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) 1996-2012, 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         long            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 = (long) Min(planstate->plan->plan_rows, (double) LONG_MAX);
 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->curArray = PointerGetDatum(NULL);
 672         sstate->projLeft = NULL;
 673         sstate->projRight = NULL;
 674         sstate->hashtable = NULL;
 675         sstate->hashnulls = NULL;
 676         sstate->hashtablecxt = NULL;
 677         sstate->hashtempcxt = NULL;
 678         sstate->innerecontext = NULL;
 679         sstate->keyColIdx = NULL;
 680         sstate->tab_hash_funcs = NULL;
 681         sstate->tab_eq_funcs = NULL;
 682         sstate->lhs_hash_funcs = NULL;
 683         sstate->cur_eq_funcs = NULL;
 684
 685         /*
 686          * If this plan is un-correlated or undirect correlated one and want to
 687          * set params for parent plan then mark parameters as needing evaluation.
 688          *
 689          * A CTE subplan's output parameter is never to be evaluated in the normal
 690          * way, so skip this in that case.
 691          *
 692          * Note that in the case of un-correlated subqueries we don't care about
 693          * setting parent->chgParam here: indices take care about it, for others -
 694          * it doesn't matter...
 695          */
 696         if (subplan->setParam != NIL && subplan->subLinkType != CTE_SUBLINK)
 697         {
 698                 ListCell   *lst;
 699
 700                 foreach(lst, subplan->setParam)
 701                 {
 702                         int                     paramid = lfirst_int(lst);
 703                         ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
 704
 705                         prm->execPlan = sstate;
 706                 }
 707         }
 708
 709         /*
 710          * If we are going to hash the subquery output, initialize relevant stuff.
 711          * (We don't create the hashtable until needed, though.)
 712          */
 713         if (subplan->useHashTable)
 714         {
 715                 int                     ncols,
 716                                         i;
 717                 TupleDesc       tupDesc;
 718                 TupleTableSlot *slot;
 719                 List       *oplist,
 720                                    *lefttlist,
 721                                    *righttlist,
 722                                    *leftptlist,
 723                                    *rightptlist;
 724                 ListCell   *l;
 725
 726                 /* We need a memory context to hold the hash table(s) */
 727                 sstate->hashtablecxt =
 728                         AllocSetContextCreate(CurrentMemoryContext,
 729                                                                   "Subplan HashTable Context",
 730                                                                   ALLOCSET_DEFAULT_MINSIZE,
 731                                                                   ALLOCSET_DEFAULT_INITSIZE,
 732                                                                   ALLOCSET_DEFAULT_MAXSIZE);
 733                 /* and a small one for the hash tables to use as temp storage */
 734                 sstate->hashtempcxt =
 735                         AllocSetContextCreate(CurrentMemoryContext,
 736                                                                   "Subplan HashTable Temp Context",
 737                                                                   ALLOCSET_SMALL_MINSIZE,
 738                                                                   ALLOCSET_SMALL_INITSIZE,
 739                                                                   ALLOCSET_SMALL_MAXSIZE);
 740                 /* and a short-lived exprcontext for function evaluation */
 741                 sstate->innerecontext = CreateExprContext(estate);
 742                 /* Silly little array of column numbers 1..n */
 743                 ncols = list_length(subplan->paramIds);
 744                 sstate->keyColIdx = (AttrNumber *) palloc(ncols * sizeof(AttrNumber));
 745                 for (i = 0; i < ncols; i++)
 746                         sstate->keyColIdx[i] = i + 1;
 747
 748                 /*
 749                  * We use ExecProject to evaluate the lefthand and righthand
 750                  * expression lists and form tuples.  (You might think that we could
 751                  * use the sub-select's output tuples directly, but that is not the
 752                  * case if we had to insert any run-time coercions of the sub-select's
 753                  * output datatypes; anyway this avoids storing any resjunk columns
 754                  * that might be in the sub-select's output.) Run through the
 755                  * combining expressions to build tlists for the lefthand and
 756                  * righthand sides.  We need both the ExprState list (for ExecProject)
 757                  * and the underlying parse Exprs (for ExecTypeFromTL).
 758                  *
 759                  * We also extract the combining operators themselves to initialize
 760                  * the equality and hashing functions for the hash tables.
 761                  */
 762                 if (IsA(sstate->testexpr->expr, OpExpr))
 763                 {
 764                         /* single combining operator */
 765                         oplist = list_make1(sstate->testexpr);
 766                 }
 767                 else if (and_clause((Node *) sstate->testexpr->expr))
 768                 {
 769                         /* multiple combining operators */
 770                         Assert(IsA(sstate->testexpr, BoolExprState));
 771                         oplist = ((BoolExprState *) sstate->testexpr)->args;
 772                 }
 773                 else
 774                 {
 775                         /* shouldn't see anything else in a hashable subplan */
 776                         elog(ERROR, "unrecognized testexpr type: %d",
 777                                  (int) nodeTag(sstate->testexpr->expr));
 778                         oplist = NIL;           /* keep compiler quiet */
 779                 }
 780                 Assert(list_length(oplist) == ncols);
 781
 782                 lefttlist = righttlist = NIL;
 783                 leftptlist = rightptlist = NIL;
 784                 sstate->tab_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 785                 sstate->tab_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 786                 sstate->lhs_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 787                 sstate->cur_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 788                 i = 1;
 789                 foreach(l, oplist)
 790                 {
 791                         FuncExprState *fstate = (FuncExprState *) lfirst(l);
 792                         OpExpr     *opexpr = (OpExpr *) fstate->xprstate.expr;
 793                         ExprState  *exstate;
 794                         Expr       *expr;
 795                         TargetEntry *tle;
 796                         GenericExprState *tlestate;
 797                         Oid                     rhs_eq_oper;
 798                         Oid                     left_hashfn;
 799                         Oid                     right_hashfn;
 800
 801                         Assert(IsA(fstate, FuncExprState));
 802                         Assert(IsA(opexpr, OpExpr));
 803                         Assert(list_length(fstate->args) == 2);
 804
 805                         /* Process lefthand argument */
 806                         exstate = (ExprState *) linitial(fstate->args);
 807                         expr = exstate->expr;
 808                         tle = makeTargetEntry(expr,
 809                                                                   i,
 810                                                                   NULL,
 811                                                                   false);
 812                         tlestate = makeNode(GenericExprState);
 813                         tlestate->xprstate.expr = (Expr *) tle;
 814                         tlestate->xprstate.evalfunc = NULL;
 815                         tlestate->arg = exstate;
 816                         lefttlist = lappend(lefttlist, tlestate);
 817                         leftptlist = lappend(leftptlist, tle);
 818
 819                         /* Process righthand argument */
 820                         exstate = (ExprState *) lsecond(fstate->args);
 821                         expr = exstate->expr;
 822                         tle = makeTargetEntry(expr,
 823                                                                   i,
 824                                                                   NULL,
 825                                                                   false);
 826                         tlestate = makeNode(GenericExprState);
 827                         tlestate->xprstate.expr = (Expr *) tle;
 828                         tlestate->xprstate.evalfunc = NULL;
 829                         tlestate->arg = exstate;
 830                         righttlist = lappend(righttlist, tlestate);
 831                         rightptlist = lappend(rightptlist, tle);
 832
 833                         /* Lookup the equality function (potentially cross-type) */
 834                         fmgr_info(opexpr->opfuncid, &sstate->cur_eq_funcs[i - 1]);
 835                         fmgr_info_set_expr((Node *) opexpr, &sstate->cur_eq_funcs[i - 1]);
 836
 837                         /* Look up the equality function for the RHS type */
 838                         if (!get_compatible_hash_operators(opexpr->opno,
 839                                                                                            NULL, &rhs_eq_oper))
 840                                 elog(ERROR, "could not find compatible hash operator for operator %u",
 841                                          opexpr->opno);
 842                         fmgr_info(get_opcode(rhs_eq_oper), &sstate->tab_eq_funcs[i - 1]);
 843
 844                         /* Lookup the associated hash functions */
 845                         if (!get_op_hash_functions(opexpr->opno,
 846                                                                            &left_hashfn, &right_hashfn))
 847                                 elog(ERROR, "could not find hash function for hash operator %u",
 848                                          opexpr->opno);
 849                         fmgr_info(left_hashfn, &sstate->lhs_hash_funcs[i - 1]);
 850                         fmgr_info(right_hashfn, &sstate->tab_hash_funcs[i - 1]);
 851
 852                         i++;
 853                 }
 854
 855                 /*
 856                  * Construct tupdescs, slots and projection nodes for left and right
 857                  * sides.  The lefthand expressions will be evaluated in the parent
 858                  * plan node's exprcontext, which we don't have access to here.
 859                  * Fortunately we can just pass NULL for now and fill it in later
 860                  * (hack alert!).  The righthand expressions will be evaluated in our
 861                  * own innerecontext.
 862                  */
 863                 tupDesc = ExecTypeFromTL(leftptlist, false);
 864                 slot = ExecInitExtraTupleSlot(estate);
 865                 ExecSetSlotDescriptor(slot, tupDesc);
 866                 sstate->projLeft = ExecBuildProjectionInfo(lefttlist,
 867                                                                                                    NULL,
 868                                                                                                    slot,
 869                                                                                                    NULL);
 870
 871                 tupDesc = ExecTypeFromTL(rightptlist, false);
 872                 slot = ExecInitExtraTupleSlot(estate);
 873                 ExecSetSlotDescriptor(slot, tupDesc);
 874                 sstate->projRight = ExecBuildProjectionInfo(righttlist,
 875                                                                                                         sstate->innerecontext,
 876                                                                                                         slot,
 877                                                                                                         NULL);
 878         }
 879
 880         return sstate;
 881 }
 882
 883 /* ----------------------------------------------------------------
 884  *              ExecSetParamPlan
 885  *
 886  *              Executes an InitPlan subplan and sets its output parameters.
 887  *
 888  * This is called from ExecEvalParamExec() when the value of a PARAM_EXEC
 889  * parameter is requested and the param's execPlan field is set (indicating
 890  * that the param has not yet been evaluated).  This allows lazy evaluation
 891  * of initplans: we don't run the subplan until/unless we need its output.
 892  * Note that this routine MUST clear the execPlan fields of the plan's
 893  * output parameters after evaluating them!
 894  * ----------------------------------------------------------------
 895  */
 896 void
 897 ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
 898 {
 899         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 900         PlanState  *planstate = node->planstate;
 901         SubLinkType subLinkType = subplan->subLinkType;
 902         MemoryContext oldcontext;
 903         TupleTableSlot *slot;
 904         ListCell   *l;
 905         bool            found = false;
 906         ArrayBuildState *astate = NULL;
 907
 908         if (subLinkType == ANY_SUBLINK ||
 909                 subLinkType == ALL_SUBLINK)
 910                 elog(ERROR, "ANY/ALL subselect unsupported as initplan");
 911         if (subLinkType == CTE_SUBLINK)
 912                 elog(ERROR, "CTE subplans should not be executed via ExecSetParamPlan");
 913
 914         /*
 915          * Must switch to per-query memory context.
 916          */
 917         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 918
 919         /*
 920          * Run the plan.  (If it needs to be rescanned, the first ExecProcNode
 921          * call will take care of that.)
 922          */
 923         for (slot = ExecProcNode(planstate);
 924                  !TupIsNull(slot);
 925                  slot = ExecProcNode(planstate))
 926         {
 927                 TupleDesc       tdesc = slot->tts_tupleDescriptor;
 928                 int                     i = 1;
 929
 930                 if (subLinkType == EXISTS_SUBLINK)
 931                 {
 932                         /* There can be only one setParam... */
 933                         int                     paramid = linitial_int(subplan->setParam);
 934                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 935
 936                         prm->execPlan = NULL;
 937                         prm->value = BoolGetDatum(true);
 938                         prm->isnull = false;
 939                         found = true;
 940                         break;
 941                 }
 942
 943                 if (subLinkType == ARRAY_SUBLINK)
 944                 {
 945                         Datum           dvalue;
 946                         bool            disnull;
 947
 948                         found = true;
 949                         /* stash away current value */
 950                         Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
 951                         dvalue = slot_getattr(slot, 1, &disnull);
 952                         astate = accumArrayResult(astate, dvalue, disnull,
 953                                                                           subplan->firstColType, oldcontext);
 954                         /* keep scanning subplan to collect all values */
 955                         continue;
 956                 }
 957
 958                 if (found &&
 959                         (subLinkType == EXPR_SUBLINK ||
 960                          subLinkType == ROWCOMPARE_SUBLINK))
 961                         ereport(ERROR,
 962                                         (errcode(ERRCODE_CARDINALITY_VIOLATION),
 963                                          errmsg("more than one row returned by a subquery used as an expression")));
 964
 965                 found = true;
 966
 967                 /*
 968                  * We need to copy the subplan's tuple into our own context, in case
 969                  * any of the params are pass-by-ref type --- the pointers stored in
 970                  * the param structs will point at this copied tuple! node->curTuple
 971                  * keeps track of the copied tuple for eventual freeing.
 972                  */
 973                 if (node->curTuple)
 974                         heap_freetuple(node->curTuple);
 975                 node->curTuple = ExecCopySlotTuple(slot);
 976
 977                 /*
 978                  * Now set all the setParam params from the columns of the tuple
 979                  */
 980                 foreach(l, subplan->setParam)
 981                 {
 982                         int                     paramid = lfirst_int(l);
 983                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 984
 985                         prm->execPlan = NULL;
 986                         prm->value = heap_getattr(node->curTuple, i, tdesc,
 987                                                                           &(prm->isnull));
 988                         i++;
 989                 }
 990         }
 991
 992         if (subLinkType == ARRAY_SUBLINK)
 993         {
 994                 /* There can be only one setParam... */
 995                 int                     paramid = linitial_int(subplan->setParam);
 996                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 997
 998                 /*
 999                  * We build the result array in query context so it won't disappear;
1000                  * to avoid leaking memory across repeated calls, we have to remember
1001                  * the latest value, much as for curTuple above.
1002                  */
1003                 if (node->curArray != PointerGetDatum(NULL))
1004                         pfree(DatumGetPointer(node->curArray));
1005                 if (astate != NULL)
1006                         node->curArray = makeArrayResult(astate,
1007                                                                                          econtext->ecxt_per_query_memory);
1008                 else
1009                 {
1010                         MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
1011                         node->curArray = PointerGetDatum(construct_empty_array(subplan->firstColType));
1012                 }
1013                 prm->execPlan = NULL;
1014                 prm->value = node->curArray;
1015                 prm->isnull = false;
1016         }
1017         else if (!found)
1018         {
1019                 if (subLinkType == EXISTS_SUBLINK)
1020                 {
1021                         /* There can be only one setParam... */
1022                         int                     paramid = linitial_int(subplan->setParam);
1023                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1024
1025                         prm->execPlan = NULL;
1026                         prm->value = BoolGetDatum(false);
1027                         prm->isnull = false;
1028                 }
1029                 else
1030                 {
1031                         foreach(l, subplan->setParam)
1032                         {
1033                                 int                     paramid = lfirst_int(l);
1034                                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1035
1036                                 prm->execPlan = NULL;
1037                                 prm->value = (Datum) 0;
1038                                 prm->isnull = true;
1039                         }
1040                 }
1041         }
1042
1043         MemoryContextSwitchTo(oldcontext);
1044 }
1045
1046 /*
1047  * Mark an initplan as needing recalculation
1048  */
1049 void
1050 ExecReScanSetParamPlan(SubPlanState *node, PlanState *parent)
1051 {
1052         PlanState  *planstate = node->planstate;
1053         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
1054         EState     *estate = parent->state;
1055         ListCell   *l;
1056
1057         /* sanity checks */
1058         if (subplan->parParam != NIL)
1059                 elog(ERROR, "direct correlated subquery unsupported as initplan");
1060         if (subplan->setParam == NIL)
1061                 elog(ERROR, "setParam list of initplan is empty");
1062         if (bms_is_empty(planstate->plan->extParam))
1063                 elog(ERROR, "extParam set of initplan is empty");
1064
1065         /*
1066          * Don't actually re-scan: it'll happen inside ExecSetParamPlan if needed.
1067          */
1068
1069         /*
1070          * Mark this subplan's output parameters as needing recalculation.
1071          *
1072          * CTE subplans are never executed via parameter recalculation; instead
1073          * they get run when called by nodeCtescan.c.  So don't mark the output
1074          * parameter of a CTE subplan as dirty, but do set the chgParam bit for it
1075          * so that dependent plan nodes will get told to rescan.
1076          */
1077         foreach(l, subplan->setParam)
1078         {
1079                 int                     paramid = lfirst_int(l);
1080                 ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
1081
1082                 if (subplan->subLinkType != CTE_SUBLINK)
1083                         prm->execPlan = node;
1084
1085                 parent->chgParam = bms_add_member(parent->chgParam, paramid);
1086         }
1087 }
1088
1089
1090 /*
1091  * ExecInitAlternativeSubPlan
1092  *
1093  * Initialize for execution of one of a set of alternative subplans.
1094  */
1095 AlternativeSubPlanState *
1096 ExecInitAlternativeSubPlan(AlternativeSubPlan *asplan, PlanState *parent)
1097 {
1098         AlternativeSubPlanState *asstate = makeNode(AlternativeSubPlanState);
1099         double          num_calls;
1100         SubPlan    *subplan1;
1101         SubPlan    *subplan2;
1102         Cost            cost1;
1103         Cost            cost2;
1104
1105         asstate->xprstate.evalfunc = (ExprStateEvalFunc) ExecAlternativeSubPlan;
1106         asstate->xprstate.expr = (Expr *) asplan;
1107
1108         /*
1109          * Initialize subplans.  (Can we get away with only initializing the one
1110          * we're going to use?)
1111          */
1112         asstate->subplans = (List *) ExecInitExpr((Expr *) asplan->subplans,
1113                                                                                           parent);
1114
1115         /*
1116          * Select the one to be used.  For this, we need an estimate of the number
1117          * of executions of the subplan.  We use the number of output rows
1118          * expected from the parent plan node.  This is a good estimate if we are
1119          * in the parent's targetlist, and an underestimate (but probably not by
1120          * more than a factor of 2) if we are in the qual.
1121          */
1122         num_calls = parent->plan->plan_rows;
1123
1124         /*
1125          * The planner saved enough info so that we don't have to work very hard
1126          * to estimate the total cost, given the number-of-calls estimate.
1127          */
1128         Assert(list_length(asplan->subplans) == 2);
1129         subplan1 = (SubPlan *) linitial(asplan->subplans);
1130         subplan2 = (SubPlan *) lsecond(asplan->subplans);
1131
1132         cost1 = subplan1->startup_cost + num_calls * subplan1->per_call_cost;
1133         cost2 = subplan2->startup_cost + num_calls * subplan2->per_call_cost;
1134
1135         if (cost1 < cost2)
1136                 asstate->active = 0;
1137         else
1138                 asstate->active = 1;
1139
1140         return asstate;
1141 }
1142
1143 /*
1144  * ExecAlternativeSubPlan
1145  *
1146  * Execute one of a set of alternative subplans.
1147  *
1148  * Note: in future we might consider changing to different subplans on the
1149  * fly, in case the original rowcount estimate turns out to be way off.
1150  */
1151 static Datum
1152 ExecAlternativeSubPlan(AlternativeSubPlanState *node,
1153                                            ExprContext *econtext,
1154                                            bool *isNull,
1155                                            ExprDoneCond *isDone)
1156 {
1157         /* Just pass control to the active subplan */
1158         SubPlanState *activesp = (SubPlanState *) list_nth(node->subplans,
1159                                                                                                            node->active);
1160
1161         Assert(IsA(activesp, SubPlanState));
1162
1163         return ExecSubPlan(activesp,
1164                                            econtext,
1165                                            isNull,
1166                                            isDone);
1167 }