1 /*-------------------------------------------------------------------------
4 * Planning routines for subselects and parameters.
6 * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
7 * Portions Copyright (c) 1994, Regents of the University of California
10 * $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.46 2000/11/21 00:17:59 tgl Exp $
12 *-------------------------------------------------------------------------
16 #include "catalog/pg_operator.h"
17 #include "catalog/pg_type.h"
18 #include "nodes/makefuncs.h"
19 #include "optimizer/clauses.h"
20 #include "optimizer/cost.h"
21 #include "optimizer/planmain.h"
22 #include "optimizer/planner.h"
23 #include "optimizer/subselect.h"
24 #include "parser/parse_expr.h"
25 #include "parser/parse_oper.h"
26 #include "utils/syscache.h"
29 Index PlannerQueryLevel; /* level of current query */
30 List *PlannerInitPlan; /* init subplans for current query */
31 List *PlannerParamVar; /* to get Var from Param->paramid */
33 int PlannerPlanId = 0; /* to assign unique ID to subquery plans */
35 /*--------------------
36 * PlannerParamVar is a list of Var nodes, wherein the n'th entry
37 * (n counts from 0) corresponds to Param->paramid = n. The Var nodes
38 * are ordinary except for one thing: their varlevelsup field does NOT
39 * have the usual interpretation of "subplan levels out from current".
40 * Instead, it contains the absolute plan level, with the outermost
41 * plan being level 1 and nested plans having higher level numbers.
42 * This nonstandardness is useful because we don't have to run around
43 * and update the list elements when we enter or exit a subplan
44 * recursion level. But we must pay attention not to confuse this
45 * meaning with the normal meaning of varlevelsup.
51 * Create a new entry in the PlannerParamVar list, and return its index.
53 * var contains the data to be copied, except for varlevelsup which
54 * is set from the absolute level value given by varlevel.
57 new_param(Var *var, Index varlevel)
59 Var *paramVar = (Var *) copyObject(var);
61 paramVar->varlevelsup = varlevel;
63 PlannerParamVar = lappend(PlannerParamVar, paramVar);
65 return length(PlannerParamVar) - 1;
69 * Generate a Param node to replace the given Var,
70 * which is expected to have varlevelsup > 0 (ie, it is not local).
80 Assert(var->varlevelsup > 0 && var->varlevelsup < PlannerQueryLevel);
81 varlevel = PlannerQueryLevel - var->varlevelsup;
84 * If there's already a PlannerParamVar entry for this same Var, just
85 * use it. NOTE: in sufficiently complex querytrees, it is
86 * possible for the same varno/varlevel to refer to different RTEs in
87 * different parts of the parsetree, so that different fields might
88 * end up sharing the same Param number. As long as we check the
89 * vartype as well, I believe that this sort of aliasing will cause no
90 * trouble. The correct field should get stored into the Param slot at
91 * execution in each part of the tree.
94 foreach(ppv, PlannerParamVar)
96 Var *pvar = lfirst(ppv);
98 if (pvar->varno == var->varno &&
99 pvar->varattno == var->varattno &&
100 pvar->varlevelsup == varlevel &&
101 pvar->vartype == var->vartype)
108 /* Nope, so make a new one */
109 i = new_param(var, varlevel);
112 retval = makeNode(Param);
113 retval->paramkind = PARAM_EXEC;
114 retval->paramid = (AttrNumber) i;
115 retval->paramtype = var->vartype;
121 * Convert a bare SubLink (as created by the parser) into a SubPlan.
124 make_subplan(SubLink *slink)
126 SubPlan *node = makeNode(SubPlan);
127 Query *subquery = (Query *) (slink->subselect);
128 double tuple_fraction;
134 * Check to see if this node was already processed; if so we have
135 * trouble. We check to see if the linked-to Query appears to have
136 * been planned already, too.
138 if (subquery == NULL)
139 elog(ERROR, "make_subplan: invalid expression structure (SubLink already processed?)");
140 if (subquery->base_rel_list != NIL)
141 elog(ERROR, "make_subplan: invalid expression structure (subquery already processed?)");
144 * Copy the source Query node. This is a quick and dirty kluge to resolve
145 * the fact that the parser can generate trees with multiple links to the
146 * same sub-Query node, but the planner wants to scribble on the Query.
147 * Try to clean this up when we do querytree redesign...
149 subquery = (Query *) copyObject(subquery);
152 * For an EXISTS subplan, tell lower-level planner to expect that only
153 * the first tuple will be retrieved. For ALL and ANY subplans, we
154 * will be able to stop evaluating if the test condition fails, so
155 * very often not all the tuples will be retrieved; for lack of a
156 * better idea, specify 50% retrieval. For EXPR and MULTIEXPR
157 * subplans, use default behavior (we're only expecting one row out,
160 * NOTE: if you change these numbers, also change cost_qual_eval_walker()
161 * in path/costsize.c.
163 * XXX If an ALL/ANY subplan is uncorrelated, we may decide to
164 * materialize its result below. In that case it would've been better
165 * to specify full retrieval. At present, however, we can only detect
166 * correlation or lack of it after we've made the subplan :-(. Perhaps
167 * detection of correlation should be done as a separate step.
168 * Meanwhile, we don't want to be too optimistic about the percentage
169 * of tuples retrieved, for fear of selecting a plan that's bad for
170 * the materialization case.
172 if (slink->subLinkType == EXISTS_SUBLINK)
173 tuple_fraction = 1.0; /* just like a LIMIT 1 */
174 else if (slink->subLinkType == ALL_SUBLINK ||
175 slink->subLinkType == ANY_SUBLINK)
176 tuple_fraction = 0.5; /* 50% */
178 tuple_fraction = -1.0; /* default behavior */
181 * Generate the plan for the subquery.
183 node->plan = plan = subquery_planner(subquery, tuple_fraction);
185 node->plan_id = PlannerPlanId++; /* Assign unique ID to this SubPlan */
187 node->rtable = subquery->rtable;
188 node->sublink = slink;
190 slink->subselect = NULL; /* cool ?! see error check above! */
193 * Make parParam list of params that current query level will pass
194 * to this child plan.
196 foreach(lst, plan->extParam)
198 int paramid = lfirsti(lst);
199 Var *var = nth(paramid, PlannerParamVar);
201 /* note varlevelsup is absolute level number */
202 if (var->varlevelsup == PlannerQueryLevel)
203 node->parParam = lappendi(node->parParam, paramid);
207 * Un-correlated or undirect correlated plans of EXISTS, EXPR, or
208 * MULTIEXPR types can be used as initPlans. For EXISTS or EXPR, we
209 * just produce a Param referring to the result of evaluating the
210 * initPlan. For MULTIEXPR, we must build an AND or OR-clause of the
211 * individual comparison operators, using the appropriate lefthand
212 * side expressions and Params for the initPlan's target items.
214 if (node->parParam == NIL && slink->subLinkType == EXISTS_SUBLINK)
216 Var *var = makeVar(0, 0, BOOLOID, -1, 0);
217 Param *prm = makeNode(Param);
219 prm->paramkind = PARAM_EXEC;
220 prm->paramid = (AttrNumber) new_param(var, PlannerQueryLevel);
221 prm->paramtype = var->vartype;
222 pfree(var); /* var is only needed for new_param */
223 node->setParam = lappendi(node->setParam, prm->paramid);
224 PlannerInitPlan = lappend(PlannerInitPlan, node);
225 result = (Node *) prm;
227 else if (node->parParam == NIL && slink->subLinkType == EXPR_SUBLINK)
229 TargetEntry *te = lfirst(plan->targetlist);
231 /* need a var node just to pass to new_param()... */
232 Var *var = makeVar(0, 0, te->resdom->restype,
233 te->resdom->restypmod, 0);
234 Param *prm = makeNode(Param);
236 prm->paramkind = PARAM_EXEC;
237 prm->paramid = (AttrNumber) new_param(var, PlannerQueryLevel);
238 prm->paramtype = var->vartype;
239 pfree(var); /* var is only needed for new_param */
240 node->setParam = lappendi(node->setParam, prm->paramid);
241 PlannerInitPlan = lappend(PlannerInitPlan, node);
242 result = (Node *) prm;
244 else if (node->parParam == NIL && slink->subLinkType == MULTIEXPR_SUBLINK)
250 * Convert oper list of Opers into a list of Exprs, using lefthand
251 * arguments and Params representing inside results.
253 foreach(lst, slink->oper)
255 Oper *oper = (Oper *) lfirst(lst);
256 Node *lefthand = nth(i, slink->lefthand);
257 TargetEntry *te = nth(i, plan->targetlist);
259 /* need a var node just to pass to new_param()... */
260 Var *var = makeVar(0, 0, te->resdom->restype,
261 te->resdom->restypmod, 0);
262 Param *prm = makeNode(Param);
264 Form_pg_operator opform;
268 prm->paramkind = PARAM_EXEC;
269 prm->paramid = (AttrNumber) new_param(var, PlannerQueryLevel);
270 prm->paramtype = var->vartype;
271 pfree(var); /* var is only needed for new_param */
273 Assert(IsA(oper, Oper));
274 tup = SearchSysCache(OPEROID,
275 ObjectIdGetDatum(oper->opno),
277 if (! HeapTupleIsValid(tup))
278 elog(ERROR, "cache lookup failed for operator %u", oper->opno);
279 opform = (Form_pg_operator) GETSTRUCT(tup);
282 * Note: we use make_operand in case runtime type conversion
283 * function calls must be inserted for this operator!
285 left = make_operand("", lefthand,
286 exprType(lefthand), opform->oprleft);
287 right = make_operand("", (Node *) prm,
288 prm->paramtype, opform->oprright);
289 ReleaseSysCache(tup);
291 newoper = lappend(newoper,
295 node->setParam = lappendi(node->setParam, prm->paramid);
298 slink->oper = newoper;
299 slink->lefthand = NIL;
300 PlannerInitPlan = lappend(PlannerInitPlan, node);
302 result = (Node *) ((slink->useor) ? make_orclause(newoper) :
303 make_andclause(newoper));
305 result = (Node *) lfirst(newoper);
309 Expr *expr = makeNode(Expr);
315 * We can't convert subplans of ALL_SUBLINK or ANY_SUBLINK types
316 * to initPlans, even when they are uncorrelated or undirect
317 * correlated, because we need to scan the output of the subplan
318 * for each outer tuple. However, we have the option to tack a
319 * MATERIAL node onto the top of an uncorrelated/undirect
320 * correlated subplan, which lets us do the work of evaluating the
321 * subplan only once. We do this if the subplan's top plan node
322 * is anything more complicated than a plain sequential scan, and
323 * we do it even for seqscan if the qual appears selective enough
324 * to eliminate many tuples.
326 if (node->parParam == NIL)
330 switch (nodeTag(plan))
333 if (plan->initPlan || plan->subPlan)
339 qualsel = clauselist_selectivity(subquery,
342 /* Is 10% selectivity a good threshold?? */
343 use_material = qualsel < 0.10;
350 * Don't add another Material node if there's one
351 * already, nor if the top node is a Sort, since Sort
352 * materializes its output anyway. (I doubt either
353 * case can happen in practice for a subplan, but...)
355 use_material = false;
363 plan = (Plan *) make_material(plan->targetlist, plan);
369 * Make expression of SUBPLAN type
371 expr->typeOid = BOOLOID;/* bogus, but we don't really care */
372 expr->opType = SUBPLAN_EXPR;
373 expr->oper = (Node *) node;
376 * Make expr->args from parParam.
378 foreach(lst, node->parParam)
380 Var *var = nth(lfirsti(lst), PlannerParamVar);
382 var = (Var *) copyObject(var);
385 * Must fix absolute-level varlevelsup from the
386 * PlannerParamVar entry. But since var is at current subplan
387 * level, this is easy:
389 var->varlevelsup = 0;
390 args = lappend(args, var);
395 * Convert oper list of Opers into a list of Exprs, using lefthand
396 * arguments and Consts representing inside results.
398 foreach(lst, slink->oper)
400 Oper *oper = (Oper *) lfirst(lst);
401 Node *lefthand = nth(i, slink->lefthand);
402 TargetEntry *te = nth(i, plan->targetlist);
405 Form_pg_operator opform;
409 con = makeNullConst(te->resdom->restype);
411 Assert(IsA(oper, Oper));
412 tup = SearchSysCache(OPEROID,
413 ObjectIdGetDatum(oper->opno),
415 if (! HeapTupleIsValid(tup))
416 elog(ERROR, "cache lookup failed for operator %u", oper->opno);
417 opform = (Form_pg_operator) GETSTRUCT(tup);
420 * Note: we use make_operand in case runtime type conversion
421 * function calls must be inserted for this operator!
423 left = make_operand("", lefthand,
424 exprType(lefthand), opform->oprleft);
425 right = make_operand("", (Node *) con,
426 con->consttype, opform->oprright);
427 ReleaseSysCache(tup);
429 newoper = lappend(newoper,
435 slink->oper = newoper;
436 slink->lefthand = NIL;
437 result = (Node *) expr;
444 * finalize_primnode: build lists of subplans and params appearing
445 * in the given expression tree. NOTE: items are added to lists passed in,
446 * so caller must initialize lists to NIL before first call!
448 * Note: the subplan list that is constructed here and assigned to the
449 * plan's subPlan field will be replaced with an up-to-date list in
450 * set_plan_references(). We could almost dispense with building this
451 * subplan list at all; I believe the only place that uses it is the
452 * check in make_subplan to see whether a subselect has any subselects.
455 typedef struct finalize_primnode_results
457 List *subplans; /* List of subplans found in expr */
458 List *paramids; /* List of PARAM_EXEC paramids found */
459 } finalize_primnode_results;
462 finalize_primnode(Node *node, finalize_primnode_results *results)
466 if (IsA(node, Param))
468 if (((Param *) node)->paramkind == PARAM_EXEC)
470 int paramid = (int) ((Param *) node)->paramid;
472 if (!intMember(paramid, results->paramids))
473 results->paramids = lconsi(paramid, results->paramids);
475 return false; /* no more to do here */
477 if (is_subplan(node))
479 SubPlan *subplan = (SubPlan *) ((Expr *) node)->oper;
482 /* Add subplan to subplans list */
483 results->subplans = lappend(results->subplans, subplan);
484 /* Check extParam list for params to add to paramids */
485 foreach(lst, subplan->plan->extParam)
487 int paramid = lfirsti(lst);
488 Var *var = nth(paramid, PlannerParamVar);
490 /* note varlevelsup is absolute level number */
491 if (var->varlevelsup < PlannerQueryLevel &&
492 !intMember(paramid, results->paramids))
493 results->paramids = lconsi(paramid, results->paramids);
495 /* fall through to recurse into subplan args */
497 return expression_tree_walker(node, finalize_primnode,
502 * Replace correlation vars (uplevel vars) with Params.
505 static Node *replace_correlation_vars_mutator(Node *node, void *context);
508 SS_replace_correlation_vars(Node *expr)
510 /* No setup needed for tree walk, so away we go */
511 return replace_correlation_vars_mutator(expr, NULL);
515 replace_correlation_vars_mutator(Node *node, void *context)
521 if (((Var *) node)->varlevelsup > 0)
522 return (Node *) replace_var((Var *) node);
524 return expression_tree_mutator(node,
525 replace_correlation_vars_mutator,
530 * Expand SubLinks to SubPlans in the given expression.
533 static Node *process_sublinks_mutator(Node *node, void *context);
536 SS_process_sublinks(Node *expr)
538 /* No setup needed for tree walk, so away we go */
539 return process_sublinks_mutator(expr, NULL);
543 process_sublinks_mutator(Node *node, void *context)
547 if (IsA(node, SubLink))
549 SubLink *sublink = (SubLink *) node;
552 * First, scan the lefthand-side expressions, if any. This is a
553 * tad klugy since we modify the input SubLink node, but that
554 * should be OK (make_subplan does it too!)
556 sublink->lefthand = (List *)
557 process_sublinks_mutator((Node *) sublink->lefthand, context);
558 /* Now build the SubPlan node and make the expr to return */
559 return make_subplan(sublink);
563 * Note that we will never see a SubPlan expression in the input
564 * (since this is the very routine that creates 'em to begin with). So
565 * the code in expression_tree_mutator() that might do inappropriate
566 * things with SubPlans or SubLinks will not be exercised.
568 Assert(!is_subplan(node));
570 return expression_tree_mutator(node,
571 process_sublinks_mutator,
576 SS_finalize_plan(Plan *plan)
578 List *extParam = NIL;
579 List *locParam = NIL;
580 finalize_primnode_results results;
586 results.subplans = NIL; /* initialize lists to NIL */
587 results.paramids = NIL;
590 * When we call finalize_primnode, results.paramids lists are
591 * automatically merged together. But when recursing to self, we have
592 * to do it the hard way. We want the paramids list to include params
593 * in subplans as well as at this level. (We don't care about finding
594 * subplans of subplans, though.)
597 /* Find params and subplans in targetlist and qual */
598 finalize_primnode((Node *) plan->targetlist, &results);
599 finalize_primnode((Node *) plan->qual, &results);
601 /* Check additional node-type-specific fields */
602 switch (nodeTag(plan))
605 finalize_primnode(((Result *) plan)->resconstantqual,
610 foreach(lst, ((Append *) plan)->appendplans)
611 results.paramids = set_unioni(results.paramids,
612 SS_finalize_plan((Plan *) lfirst(lst)));
617 * In a SubqueryScan, SS_finalize_plan has already been run
618 * on the subplan by the inner invocation of subquery_planner,
619 * so there's no need to do it again. Instead, just pull out
620 * the subplan's extParams list, which represents the params
621 * it needs from my level and higher levels.
623 results.paramids = set_unioni(results.paramids,
624 ((SubqueryScan *) plan)->subplan->extParam);
628 finalize_primnode((Node *) ((IndexScan *) plan)->indxqual,
632 * we need not look at indxqualorig, since it will have the
633 * same param references as indxqual, and we aren't really
634 * concerned yet about having a complete subplan list.
639 finalize_primnode((Node *) ((Join *) plan)->joinqual,
644 finalize_primnode((Node *) ((Join *) plan)->joinqual,
646 finalize_primnode((Node *) ((MergeJoin *) plan)->mergeclauses,
651 finalize_primnode((Node *) ((Join *) plan)->joinqual,
653 finalize_primnode((Node *) ((HashJoin *) plan)->hashclauses,
658 finalize_primnode(((Hash *) plan)->hashkey,
663 finalize_primnode((Node *) ((TidScan *) plan)->tideval,
678 elog(ERROR, "SS_finalize_plan: node %d unsupported",
682 /* Process left and right subplans, if any */
683 results.paramids = set_unioni(results.paramids,
684 SS_finalize_plan(plan->lefttree));
685 results.paramids = set_unioni(results.paramids,
686 SS_finalize_plan(plan->righttree));
688 /* Now we have all the paramids and subplans */
690 foreach(lst, results.paramids)
692 int paramid = lfirsti(lst);
693 Var *var = nth(paramid, PlannerParamVar);
695 /* note varlevelsup is absolute level number */
696 if (var->varlevelsup < PlannerQueryLevel)
697 extParam = lappendi(extParam, paramid);
698 else if (var->varlevelsup > PlannerQueryLevel)
699 elog(ERROR, "SS_finalize_plan: plan shouldn't reference subplan's variable");
702 Assert(var->varno == 0 && var->varattno == 0);
703 locParam = lappendi(locParam, paramid);
707 plan->extParam = extParam;
708 plan->locParam = locParam;
709 plan->subPlan = results.subplans;
711 return results.paramids;