src/backend/executor/nodeSubplan.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * nodeSubplan.c
   4  *        routines to support subselects
   5  *
   6  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  * IDENTIFICATION
  10  *        $PostgreSQL$
  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         ExprContext *innerecontext = node->innerecontext;
  93         TupleTableSlot *slot;
  94
  95         /* Shouldn't have any direct correlation Vars */
  96         if (subplan->parParam != NIL || node->args != NIL)
  97                 elog(ERROR, "hashed subplan with direct correlation not supported");
  98
  99         /*
 100          * If first time through or we need to rescan the subplan, build the hash
 101          * table.
 102          */
 103         if (node->hashtable == NULL || planstate->chgParam != NULL)
 104                 buildSubPlanHash(node, econtext);
 105
 106         /*
 107          * The result for an empty subplan is always FALSE; no need to evaluate
 108          * lefthand side.
 109          */
 110         *isNull = false;
 111         if (!node->havehashrows && !node->havenullrows)
 112                 return BoolGetDatum(false);
 113
 114         /*
 115          * Evaluate lefthand expressions and form a projection tuple. First we
 116          * have to set the econtext to use (hack alert!).
 117          */
 118         node->projLeft->pi_exprContext = econtext;
 119         slot = ExecProject(node->projLeft, NULL);
 120
 121         /*
 122          * Note: because we are typically called in a per-tuple context, we have
 123          * to explicitly clear the projected tuple before returning. Otherwise,
 124          * we'll have a double-free situation: the per-tuple context will probably
 125          * be reset before we're called again, and then the tuple slot will think
 126          * it still needs to free the tuple.
 127          */
 128
 129         /*
 130          * Since the hashtable routines will use innerecontext's per-tuple memory
 131          * as working memory, be sure to reset it for each tuple.
 132          */
 133         ResetExprContext(innerecontext);
 134
 135         /*
 136          * If the LHS is all non-null, probe for an exact match in the main hash
 137          * table.  If we find one, the result is TRUE. Otherwise, scan the
 138          * partly-null table to see if there are any rows that aren't provably
 139          * unequal to the LHS; if so, the result is UNKNOWN.  (We skip that part
 140          * if we don't care about UNKNOWN.) Otherwise, the result is FALSE.
 141          *
 142          * Note: the reason we can avoid a full scan of the main hash table is
 143          * that the combining operators are assumed never to yield NULL when both
 144          * inputs are non-null.  If they were to do so, we might need to produce
 145          * UNKNOWN instead of FALSE because of an UNKNOWN result in comparing the
 146          * LHS to some main-table entry --- which is a comparison we will not even
 147          * make, unless there's a chance match of hash keys.
 148          */
 149         if (slotNoNulls(slot))
 150         {
 151                 if (node->havehashrows &&
 152                         FindTupleHashEntry(node->hashtable,
 153                                                            slot,
 154                                                            node->cur_eq_funcs,
 155                                                            node->lhs_hash_funcs) != NULL)
 156                 {
 157                         ExecClearTuple(slot);
 158                         return BoolGetDatum(true);
 159                 }
 160                 if (node->havenullrows &&
 161                         findPartialMatch(node->hashnulls, slot))
 162                 {
 163                         ExecClearTuple(slot);
 164                         *isNull = true;
 165                         return BoolGetDatum(false);
 166                 }
 167                 ExecClearTuple(slot);
 168                 return BoolGetDatum(false);
 169         }
 170
 171         /*
 172          * When the LHS is partly or wholly NULL, we can never return TRUE. If we
 173          * don't care about UNKNOWN, just return FALSE.  Otherwise, if the LHS is
 174          * wholly NULL, immediately return UNKNOWN.  (Since the combining
 175          * operators are strict, the result could only be FALSE if the sub-select
 176          * were empty, but we already handled that case.) Otherwise, we must scan
 177          * both the main and partly-null tables to see if there are any rows that
 178          * aren't provably unequal to the LHS; if so, the result is UNKNOWN.
 179          * Otherwise, the result is FALSE.
 180          */
 181         if (node->hashnulls == NULL)
 182         {
 183                 ExecClearTuple(slot);
 184                 return BoolGetDatum(false);
 185         }
 186         if (slotAllNulls(slot))
 187         {
 188                 ExecClearTuple(slot);
 189                 *isNull = true;
 190                 return BoolGetDatum(false);
 191         }
 192         /* Scan partly-null table first, since more likely to get a match */
 193         if (node->havenullrows &&
 194                 findPartialMatch(node->hashnulls, slot))
 195         {
 196                 ExecClearTuple(slot);
 197                 *isNull = true;
 198                 return BoolGetDatum(false);
 199         }
 200         if (node->havehashrows &&
 201                 findPartialMatch(node->hashtable, slot))
 202         {
 203                 ExecClearTuple(slot);
 204                 *isNull = true;
 205                 return BoolGetDatum(false);
 206         }
 207         ExecClearTuple(slot);
 208         return BoolGetDatum(false);
 209 }
 210
 211 /*
 212  * ExecScanSubPlan: default case where we have to rescan subplan each time
 213  */
 214 static Datum
 215 ExecScanSubPlan(SubPlanState *node,
 216                                 ExprContext *econtext,
 217                                 bool *isNull)
 218 {
 219         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 220         PlanState  *planstate = node->planstate;
 221         SubLinkType subLinkType = subplan->subLinkType;
 222         MemoryContext oldcontext;
 223         TupleTableSlot *slot;
 224         Datum           result;
 225         bool            found = false;  /* TRUE if got at least one subplan tuple */
 226         ListCell   *pvar;
 227         ListCell   *l;
 228         ArrayBuildState *astate = NULL;
 229
 230         /*
 231          * We are probably in a short-lived expression-evaluation context. Switch
 232          * to the per-query context for manipulating the child plan's chgParam,
 233          * calling ExecProcNode on it, etc.
 234          */
 235         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 236
 237         /*
 238          * Set Params of this plan from parent plan correlation values. (Any
 239          * calculation we have to do is done in the parent econtext, since the
 240          * Param values don't need to have per-query lifetime.)
 241          */
 242         Assert(list_length(subplan->parParam) == list_length(node->args));
 243
 244         forboth(l, subplan->parParam, pvar, node->args)
 245         {
 246                 int                     paramid = lfirst_int(l);
 247                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 248
 249                 prm->value = ExecEvalExprSwitchContext((ExprState *) lfirst(pvar),
 250                                                                                            econtext,
 251                                                                                            &(prm->isnull),
 252                                                                                            NULL);
 253                 planstate->chgParam = bms_add_member(planstate->chgParam, paramid);
 254         }
 255
 256         /*
 257          * Now that we've set up its parameters, we can reset the subplan.
 258          */
 259         ExecReScan(planstate, NULL);
 260
 261         /*
 262          * For all sublink types except EXPR_SUBLINK and ARRAY_SUBLINK, the result
 263          * is boolean as are the results of the combining operators. We combine
 264          * results across tuples (if the subplan produces more than one) using OR
 265          * semantics for ANY_SUBLINK or AND semantics for ALL_SUBLINK.
 266          * (ROWCOMPARE_SUBLINK doesn't allow multiple tuples from the subplan.)
 267          * NULL results from the combining operators are handled according to the
 268          * usual SQL semantics for OR and AND.  The result for no input tuples is
 269          * FALSE for ANY_SUBLINK, TRUE for ALL_SUBLINK, NULL for
 270          * ROWCOMPARE_SUBLINK.
 271          *
 272          * For EXPR_SUBLINK we require the subplan to produce no more than one
 273          * tuple, else an error is raised.      If zero tuples are produced, we return
 274          * NULL.  Assuming we get a tuple, we just use its first column (there can
 275          * be only one non-junk column in this case).
 276          *
 277          * For ARRAY_SUBLINK we allow the subplan to produce any number of tuples,
 278          * and form an array of the first column's values.  Note in particular
 279          * that we produce a zero-element array if no tuples are produced (this is
 280          * a change from pre-8.3 behavior of returning NULL).
 281          */
 282         result = BoolGetDatum(subLinkType == ALL_SUBLINK);
 283         *isNull = false;
 284
 285         for (slot = ExecProcNode(planstate);
 286                  !TupIsNull(slot);
 287                  slot = ExecProcNode(planstate))
 288         {
 289                 TupleDesc       tdesc = slot->tts_tupleDescriptor;
 290                 Datum           rowresult;
 291                 bool            rownull;
 292                 int                     col;
 293                 ListCell   *plst;
 294
 295                 if (subLinkType == EXISTS_SUBLINK)
 296                 {
 297                         found = true;
 298                         result = BoolGetDatum(true);
 299                         break;
 300                 }
 301
 302                 if (subLinkType == EXPR_SUBLINK)
 303                 {
 304                         /* cannot allow multiple input tuples for EXPR sublink */
 305                         if (found)
 306                                 ereport(ERROR,
 307                                                 (errcode(ERRCODE_CARDINALITY_VIOLATION),
 308                                                  errmsg("more than one row returned by a subquery used as an expression")));
 309                         found = true;
 310
 311                         /*
 312                          * We need to copy the subplan's tuple in case the result is of
 313                          * pass-by-ref type --- our return value will point into this
 314                          * copied tuple!  Can't use the subplan's instance of the tuple
 315                          * since it won't still be valid after next ExecProcNode() call.
 316                          * node->curTuple keeps track of the copied tuple for eventual
 317                          * freeing.
 318                          */
 319                         if (node->curTuple)
 320                                 heap_freetuple(node->curTuple);
 321                         node->curTuple = ExecCopySlotTuple(slot);
 322
 323                         result = heap_getattr(node->curTuple, 1, tdesc, isNull);
 324                         /* keep scanning subplan to make sure there's only one tuple */
 325                         continue;
 326                 }
 327
 328                 if (subLinkType == ARRAY_SUBLINK)
 329                 {
 330                         Datum           dvalue;
 331                         bool            disnull;
 332
 333                         found = true;
 334                         /* stash away current value */
 335                         Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
 336                         dvalue = slot_getattr(slot, 1, &disnull);
 337                         astate = accumArrayResult(astate, dvalue, disnull,
 338                                                                           subplan->firstColType, oldcontext);
 339                         /* keep scanning subplan to collect all values */
 340                         continue;
 341                 }
 342
 343                 /* cannot allow multiple input tuples for ROWCOMPARE sublink either */
 344                 if (subLinkType == ROWCOMPARE_SUBLINK && found)
 345                         ereport(ERROR,
 346                                         (errcode(ERRCODE_CARDINALITY_VIOLATION),
 347                                          errmsg("more than one row returned by a subquery used as an expression")));
 348
 349                 found = true;
 350
 351                 /*
 352                  * For ALL, ANY, and ROWCOMPARE sublinks, load up the Params
 353                  * representing the columns of the sub-select, and then evaluate the
 354                  * combining expression.
 355                  */
 356                 col = 1;
 357                 foreach(plst, subplan->paramIds)
 358                 {
 359                         int                     paramid = lfirst_int(plst);
 360                         ParamExecData *prmdata;
 361
 362                         prmdata = &(econtext->ecxt_param_exec_vals[paramid]);
 363                         Assert(prmdata->execPlan == NULL);
 364                         prmdata->value = slot_getattr(slot, col, &(prmdata->isnull));
 365                         col++;
 366                 }
 367
 368                 rowresult = ExecEvalExprSwitchContext(node->testexpr, econtext,
 369                                                                                           &rownull, NULL);
 370
 371                 if (subLinkType == ANY_SUBLINK)
 372                 {
 373                         /* combine across rows per OR semantics */
 374                         if (rownull)
 375                                 *isNull = true;
 376                         else if (DatumGetBool(rowresult))
 377                         {
 378                                 result = BoolGetDatum(true);
 379                                 *isNull = false;
 380                                 break;                  /* needn't look at any more rows */
 381                         }
 382                 }
 383                 else if (subLinkType == ALL_SUBLINK)
 384                 {
 385                         /* combine across rows per AND semantics */
 386                         if (rownull)
 387                                 *isNull = true;
 388                         else if (!DatumGetBool(rowresult))
 389                         {
 390                                 result = BoolGetDatum(false);
 391                                 *isNull = false;
 392                                 break;                  /* needn't look at any more rows */
 393                         }
 394                 }
 395                 else
 396                 {
 397                         /* must be ROWCOMPARE_SUBLINK */
 398                         result = rowresult;
 399                         *isNull = rownull;
 400                 }
 401         }
 402
 403         MemoryContextSwitchTo(oldcontext);
 404
 405         if (subLinkType == ARRAY_SUBLINK)
 406         {
 407                 /* We return the result in the caller's context */
 408                 if (astate != NULL)
 409                         result = makeArrayResult(astate, oldcontext);
 410                 else
 411                         result = PointerGetDatum(construct_empty_array(subplan->firstColType));
 412         }
 413         else if (!found)
 414         {
 415                 /*
 416                  * deal with empty subplan result.      result/isNull were previously
 417                  * initialized correctly for all sublink types except EXPR and
 418                  * ROWCOMPARE; for those, return NULL.
 419                  */
 420                 if (subLinkType == EXPR_SUBLINK ||
 421                         subLinkType == ROWCOMPARE_SUBLINK)
 422                 {
 423                         result = (Datum) 0;
 424                         *isNull = true;
 425                 }
 426         }
 427
 428         return result;
 429 }
 430
 431 /*
 432  * buildSubPlanHash: load hash table by scanning subplan output.
 433  */
 434 static void
 435 buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
 436 {
 437         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 438         PlanState  *planstate = node->planstate;
 439         int                     ncols = list_length(subplan->paramIds);
 440         ExprContext *innerecontext = node->innerecontext;
 441         MemoryContext tempcxt = innerecontext->ecxt_per_tuple_memory;
 442         MemoryContext oldcontext;
 443         int                     nbuckets;
 444         TupleTableSlot *slot;
 445
 446         Assert(subplan->subLinkType == ANY_SUBLINK);
 447
 448         /*
 449          * If we already had any hash tables, destroy 'em; then create empty hash
 450          * table(s).
 451          *
 452          * If we need to distinguish accurately between FALSE and UNKNOWN (i.e.,
 453          * NULL) results of the IN operation, then we have to store subplan output
 454          * rows that are partly or wholly NULL.  We store such rows in a separate
 455          * hash table that we expect will be much smaller than the main table. (We
 456          * can use hashing to eliminate partly-null rows that are not distinct. We
 457          * keep them separate to minimize the cost of the inevitable full-table
 458          * searches; see findPartialMatch.)
 459          *
 460          * If it's not necessary to distinguish FALSE and UNKNOWN, then we don't
 461          * need to store subplan output rows that contain NULL.
 462          */
 463         MemoryContextReset(node->tablecxt);
 464         node->hashtable = NULL;
 465         node->hashnulls = NULL;
 466         node->havehashrows = false;
 467         node->havenullrows = false;
 468
 469         nbuckets = (int) ceil(planstate->plan->plan_rows);
 470         if (nbuckets < 1)
 471                 nbuckets = 1;
 472
 473         node->hashtable = BuildTupleHashTable(ncols,
 474                                                                                   node->keyColIdx,
 475                                                                                   node->tab_eq_funcs,
 476                                                                                   node->tab_hash_funcs,
 477                                                                                   nbuckets,
 478                                                                                   sizeof(TupleHashEntryData),
 479                                                                                   node->tablecxt,
 480                                                                                   tempcxt);
 481
 482         if (!subplan->unknownEqFalse)
 483         {
 484                 if (ncols == 1)
 485                         nbuckets = 1;           /* there can only be one entry */
 486                 else
 487                 {
 488                         nbuckets /= 16;
 489                         if (nbuckets < 1)
 490                                 nbuckets = 1;
 491                 }
 492                 node->hashnulls = BuildTupleHashTable(ncols,
 493                                                                                           node->keyColIdx,
 494                                                                                           node->tab_eq_funcs,
 495                                                                                           node->tab_hash_funcs,
 496                                                                                           nbuckets,
 497                                                                                           sizeof(TupleHashEntryData),
 498                                                                                           node->tablecxt,
 499                                                                                           tempcxt);
 500         }
 501
 502         /*
 503          * We are probably in a short-lived expression-evaluation context. Switch
 504          * to the per-query context for manipulating the child plan.
 505          */
 506         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 507
 508         /*
 509          * Reset subplan to start.
 510          */
 511         ExecReScan(planstate, NULL);
 512
 513         /*
 514          * Scan the subplan and load the hash table(s).  Note that when there are
 515          * duplicate rows coming out of the sub-select, only one copy is stored.
 516          */
 517         for (slot = ExecProcNode(planstate);
 518                  !TupIsNull(slot);
 519                  slot = ExecProcNode(planstate))
 520         {
 521                 int                     col = 1;
 522                 ListCell   *plst;
 523                 bool            isnew;
 524
 525                 /*
 526                  * Load up the Params representing the raw sub-select outputs, then
 527                  * form the projection tuple to store in the hashtable.
 528                  */
 529                 foreach(plst, subplan->paramIds)
 530                 {
 531                         int                     paramid = lfirst_int(plst);
 532                         ParamExecData *prmdata;
 533
 534                         prmdata = &(innerecontext->ecxt_param_exec_vals[paramid]);
 535                         Assert(prmdata->execPlan == NULL);
 536                         prmdata->value = slot_getattr(slot, col,
 537                                                                                   &(prmdata->isnull));
 538                         col++;
 539                 }
 540                 slot = ExecProject(node->projRight, NULL);
 541
 542                 /*
 543                  * If result contains any nulls, store separately or not at all.
 544                  */
 545                 if (slotNoNulls(slot))
 546                 {
 547                         (void) LookupTupleHashEntry(node->hashtable, slot, &isnew);
 548                         node->havehashrows = true;
 549                 }
 550                 else if (node->hashnulls)
 551                 {
 552                         (void) LookupTupleHashEntry(node->hashnulls, slot, &isnew);
 553                         node->havenullrows = true;
 554                 }
 555
 556                 /*
 557                  * Reset innerecontext after each inner tuple to free any memory used
 558                  * in hash computation or comparison routines.
 559                  */
 560                 ResetExprContext(innerecontext);
 561         }
 562
 563         /*
 564          * Since the projected tuples are in the sub-query's context and not the
 565          * main context, we'd better clear the tuple slot before there's any
 566          * chance of a reset of the sub-query's context.  Else we will have the
 567          * potential for a double free attempt.  (XXX possibly no longer needed,
 568          * but can't hurt.)
 569          */
 570         ExecClearTuple(node->projRight->pi_slot);
 571
 572         MemoryContextSwitchTo(oldcontext);
 573 }
 574
 575 /*
 576  * findPartialMatch: does the hashtable contain an entry that is not
 577  * provably distinct from the tuple?
 578  *
 579  * We have to scan the whole hashtable; we can't usefully use hashkeys
 580  * to guide probing, since we might get partial matches on tuples with
 581  * hashkeys quite unrelated to what we'd get from the given tuple.
 582  */
 583 static bool
 584 findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot)
 585 {
 586         int                     numCols = hashtable->numCols;
 587         AttrNumber *keyColIdx = hashtable->keyColIdx;
 588         TupleHashIterator hashiter;
 589         TupleHashEntry entry;
 590
 591         InitTupleHashIterator(hashtable, &hashiter);
 592         while ((entry = ScanTupleHashTable(&hashiter)) != NULL)
 593         {
 594                 ExecStoreMinimalTuple(entry->firstTuple, hashtable->tableslot, false);
 595                 if (!execTuplesUnequal(slot, hashtable->tableslot,
 596                                                            numCols, keyColIdx,
 597                                                            hashtable->cur_eq_funcs,
 598                                                            hashtable->tempcxt))
 599                 {
 600                         TermTupleHashIterator(&hashiter);
 601                         return true;
 602                 }
 603         }
 604         /* No TermTupleHashIterator call needed here */
 605         return false;
 606 }
 607
 608 /*
 609  * slotAllNulls: is the slot completely NULL?
 610  *
 611  * This does not test for dropped columns, which is OK because we only
 612  * use it on projected tuples.
 613  */
 614 static bool
 615 slotAllNulls(TupleTableSlot *slot)
 616 {
 617         int                     ncols = slot->tts_tupleDescriptor->natts;
 618         int                     i;
 619
 620         for (i = 1; i <= ncols; i++)
 621         {
 622                 if (!slot_attisnull(slot, i))
 623                         return false;
 624         }
 625         return true;
 626 }
 627
 628 /*
 629  * slotNoNulls: is the slot entirely not NULL?
 630  *
 631  * This does not test for dropped columns, which is OK because we only
 632  * use it on projected tuples.
 633  */
 634 static bool
 635 slotNoNulls(TupleTableSlot *slot)
 636 {
 637         int                     ncols = slot->tts_tupleDescriptor->natts;
 638         int                     i;
 639
 640         for (i = 1; i <= ncols; i++)
 641         {
 642                 if (slot_attisnull(slot, i))
 643                         return false;
 644         }
 645         return true;
 646 }
 647
 648 /* ----------------------------------------------------------------
 649  *              ExecInitSubPlan
 650  *
 651  * Create a SubPlanState for a SubPlan; this is the SubPlan-specific part
 652  * of ExecInitExpr().  We split it out so that it can be used for InitPlans
 653  * as well as regular SubPlans.  Note that we don't link the SubPlan into
 654  * the parent's subPlan list, because that shouldn't happen for InitPlans.
 655  * Instead, ExecInitExpr() does that one part.
 656  * ----------------------------------------------------------------
 657  */
 658 SubPlanState *
 659 ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
 660 {
 661         SubPlanState *sstate = makeNode(SubPlanState);
 662         EState     *estate = parent->state;
 663
 664         sstate->xprstate.evalfunc = (ExprStateEvalFunc) ExecSubPlan;
 665         sstate->xprstate.expr = (Expr *) subplan;
 666
 667         /* Link the SubPlanState to already-initialized subplan */
 668         sstate->planstate = (PlanState *) list_nth(estate->es_subplanstates,
 669                                                                                            subplan->plan_id - 1);
 670
 671         /* Initialize subexpressions */
 672         sstate->testexpr = ExecInitExpr((Expr *) subplan->testexpr, parent);
 673         sstate->args = (List *) ExecInitExpr((Expr *) subplan->args, parent);
 674
 675         /*
 676          * initialize my state
 677          */
 678         sstate->curTuple = NULL;
 679         sstate->projLeft = NULL;
 680         sstate->projRight = NULL;
 681         sstate->hashtable = NULL;
 682         sstate->hashnulls = NULL;
 683         sstate->tablecxt = NULL;
 684         sstate->innerecontext = NULL;
 685         sstate->keyColIdx = NULL;
 686         sstate->tab_hash_funcs = NULL;
 687         sstate->tab_eq_funcs = NULL;
 688         sstate->lhs_hash_funcs = NULL;
 689         sstate->cur_eq_funcs = NULL;
 690
 691         /*
 692          * If this plan is un-correlated or undirect correlated one and want to
 693          * set params for parent plan then mark parameters as needing evaluation.
 694          *
 695          * A CTE subplan's output parameter is never to be evaluated in the normal
 696          * way, so skip this in that case.
 697          *
 698          * Note that in the case of un-correlated subqueries we don't care about
 699          * setting parent->chgParam here: indices take care about it, for others -
 700          * it doesn't matter...
 701          */
 702         if (subplan->setParam != NIL && subplan->subLinkType != CTE_SUBLINK)
 703         {
 704                 ListCell   *lst;
 705
 706                 foreach(lst, subplan->setParam)
 707                 {
 708                         int                     paramid = lfirst_int(lst);
 709                         ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
 710
 711                         prm->execPlan = sstate;
 712                 }
 713         }
 714
 715         /*
 716          * If we are going to hash the subquery output, initialize relevant stuff.
 717          * (We don't create the hashtable until needed, though.)
 718          */
 719         if (subplan->useHashTable)
 720         {
 721                 int                     ncols,
 722                                         i;
 723                 TupleDesc       tupDesc;
 724                 TupleTable      tupTable;
 725                 TupleTableSlot *slot;
 726                 List       *oplist,
 727                                    *lefttlist,
 728                                    *righttlist,
 729                                    *leftptlist,
 730                                    *rightptlist;
 731                 ListCell   *l;
 732
 733                 /* We need a memory context to hold the hash table(s) */
 734                 sstate->tablecxt =
 735                         AllocSetContextCreate(CurrentMemoryContext,
 736                                                                   "Subplan HashTable Context",
 737                                                                   ALLOCSET_DEFAULT_MINSIZE,
 738                                                                   ALLOCSET_DEFAULT_INITSIZE,
 739                                                                   ALLOCSET_DEFAULT_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                         sstate->cur_eq_funcs[i - 1].fn_expr = (Node *) opexpr;
 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                  * Create a tupletable to hold these tuples.  (Note: we never bother
 857                  * to free the tupletable explicitly; that's okay because it will
 858                  * never store raw disk tuples that might have associated buffer pins.
 859                  * The only resource involved is memory, which will be cleaned up by
 860                  * freeing the query context.)
 861                  */
 862                 tupTable = ExecCreateTupleTable(2);
 863
 864                 /*
 865                  * Construct tupdescs, slots and projection nodes for left and right
 866                  * sides.  The lefthand expressions will be evaluated in the parent
 867                  * plan node's exprcontext, which we don't have access to here.
 868                  * Fortunately we can just pass NULL for now and fill it in later
 869                  * (hack alert!).  The righthand expressions will be evaluated in our
 870                  * own innerecontext.
 871                  */
 872                 tupDesc = ExecTypeFromTL(leftptlist, false);
 873                 slot = ExecAllocTableSlot(tupTable);
 874                 ExecSetSlotDescriptor(slot, tupDesc);
 875                 sstate->projLeft = ExecBuildProjectionInfo(lefttlist,
 876                                                                                                    NULL,
 877                                                                                                    slot,
 878                                                                                                    NULL);
 879
 880                 tupDesc = ExecTypeFromTL(rightptlist, false);
 881                 slot = ExecAllocTableSlot(tupTable);
 882                 ExecSetSlotDescriptor(slot, tupDesc);
 883                 sstate->projRight = ExecBuildProjectionInfo(righttlist,
 884                                                                                                         sstate->innerecontext,
 885                                                                                                         slot,
 886                                                                                                         NULL);
 887         }
 888
 889         return sstate;
 890 }
 891
 892 /* ----------------------------------------------------------------
 893  *              ExecSetParamPlan
 894  *
 895  *              Executes an InitPlan subplan and sets its output parameters.
 896  *
 897  * This is called from ExecEvalParam() when the value of a PARAM_EXEC
 898  * parameter is requested and the param's execPlan field is set (indicating
 899  * that the param has not yet been evaluated).  This allows lazy evaluation
 900  * of initplans: we don't run the subplan until/unless we need its output.
 901  * Note that this routine MUST clear the execPlan fields of the plan's
 902  * output parameters after evaluating them!
 903  * ----------------------------------------------------------------
 904  */
 905 void
 906 ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
 907 {
 908         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 909         PlanState  *planstate = node->planstate;
 910         SubLinkType subLinkType = subplan->subLinkType;
 911         MemoryContext oldcontext;
 912         TupleTableSlot *slot;
 913         ListCell   *l;
 914         bool            found = false;
 915         ArrayBuildState *astate = NULL;
 916
 917         if (subLinkType == ANY_SUBLINK ||
 918                 subLinkType == ALL_SUBLINK)
 919                 elog(ERROR, "ANY/ALL subselect unsupported as initplan");
 920         if (subLinkType == CTE_SUBLINK)
 921                 elog(ERROR, "CTE subplans should not be executed via ExecSetParamPlan");
 922
 923         /*
 924          * Must switch to per-query memory context.
 925          */
 926         oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
 927
 928         /*
 929          * Run the plan.  (If it needs to be rescanned, the first ExecProcNode
 930          * call will take care of that.)
 931          */
 932         for (slot = ExecProcNode(planstate);
 933                  !TupIsNull(slot);
 934                  slot = ExecProcNode(planstate))
 935         {
 936                 TupleDesc       tdesc = slot->tts_tupleDescriptor;
 937                 int                     i = 1;
 938
 939                 if (subLinkType == EXISTS_SUBLINK)
 940                 {
 941                         /* There can be only one setParam... */
 942                         int                     paramid = linitial_int(subplan->setParam);
 943                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 944
 945                         prm->execPlan = NULL;
 946                         prm->value = BoolGetDatum(true);
 947                         prm->isnull = false;
 948                         found = true;
 949                         break;
 950                 }
 951
 952                 if (subLinkType == ARRAY_SUBLINK)
 953                 {
 954                         Datum           dvalue;
 955                         bool            disnull;
 956
 957                         found = true;
 958                         /* stash away current value */
 959                         Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
 960                         dvalue = slot_getattr(slot, 1, &disnull);
 961                         astate = accumArrayResult(astate, dvalue, disnull,
 962                                                                           subplan->firstColType, oldcontext);
 963                         /* keep scanning subplan to collect all values */
 964                         continue;
 965                 }
 966
 967                 if (found &&
 968                         (subLinkType == EXPR_SUBLINK ||
 969                          subLinkType == ROWCOMPARE_SUBLINK))
 970                         ereport(ERROR,
 971                                         (errcode(ERRCODE_CARDINALITY_VIOLATION),
 972                                          errmsg("more than one row returned by a subquery used as an expression")));
 973
 974                 found = true;
 975
 976                 /*
 977                  * We need to copy the subplan's tuple into our own context, in case
 978                  * any of the params are pass-by-ref type --- the pointers stored in
 979                  * the param structs will point at this copied tuple! node->curTuple
 980                  * keeps track of the copied tuple for eventual freeing.
 981                  */
 982                 if (node->curTuple)
 983                         heap_freetuple(node->curTuple);
 984                 node->curTuple = ExecCopySlotTuple(slot);
 985
 986                 /*
 987                  * Now set all the setParam params from the columns of the tuple
 988                  */
 989                 foreach(l, subplan->setParam)
 990                 {
 991                         int                     paramid = lfirst_int(l);
 992                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
 993
 994                         prm->execPlan = NULL;
 995                         prm->value = heap_getattr(node->curTuple, i, tdesc,
 996                                                                           &(prm->isnull));
 997                         i++;
 998                 }
 999         }
1000
1001         if (subLinkType == ARRAY_SUBLINK)
1002         {
1003                 /* There can be only one setParam... */
1004                 int                     paramid = linitial_int(subplan->setParam);
1005                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1006
1007                 prm->execPlan = NULL;
1008                 /* We build the result in query context so it won't disappear */
1009                 if (astate != NULL)
1010                         prm->value = makeArrayResult(astate,
1011                                                                                  econtext->ecxt_per_query_memory);
1012                 else
1013                 {
1014                         MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
1015                         prm->value = PointerGetDatum(construct_empty_array(subplan->firstColType));
1016                 }
1017                 prm->isnull = false;
1018         }
1019         else if (!found)
1020         {
1021                 if (subLinkType == EXISTS_SUBLINK)
1022                 {
1023                         /* There can be only one setParam... */
1024                         int                     paramid = linitial_int(subplan->setParam);
1025                         ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1026
1027                         prm->execPlan = NULL;
1028                         prm->value = BoolGetDatum(false);
1029                         prm->isnull = false;
1030                 }
1031                 else
1032                 {
1033                         foreach(l, subplan->setParam)
1034                         {
1035                                 int                     paramid = lfirst_int(l);
1036                                 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1037
1038                                 prm->execPlan = NULL;
1039                                 prm->value = (Datum) 0;
1040                                 prm->isnull = true;
1041                         }
1042                 }
1043         }
1044
1045         MemoryContextSwitchTo(oldcontext);
1046 }
1047
1048 /*
1049  * Mark an initplan as needing recalculation
1050  */
1051 void
1052 ExecReScanSetParamPlan(SubPlanState *node, PlanState *parent)
1053 {
1054         PlanState  *planstate = node->planstate;
1055         SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
1056         EState     *estate = parent->state;
1057         ListCell   *l;
1058
1059         /* sanity checks */
1060         if (subplan->parParam != NIL)
1061                 elog(ERROR, "direct correlated subquery unsupported as initplan");
1062         if (subplan->setParam == NIL)
1063                 elog(ERROR, "setParam list of initplan is empty");
1064         if (bms_is_empty(planstate->plan->extParam))
1065                 elog(ERROR, "extParam set of initplan is empty");
1066
1067         /*
1068          * Don't actually re-scan: it'll happen inside ExecSetParamPlan if needed.
1069          */
1070
1071         /*
1072          * Mark this subplan's output parameters as needing recalculation.
1073          *
1074          * CTE subplans are never executed via parameter recalculation; instead
1075          * they get run when called by nodeCtescan.c.  So don't mark the output
1076          * parameter of a CTE subplan as dirty, but do set the chgParam bit
1077          * for it so that dependent plan nodes will get told to rescan.
1078          */
1079         foreach(l, subplan->setParam)
1080         {
1081                 int                     paramid = lfirst_int(l);
1082                 ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
1083
1084                 if (subplan->subLinkType != CTE_SUBLINK)
1085                         prm->execPlan = node;
1086
1087                 parent->chgParam = bms_add_member(parent->chgParam, paramid);
1088         }
1089 }
1090
1091
1092 /*
1093  * ExecInitAlternativeSubPlan
1094  *
1095  * Initialize for execution of one of a set of alternative subplans.
1096  */
1097 AlternativeSubPlanState *
1098 ExecInitAlternativeSubPlan(AlternativeSubPlan *asplan, PlanState *parent)
1099 {
1100         AlternativeSubPlanState *asstate = makeNode(AlternativeSubPlanState);
1101         double          num_calls;
1102         SubPlan    *subplan1;
1103         SubPlan    *subplan2;
1104         Cost            cost1;
1105         Cost            cost2;
1106
1107         asstate->xprstate.evalfunc = (ExprStateEvalFunc) ExecAlternativeSubPlan;
1108         asstate->xprstate.expr = (Expr *) asplan;
1109
1110         /*
1111          * Initialize subplans.  (Can we get away with only initializing the
1112          * one we're going to use?)
1113          */
1114         asstate->subplans = (List *) ExecInitExpr((Expr *) asplan->subplans,
1115                                                                                           parent);
1116
1117         /*
1118          * Select the one to be used.  For this, we need an estimate of the
1119          * number of executions of the subplan.  We use the number of output
1120          * rows expected from the parent plan node.  This is a good estimate
1121          * if we are in the parent's targetlist, and an underestimate (but
1122          * probably not by more than a factor of 2) if we are in the qual.
1123          */
1124         num_calls = parent->plan->plan_rows;
1125
1126         /*
1127          * The planner saved enough info so that we don't have to work very hard
1128          * to estimate the total cost, given the number-of-calls estimate.
1129          */
1130         Assert(list_length(asplan->subplans) == 2);
1131         subplan1 = (SubPlan *) linitial(asplan->subplans);
1132         subplan2 = (SubPlan *) lsecond(asplan->subplans);
1133
1134         cost1 = subplan1->startup_cost + num_calls * subplan1->per_call_cost;
1135         cost2 = subplan2->startup_cost + num_calls * subplan2->per_call_cost;
1136
1137         if (cost1 < cost2)
1138                 asstate->active = 0;
1139         else
1140                 asstate->active = 1;
1141
1142         return asstate;
1143 }
1144
1145 /*
1146  * ExecAlternativeSubPlan
1147  *
1148  * Execute one of a set of alternative subplans.
1149  *
1150  * Note: in future we might consider changing to different subplans on the
1151  * fly, in case the original rowcount estimate turns out to be way off.
1152  */
1153 static Datum
1154 ExecAlternativeSubPlan(AlternativeSubPlanState *node,
1155                                            ExprContext *econtext,
1156                                            bool *isNull,
1157                                            ExprDoneCond *isDone)
1158 {
1159         /* Just pass control to the active subplan */
1160         SubPlanState   *activesp = (SubPlanState *) list_nth(node->subplans,
1161                                                                                                                  node->active);
1162
1163         Assert(IsA(activesp, SubPlanState));
1164
1165         return ExecSubPlan(activesp,
1166                                            econtext,
1167                                            isNull,
1168                                            isDone);
1169 }