1 /*-------------------------------------------------------------------------
2 *
3 * nodeSubplan.c
4 * routines to support sub-selects appearing in expressions
5 *
6 * This module is concerned with executing SubPlan expression nodes, which
7 * should not be confused with sub-SELECTs appearing in FROM. SubPlans are
8 * divided into "initplans", which are those that need only one evaluation per
9 * query (among other restrictions, this requires that they don't use any
10 * direct correlation variables from the parent plan level), and "regular"
11 * subplans, which are re-evaluated every time their result is required.
12 *
13 *
14 * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
15 * Portions Copyright (c) 1994, Regents of the University of California
16 *
17 * IDENTIFICATION
18 * src/backend/executor/nodeSubplan.c
19 *
20 *-------------------------------------------------------------------------
21 */
22 /*
23 * INTERFACE ROUTINES
24 * ExecSubPlan - process a subselect
25 * ExecInitSubPlan - initialize a subselect
26 */
27 #include "postgres.h"
28
29 #include <limits.h>
30 #include <math.h>
31
32 #include "access/htup_details.h"
33 #include "executor/executor.h"
34 #include "executor/nodeSubplan.h"
35 #include "nodes/makefuncs.h"
36 #include "optimizer/clauses.h"
37 #include "utils/array.h"
38 #include "utils/lsyscache.h"
39 #include "utils/memutils.h"
40
41
42 static Datum ExecSubPlan(SubPlanState *node,
43 ExprContext *econtext,
44 bool *isNull,
45 ExprDoneCond *isDone);
46 static Datum ExecAlternativeSubPlan(AlternativeSubPlanState *node,
47 ExprContext *econtext,
48 bool *isNull,
49 ExprDoneCond *isDone);
50 static Datum ExecHashSubPlan(SubPlanState *node,
51 ExprContext *econtext,
52 bool *isNull);
53 static Datum ExecScanSubPlan(SubPlanState *node,
54 ExprContext *econtext,
55 bool *isNull);
56 static void buildSubPlanHash(SubPlanState *node, ExprContext *econtext);
57 static bool findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot,
58 FmgrInfo *eqfunctions);
59 static bool slotAllNulls(TupleTableSlot *slot);
60 static bool slotNoNulls(TupleTableSlot *slot);
61
62
63 /* ----------------------------------------------------------------
64 * ExecSubPlan
65 *
66 * This is the main entry point for execution of a regular SubPlan.
67 * ----------------------------------------------------------------
68 */
69 static Datum
ExecSubPlan(SubPlanState * node,ExprContext * econtext,bool * isNull,ExprDoneCond * isDone)70 ExecSubPlan(SubPlanState *node,
71 ExprContext *econtext,
72 bool *isNull,
73 ExprDoneCond *isDone)
74 {
75 SubPlan *subplan = (SubPlan *) node->xprstate.expr;
76 EState *estate = node->planstate->state;
77 ScanDirection dir = estate->es_direction;
78 Datum retval;
79
80 /* Set default values for result flags: non-null, not a set result */
81 *isNull = false;
82 if (isDone)
83 *isDone = ExprSingleResult;
84
85 /* Sanity checks */
86 if (subplan->subLinkType == CTE_SUBLINK)
87 elog(ERROR, "CTE subplans should not be executed via ExecSubPlan");
88 if (subplan->setParam != NIL && subplan->subLinkType != MULTIEXPR_SUBLINK)
89 elog(ERROR, "cannot set parent params from subquery");
90
91 /* Force forward-scan mode for evaluation */
92 estate->es_direction = ForwardScanDirection;
93
94 /* Select appropriate evaluation strategy */
95 if (subplan->useHashTable)
96 retval = ExecHashSubPlan(node, econtext, isNull);
97 else
98 retval = ExecScanSubPlan(node, econtext, isNull);
99
100 /* restore scan direction */
101 estate->es_direction = dir;
102
103 return retval;
104 }
105
106 /*
107 * ExecHashSubPlan: store subselect result in an in-memory hash table
108 */
109 static Datum
ExecHashSubPlan(SubPlanState * node,ExprContext * econtext,bool * isNull)110 ExecHashSubPlan(SubPlanState *node,
111 ExprContext *econtext,
112 bool *isNull)
113 {
114 SubPlan *subplan = (SubPlan *) node->xprstate.expr;
115 PlanState *planstate = node->planstate;
116 TupleTableSlot *slot;
117
118 /* Shouldn't have any direct correlation Vars */
119 if (subplan->parParam != NIL || node->args != NIL)
120 elog(ERROR, "hashed subplan with direct correlation not supported");
121
122 /*
123 * If first time through or we need to rescan the subplan, build the hash
124 * table.
125 */
126 if (node->hashtable == NULL || planstate->chgParam != NULL)
127 buildSubPlanHash(node, econtext);
128
129 /*
130 * The result for an empty subplan is always FALSE; no need to evaluate
131 * lefthand side.
132 */
133 *isNull = false;
134 if (!node->havehashrows && !node->havenullrows)
135 return BoolGetDatum(false);
136
137 /*
138 * Evaluate lefthand expressions and form a projection tuple. First we
139 * have to set the econtext to use (hack alert!).
140 */
141 node->projLeft->pi_exprContext = econtext;
142 slot = ExecProject(node->projLeft, NULL);
143
144 /*
145 * Note: because we are typically called in a per-tuple context, we have
146 * to explicitly clear the projected tuple before returning. Otherwise,
147 * we'll have a double-free situation: the per-tuple context will probably
148 * be reset before we're called again, and then the tuple slot will think
149 * it still needs to free the tuple.
150 */
151
152 /*
153 * If the LHS is all non-null, probe for an exact match in the main hash
154 * table. If we find one, the result is TRUE. Otherwise, scan the
155 * partly-null table to see if there are any rows that aren't provably
156 * unequal to the LHS; if so, the result is UNKNOWN. (We skip that part
157 * if we don't care about UNKNOWN.) Otherwise, the result is FALSE.
158 *
159 * Note: the reason we can avoid a full scan of the main hash table is
160 * that the combining operators are assumed never to yield NULL when both
161 * inputs are non-null. If they were to do so, we might need to produce
162 * UNKNOWN instead of FALSE because of an UNKNOWN result in comparing the
163 * LHS to some main-table entry --- which is a comparison we will not even
164 * make, unless there's a chance match of hash keys.
165 */
166 if (slotNoNulls(slot))
167 {
168 if (node->havehashrows &&
169 FindTupleHashEntry(node->hashtable,
170 slot,
171 node->cur_eq_funcs,
172 node->lhs_hash_funcs) != NULL)
173 {
174 ExecClearTuple(slot);
175 return BoolGetDatum(true);
176 }
177 if (node->havenullrows &&
178 findPartialMatch(node->hashnulls, slot, node->cur_eq_funcs))
179 {
180 ExecClearTuple(slot);
181 *isNull = true;
182 return BoolGetDatum(false);
183 }
184 ExecClearTuple(slot);
185 return BoolGetDatum(false);
186 }
187
188 /*
189 * When the LHS is partly or wholly NULL, we can never return TRUE. If we
190 * don't care about UNKNOWN, just return FALSE. Otherwise, if the LHS is
191 * wholly NULL, immediately return UNKNOWN. (Since the combining
192 * operators are strict, the result could only be FALSE if the sub-select
193 * were empty, but we already handled that case.) Otherwise, we must scan
194 * both the main and partly-null tables to see if there are any rows that
195 * aren't provably unequal to the LHS; if so, the result is UNKNOWN.
196 * Otherwise, the result is FALSE.
197 */
198 if (node->hashnulls == NULL)
199 {
200 ExecClearTuple(slot);
201 return BoolGetDatum(false);
202 }
203 if (slotAllNulls(slot))
204 {
205 ExecClearTuple(slot);
206 *isNull = true;
207 return BoolGetDatum(false);
208 }
209 /* Scan partly-null table first, since more likely to get a match */
210 if (node->havenullrows &&
211 findPartialMatch(node->hashnulls, slot, node->cur_eq_funcs))
212 {
213 ExecClearTuple(slot);
214 *isNull = true;
215 return BoolGetDatum(false);
216 }
217 if (node->havehashrows &&
218 findPartialMatch(node->hashtable, slot, node->cur_eq_funcs))
219 {
220 ExecClearTuple(slot);
221 *isNull = true;
222 return BoolGetDatum(false);
223 }
224 ExecClearTuple(slot);
225 return BoolGetDatum(false);
226 }
227
228 /*
229 * ExecScanSubPlan: default case where we have to rescan subplan each time
230 */
231 static Datum
ExecScanSubPlan(SubPlanState * node,ExprContext * econtext,bool * isNull)232 ExecScanSubPlan(SubPlanState *node,
233 ExprContext *econtext,
234 bool *isNull)
235 {
236 SubPlan *subplan = (SubPlan *) node->xprstate.expr;
237 PlanState *planstate = node->planstate;
238 SubLinkType subLinkType = subplan->subLinkType;
239 MemoryContext oldcontext;
240 TupleTableSlot *slot;
241 Datum result;
242 bool found = false; /* TRUE if got at least one subplan tuple */
243 ListCell *pvar;
244 ListCell *l;
245 ArrayBuildStateAny *astate = NULL;
246
247 /*
248 * MULTIEXPR subplans, when "executed", just return NULL; but first we
249 * mark the subplan's output parameters as needing recalculation. (This
250 * is a bit of a hack: it relies on the subplan appearing later in its
251 * targetlist than any of the referencing Params, so that all the Params
252 * have been evaluated before we re-mark them for the next evaluation
253 * cycle. But in general resjunk tlist items appear after non-resjunk
254 * ones, so this should be safe.) Unlike ExecReScanSetParamPlan, we do
255 * *not* set bits in the parent plan node's chgParam, because we don't
256 * want to cause a rescan of the parent.
257 */
258 if (subLinkType == MULTIEXPR_SUBLINK)
259 {
260 EState *estate = node->parent->state;
261
262 foreach(l, subplan->setParam)
263 {
264 int paramid = lfirst_int(l);
265 ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
266
267 prm->execPlan = node;
268 }
269 *isNull = true;
270 return (Datum) 0;
271 }
272
273 /* Initialize ArrayBuildStateAny in caller's context, if needed */
274 if (subLinkType == ARRAY_SUBLINK)
275 astate = initArrayResultAny(subplan->firstColType,
276 CurrentMemoryContext, true);
277
278 /*
279 * We are probably in a short-lived expression-evaluation context. Switch
280 * to the per-query context for manipulating the child plan's chgParam,
281 * calling ExecProcNode on it, etc.
282 */
283 oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
284
285 /*
286 * Set Params of this plan from parent plan correlation values. (Any
287 * calculation we have to do is done in the parent econtext, since the
288 * Param values don't need to have per-query lifetime.)
289 */
290 Assert(list_length(subplan->parParam) == list_length(node->args));
291
292 forboth(l, subplan->parParam, pvar, node->args)
293 {
294 int paramid = lfirst_int(l);
295 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
296
297 prm->value = ExecEvalExprSwitchContext((ExprState *) lfirst(pvar),
298 econtext,
299 &(prm->isnull),
300 NULL);
301 planstate->chgParam = bms_add_member(planstate->chgParam, paramid);
302 }
303
304 /*
305 * Now that we've set up its parameters, we can reset the subplan.
306 */
307 ExecReScan(planstate);
308
309 /*
310 * For all sublink types except EXPR_SUBLINK and ARRAY_SUBLINK, the result
311 * is boolean as are the results of the combining operators. We combine
312 * results across tuples (if the subplan produces more than one) using OR
313 * semantics for ANY_SUBLINK or AND semantics for ALL_SUBLINK.
314 * (ROWCOMPARE_SUBLINK doesn't allow multiple tuples from the subplan.)
315 * NULL results from the combining operators are handled according to the
316 * usual SQL semantics for OR and AND. The result for no input tuples is
317 * FALSE for ANY_SUBLINK, TRUE for ALL_SUBLINK, NULL for
318 * ROWCOMPARE_SUBLINK.
319 *
320 * For EXPR_SUBLINK we require the subplan to produce no more than one
321 * tuple, else an error is raised. If zero tuples are produced, we return
322 * NULL. Assuming we get a tuple, we just use its first column (there can
323 * be only one non-junk column in this case).
324 *
325 * For ARRAY_SUBLINK we allow the subplan to produce any number of tuples,
326 * and form an array of the first column's values. Note in particular
327 * that we produce a zero-element array if no tuples are produced (this is
328 * a change from pre-8.3 behavior of returning NULL).
329 */
330 result = BoolGetDatum(subLinkType == ALL_SUBLINK);
331 *isNull = false;
332
333 for (slot = ExecProcNode(planstate);
334 !TupIsNull(slot);
335 slot = ExecProcNode(planstate))
336 {
337 TupleDesc tdesc = slot->tts_tupleDescriptor;
338 Datum rowresult;
339 bool rownull;
340 int col;
341 ListCell *plst;
342
343 if (subLinkType == EXISTS_SUBLINK)
344 {
345 found = true;
346 result = BoolGetDatum(true);
347 break;
348 }
349
350 if (subLinkType == EXPR_SUBLINK)
351 {
352 /* cannot allow multiple input tuples for EXPR sublink */
353 if (found)
354 ereport(ERROR,
355 (errcode(ERRCODE_CARDINALITY_VIOLATION),
356 errmsg("more than one row returned by a subquery used as an expression")));
357 found = true;
358
359 /*
360 * We need to copy the subplan's tuple in case the result is of
361 * pass-by-ref type --- our return value will point into this
362 * copied tuple! Can't use the subplan's instance of the tuple
363 * since it won't still be valid after next ExecProcNode() call.
364 * node->curTuple keeps track of the copied tuple for eventual
365 * freeing.
366 */
367 if (node->curTuple)
368 heap_freetuple(node->curTuple);
369 node->curTuple = ExecCopySlotTuple(slot);
370
371 result = heap_getattr(node->curTuple, 1, tdesc, isNull);
372 /* keep scanning subplan to make sure there's only one tuple */
373 continue;
374 }
375
376 if (subLinkType == ARRAY_SUBLINK)
377 {
378 Datum dvalue;
379 bool disnull;
380
381 found = true;
382 /* stash away current value */
383 Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
384 dvalue = slot_getattr(slot, 1, &disnull);
385 astate = accumArrayResultAny(astate, dvalue, disnull,
386 subplan->firstColType, oldcontext);
387 /* keep scanning subplan to collect all values */
388 continue;
389 }
390
391 /* cannot allow multiple input tuples for ROWCOMPARE sublink either */
392 if (subLinkType == ROWCOMPARE_SUBLINK && found)
393 ereport(ERROR,
394 (errcode(ERRCODE_CARDINALITY_VIOLATION),
395 errmsg("more than one row returned by a subquery used as an expression")));
396
397 found = true;
398
399 /*
400 * For ALL, ANY, and ROWCOMPARE sublinks, load up the Params
401 * representing the columns of the sub-select, and then evaluate the
402 * combining expression.
403 */
404 col = 1;
405 foreach(plst, subplan->paramIds)
406 {
407 int paramid = lfirst_int(plst);
408 ParamExecData *prmdata;
409
410 prmdata = &(econtext->ecxt_param_exec_vals[paramid]);
411 Assert(prmdata->execPlan == NULL);
412 prmdata->value = slot_getattr(slot, col, &(prmdata->isnull));
413 col++;
414 }
415
416 rowresult = ExecEvalExprSwitchContext(node->testexpr, econtext,
417 &rownull, NULL);
418
419 if (subLinkType == ANY_SUBLINK)
420 {
421 /* combine across rows per OR semantics */
422 if (rownull)
423 *isNull = true;
424 else if (DatumGetBool(rowresult))
425 {
426 result = BoolGetDatum(true);
427 *isNull = false;
428 break; /* needn't look at any more rows */
429 }
430 }
431 else if (subLinkType == ALL_SUBLINK)
432 {
433 /* combine across rows per AND semantics */
434 if (rownull)
435 *isNull = true;
436 else if (!DatumGetBool(rowresult))
437 {
438 result = BoolGetDatum(false);
439 *isNull = false;
440 break; /* needn't look at any more rows */
441 }
442 }
443 else
444 {
445 /* must be ROWCOMPARE_SUBLINK */
446 result = rowresult;
447 *isNull = rownull;
448 }
449 }
450
451 MemoryContextSwitchTo(oldcontext);
452
453 if (subLinkType == ARRAY_SUBLINK)
454 {
455 /* We return the result in the caller's context */
456 result = makeArrayResultAny(astate, oldcontext, true);
457 }
458 else if (!found)
459 {
460 /*
461 * deal with empty subplan result. result/isNull were previously
462 * initialized correctly for all sublink types except EXPR and
463 * ROWCOMPARE; for those, return NULL.
464 */
465 if (subLinkType == EXPR_SUBLINK ||
466 subLinkType == ROWCOMPARE_SUBLINK)
467 {
468 result = (Datum) 0;
469 *isNull = true;
470 }
471 }
472
473 return result;
474 }
475
476 /*
477 * buildSubPlanHash: load hash table by scanning subplan output.
478 */
479 static void
buildSubPlanHash(SubPlanState * node,ExprContext * econtext)480 buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
481 {
482 SubPlan *subplan = (SubPlan *) node->xprstate.expr;
483 PlanState *planstate = node->planstate;
484 int ncols = node->numCols;
485 ExprContext *innerecontext = node->innerecontext;
486 MemoryContext oldcontext;
487 long nbuckets;
488 TupleTableSlot *slot;
489
490 Assert(subplan->subLinkType == ANY_SUBLINK);
491
492 /*
493 * If we already had any hash tables, destroy 'em; then create empty hash
494 * table(s).
495 *
496 * If we need to distinguish accurately between FALSE and UNKNOWN (i.e.,
497 * NULL) results of the IN operation, then we have to store subplan output
498 * rows that are partly or wholly NULL. We store such rows in a separate
499 * hash table that we expect will be much smaller than the main table. (We
500 * can use hashing to eliminate partly-null rows that are not distinct. We
501 * keep them separate to minimize the cost of the inevitable full-table
502 * searches; see findPartialMatch.)
503 *
504 * If it's not necessary to distinguish FALSE and UNKNOWN, then we don't
505 * need to store subplan output rows that contain NULL.
506 */
507 MemoryContextReset(node->hashtablecxt);
508 node->hashtable = NULL;
509 node->hashnulls = NULL;
510 node->havehashrows = false;
511 node->havenullrows = false;
512
513 nbuckets = (long) Min(planstate->plan->plan_rows, (double) LONG_MAX);
514 if (nbuckets < 1)
515 nbuckets = 1;
516
517 node->hashtable = BuildTupleHashTable(ncols,
518 node->keyColIdx,
519 node->tab_eq_funcs,
520 node->tab_hash_funcs,
521 nbuckets,
522 sizeof(TupleHashEntryData),
523 node->hashtablecxt,
524 node->hashtempcxt);
525
526 if (!subplan->unknownEqFalse)
527 {
528 if (ncols == 1)
529 nbuckets = 1; /* there can only be one entry */
530 else
531 {
532 nbuckets /= 16;
533 if (nbuckets < 1)
534 nbuckets = 1;
535 }
536 node->hashnulls = BuildTupleHashTable(ncols,
537 node->keyColIdx,
538 node->tab_eq_funcs,
539 node->tab_hash_funcs,
540 nbuckets,
541 sizeof(TupleHashEntryData),
542 node->hashtablecxt,
543 node->hashtempcxt);
544 }
545
546 /*
547 * We are probably in a short-lived expression-evaluation context. Switch
548 * to the per-query context for manipulating the child plan.
549 */
550 oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
551
552 /*
553 * Reset subplan to start.
554 */
555 ExecReScan(planstate);
556
557 /*
558 * Scan the subplan and load the hash table(s). Note that when there are
559 * duplicate rows coming out of the sub-select, only one copy is stored.
560 */
561 for (slot = ExecProcNode(planstate);
562 !TupIsNull(slot);
563 slot = ExecProcNode(planstate))
564 {
565 int col = 1;
566 ListCell *plst;
567 bool isnew;
568
569 /*
570 * Load up the Params representing the raw sub-select outputs, then
571 * form the projection tuple to store in the hashtable.
572 */
573 foreach(plst, subplan->paramIds)
574 {
575 int paramid = lfirst_int(plst);
576 ParamExecData *prmdata;
577
578 prmdata = &(innerecontext->ecxt_param_exec_vals[paramid]);
579 Assert(prmdata->execPlan == NULL);
580 prmdata->value = slot_getattr(slot, col,
581 &(prmdata->isnull));
582 col++;
583 }
584 slot = ExecProject(node->projRight, NULL);
585
586 /*
587 * If result contains any nulls, store separately or not at all.
588 */
589 if (slotNoNulls(slot))
590 {
591 (void) LookupTupleHashEntry(node->hashtable, slot, &isnew);
592 node->havehashrows = true;
593 }
594 else if (node->hashnulls)
595 {
596 (void) LookupTupleHashEntry(node->hashnulls, slot, &isnew);
597 node->havenullrows = true;
598 }
599
600 /*
601 * Reset innerecontext after each inner tuple to free any memory used
602 * during ExecProject.
603 */
604 ResetExprContext(innerecontext);
605 }
606
607 /*
608 * Since the projected tuples are in the sub-query's context and not the
609 * main context, we'd better clear the tuple slot before there's any
610 * chance of a reset of the sub-query's context. Else we will have the
611 * potential for a double free attempt. (XXX possibly no longer needed,
612 * but can't hurt.)
613 */
614 ExecClearTuple(node->projRight->pi_slot);
615
616 MemoryContextSwitchTo(oldcontext);
617 }
618
619 /*
620 * findPartialMatch: does the hashtable contain an entry that is not
621 * provably distinct from the tuple?
622 *
623 * We have to scan the whole hashtable; we can't usefully use hashkeys
624 * to guide probing, since we might get partial matches on tuples with
625 * hashkeys quite unrelated to what we'd get from the given tuple.
626 *
627 * Caller must provide the equality functions to use, since in cross-type
628 * cases these are different from the hashtable's internal functions.
629 */
630 static bool
findPartialMatch(TupleHashTable hashtable,TupleTableSlot * slot,FmgrInfo * eqfunctions)631 findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot,
632 FmgrInfo *eqfunctions)
633 {
634 int numCols = hashtable->numCols;
635 AttrNumber *keyColIdx = hashtable->keyColIdx;
636 TupleHashIterator hashiter;
637 TupleHashEntry entry;
638
639 InitTupleHashIterator(hashtable, &hashiter);
640 while ((entry = ScanTupleHashTable(&hashiter)) != NULL)
641 {
642 ExecStoreMinimalTuple(entry->firstTuple, hashtable->tableslot, false);
643 if (!execTuplesUnequal(slot, hashtable->tableslot,
644 numCols, keyColIdx,
645 eqfunctions,
646 hashtable->tempcxt))
647 {
648 TermTupleHashIterator(&hashiter);
649 return true;
650 }
651 }
652 /* No TermTupleHashIterator call needed here */
653 return false;
654 }
655
656 /*
657 * slotAllNulls: is the slot completely NULL?
658 *
659 * This does not test for dropped columns, which is OK because we only
660 * use it on projected tuples.
661 */
662 static bool
slotAllNulls(TupleTableSlot * slot)663 slotAllNulls(TupleTableSlot *slot)
664 {
665 int ncols = slot->tts_tupleDescriptor->natts;
666 int i;
667
668 for (i = 1; i <= ncols; i++)
669 {
670 if (!slot_attisnull(slot, i))
671 return false;
672 }
673 return true;
674 }
675
676 /*
677 * slotNoNulls: is the slot entirely not NULL?
678 *
679 * This does not test for dropped columns, which is OK because we only
680 * use it on projected tuples.
681 */
682 static bool
slotNoNulls(TupleTableSlot * slot)683 slotNoNulls(TupleTableSlot *slot)
684 {
685 int ncols = slot->tts_tupleDescriptor->natts;
686 int i;
687
688 for (i = 1; i <= ncols; i++)
689 {
690 if (slot_attisnull(slot, i))
691 return false;
692 }
693 return true;
694 }
695
696 /* ----------------------------------------------------------------
697 * ExecInitSubPlan
698 *
699 * Create a SubPlanState for a SubPlan; this is the SubPlan-specific part
700 * of ExecInitExpr(). We split it out so that it can be used for InitPlans
701 * as well as regular SubPlans. Note that we don't link the SubPlan into
702 * the parent's subPlan list, because that shouldn't happen for InitPlans.
703 * Instead, ExecInitExpr() does that one part.
704 * ----------------------------------------------------------------
705 */
706 SubPlanState *
ExecInitSubPlan(SubPlan * subplan,PlanState * parent)707 ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
708 {
709 SubPlanState *sstate = makeNode(SubPlanState);
710 EState *estate = parent->state;
711
712 sstate->xprstate.evalfunc = (ExprStateEvalFunc) ExecSubPlan;
713 sstate->xprstate.expr = (Expr *) subplan;
714
715 /* Link the SubPlanState to already-initialized subplan */
716 sstate->planstate = (PlanState *) list_nth(estate->es_subplanstates,
717 subplan->plan_id - 1);
718
719 /* ... and to its parent's state */
720 sstate->parent = parent;
721
722 /* Initialize subexpressions */
723 sstate->testexpr = ExecInitExpr((Expr *) subplan->testexpr, parent);
724 sstate->args = (List *) ExecInitExpr((Expr *) subplan->args, parent);
725
726 /*
727 * initialize my state
728 */
729 sstate->curTuple = NULL;
730 sstate->curArray = PointerGetDatum(NULL);
731 sstate->projLeft = NULL;
732 sstate->projRight = NULL;
733 sstate->hashtable = NULL;
734 sstate->hashnulls = NULL;
735 sstate->hashtablecxt = NULL;
736 sstate->hashtempcxt = NULL;
737 sstate->innerecontext = NULL;
738 sstate->keyColIdx = NULL;
739 sstate->tab_hash_funcs = NULL;
740 sstate->tab_eq_funcs = NULL;
741 sstate->lhs_hash_funcs = NULL;
742 sstate->cur_eq_funcs = NULL;
743
744 /*
745 * If this is an initplan or MULTIEXPR subplan, it has output parameters
746 * that the parent plan will use, so mark those parameters as needing
747 * evaluation. We don't actually run the subplan until we first need one
748 * of its outputs.
749 *
750 * A CTE subplan's output parameter is never to be evaluated in the normal
751 * way, so skip this in that case.
752 *
753 * Note that we don't set parent->chgParam here: the parent plan hasn't
754 * been run yet, so no need to force it to re-run.
755 */
756 if (subplan->setParam != NIL && subplan->subLinkType != CTE_SUBLINK)
757 {
758 ListCell *lst;
759
760 foreach(lst, subplan->setParam)
761 {
762 int paramid = lfirst_int(lst);
763 ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
764
765 prm->execPlan = sstate;
766 }
767 }
768
769 /*
770 * If we are going to hash the subquery output, initialize relevant stuff.
771 * (We don't create the hashtable until needed, though.)
772 */
773 if (subplan->useHashTable)
774 {
775 int ncols,
776 i;
777 TupleDesc tupDesc;
778 TupleTableSlot *slot;
779 List *oplist,
780 *lefttlist,
781 *righttlist,
782 *leftptlist,
783 *rightptlist;
784 ListCell *l;
785
786 /* We need a memory context to hold the hash table(s) */
787 sstate->hashtablecxt =
788 AllocSetContextCreate(CurrentMemoryContext,
789 "Subplan HashTable Context",
790 ALLOCSET_DEFAULT_SIZES);
791 /* and a small one for the hash tables to use as temp storage */
792 sstate->hashtempcxt =
793 AllocSetContextCreate(CurrentMemoryContext,
794 "Subplan HashTable Temp Context",
795 ALLOCSET_SMALL_SIZES);
796 /* and a short-lived exprcontext for function evaluation */
797 sstate->innerecontext = CreateExprContext(estate);
798
799 /*
800 * We use ExecProject to evaluate the lefthand and righthand
801 * expression lists and form tuples. (You might think that we could
802 * use the sub-select's output tuples directly, but that is not the
803 * case if we had to insert any run-time coercions of the sub-select's
804 * output datatypes; anyway this avoids storing any resjunk columns
805 * that might be in the sub-select's output.) Run through the
806 * combining expressions to build tlists for the lefthand and
807 * righthand sides. We need both the ExprState list (for ExecProject)
808 * and the underlying parse Exprs (for ExecTypeFromTL).
809 *
810 * We also extract the combining operators themselves to initialize
811 * the equality and hashing functions for the hash tables.
812 */
813 if (IsA(sstate->testexpr->expr, OpExpr))
814 {
815 /* single combining operator */
816 oplist = list_make1(sstate->testexpr);
817 }
818 else if (and_clause((Node *) sstate->testexpr->expr))
819 {
820 /* multiple combining operators */
821 Assert(IsA(sstate->testexpr, BoolExprState));
822 oplist = ((BoolExprState *) sstate->testexpr)->args;
823 }
824 else
825 {
826 /* shouldn't see anything else in a hashable subplan */
827 elog(ERROR, "unrecognized testexpr type: %d",
828 (int) nodeTag(sstate->testexpr->expr));
829 oplist = NIL; /* keep compiler quiet */
830 }
831 ncols = list_length(oplist);
832
833 lefttlist = righttlist = NIL;
834 leftptlist = rightptlist = NIL;
835 sstate->numCols = ncols;
836 sstate->keyColIdx = (AttrNumber *) palloc(ncols * sizeof(AttrNumber));
837 sstate->tab_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
838 sstate->tab_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
839 sstate->lhs_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
840 sstate->cur_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
841 i = 1;
842 foreach(l, oplist)
843 {
844 FuncExprState *fstate = (FuncExprState *) lfirst(l);
845 OpExpr *opexpr = (OpExpr *) fstate->xprstate.expr;
846 ExprState *exstate;
847 Expr *expr;
848 TargetEntry *tle;
849 GenericExprState *tlestate;
850 Oid rhs_eq_oper;
851 Oid left_hashfn;
852 Oid right_hashfn;
853
854 Assert(IsA(fstate, FuncExprState));
855 Assert(IsA(opexpr, OpExpr));
856 Assert(list_length(fstate->args) == 2);
857
858 /* Process lefthand argument */
859 exstate = (ExprState *) linitial(fstate->args);
860 expr = exstate->expr;
861 tle = makeTargetEntry(expr,
862 i,
863 NULL,
864 false);
865 tlestate = makeNode(GenericExprState);
866 tlestate->xprstate.expr = (Expr *) tle;
867 tlestate->xprstate.evalfunc = NULL;
868 tlestate->arg = exstate;
869 lefttlist = lappend(lefttlist, tlestate);
870 leftptlist = lappend(leftptlist, tle);
871
872 /* Process righthand argument */
873 exstate = (ExprState *) lsecond(fstate->args);
874 expr = exstate->expr;
875 tle = makeTargetEntry(expr,
876 i,
877 NULL,
878 false);
879 tlestate = makeNode(GenericExprState);
880 tlestate->xprstate.expr = (Expr *) tle;
881 tlestate->xprstate.evalfunc = NULL;
882 tlestate->arg = exstate;
883 righttlist = lappend(righttlist, tlestate);
884 rightptlist = lappend(rightptlist, tle);
885
886 /* Lookup the equality function (potentially cross-type) */
887 fmgr_info(opexpr->opfuncid, &sstate->cur_eq_funcs[i - 1]);
888 fmgr_info_set_expr((Node *) opexpr, &sstate->cur_eq_funcs[i - 1]);
889
890 /* Look up the equality function for the RHS type */
891 if (!get_compatible_hash_operators(opexpr->opno,
892 NULL, &rhs_eq_oper))
893 elog(ERROR, "could not find compatible hash operator for operator %u",
894 opexpr->opno);
895 fmgr_info(get_opcode(rhs_eq_oper), &sstate->tab_eq_funcs[i - 1]);
896
897 /* Lookup the associated hash functions */
898 if (!get_op_hash_functions(opexpr->opno,
899 &left_hashfn, &right_hashfn))
900 elog(ERROR, "could not find hash function for hash operator %u",
901 opexpr->opno);
902 fmgr_info(left_hashfn, &sstate->lhs_hash_funcs[i - 1]);
903 fmgr_info(right_hashfn, &sstate->tab_hash_funcs[i - 1]);
904
905 /* keyColIdx is just column numbers 1..n */
906 sstate->keyColIdx[i - 1] = i;
907
908 i++;
909 }
910
911 /*
912 * Construct tupdescs, slots and projection nodes for left and right
913 * sides. The lefthand expressions will be evaluated in the parent
914 * plan node's exprcontext, which we don't have access to here.
915 * Fortunately we can just pass NULL for now and fill it in later
916 * (hack alert!). The righthand expressions will be evaluated in our
917 * own innerecontext.
918 */
919 tupDesc = ExecTypeFromTL(leftptlist, false);
920 slot = ExecInitExtraTupleSlot(estate);
921 ExecSetSlotDescriptor(slot, tupDesc);
922 sstate->projLeft = ExecBuildProjectionInfo(lefttlist,
923 NULL,
924 slot,
925 NULL);
926
927 tupDesc = ExecTypeFromTL(rightptlist, false);
928 slot = ExecInitExtraTupleSlot(estate);
929 ExecSetSlotDescriptor(slot, tupDesc);
930 sstate->projRight = ExecBuildProjectionInfo(righttlist,
931 sstate->innerecontext,
932 slot,
933 NULL);
934 }
935
936 return sstate;
937 }
938
939 /* ----------------------------------------------------------------
940 * ExecSetParamPlan
941 *
942 * Executes a subplan and sets its output parameters.
943 *
944 * This is called from ExecEvalParamExec() when the value of a PARAM_EXEC
945 * parameter is requested and the param's execPlan field is set (indicating
946 * that the param has not yet been evaluated). This allows lazy evaluation
947 * of initplans: we don't run the subplan until/unless we need its output.
948 * Note that this routine MUST clear the execPlan fields of the plan's
949 * output parameters after evaluating them!
950 *
951 * The results of this function are stored in the EState associated with the
952 * ExprContext (particularly, its ecxt_param_exec_vals); any pass-by-ref
953 * result Datums are allocated in the EState's per-query memory. The passed
954 * econtext can be any ExprContext belonging to that EState; which one is
955 * important only to the extent that the ExprContext's per-tuple memory
956 * context is used to evaluate any parameters passed down to the subplan.
957 * (Thus in principle, the shorter-lived the ExprContext the better, since
958 * that data isn't needed after we return. In practice, because initplan
959 * parameters are never more complex than Vars, Aggrefs, etc, evaluating them
960 * currently never leaks any memory anyway.)
961 * ----------------------------------------------------------------
962 */
963 void
ExecSetParamPlan(SubPlanState * node,ExprContext * econtext)964 ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
965 {
966 SubPlan *subplan = (SubPlan *) node->xprstate.expr;
967 PlanState *planstate = node->planstate;
968 SubLinkType subLinkType = subplan->subLinkType;
969 EState *estate = planstate->state;
970 ScanDirection dir = estate->es_direction;
971 MemoryContext oldcontext;
972 TupleTableSlot *slot;
973 ListCell *pvar;
974 ListCell *l;
975 bool found = false;
976 ArrayBuildStateAny *astate = NULL;
977
978 if (subLinkType == ANY_SUBLINK ||
979 subLinkType == ALL_SUBLINK)
980 elog(ERROR, "ANY/ALL subselect unsupported as initplan");
981 if (subLinkType == CTE_SUBLINK)
982 elog(ERROR, "CTE subplans should not be executed via ExecSetParamPlan");
983
984 /*
985 * Enforce forward scan direction regardless of caller. It's hard but not
986 * impossible to get here in backward scan, so make it work anyway.
987 */
988 estate->es_direction = ForwardScanDirection;
989
990 /* Initialize ArrayBuildStateAny in caller's context, if needed */
991 if (subLinkType == ARRAY_SUBLINK)
992 astate = initArrayResultAny(subplan->firstColType,
993 CurrentMemoryContext, true);
994
995 /*
996 * Must switch to per-query memory context.
997 */
998 oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
999
1000 /*
1001 * Set Params of this plan from parent plan correlation values. (Any
1002 * calculation we have to do is done in the parent econtext, since the
1003 * Param values don't need to have per-query lifetime.) Currently, we
1004 * expect only MULTIEXPR_SUBLINK plans to have any correlation values.
1005 */
1006 Assert(subplan->parParam == NIL || subLinkType == MULTIEXPR_SUBLINK);
1007 Assert(list_length(subplan->parParam) == list_length(node->args));
1008
1009 forboth(l, subplan->parParam, pvar, node->args)
1010 {
1011 int paramid = lfirst_int(l);
1012 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1013
1014 prm->value = ExecEvalExprSwitchContext((ExprState *) lfirst(pvar),
1015 econtext,
1016 &(prm->isnull),
1017 NULL);
1018 planstate->chgParam = bms_add_member(planstate->chgParam, paramid);
1019 }
1020
1021 /*
1022 * Run the plan. (If it needs to be rescanned, the first ExecProcNode
1023 * call will take care of that.)
1024 */
1025 for (slot = ExecProcNode(planstate);
1026 !TupIsNull(slot);
1027 slot = ExecProcNode(planstate))
1028 {
1029 TupleDesc tdesc = slot->tts_tupleDescriptor;
1030 int i = 1;
1031
1032 if (subLinkType == EXISTS_SUBLINK)
1033 {
1034 /* There can be only one setParam... */
1035 int paramid = linitial_int(subplan->setParam);
1036 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1037
1038 prm->execPlan = NULL;
1039 prm->value = BoolGetDatum(true);
1040 prm->isnull = false;
1041 found = true;
1042 break;
1043 }
1044
1045 if (subLinkType == ARRAY_SUBLINK)
1046 {
1047 Datum dvalue;
1048 bool disnull;
1049
1050 found = true;
1051 /* stash away current value */
1052 Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
1053 dvalue = slot_getattr(slot, 1, &disnull);
1054 astate = accumArrayResultAny(astate, dvalue, disnull,
1055 subplan->firstColType, oldcontext);
1056 /* keep scanning subplan to collect all values */
1057 continue;
1058 }
1059
1060 if (found &&
1061 (subLinkType == EXPR_SUBLINK ||
1062 subLinkType == MULTIEXPR_SUBLINK ||
1063 subLinkType == ROWCOMPARE_SUBLINK))
1064 ereport(ERROR,
1065 (errcode(ERRCODE_CARDINALITY_VIOLATION),
1066 errmsg("more than one row returned by a subquery used as an expression")));
1067
1068 found = true;
1069
1070 /*
1071 * We need to copy the subplan's tuple into our own context, in case
1072 * any of the params are pass-by-ref type --- the pointers stored in
1073 * the param structs will point at this copied tuple! node->curTuple
1074 * keeps track of the copied tuple for eventual freeing.
1075 */
1076 if (node->curTuple)
1077 heap_freetuple(node->curTuple);
1078 node->curTuple = ExecCopySlotTuple(slot);
1079
1080 /*
1081 * Now set all the setParam params from the columns of the tuple
1082 */
1083 foreach(l, subplan->setParam)
1084 {
1085 int paramid = lfirst_int(l);
1086 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1087
1088 prm->execPlan = NULL;
1089 prm->value = heap_getattr(node->curTuple, i, tdesc,
1090 &(prm->isnull));
1091 i++;
1092 }
1093 }
1094
1095 if (subLinkType == ARRAY_SUBLINK)
1096 {
1097 /* There can be only one setParam... */
1098 int paramid = linitial_int(subplan->setParam);
1099 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1100
1101 /*
1102 * We build the result array in query context so it won't disappear;
1103 * to avoid leaking memory across repeated calls, we have to remember
1104 * the latest value, much as for curTuple above.
1105 */
1106 if (node->curArray != PointerGetDatum(NULL))
1107 pfree(DatumGetPointer(node->curArray));
1108 node->curArray = makeArrayResultAny(astate,
1109 econtext->ecxt_per_query_memory,
1110 true);
1111 prm->execPlan = NULL;
1112 prm->value = node->curArray;
1113 prm->isnull = false;
1114 }
1115 else if (!found)
1116 {
1117 if (subLinkType == EXISTS_SUBLINK)
1118 {
1119 /* There can be only one setParam... */
1120 int paramid = linitial_int(subplan->setParam);
1121 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1122
1123 prm->execPlan = NULL;
1124 prm->value = BoolGetDatum(false);
1125 prm->isnull = false;
1126 }
1127 else
1128 {
1129 /* For other sublink types, set all the output params to NULL */
1130 foreach(l, subplan->setParam)
1131 {
1132 int paramid = lfirst_int(l);
1133 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1134
1135 prm->execPlan = NULL;
1136 prm->value = (Datum) 0;
1137 prm->isnull = true;
1138 }
1139 }
1140 }
1141
1142 MemoryContextSwitchTo(oldcontext);
1143
1144 /* restore scan direction */
1145 estate->es_direction = dir;
1146 }
1147
1148 /*
1149 * ExecSetParamPlanMulti
1150 *
1151 * Apply ExecSetParamPlan to evaluate any not-yet-evaluated initplan output
1152 * parameters whose ParamIDs are listed in "params". Any listed params that
1153 * are not initplan outputs are ignored.
1154 *
1155 * As with ExecSetParamPlan, any ExprContext belonging to the current EState
1156 * can be used, but in principle a shorter-lived ExprContext is better than a
1157 * longer-lived one.
1158 */
1159 void
ExecSetParamPlanMulti(const Bitmapset * params,ExprContext * econtext)1160 ExecSetParamPlanMulti(const Bitmapset *params, ExprContext *econtext)
1161 {
1162 int paramid;
1163
1164 paramid = -1;
1165 while ((paramid = bms_next_member(params, paramid)) >= 0)
1166 {
1167 ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
1168
1169 if (prm->execPlan != NULL)
1170 {
1171 /* Parameter not evaluated yet, so go do it */
1172 ExecSetParamPlan(prm->execPlan, econtext);
1173 /* ExecSetParamPlan should have processed this param... */
1174 Assert(prm->execPlan == NULL);
1175 }
1176 }
1177 }
1178
1179 /*
1180 * Mark an initplan as needing recalculation
1181 */
1182 void
ExecReScanSetParamPlan(SubPlanState * node,PlanState * parent)1183 ExecReScanSetParamPlan(SubPlanState *node, PlanState *parent)
1184 {
1185 PlanState *planstate = node->planstate;
1186 SubPlan *subplan = (SubPlan *) node->xprstate.expr;
1187 EState *estate = parent->state;
1188 ListCell *l;
1189
1190 /* sanity checks */
1191 if (subplan->parParam != NIL)
1192 elog(ERROR, "direct correlated subquery unsupported as initplan");
1193 if (subplan->setParam == NIL)
1194 elog(ERROR, "setParam list of initplan is empty");
1195 if (bms_is_empty(planstate->plan->extParam))
1196 elog(ERROR, "extParam set of initplan is empty");
1197
1198 /*
1199 * Don't actually re-scan: it'll happen inside ExecSetParamPlan if needed.
1200 */
1201
1202 /*
1203 * Mark this subplan's output parameters as needing recalculation.
1204 *
1205 * CTE subplans are never executed via parameter recalculation; instead
1206 * they get run when called by nodeCtescan.c. So don't mark the output
1207 * parameter of a CTE subplan as dirty, but do set the chgParam bit for it
1208 * so that dependent plan nodes will get told to rescan.
1209 */
1210 foreach(l, subplan->setParam)
1211 {
1212 int paramid = lfirst_int(l);
1213 ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
1214
1215 if (subplan->subLinkType != CTE_SUBLINK)
1216 prm->execPlan = node;
1217
1218 parent->chgParam = bms_add_member(parent->chgParam, paramid);
1219 }
1220 }
1221
1222
1223 /*
1224 * ExecInitAlternativeSubPlan
1225 *
1226 * Initialize for execution of one of a set of alternative subplans.
1227 */
1228 AlternativeSubPlanState *
ExecInitAlternativeSubPlan(AlternativeSubPlan * asplan,PlanState * parent)1229 ExecInitAlternativeSubPlan(AlternativeSubPlan *asplan, PlanState *parent)
1230 {
1231 AlternativeSubPlanState *asstate = makeNode(AlternativeSubPlanState);
1232 double num_calls;
1233 SubPlan *subplan1;
1234 SubPlan *subplan2;
1235 Cost cost1;
1236 Cost cost2;
1237
1238 asstate->xprstate.evalfunc = (ExprStateEvalFunc) ExecAlternativeSubPlan;
1239 asstate->xprstate.expr = (Expr *) asplan;
1240
1241 /*
1242 * Initialize subplans. (Can we get away with only initializing the one
1243 * we're going to use?)
1244 */
1245 asstate->subplans = (List *) ExecInitExpr((Expr *) asplan->subplans,
1246 parent);
1247
1248 /*
1249 * Select the one to be used. For this, we need an estimate of the number
1250 * of executions of the subplan. We use the number of output rows
1251 * expected from the parent plan node. This is a good estimate if we are
1252 * in the parent's targetlist, and an underestimate (but probably not by
1253 * more than a factor of 2) if we are in the qual.
1254 */
1255 num_calls = parent->plan->plan_rows;
1256
1257 /*
1258 * The planner saved enough info so that we don't have to work very hard
1259 * to estimate the total cost, given the number-of-calls estimate.
1260 */
1261 Assert(list_length(asplan->subplans) == 2);
1262 subplan1 = (SubPlan *) linitial(asplan->subplans);
1263 subplan2 = (SubPlan *) lsecond(asplan->subplans);
1264
1265 cost1 = subplan1->startup_cost + num_calls * subplan1->per_call_cost;
1266 cost2 = subplan2->startup_cost + num_calls * subplan2->per_call_cost;
1267
1268 if (cost1 < cost2)
1269 asstate->active = 0;
1270 else
1271 asstate->active = 1;
1272
1273 return asstate;
1274 }
1275
1276 /*
1277 * ExecAlternativeSubPlan
1278 *
1279 * Execute one of a set of alternative subplans.
1280 *
1281 * Note: in future we might consider changing to different subplans on the
1282 * fly, in case the original rowcount estimate turns out to be way off.
1283 */
1284 static Datum
ExecAlternativeSubPlan(AlternativeSubPlanState * node,ExprContext * econtext,bool * isNull,ExprDoneCond * isDone)1285 ExecAlternativeSubPlan(AlternativeSubPlanState *node,
1286 ExprContext *econtext,
1287 bool *isNull,
1288 ExprDoneCond *isDone)
1289 {
1290 /* Just pass control to the active subplan */
1291 SubPlanState *activesp = (SubPlanState *) list_nth(node->subplans,
1292 node->active);
1293
1294 Assert(IsA(activesp, SubPlanState));
1295
1296 return ExecSubPlan(activesp,
1297 econtext,
1298 isNull,
1299 isDone);
1300 }
1301