS; if so, the result is UNKNOWN.  (We skip that part
 133          * if we don't care about UNKNOWN.) Otherwise, the result is FALSE.
 134          *
 135          * Note: the reason we can avoid a full scan of the main hash table is
 136          * that the combining operators are assumed never to yield NULL when both
 137          * inputs are non-null.  If they were to do so, we might need to produce
 138          * UNKNOWN instead of FALSE because of an UNKNOWN result in comparing the
 139          * LHS to some main-table entry --- which is a comparison we will not even
 140          * make, unless there's a chance match of hash keys.
 141          */
 142         if (slotNoNulls(slot))
 143         {
 144                 if (node->havehashrows &&
 145                         FindTupleHashEntry(node->hashtable,
 146                                                            slot,
 147                                                            node->cur_eq_funcs,
 148                                                            node->lhs_hash_funcs) != NULL)
 149                 {
 150                         ExecClearTuple(slot);
 151                         return BoolGetDatum(true);
 152                 }
 153                 if (node->havenullrows &&
 154                         findPartialMatch(node->hashnulls, slot))
 155                 {
 156                         ExecClearTuple(slot);
 157                         *isNull = true;
 158                         return BoolGetDatum(false);
 159                 }
 160                 ExecClearTuple(slot);
 161                 return BoolGetDatum(false);
 162         }
 163
 164         /*
 165          * When the LHS is partly or wholly NULL, we can never return TRUE. If we
 166          * don't care about UNKNOWN, just return FALSE.  Otherwise, if the LHS is
 167          * wholly NULL, immediately return UNKNOWN.  (Since the combining
 168          * operators are strict, the result could only be FALSE if the sub-select
 169          * were empty, but we already handled that case.) Otherwise, we must scan
 170          * both the main and partly-null tables to see if there are any rows that
 171          * aren't provably unequal to the LHS; if so, the result is UNKNOWN.
 172          * Otherwise, the result is FALSE.
 173          */
 174         if (node->hashnulls == NULL)
 175         {
 176                 ExecClearTuple(slot);
 177                 return BoolGetDatum(false);
 178         }
 179         if (slotAllNulls(slot))
 180         {
 181                 ExecClearTuple(slot);
 182                 *isNull = true;
 183                 return BoolGetDatum(false);
 184         }
 185         /* Scan partly-null table first, since more likely to get a match */
 186         if (node->havenullrows &&
 187                 findPartialMatch(node->hashnulls, slot))
 188         {
 189                 ExecClearTuple(slot);
 190                 *isNull = true;
 191                 return BoolGetDatum(false);
 192         }
 193         if (node->havehashrows &&
 194                 findPartialMatch(node->hashtable, slot))
 195         {
 196                 ExecClearTuple(slot);
 197                 *isNull = true;
 198                 return BoolGetDatum(false);
 199         }
 200         ExecClearTuple(slot);
 201         return BoolGetDatum(false);
 202 }
 203
 204 /*
 205  * ExecScanSubPlan: default case where we have to rescan subplan each time
 206  */
 207 static Datum
 208 ExecScanSubPlan(SubPlanState *node,
 209                                 ExprContext *econtext,
 210                                 bool *isNull)
 211 {
 212         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 213         PlanState  *planstate = node->planstate;
 214         SubLinkType subLinkType = subplan->subLinkType;
 215         MemoryContext oldcontext;
 216         TupleTableSlot *slot;
 217         Datum           result;
 218         bool            found = false;  /* TRUE if got at least one subplan tuple */
 219         ListCell   *pvar;
 220         ListCell   *l;
 221         ArrayBuildState *astate = NULL;
 222
 223         /*
 224          * We are probably in a short-lived expression-evaluation context. Switch
 225          * to the per-query context for manipulating the child plan's chgParam,
 226          * calling ExecProcNode on it, etc.
 227          */
 228         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 229
 230         /*
 231          * Set Params of this plan from parent plan correlation values. (Any
 232          * calculation we have to do is done in the parent econtext, since the
 233          * Param values don't need to have per-query lifetime.)
 234          */
 235         Assert(list_length(subplan->parParam) == list_length(node->args));
 236
 237         forboth(l, subplan->parParam, pvar, node->args)
 238         {
 239                 int                     paramid = lfirst_int(l);
 240                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 241
 242                 prm->value = ExecEvalExprSwitchContext((ExprState *) lfirst(pvar),
 243                                                                                            econtext,
 244                                                                                            &(prm->isnull),
 245                                                                                            NULL);
 246                 planstate->chgParam = bms_add_member(planstate->chgParam, paramid);
 247         }
 248
 249         /*
 250          * Now that we've set up its parameters, we can reset the subplan.
 251          */
 252         ExecReScan(planstate);
 253
 254         /*
 255          * For all sublink types except EXPR_SUBLINK and ARRAY_SUBLINK, the result
 256          * is boolean as are the results of the combining operators. We combine
 257          * results across tuples (if the subplan produces more than one) using OR
 258          * semantics for ANY_SUBLINK or AND semantics for ALL_SUBLINK.
 259          * (ROWCOMPARE_SUBLINK doesn't allow multiple tuples from the subplan.)
 260          * NULL results from the combining operators are handled according to the
 261          * usual SQL semantics for OR and AND.  The result for no input tuples is
 262          * FALSE for ANY_SUBLINK, TRUE for ALL_SUBLINK, NULL for
 263          * ROWCOMPARE_SUBLINK.
 264          *
 265          * For EXPR_SUBLINK we require the subplan to produce no more than one
 266          * tuple, else an error is raised.      If zero tuples are produced, we return
 267          * NULL.  Assuming we get a tuple, we just use its first column (there can
 268          * be only one non-junk column in this case).
 269          *
 270          * For ARRAY_SUBLINK we allow the subplan to produce any number of tuples,
 271          * and form an array of the first column's values.  Note in particular
 272          * that we produce a zero-element array if no tuples are produced (this is
 273          * a change from pre-8.3 behavior of returning NULL).
 274          */
 275         result = BoolGetDatum(subLinkType == ALL_SUBLINK);
 276         *isNull = false;
 277
 278         for (slot = ExecProcNode(planstate);
 279                  !TupIsNull(slot);
 280                  slot = ExecProcNode(planstate))
 281         {
 282                 TupleDesc       tdesc = slot->tts_tupleDescriptor;
 283                 Datum           rowresult;
 284                 bool            rownull;
 285                 int                     col;
 286                 ListCell   *plst;
 287
 288                 if (subLinkType == EXISTS_SUBLINK)
 289                 {
 290                         found = true;
 291                         result = BoolGetDatum(true);
 292                         break;
 293                 }
 294
 295                 if (subLinkType == EXPR_SUBLINK)
 296                 {
 297                         /* cannot allow multiple input tuples for EXPR sublink */
 298                         if (found)
 299                                 ereport(ERROR,
 300                                                 (errcode(ERRCODE_CARDINALITY_VIOLATION),
 301                                                  errmsg("more than one row returned by a subquery used as an expression")));
 302                         found = true;
 303
 304                         /*
 305                          * We need to copy the subplan's tuple in case the result is of
 306                          * pass-by-ref type --- our return value will point into this
 307                          * copied tuple!  Can't use the subplan's instance of the tuple
 308                          * since it won't still be valid after next ExecProcNode() call.
 309                          * node->curTuple keeps track of the copied tuple for eventual
 310                          * freeing.
 311                          */
 312                         if (node->curTuple)
 313                                 heap_freetuple(node->curTuple);
 314                         node->curTuple = ExecCopySlotTuple(slot);
 315
 316                         result = heap_getattr(node->curTuple, 1, tdesc, isNull);
 317                         /* keep scanning subplan to make sure there's only one tuple */
 318                         continue;
 319                 }
 320
 321                 if (subLinkType == ARRAY_SUBLINK)
 322                 {
 323                         Datum           dvalue;
 324                         bool            disnull;
 325
 326                         found = true;
 327                         /* stash away current value */
 328                         Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
 329                         dvalue = slot_getattr(slot, 1, &disnull);
 330                         astate = accumArrayResult(astate, dvalue, disnull,
 331                                                                           subplan->firstColType, oldcontext);
 332                         /* keep scanning subplan to collect all values */
 333                         continue;
 334                 }
 335
 336                 /* cannot allow multiple input tuples for ROWCOMPARE sublink either */
 337                 if (subLinkType == ROWCOMPARE_SUBLINK && found)
 338                         ereport(ERROR,
 339                                         (errcode(ERRCODE_CARDINALITY_VIOLATION),
 340                                          errmsg("more than one row returned by a subquery used as an expression")));
 341
 342                 found = true;
 343
 344                 /*
 345                  * For ALL, ANY, and ROWCOMPARE sublinks, load up the Params
 346                  * representing the columns of the sub-select, and then evaluate the
 347                  * combining expression.
 348                  */
 349                 col = 1;
 350                 foreach(plst, subplan->paramIds)
 351                 {
 352                         int                     paramid = lfirst_int(plst);
 353                         ParamExecData *prmdata;
 354
 355                         prmdata = &(econtext->ecxt_param_exec_vals[paramid]);
 356                         Assert(prmdata->execPlan == NULL);
 357                         prmdata->value = slot_getattr(slot, col, &(prmdata->isnull));
 358                         col++;
 359                 }
 360
 361                 rowresult = ExecEvalExprSwitchContext(node->testexpr, econtext,
 362                                                                                           &rownull, NULL);
 363
 364                 if (subLinkType == ANY_SUBLINK)
 365                 {
 366                         /* combine across rows per OR semantics */
 367                         if (rownull)
 368                                 *isNull = true;
 369                         else if (DatumGetBool(rowresult))
 370                         {
 371                                 result = BoolGetDatum(true);
 372                                 *isNull = false;
 373                                 break;                  /* needn't look at any more rows */
 374                         }
 375                 }
 376                 else if (subLinkType == ALL_SUBLINK)
 377                 {
 378                         /* combine across rows per AND semantics */
 379                         if (rownull)
 380                                 *isNull = true;
 381                         else if (!DatumGetBool(rowresult))
 382                         {
 383                                 result = BoolGetDatum(false);
 384                                 *isNull = false;
 385                                 break;                  /* needn't look at any more rows */
 386                         }
 387                 }
 388                 else
 389                 {
 390                         /* must be ROWCOMPARE_SUBLINK */
 391                         result = rowresult;
 392                         *isNull = rownull;
 393                 }
 394         }
 395
 396         MemoryContextSwitchTo(oldcontext);
 397
 398         if (subLinkType == ARRAY_SUBLINK)
 399         {
 400                 /* We return the result in the caller's context */
 401                 if (astate != NULL)
 402                         result = makeArrayResult(astate, oldcontext);
 403                 else
 404                         result = PointerGetDatum(construct_empty_array(subplan->firstColType));
 405         }
 406         else if (!found)
 407         {
 408                 /*
 409                  * deal with empty subplan result.      result/isNull were previously
 410                  * initialized correctly for all sublink types except EXPR and
 411                  * ROWCOMPARE; for those, return NULL.
 412                  */
 413                 if (subLinkType == EXPR_SUBLINK ||
 414                         subLinkType == ROWCOMPARE_SUBLINK)
 415                 {
 416                         result = (Datum) 0;
 417                         *isNull = true;
 418                 }
 419         }
 420
 421         return result;
 422 }
 423
 424 /*
 425  * buildSubPlanHash: load hash table by scanning subplan output.
 426  */
 427 static void
 428 buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
 429 {
 430         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 431         PlanState  *planstate = node->planstate;
 432         int                     ncols = list_length(subplan->paramIds);
 433         ExprContext *innerecontext = node->innerecontext;
 434         MemoryContext oldcontext;
 435         int                     nbuckets;
 436         TupleTableSlot *slot;
 437
 438         Assert(subplan->subLinkType == ANY_SUBLINK);
 439
 440         /*
 441          * If we already had any hash tables, destroy 'em; then create empty hash
 442          * table(s).
 443          *
 444          * If we need to distinguish accurately between FALSE and UNKNOWN (i.e.,
 445          * NULL) results of the IN operation, then we have to store subplan output
 446          * rows that are partly or wholly NULL.  We store such rows in a separate
 447          * hash table that we expect will be much smaller than the main table. (We
 448          * can use hashing to eliminate partly-null rows that are not distinct. We
 449          * keep them separate to minimize the cost of the inevitable full-table
 450          * searches; see findPartialMatch.)
 451          *
 452          * If it's not necessary to distinguish FALSE and UNKNOWN, then we don't
 453          * need to store subplan output rows that contain NULL.
 454          */
 455         MemoryContextReset(node->hashtablecxt);
 456         node->hashtable = NULL;
 457         node->hashnulls = NULL;
 458         node->havehashrows = false;
 459         node->havenullrows = false;
 460
 461         nbuckets = (int) ceil(planstate->plan->plan_rows);
 462         if (nbuckets < 1)
 463                 nbuckets = 1;
 464
 465         node->hashtable = BuildTupleHashTable(ncols,
 466                                                                                   node->keyColIdx,
 467                                                                                   node->tab_eq_funcs,
 468                                                                                   node->tab_hash_funcs,
 469                                                                                   nbuckets,
 470                                                                                   sizeof(TupleHashEntryData),
 471                                                                                   node->hashtablecxt,
 472                                                                                   node->hashtempcxt);
 473
 474         if (!subplan->unknownEqFalse)
 475         {
 476                 if (ncols == 1)
 477                         nbuckets = 1;           /* there can only be one entry */
 478                 else
 479                 {
 480                         nbuckets /= 16;
 481                         if (nbuckets < 1)
 482                                 nbuckets = 1;
 483                 }
 484                 node->hashnulls = BuildTupleHashTable(ncols,
 485                                                                                           node->keyColIdx,
 486                                                                                           node->tab_eq_funcs,
 487                                                                                           node->tab_hash_funcs,
 488                                                                                           nbuckets,
 489                                                                                           sizeof(TupleHashEntryData),
 490                                                                                           node->hashtablecxt,
 491                                                                                           node->hashtempcxt);
 492         }
 493
 494         /*
 495          * We are probably in a short-lived expression-evaluation context. Switch
 496          * to the per-query context for manipulating the child plan.
 497          */
 498         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 499
 500         /*
 501          * Reset subplan to start.
 502          */
 503         ExecReScan(planstate);
 504
 505         /*
 506          * Scan the subplan and load the hash table(s).  Note that when there are
 507          * duplicate rows coming out of the sub-select, only one copy is stored.
 508          */
 509         for (slot = ExecProcNode(planstate);
 510                  !TupIsNull(slot);
 511                  slot = ExecProcNode(planstate))
 512         {
 513                 int                     col = 1;
 514                 ListCell   *plst;
 515                 bool            isnew;
 516
 517                 /*
 518                  * Load up the Params representing the raw sub-select outputs, then
 519                  * form the projection tuple to store in the hashtable.
 520                  */
 521                 foreach(plst, subplan->paramIds)
 522                 {
 523                         int                     paramid = lfirst_int(plst);
 524                         ParamExecData *prmdata;
 525
 526                         prmdata = &(innerecontext->ecxt_param_exec_vals[paramid]);
 527                         Assert(prmdata->execPlan == NULL);
 528                         prmdata->value = slot_getattr(slot, col,
 529                                                                                   &(prmdata->isnull));
 530                         col++;
 531                 }
 532                 slot = ExecProject(node->projRight, NULL);
 533
 534                 /*
 535                  * If result contains any nulls, store separately or not at all.
 536                  */
 537                 if (slotNoNulls(slot))
 538                 {
 539                         (void) LookupTupleHashEntry(node->hashtable, slot, &isnew);
 540                         node->havehashrows = true;
 541                 }
 542                 else if (node->hashnulls)
 543                 {
 544                         (void) LookupTupleHashEntry(node->hashnulls, slot, &isnew);
 545                         node->havenullrows = true;
 546                 }
 547
 548                 /*
 549                  * Reset innerecontext after each inner tuple to free any memory used
 550                  * during ExecProject.
 551                  */
 552                 ResetExprContext(innerecontext);
 553         }
 554
 555         /*
 556          * Since the projected tuples are in the sub-query's context and not the
 557          * main context, we'd better clear the tuple slot before there's any
 558          * chance of a reset of the sub-query's context.  Else we will have the
 559          * potential for a double free attempt.  (XXX possibly no longer needed,
 560          * but can't hurt.)
 561          */
 562         ExecClearTuple(node->projRight->pi_slot);
 563
 564         MemoryContextSwitchTo(oldcontext);
 565 }
 566
 567 /*
 568  * findPartialMatch: does the hashtable contain an entry that is not
 569  * provably distinct from the tuple?
 570  *
 571  * We have to scan the whole hashtable; we can't usefully use hashkeys
 572  * to guide probing, since we might get partial matches on tuples with
 573  * hashkeys quite unrelated to what we'd get from the given tuple.
 574  */
 575 static bool
 576 findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot)
 577 {
 578         int                     numCols = hashtable->numCols;
 579         AttrNumber *keyColIdx = hashtable->keyColIdx;
 580         TupleHashIterator hashiter;
 581         TupleHashEntry entry;
 582
 583         InitTupleHashIterator(hashtable, &hashiter);
 584         while ((entry = ScanTupleHashTable(&hashiter)) != NULL)
 585         {
 586                 ExecStoreMinimalTuple(entry->firstTuple, hashtable->tableslot, false);
 587                 if (!execTuplesUnequal(slot, hashtable->tableslot,
 588                                                            numCols, keyColIdx,
 589                                                            hashtable->cur_eq_funcs,
 590                                                            hashtable->tempcxt))
 591                 {
 592                         TermTupleHashIterator(&hashiter);
 593                         return true;
 594                 }
 595         }
 596         /* No TermTupleHashIterator call needed here */
 597         return false;
 598 }
 599
 600 /*
 601  * slotAllNulls: is the slot completely NULL?
 602  *
 603  * This does not test for dropped columns, which is OK because we only
 604  * use it on projected tuples.
 605  */
 606 static bool
 607 slotAllNulls(TupleTableSlot *slot)
 608 {
 609         int                     ncols = slot->tts_tupleDescriptor->natts;
 610         int                     i;
 611
 612         for (i = 1; i <= ncols; i++)
 613         {
 614                 if (!slot_attisnull(slot, i))
 615                         return false;
 616         }
 617         return true;
 618 }
 619
 620 /*
 621  * slotNoNulls: is the slot entirely not NULL?
 622  *
 623  * This does not test for dropped columns, which is OK because we only
 624  * use it on projected tuples.
 625  */
 626 static bool
 627 slotNoNulls(TupleTableSlot *slot)
 628 {
 629         int                     ncols = slot->tts_tupleDescriptor->natts;
 630         int                     i;
 631
 632         for (i = 1; i <= ncols; i++)
 633         {
 634                 if (slot_attisnull(slot, i))
 635                         return false;
 636         }
 637         return true;
 638 }
 639
 640 /* ----------------------------------------------------------------
 641  *              ExecInitSubPlan
 642  *
 643  * Create a SubPlanState for a SubPlan; this is the SubPlan-specific part
 644  * of ExecInitExpr().  We split it out so that it can be used for InitPlans
 645  * as well as regular SubPlans.  Note that we don't link the SubPlan into
 646  * the parent's subPlan list, because that shouldn't happen for InitPlans.
 647  * Instead, ExecInitExpr() does that one part.
 648  * ----------------------------------------------------------------
 649  */
 650 SubPlanState *
 651 ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
 652 {
 653         SubPlanState *sstate = makeNode(SubPlanState);
 654         EState     *estate = parent->state;
 655
 656         sstate->xprstate.evalfunc = (ExprStateEvalFunc) ExecSubPlan;
 657         sstate->xprstate.expr = (Expr *) subplan;
 658
 659         /* Link the SubPlanState to already-initialized subplan */
 660         sstate->planstate = (PlanState *) list_nth(estate->es_subplanstates,
 661                                                                                            subplan->plan_id - 1);
 662
 663         /* Initialize subexpressions */
 664         sstate->testexpr = ExecInitExpr((Expr *) subplan->testexpr, parent);
 665         sstate->args = (List *) ExecInitExpr((Expr *) subplan->args, parent);
 666
 667         /*
 668          * initialize my state
 669          */
 670         sstate->curTuple = NULL;
 671         sstate->projLeft = NULL;
 672         sstate->projRight = NULL;
 673         sstate->hashtable = NULL;
 674         sstate->hashnulls = NULL;
 675         sstate->hashtablecxt = NULL;
 676         sstate->hashtempcxt = NULL;
 677         sstate->innerecontext = NULL;
 678         sstate->keyColIdx = NULL;
 679         sstate->tab_hash_funcs = NULL;
 680         sstate->tab_eq_funcs = NULL;
 681         sstate->lhs_hash_funcs = NULL;
 682         sstate->cur_eq_funcs = NULL;
 683
 684         /*
 685          * If this plan is un-correlated or undirect correlated one and want to
 686          * set params for parent plan then mark parameters as needing evaluation.
 687          *
 688          * A CTE subplan's output parameter is never to be evaluated in the normal
 689          * way, so skip this in that case.
 690          *
 691          * Note that in the case of un-correlated subqueries we don't care about
 692          * setting parent->chgParam here: indices take care about it, for others -
 693          * it doesn't matter...
 694          */
 695         if (subplan->setParam != NIL && subplan->subLinkType != CTE_SUBLINK)
 696         {
 697                 ListCell   *lst;
 698
 699                 foreach(lst, subplan->setParam)
 700                 {
 701                         int                     paramid = lfirst_int(lst);
 702                         ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
 703
 704                         prm->execPlan = sstate;
 705                 }
 706         }
 707
 708         /*
 709          * If we are going to hash the subquery output, initialize relevant stuff.
 710          * (We don't create the hashtable until needed, though.)
 711          */
 712         if (subplan->useHashTable)
 713         {
 714                 int                     ncols,
 715                                         i;
 716                 TupleDesc       tupDesc;
 717                 TupleTableSlot *slot;
 718                 List       *oplist,
 719                                    *lefttlist,
 720                                    *righttlist,
 721                                    *leftptlist,
 722                                    *rightptlist;
 723                 ListCell   *l;
 724
 725                 /* We need a memory context to hold the hash table(s) */
 726                 sstate->hashtablecxt =
 727                         AllocSetContextCreate(CurrentMemoryContext,
 728                                                                   "Subplan HashTable Context",
 729                                                                   ALLOCSET_DEFAULT_MINSIZE,
 730                                                                   ALLOCSET_DEFAULT_INITSIZE,
 731                                                                   ALLOCSET_DEFAULT_MAXSIZE);
 732                 /* and a small one for the hash tables to use as temp storage */
 733                 sstate->hashtempcxt =
 734                         AllocSetContextCreate(CurrentMemoryContext,
 735                                                                   "Subplan HashTable Temp Context",
 736                                                                   ALLOCSET_SMALL_MINSIZE,
 737                                                                   ALLOCSET_SMALL_INITSIZE,
 738                                                                   ALLOCSET_SMALL_MAXSIZE);
 739                 /* and a short-lived exprcontext for function evaluation */
 740                 sstate->innerecontext = CreateExprContext(estate);
 741                 /* Silly little array of column numbers 1..n */
 742                 ncols = list_length(subplan->paramIds);
 743                 sstate->keyColIdx = (AttrNumber *) palloc(ncols * sizeof(AttrNumber));
 744                 for (i = 0; i < ncols; i++)
 745                         sstate->keyColIdx[i] = i + 1;
 746
 747                 /*
 748                  * We use ExecProject to evaluate the lefthand and righthand
 749                  * expression lists and form tuples.  (You might think that we could
 750                  * use the sub-select's output tuples directly, but that is not the
 751                  * case if we had to insert any run-time coercions of the sub-select's
 752                  * output datatypes; anyway this avoids storing any resjunk columns
 753                  * that might be in the sub-select's output.) Run through the
 754                  * combining expressions to build tlists for the lefthand and
 755                  * righthand sides.  We need both the ExprState list (for ExecProject)
 756                  * and the underlying parse Exprs (for ExecTypeFromTL).
 757                  *
 758                  * We also extract the combining operators themselves to initialize
 759                  * the equality and hashing functions for the hash tables.
 760                  */
 761                 if (IsA(sstate->testexpr->expr, OpExpr))
 762                 {
 763                         /* single combining operator */
 764                         oplist = list_make1(sstate->testexpr);
 765                 }
 766                 else if (and_clause((Node *) sstate->testexpr->expr))
 767                 {
 768                         /* multiple combining operators */
 769                         Assert(IsA(sstate->testexpr, BoolExprState));
 770                         oplist = ((BoolExprState *) sstate->testexpr)->args;
 771                 }
 772                 else
 773                 {
 774                         /* shouldn't see anything else in a hashable subplan */
 775                         elog(ERROR, "unrecognized testexpr type: %d",
 776                                  (int) nodeTag(sstate->testexpr->expr));
 777                         oplist = NIL;           /* keep compiler quiet */
 778                 }
 779                 Assert(list_length(oplist) == ncols);
 780
 781                 lefttlist = righttlist = NIL;
 782                 leftptlist = rightptlist = NIL;
 783                 sstate->tab_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 784                 sstate->tab_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 785                 sstate->lhs_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 786                 sstate->cur_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 787                 i = 1;
 788                 foreach(l, oplist)
 789                 {
 790                         FuncExprState *fstate = (FuncExprState *) lfirst(l);
 791                         OpExpr     *opexpr = (OpExpr *) fstate->xprstate.expr;
 792                         ExprState  *exstate;
 793                         Expr       *expr;
 794                         TargetEntry *tle;
 795                         GenericExprState *tlestate;
 796                         Oid                     rhs_eq_oper;
 797                         Oid                     left_hashfn;
 798                         Oid                     right_hashfn;
 799
 800                         Assert(IsA(fstate, FuncExprState));
 801                         Assert(IsA(opexpr, OpExpr));
 802                         Assert(list_length(fstate->args) == 2);
 803
 804                         /* Process lefthand argument */
 805                         exstate = (ExprState *) linitial(fstate->args);
 806                         expr = exstate->expr;
 807                         tle = makeTargetEntry(expr,
 808                                                                   i,
 809                                                                   NULL,
 810                                                                   false);
 811                         tlestate = makeNode(GenericExprState);
 812                         tlestate->xprstate.expr = (Expr *) tle;
 813                         tlestate->xprstate.evalfunc = NULL;
 814                         tlestate->arg = exstate;
 815                         lefttlist = lappend(lefttlist, tlestate);
 816                         leftptlist = lappend(leftptlist, tle);
 817
 818                         /* Process righthand argument */
 819                         exstate = (ExprState *) lsecond(fstate->args);
 820                         expr = exstate->expr;
 821                         tle = makeTargetEntry(expr,
 822                                                                   i,
 823                                                                   NULL,
 824                                                                   false);
 825                         tlestate = makeNode(GenericExprState);
 826                         tlestate->xprstate.expr = (Expr *) tle;
 827                         tlestate->xprstate.evalfunc = NULL;
 828                         tlestate->arg = exstate;
 829                         righttlist = lappend(righttlist, tlestate);
 830                         rightptlist = lappend(rightptlist, tle);
 831
 832                         /* Lookup the equality function (potentially cross-type) */
 833                         fmgr_info(opexpr->opfuncid, &sstate->cur_eq_funcs[i - 1]);
 834                         fmgr_info_expr((Node *) opexpr, &sstate->cur_eq_funcs[i - 1]);
 835
 836                         /* Look up the equality function for the RHS type */
 837                         if (!get_compatible_hash_operators(opexpr->opno,
 838                                                                                            NULL, &rhs_eq_oper))
 839                                 elog(ERROR, "could not find compatible hash operator for operator %u",
 840                                          opexpr->opno);
 841                         fmgr_info(get_opcode(rhs_eq_oper), &sstate->tab_eq_funcs[i - 1]);
 842
 843                         /* Lookup the associated hash functions */
 844                         if (!get_op_hash_functions(opexpr->opno,
 845                                                                            &left_hashfn, &right_hashfn))
 846                                 elog(ERROR, "could not find hash function for hash operator %u",
 847                                          opexpr->opno);
 848                         fmgr_info(left_hashfn, &sstate->lhs_hash_funcs[i - 1]);
 849                         fmgr_info(right_hashfn, &sstate->tab_hash_funcs[i - 1]);
 850
 851                         i++;
 852                 }
 853
 854                 /*
 855                  * Construct tupdescs, slots and projection nodes for left and right
 856                  * sides.  The lefthand expressions will be evaluated in the parent
 857                  * plan node's exprcontext, which we don't have access to here.
 858                  * Fortunately we can just pass NULL for now and fill it in later
 859                  * (hack alert!).  The righthand expressions will be evaluated in our
 860                  * own innerecontext.
 861                  */
 862                 tupDesc = ExecTypeFromTL(leftptlist, false);
 863                 slot = ExecInitExtraTupleSlot(estate);
 864                 ExecSetSlotDescriptor(slot, tupDesc);
 865                 sstate->projLeft = ExecBuildProjectionInfo(lefttlist,
 866                                                                                                    NULL,
 867                                                                                                    slot,
 868                                                                                                    NULL);
 869
 870                 tupDesc = ExecTypeFromTL(rightptlist, false);
 871                 slot = ExecInitExtraTupleSlot(estate);
 872                 ExecSetSlotDescriptor(slot, tupDesc);
 873                 sstate->projRight = ExecBuildProjectionInfo(righttlist,
 874                                                                                                         sstate->innerecontext,
 875                                                                                                         slot,
 876                                                                                                         NULL);
 877         }
 878
 879         return sstate;
 880 }
 881
 882 /* ----------------------------------------------------------------
 883  *              ExecSetParamPlan
 884  *
 885  *              Executes an InitPlan subplan and sets its output parameters.
 886  *
 887  * This is called from ExecEvalParamExec() when the value of a PARAM_EXEC
 888  * parameter is requested and the param's execPlan field is set (indicating
 889  * that the param has not yet been evaluated).  This allows lazy evaluation
 890  * of initplans: we don't run the subplan until/unless we need its output.
 891  * Note that this routine MUST clear the execPlan fields of the plan's
 892  * output parameters after evaluating them!
 893  * ----------------------------------------------------------------
 894  */
 895 void
 896 ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
 897 {
 898         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 899         PlanState  *planstate = node->planstate;
 900         SubLinkType subLinkType = subplan->subLinkType;
 901         MemoryContext oldcontext;
 902         TupleTableSlot *slot;
 903         ListCell   *l;
 904         bool            found = false;
 905         ArrayBuildState *astate = NULL;
 906
 907         if (subLinkType == ANY_SUBLINK ||
 908                 subLinkType == ALL_SUBLINK)
 909                 elog(ERROR, "ANY/ALL subselect unsupported as initplan");
 910         if (subLinkType == CTE_SUBLINK)
 911                 elog(ERROR, "CTE subplans should not be executed via ExecSetParamPlan");
 912
 913         /*
 914          * Must switch to per-query memory context.
 915          */
 916         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 917
 918         /*
 919          * Run the plan.  (If it needs to be rescanned, the first ExecProcNode
 920          * call will take care of that.)
 921          */
 922         for (slot = ExecProcNode(planstate);
 923                  !TupIsNull(slot);
 924                  slot = ExecProcNode(planstate))
 925         {
 926                 TupleDesc       tdesc = slot->tts_tupleDescriptor;
 927                 int                     i = 1;
 928
 929                 if (subLinkType == EXISTS_SUBLINK)
 930                 {
 931                         /* There can be only one setParam... */
 932                         int                     paramid = linitial_int(subplan->setParam);
 933                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 934
 935                         prm->execPlan = NULL;
 936                         prm->value = BoolGetDatum(true);
 937                         prm->isnull = false;
 938                         found = true;
 939                         break;
 940                 }
 941
 942                 if (subLinkType == ARRAY_SUBLINK)
 943                 {
 944                         Datum           dvalue;
 945                         bool            disnull;
 946
 947                         found = true;
 948                         /* stash away current value */
 949                         Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
 950                         dvalue = slot_getattr(slot, 1, &disnull);
 951                         astate = accumArrayResult(astate, dvalue, disnull,
 952                                                                           subplan->firstColType, oldcontext);
 953                         /* keep scanning subplan to collect all values */
 954                         continue;
 955                 }
 956
 957                 if (found &&
 958                         (subLinkType == EXPR_SUBLINK ||
 959                          subLinkType == ROWCOMPARE_SUBLINK))
 960                         ereport(ERROR,
 961                                         (errcode(ERRCODE_CARDINALITY_VIOLATION),
 962                                          errmsg("more than one row returned by a subquery used as an expression")));
 963
 964                 found = true;
 965
 966                 /*
 967                  * We need to copy the subplan's tuple into our own context, in case
 968                  * any of the params are pass-by-ref type --- the pointers stored in
 969                  * the param structs will point at this copied tuple! node->curTuple
 970                  * keeps track of the copied tuple for eventual freeing.
 971                  */
 972                 if (node->curTuple)
 973                         heap_freetuple(node->curTuple);
 974                 node->curTuple = ExecCopySlotTuple(slot);
 975
 976                 /*
 977                  * Now set all the setParam params from the columns of the tuple
 978                  */
 979                 foreach(l, subplan->setParam)
 980                 {
 981                         int                     paramid = lfirst_int(l);
 982                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 983
 984                         prm->execPlan = NULL;
 985                         prm->value = heap_getattr(node->curTuple, i, tdesc,
 986                                                                           &(prm->isnull));
 987                         i++;
 988                 }
 989         }
 990
 991         if (subLinkType == ARRAY_SUBLINK)
 992         {
 993                 /* There can be only one setParam... */
 994                 int                     paramid = linitial_int(subplan->setParam);
 995                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 996
 997                 prm->execPlan = NULL;
 998                 /* We build the result in query context so it won't disappear */
 999                 if (astate != NULL)
1000                         prm->value = makeArrayResult(astate,
1001                                                                                  econtext->ecxt_per_query_memory);
1002                 else
1003                 {
1004                         MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
1005                         prm->value = PointerGetDatum(construct_empty_array(subplan->firstColType));
1006                 }
1007                 prm->isnull = false;
1008         }
1009         else if (!found)
1010         {
1011                 if (subLinkType == EXISTS_SUBLINK)
1012                 {
1013                         /* There can be only one setParam... */
1014                         int                     paramid = linitial_int(subplan->setParam);
1015                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1016
1017                         prm->execPlan = NULL;
1018                         prm->value = BoolGetDatum(false);
1019                         prm->isnull = false;
1020                 }
1021                 else
1022                 {
1023                         foreach(l, subplan->setParam)
1024                         {
1025                                 int                     paramid = lfirst_int(l);
1026                                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1027
1028                                 prm->execPlan = NULL;
1029                                 prm->value = (Datum) 0;
1030                                 prm->isnull = true;
1031                         }
1032                 }
1033         }
1034
1035         MemoryContextSwitchTo(oldcontext);
1036 }
1037
1038 /*
1039  * Mark an initplan as needing recalculation
1040  */
1041 void
1042 ExecReScanSetParamPlan(SubPlanState *node, PlanState *parent)
1043 {
1044         PlanState  *planstate = node->planstate;
1045         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
1046         EState     *estate = parent->state;
1047         ListCell   *l;
1048
1049         /* sanity checks */
1050         if (subplan->parParam != NIL)
1051                 elog(ERROR, "direct correlated subquery unsupported as initplan");
1052         if (subplan->setParam == NIL)
1053                 elog(ERROR, "setParam list of initplan is empty");
1054         if (bms_is_empty(planstate->plan->extParam))
1055                 elog(ERROR, "extParam set of initplan is empty");
1056
1057         /*
1058          * Don't actually re-scan: it'll happen inside ExecSetParamPlan if needed.
1059          */
1060
1061         /*
1062          * Mark this subplan's output parameters as needing recalculation.
1063          *
1064          * CTE subplans are never executed via parameter recalculation; instead
1065          * they get run when called by nodeCtescan.c.  So don't mark the output
1066          * parameter of a CTE subplan as dirty, but do set the chgParam bit for it
1067          * so that dependent plan nodes will get told to rescan.
1068          */
1069         foreach(l, subplan->setParam)
1070         {
1071                 int                     paramid = lfirst_int(l);
1072                 ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
1073
1074                 if (subplan->subLinkType != CTE_SUBLINK)
1075                         prm->execPlan = node;
1076
1077                 parent->chgParam = bms_add_member(parent->chgParam, paramid);
1078         }
1079 }
1080
1081
1082 /*
1083  * ExecInitAlternativeSubPlan
1084  *
1085  * Initialize for execution of one of a set of alternative subplans.
1086  */
1087 AlternativeSubPlanState *
1088 ExecInitAlternativeSubPlan(AlternativeSubPlan *asplan, PlanState *parent)
1089 {
1090         AlternativeSubPlanState *asstate = makeNode(AlternativeSubPlanState);
1091         double          num_calls;
1092         SubPlan    *subplan1;
1093         SubPlan    *subplan2;
1094         Cost            cost1;
1095         Cost            cost2;
1096
1097         asstate->xprstate.evalfunc = (ExprStateEvalFunc) ExecAlternativeSubPlan;
1098         asstate->xprstate.expr = (Expr *) asplan;
1099
1100         /*
1101          * Initialize subplans.  (Can we get away with only initializing the one
1102          * we're going to use?)
1103          */
1104         asstate->subplans = (List *) ExecInitExpr((Expr *) asplan->subplans,
1105                                                                                           parent);
1106
1107         /*
1108          * Select the one to be used.  For this, we need an estimate of the number
1109          * of executions of the subplan.  We use the number of output rows
1110          * expected from the parent plan node.  This is a good estimate if we are
1111          * in the parent's targetlist, and an underestimate (but probably not by
1112          * more than a factor of 2) if we are in the qual.
1113          */
1114         num_calls = parent->plan->plan_rows;
1115
1116         /*
1117          * The planner saved enough info so that we don't have to work very hard
1118          * to estimate the total cost, given the number-of-calls estimate.
1119          */
1120         Assert(list_length(asplan->subplans) == 2);
1121         subplan1 = (SubPlan *) linitial(asplan->subplans);
1122         subplan2 = (SubPlan *) lsecond(asplan->subplans);
1123
1124         cost1 = subplan1->startup_cost + num_calls * subplan1->per_call_cost;
1125         cost2 = subplan2->startup_cost + num_calls * subplan2->per_call_cost;
1126
1127         if (cost1 < cost2)
1128                 asstate->active = 0;
1129         else
1130                 asstate->active = 1;
1131
1132         return asstate;
1133 }
1134
1135 /*
1136  * ExecAlternativeSubPlan
1137  *
1138  * Execute one of a set of alternative subplans.
1139  *
1140  * Note: in future we might consider changing to different subplans on the
1141  * fly, in case the original rowcount estimate turns out to be way off.
1142  */
1143 static Datum
1144 ExecAlternativeSubPlan(AlternativeSubPlanState *node,
1145                                            ExprContext *econtext,
1146                                            bool *isNull,
1147                                            ExprDoneCond *isDone)
1148 {
1149         /* Just pass control to the active subplan */
1150         SubPlanState *activesp = (SubPlanState *) list_nth(node->subplans,
1151                                                                                                            node->active);
1152
1153         Assert(IsA(activesp, SubPlanState));
1154
1155         return ExecSubPlan(activesp,
1156                                            econtext,
1157                                            isNull,
1158                                            isDone);
1159 }