1/*-------------------------------------------------------------------------
2 *
3 * plancache.c
4 * Plan cache management.
5 *
6 * The plan cache manager has two principal responsibilities: deciding when
7 * to use a generic plan versus a custom (parameter-value-specific) plan,
8 * and tracking whether cached plans need to be invalidated because of schema
9 * changes in the objects they depend on.
10 *
11 * The logic for choosing generic or custom plans is in choose_custom_plan,
12 * which see for comments.
13 *
14 * Cache invalidation is driven off sinval events. Any CachedPlanSource
15 * that matches the event is marked invalid, as is its generic CachedPlan
16 * if it has one. When (and if) the next demand for a cached plan occurs,
17 * parse analysis and rewrite is repeated to build a new valid query tree,
18 * and then planning is performed as normal. We also force re-analysis and
19 * re-planning if the active search_path is different from the previous time
20 * or, if RLS is involved, if the user changes or the RLS environment changes.
21 *
22 * Note that if the sinval was a result of user DDL actions, parse analysis
23 * could throw an error, for example if a column referenced by the query is
24 * no longer present. Another possibility is for the query's output tupdesc
25 * to change (for instance "SELECT *" might expand differently than before).
26 * The creator of a cached plan can specify whether it is allowable for the
27 * query to change output tupdesc on replan --- if so, it's up to the
28 * caller to notice changes and cope with them.
29 *
30 * Currently, we track exactly the dependencies of plans on relations,
31 * user-defined functions, and domains. On relcache invalidation events or
32 * pg_proc or pg_type syscache invalidation events, we invalidate just those
33 * plans that depend on the particular object being modified. (Note: this
34 * scheme assumes that any table modification that requires replanning will
35 * generate a relcache inval event.) We also watch for inval events on
36 * certain other system catalogs, such as pg_namespace; but for them, our
37 * response is just to invalidate all plans. We expect updates on those
38 * catalogs to be infrequent enough that more-detailed tracking is not worth
39 * the effort.
40 *
41 * In addition to full-fledged query plans, we provide a facility for
42 * detecting invalidations of simple scalar expressions. This is fairly
43 * bare-bones; it's the caller's responsibility to build a new expression
44 * if the old one gets invalidated.
45 *
46 *
47 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
48 * Portions Copyright (c) 1994, Regents of the University of California
49 *
50 * IDENTIFICATION
51 * src/backend/utils/cache/plancache.c
52 *
53 *-------------------------------------------------------------------------
54 */
55#include "postgres.h"
56
57#include <limits.h>
58
59#include "access/transam.h"
60#include "catalog/namespace.h"
61#include "executor/executor.h"
62#include "miscadmin.h"
63#include "nodes/nodeFuncs.h"
64#include "optimizer/optimizer.h"
65#include "parser/analyze.h"
66#include "parser/parsetree.h"
67#include "storage/lmgr.h"
68#include "tcop/pquery.h"
69#include "tcop/utility.h"
70#include "utils/inval.h"
71#include "utils/memutils.h"
72#include "utils/resowner_private.h"
73#include "utils/rls.h"
74#include "utils/snapmgr.h"
75#include "utils/syscache.h"
76
77
78/*
79 * We must skip "overhead" operations that involve database access when the
80 * cached plan's subject statement is a transaction control command.
81 */
82#define IsTransactionStmtPlan(plansource) \
83 ((plansource)->raw_parse_tree && \
84 IsA((plansource)->raw_parse_tree->stmt, TransactionStmt))
85
86/*
87 * This is the head of the backend's list of "saved" CachedPlanSources (i.e.,
88 * those that are in long-lived storage and are examined for sinval events).
89 * We use a dlist instead of separate List cells so that we can guarantee
90 * to save a CachedPlanSource without error.
91 */
92static dlist_head saved_plan_list = DLIST_STATIC_INIT(saved_plan_list);
93
94/*
95 * This is the head of the backend's list of CachedExpressions.
96 */
97static dlist_head cached_expression_list = DLIST_STATIC_INIT(cached_expression_list);
98
99static void ReleaseGenericPlan(CachedPlanSource *plansource);
100static List *RevalidateCachedQuery(CachedPlanSource *plansource,
101 QueryEnvironment *queryEnv);
102static bool CheckCachedPlan(CachedPlanSource *plansource);
103static CachedPlan *BuildCachedPlan(CachedPlanSource *plansource, List *qlist,
104 ParamListInfo boundParams, QueryEnvironment *queryEnv);
105static bool choose_custom_plan(CachedPlanSource *plansource,
106 ParamListInfo boundParams);
107static double cached_plan_cost(CachedPlan *plan, bool include_planner);
108static Query *QueryListGetPrimaryStmt(List *stmts);
109static void AcquireExecutorLocks(List *stmt_list, bool acquire);
110static void AcquirePlannerLocks(List *stmt_list, bool acquire);
111static void ScanQueryForLocks(Query *parsetree, bool acquire);
112static bool ScanQueryWalker(Node *node, bool *acquire);
113static TupleDesc PlanCacheComputeResultDesc(List *stmt_list);
114static void PlanCacheRelCallback(Datum arg, Oid relid);
115static void PlanCacheObjectCallback(Datum arg, int cacheid, uint32 hashvalue);
116static void PlanCacheSysCallback(Datum arg, int cacheid, uint32 hashvalue);
117
118/* GUC parameter */
119int plan_cache_mode;
120
121/*
122 * InitPlanCache: initialize module during InitPostgres.
123 *
124 * All we need to do is hook into inval.c's callback lists.
125 */
126void
127InitPlanCache(void)
128{
129 CacheRegisterRelcacheCallback(PlanCacheRelCallback, (Datum) 0);
130 CacheRegisterSyscacheCallback(PROCOID, PlanCacheObjectCallback, (Datum) 0);
131 CacheRegisterSyscacheCallback(TYPEOID, PlanCacheObjectCallback, (Datum) 0);
132 CacheRegisterSyscacheCallback(NAMESPACEOID, PlanCacheSysCallback, (Datum) 0);
133 CacheRegisterSyscacheCallback(OPEROID, PlanCacheSysCallback, (Datum) 0);
134 CacheRegisterSyscacheCallback(AMOPOPID, PlanCacheSysCallback, (Datum) 0);
135 CacheRegisterSyscacheCallback(FOREIGNSERVEROID, PlanCacheSysCallback, (Datum) 0);
136 CacheRegisterSyscacheCallback(FOREIGNDATAWRAPPEROID, PlanCacheSysCallback, (Datum) 0);
137}
138
139/*
140 * CreateCachedPlan: initially create a plan cache entry.
141 *
142 * Creation of a cached plan is divided into two steps, CreateCachedPlan and
143 * CompleteCachedPlan. CreateCachedPlan should be called after running the
144 * query through raw_parser, but before doing parse analysis and rewrite;
145 * CompleteCachedPlan is called after that. The reason for this arrangement
146 * is that it can save one round of copying of the raw parse tree, since
147 * the parser will normally scribble on the raw parse tree. Callers would
148 * otherwise need to make an extra copy of the parse tree to ensure they
149 * still had a clean copy to present at plan cache creation time.
150 *
151 * All arguments presented to CreateCachedPlan are copied into a memory
152 * context created as a child of the call-time CurrentMemoryContext, which
153 * should be a reasonably short-lived working context that will go away in
154 * event of an error. This ensures that the cached plan data structure will
155 * likewise disappear if an error occurs before we have fully constructed it.
156 * Once constructed, the cached plan can be made longer-lived, if needed,
157 * by calling SaveCachedPlan.
158 *
159 * raw_parse_tree: output of raw_parser(), or NULL if empty query
160 * query_string: original query text
161 * commandTag: compile-time-constant tag for query, or NULL if empty query
162 */
163CachedPlanSource *
164CreateCachedPlan(RawStmt *raw_parse_tree,
165 const char *query_string,
166 const char *commandTag)
167{
168 CachedPlanSource *plansource;
169 MemoryContext source_context;
170 MemoryContext oldcxt;
171
172 Assert(query_string != NULL); /* required as of 8.4 */
173
174 /*
175 * Make a dedicated memory context for the CachedPlanSource and its
176 * permanent subsidiary data. It's probably not going to be large, but
177 * just in case, allow it to grow large. Initially it's a child of the
178 * caller's context (which we assume to be transient), so that it will be
179 * cleaned up on error.
180 */
181 source_context = AllocSetContextCreate(CurrentMemoryContext,
182 "CachedPlanSource",
183 ALLOCSET_START_SMALL_SIZES);
184
185 /*
186 * Create and fill the CachedPlanSource struct within the new context.
187 * Most fields are just left empty for the moment.
188 */
189 oldcxt = MemoryContextSwitchTo(source_context);
190
191 plansource = (CachedPlanSource *) palloc0(sizeof(CachedPlanSource));
192 plansource->magic = CACHEDPLANSOURCE_MAGIC;
193 plansource->raw_parse_tree = copyObject(raw_parse_tree);
194 plansource->query_string = pstrdup(query_string);
195 MemoryContextSetIdentifier(source_context, plansource->query_string);
196 plansource->commandTag = commandTag;
197 plansource->param_types = NULL;
198 plansource->num_params = 0;
199 plansource->parserSetup = NULL;
200 plansource->parserSetupArg = NULL;
201 plansource->cursor_options = 0;
202 plansource->fixed_result = false;
203 plansource->resultDesc = NULL;
204 plansource->context = source_context;
205 plansource->query_list = NIL;
206 plansource->relationOids = NIL;
207 plansource->invalItems = NIL;
208 plansource->search_path = NULL;
209 plansource->query_context = NULL;
210 plansource->rewriteRoleId = InvalidOid;
211 plansource->rewriteRowSecurity = false;
212 plansource->dependsOnRLS = false;
213 plansource->gplan = NULL;
214 plansource->is_oneshot = false;
215 plansource->is_complete = false;
216 plansource->is_saved = false;
217 plansource->is_valid = false;
218 plansource->generation = 0;
219 plansource->generic_cost = -1;
220 plansource->total_custom_cost = 0;
221 plansource->num_custom_plans = 0;
222
223 MemoryContextSwitchTo(oldcxt);
224
225 return plansource;
226}
227
228/*
229 * CreateOneShotCachedPlan: initially create a one-shot plan cache entry.
230 *
231 * This variant of CreateCachedPlan creates a plan cache entry that is meant
232 * to be used only once. No data copying occurs: all data structures remain
233 * in the caller's memory context (which typically should get cleared after
234 * completing execution). The CachedPlanSource struct itself is also created
235 * in that context.
236 *
237 * A one-shot plan cannot be saved or copied, since we make no effort to
238 * preserve the raw parse tree unmodified. There is also no support for
239 * invalidation, so plan use must be completed in the current transaction,
240 * and DDL that might invalidate the querytree_list must be avoided as well.
241 *
242 * raw_parse_tree: output of raw_parser(), or NULL if empty query
243 * query_string: original query text
244 * commandTag: compile-time-constant tag for query, or NULL if empty query
245 */
246CachedPlanSource *
247CreateOneShotCachedPlan(RawStmt *raw_parse_tree,
248 const char *query_string,
249 const char *commandTag)
250{
251 CachedPlanSource *plansource;
252
253 Assert(query_string != NULL); /* required as of 8.4 */
254
255 /*
256 * Create and fill the CachedPlanSource struct within the caller's memory
257 * context. Most fields are just left empty for the moment.
258 */
259 plansource = (CachedPlanSource *) palloc0(sizeof(CachedPlanSource));
260 plansource->magic = CACHEDPLANSOURCE_MAGIC;
261 plansource->raw_parse_tree = raw_parse_tree;
262 plansource->query_string = query_string;
263 plansource->commandTag = commandTag;
264 plansource->param_types = NULL;
265 plansource->num_params = 0;
266 plansource->parserSetup = NULL;
267 plansource->parserSetupArg = NULL;
268 plansource->cursor_options = 0;
269 plansource->fixed_result = false;
270 plansource->resultDesc = NULL;
271 plansource->context = CurrentMemoryContext;
272 plansource->query_list = NIL;
273 plansource->relationOids = NIL;
274 plansource->invalItems = NIL;
275 plansource->search_path = NULL;
276 plansource->query_context = NULL;
277 plansource->rewriteRoleId = InvalidOid;
278 plansource->rewriteRowSecurity = false;
279 plansource->dependsOnRLS = false;
280 plansource->gplan = NULL;
281 plansource->is_oneshot = true;
282 plansource->is_complete = false;
283 plansource->is_saved = false;
284 plansource->is_valid = false;
285 plansource->generation = 0;
286 plansource->generic_cost = -1;
287 plansource->total_custom_cost = 0;
288 plansource->num_custom_plans = 0;
289
290 return plansource;
291}
292
293/*
294 * CompleteCachedPlan: second step of creating a plan cache entry.
295 *
296 * Pass in the analyzed-and-rewritten form of the query, as well as the
297 * required subsidiary data about parameters and such. All passed values will
298 * be copied into the CachedPlanSource's memory, except as specified below.
299 * After this is called, GetCachedPlan can be called to obtain a plan, and
300 * optionally the CachedPlanSource can be saved using SaveCachedPlan.
301 *
302 * If querytree_context is not NULL, the querytree_list must be stored in that
303 * context (but the other parameters need not be). The querytree_list is not
304 * copied, rather the given context is kept as the initial query_context of
305 * the CachedPlanSource. (It should have been created as a child of the
306 * caller's working memory context, but it will now be reparented to belong
307 * to the CachedPlanSource.) The querytree_context is normally the context in
308 * which the caller did raw parsing and parse analysis. This approach saves
309 * one tree copying step compared to passing NULL, but leaves lots of extra
310 * cruft in the query_context, namely whatever extraneous stuff parse analysis
311 * created, as well as whatever went unused from the raw parse tree. Using
312 * this option is a space-for-time tradeoff that is appropriate if the
313 * CachedPlanSource is not expected to survive long.
314 *
315 * plancache.c cannot know how to copy the data referenced by parserSetupArg,
316 * and it would often be inappropriate to do so anyway. When using that
317 * option, it is caller's responsibility that the referenced data remains
318 * valid for as long as the CachedPlanSource exists.
319 *
320 * If the CachedPlanSource is a "oneshot" plan, then no querytree copying
321 * occurs at all, and querytree_context is ignored; it is caller's
322 * responsibility that the passed querytree_list is sufficiently long-lived.
323 *
324 * plansource: structure returned by CreateCachedPlan
325 * querytree_list: analyzed-and-rewritten form of query (list of Query nodes)
326 * querytree_context: memory context containing querytree_list,
327 * or NULL to copy querytree_list into a fresh context
328 * param_types: array of fixed parameter type OIDs, or NULL if none
329 * num_params: number of fixed parameters
330 * parserSetup: alternate method for handling query parameters
331 * parserSetupArg: data to pass to parserSetup
332 * cursor_options: options bitmask to pass to planner
333 * fixed_result: true to disallow future changes in query's result tupdesc
334 */
335void
336CompleteCachedPlan(CachedPlanSource *plansource,
337 List *querytree_list,
338 MemoryContext querytree_context,
339 Oid *param_types,
340 int num_params,
341 ParserSetupHook parserSetup,
342 void *parserSetupArg,
343 int cursor_options,
344 bool fixed_result)
345{
346 MemoryContext source_context = plansource->context;
347 MemoryContext oldcxt = CurrentMemoryContext;
348
349 /* Assert caller is doing things in a sane order */
350 Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
351 Assert(!plansource->is_complete);
352
353 /*
354 * If caller supplied a querytree_context, reparent it underneath the
355 * CachedPlanSource's context; otherwise, create a suitable context and
356 * copy the querytree_list into it. But no data copying should be done
357 * for one-shot plans; for those, assume the passed querytree_list is
358 * sufficiently long-lived.
359 */
360 if (plansource->is_oneshot)
361 {
362 querytree_context = CurrentMemoryContext;
363 }
364 else if (querytree_context != NULL)
365 {
366 MemoryContextSetParent(querytree_context, source_context);
367 MemoryContextSwitchTo(querytree_context);
368 }
369 else
370 {
371 /* Again, it's a good bet the querytree_context can be small */
372 querytree_context = AllocSetContextCreate(source_context,
373 "CachedPlanQuery",
374 ALLOCSET_START_SMALL_SIZES);
375 MemoryContextSwitchTo(querytree_context);
376 querytree_list = copyObject(querytree_list);
377 }
378
379 plansource->query_context = querytree_context;
380 plansource->query_list = querytree_list;
381
382 if (!plansource->is_oneshot && !IsTransactionStmtPlan(plansource))
383 {
384 /*
385 * Use the planner machinery to extract dependencies. Data is saved
386 * in query_context. (We assume that not a lot of extra cruft is
387 * created by this call.) We can skip this for one-shot plans, and
388 * transaction control commands have no such dependencies anyway.
389 */
390 extract_query_dependencies((Node *) querytree_list,
391 &plansource->relationOids,
392 &plansource->invalItems,
393 &plansource->dependsOnRLS);
394
395 /* Update RLS info as well. */
396 plansource->rewriteRoleId = GetUserId();
397 plansource->rewriteRowSecurity = row_security;
398
399 /*
400 * Also save the current search_path in the query_context. (This
401 * should not generate much extra cruft either, since almost certainly
402 * the path is already valid.) Again, we don't really need this for
403 * one-shot plans; and we *must* skip this for transaction control
404 * commands, because this could result in catalog accesses.
405 */
406 plansource->search_path = GetOverrideSearchPath(querytree_context);
407 }
408
409 /*
410 * Save the final parameter types (or other parameter specification data)
411 * into the source_context, as well as our other parameters. Also save
412 * the result tuple descriptor.
413 */
414 MemoryContextSwitchTo(source_context);
415
416 if (num_params > 0)
417 {
418 plansource->param_types = (Oid *) palloc(num_params * sizeof(Oid));
419 memcpy(plansource->param_types, param_types, num_params * sizeof(Oid));
420 }
421 else
422 plansource->param_types = NULL;
423 plansource->num_params = num_params;
424 plansource->parserSetup = parserSetup;
425 plansource->parserSetupArg = parserSetupArg;
426 plansource->cursor_options = cursor_options;
427 plansource->fixed_result = fixed_result;
428 plansource->resultDesc = PlanCacheComputeResultDesc(querytree_list);
429
430 MemoryContextSwitchTo(oldcxt);
431
432 plansource->is_complete = true;
433 plansource->is_valid = true;
434}
435
436/*
437 * SaveCachedPlan: save a cached plan permanently
438 *
439 * This function moves the cached plan underneath CacheMemoryContext (making
440 * it live for the life of the backend, unless explicitly dropped), and adds
441 * it to the list of cached plans that are checked for invalidation when an
442 * sinval event occurs.
443 *
444 * This is guaranteed not to throw error, except for the caller-error case
445 * of trying to save a one-shot plan. Callers typically depend on that
446 * since this is called just before or just after adding a pointer to the
447 * CachedPlanSource to some permanent data structure of their own. Up until
448 * this is done, a CachedPlanSource is just transient data that will go away
449 * automatically on transaction abort.
450 */
451void
452SaveCachedPlan(CachedPlanSource *plansource)
453{
454 /* Assert caller is doing things in a sane order */
455 Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
456 Assert(plansource->is_complete);
457 Assert(!plansource->is_saved);
458
459 /* This seems worth a real test, though */
460 if (plansource->is_oneshot)
461 elog(ERROR, "cannot save one-shot cached plan");
462
463 /*
464 * In typical use, this function would be called before generating any
465 * plans from the CachedPlanSource. If there is a generic plan, moving it
466 * into CacheMemoryContext would be pretty risky since it's unclear
467 * whether the caller has taken suitable care with making references
468 * long-lived. Best thing to do seems to be to discard the plan.
469 */
470 ReleaseGenericPlan(plansource);
471
472 /*
473 * Reparent the source memory context under CacheMemoryContext so that it
474 * will live indefinitely. The query_context follows along since it's
475 * already a child of the other one.
476 */
477 MemoryContextSetParent(plansource->context, CacheMemoryContext);
478
479 /*
480 * Add the entry to the global list of cached plans.
481 */
482 dlist_push_tail(&saved_plan_list, &plansource->node);
483
484 plansource->is_saved = true;
485}
486
487/*
488 * DropCachedPlan: destroy a cached plan.
489 *
490 * Actually this only destroys the CachedPlanSource: any referenced CachedPlan
491 * is released, but not destroyed until its refcount goes to zero. That
492 * handles the situation where DropCachedPlan is called while the plan is
493 * still in use.
494 */
495void
496DropCachedPlan(CachedPlanSource *plansource)
497{
498 Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
499
500 /* If it's been saved, remove it from the list */
501 if (plansource->is_saved)
502 {
503 dlist_delete(&plansource->node);
504 plansource->is_saved = false;
505 }
506
507 /* Decrement generic CachedPlan's refcount and drop if no longer needed */
508 ReleaseGenericPlan(plansource);
509
510 /* Mark it no longer valid */
511 plansource->magic = 0;
512
513 /*
514 * Remove the CachedPlanSource and all subsidiary data (including the
515 * query_context if any). But if it's a one-shot we can't free anything.
516 */
517 if (!plansource->is_oneshot)
518 MemoryContextDelete(plansource->context);
519}
520
521/*
522 * ReleaseGenericPlan: release a CachedPlanSource's generic plan, if any.
523 */
524static void
525ReleaseGenericPlan(CachedPlanSource *plansource)
526{
527 /* Be paranoid about the possibility that ReleaseCachedPlan fails */
528 if (plansource->gplan)
529 {
530 CachedPlan *plan = plansource->gplan;
531
532 Assert(plan->magic == CACHEDPLAN_MAGIC);
533 plansource->gplan = NULL;
534 ReleaseCachedPlan(plan, false);
535 }
536}
537
538/*
539 * RevalidateCachedQuery: ensure validity of analyzed-and-rewritten query tree.
540 *
541 * What we do here is re-acquire locks and redo parse analysis if necessary.
542 * On return, the query_list is valid and we have sufficient locks to begin
543 * planning.
544 *
545 * If any parse analysis activity is required, the caller's memory context is
546 * used for that work.
547 *
548 * The result value is the transient analyzed-and-rewritten query tree if we
549 * had to do re-analysis, and NIL otherwise. (This is returned just to save
550 * a tree copying step in a subsequent BuildCachedPlan call.)
551 */
552static List *
553RevalidateCachedQuery(CachedPlanSource *plansource,
554 QueryEnvironment *queryEnv)
555{
556 bool snapshot_set;
557 RawStmt *rawtree;
558 List *tlist; /* transient query-tree list */
559 List *qlist; /* permanent query-tree list */
560 TupleDesc resultDesc;
561 MemoryContext querytree_context;
562 MemoryContext oldcxt;
563
564 /*
565 * For one-shot plans, we do not support revalidation checking; it's
566 * assumed the query is parsed, planned, and executed in one transaction,
567 * so that no lock re-acquisition is necessary. Also, there is never any
568 * need to revalidate plans for transaction control commands (and we
569 * mustn't risk any catalog accesses when handling those).
570 */
571 if (plansource->is_oneshot || IsTransactionStmtPlan(plansource))
572 {
573 Assert(plansource->is_valid);
574 return NIL;
575 }
576
577 /*
578 * If the query is currently valid, we should have a saved search_path ---
579 * check to see if that matches the current environment. If not, we want
580 * to force replan.
581 */
582 if (plansource->is_valid)
583 {
584 Assert(plansource->search_path != NULL);
585 if (!OverrideSearchPathMatchesCurrent(plansource->search_path))
586 {
587 /* Invalidate the querytree and generic plan */
588 plansource->is_valid = false;
589 if (plansource->gplan)
590 plansource->gplan->is_valid = false;
591 }
592 }
593
594 /*
595 * If the query rewrite phase had a possible RLS dependency, we must redo
596 * it if either the role or the row_security setting has changed.
597 */
598 if (plansource->is_valid && plansource->dependsOnRLS &&
599 (plansource->rewriteRoleId != GetUserId() ||
600 plansource->rewriteRowSecurity != row_security))
601 plansource->is_valid = false;
602
603 /*
604 * If the query is currently valid, acquire locks on the referenced
605 * objects; then check again. We need to do it this way to cover the race
606 * condition that an invalidation message arrives before we get the locks.
607 */
608 if (plansource->is_valid)
609 {
610 AcquirePlannerLocks(plansource->query_list, true);
611
612 /*
613 * By now, if any invalidation has happened, the inval callback
614 * functions will have marked the query invalid.
615 */
616 if (plansource->is_valid)
617 {
618 /* Successfully revalidated and locked the query. */
619 return NIL;
620 }
621
622 /* Oops, the race case happened. Release useless locks. */
623 AcquirePlannerLocks(plansource->query_list, false);
624 }
625
626 /*
627 * Discard the no-longer-useful query tree. (Note: we don't want to do
628 * this any earlier, else we'd not have been able to release locks
629 * correctly in the race condition case.)
630 */
631 plansource->is_valid = false;
632 plansource->query_list = NIL;
633 plansource->relationOids = NIL;
634 plansource->invalItems = NIL;
635 plansource->search_path = NULL;
636
637 /*
638 * Free the query_context. We don't really expect MemoryContextDelete to
639 * fail, but just in case, make sure the CachedPlanSource is left in a
640 * reasonably sane state. (The generic plan won't get unlinked yet, but
641 * that's acceptable.)
642 */
643 if (plansource->query_context)
644 {
645 MemoryContext qcxt = plansource->query_context;
646
647 plansource->query_context = NULL;
648 MemoryContextDelete(qcxt);
649 }
650
651 /* Drop the generic plan reference if any */
652 ReleaseGenericPlan(plansource);
653
654 /*
655 * Now re-do parse analysis and rewrite. This not incidentally acquires
656 * the locks we need to do planning safely.
657 */
658 Assert(plansource->is_complete);
659
660 /*
661 * If a snapshot is already set (the normal case), we can just use that
662 * for parsing/planning. But if it isn't, install one. Note: no point in
663 * checking whether parse analysis requires a snapshot; utility commands
664 * don't have invalidatable plans, so we'd not get here for such a
665 * command.
666 */
667 snapshot_set = false;
668 if (!ActiveSnapshotSet())
669 {
670 PushActiveSnapshot(GetTransactionSnapshot());
671 snapshot_set = true;
672 }
673
674 /*
675 * Run parse analysis and rule rewriting. The parser tends to scribble on
676 * its input, so we must copy the raw parse tree to prevent corruption of
677 * the cache.
678 */
679 rawtree = copyObject(plansource->raw_parse_tree);
680 if (rawtree == NULL)
681 tlist = NIL;
682 else if (plansource->parserSetup != NULL)
683 tlist = pg_analyze_and_rewrite_params(rawtree,
684 plansource->query_string,
685 plansource->parserSetup,
686 plansource->parserSetupArg,
687 queryEnv);
688 else
689 tlist = pg_analyze_and_rewrite(rawtree,
690 plansource->query_string,
691 plansource->param_types,
692 plansource->num_params,
693 queryEnv);
694
695 /* Release snapshot if we got one */
696 if (snapshot_set)
697 PopActiveSnapshot();
698
699 /*
700 * Check or update the result tupdesc. XXX should we use a weaker
701 * condition than equalTupleDescs() here?
702 *
703 * We assume the parameter types didn't change from the first time, so no
704 * need to update that.
705 */
706 resultDesc = PlanCacheComputeResultDesc(tlist);
707 if (resultDesc == NULL && plansource->resultDesc == NULL)
708 {
709 /* OK, doesn't return tuples */
710 }
711 else if (resultDesc == NULL || plansource->resultDesc == NULL ||
712 !equalTupleDescs(resultDesc, plansource->resultDesc))
713 {
714 /* can we give a better error message? */
715 if (plansource->fixed_result)
716 ereport(ERROR,
717 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
718 errmsg("cached plan must not change result type")));
719 oldcxt = MemoryContextSwitchTo(plansource->context);
720 if (resultDesc)
721 resultDesc = CreateTupleDescCopy(resultDesc);
722 if (plansource->resultDesc)
723 FreeTupleDesc(plansource->resultDesc);
724 plansource->resultDesc = resultDesc;
725 MemoryContextSwitchTo(oldcxt);
726 }
727
728 /*
729 * Allocate new query_context and copy the completed querytree into it.
730 * It's transient until we complete the copying and dependency extraction.
731 */
732 querytree_context = AllocSetContextCreate(CurrentMemoryContext,
733 "CachedPlanQuery",
734 ALLOCSET_START_SMALL_SIZES);
735 oldcxt = MemoryContextSwitchTo(querytree_context);
736
737 qlist = copyObject(tlist);
738
739 /*
740 * Use the planner machinery to extract dependencies. Data is saved in
741 * query_context. (We assume that not a lot of extra cruft is created by
742 * this call.)
743 */
744 extract_query_dependencies((Node *) qlist,
745 &plansource->relationOids,
746 &plansource->invalItems,
747 &plansource->dependsOnRLS);
748
749 /* Update RLS info as well. */
750 plansource->rewriteRoleId = GetUserId();
751 plansource->rewriteRowSecurity = row_security;
752
753 /*
754 * Also save the current search_path in the query_context. (This should
755 * not generate much extra cruft either, since almost certainly the path
756 * is already valid.)
757 */
758 plansource->search_path = GetOverrideSearchPath(querytree_context);
759
760 MemoryContextSwitchTo(oldcxt);
761
762 /* Now reparent the finished query_context and save the links */
763 MemoryContextSetParent(querytree_context, plansource->context);
764
765 plansource->query_context = querytree_context;
766 plansource->query_list = qlist;
767
768 /*
769 * Note: we do not reset generic_cost or total_custom_cost, although we
770 * could choose to do so. If the DDL or statistics change that prompted
771 * the invalidation meant a significant change in the cost estimates, it
772 * would be better to reset those variables and start fresh; but often it
773 * doesn't, and we're better retaining our hard-won knowledge about the
774 * relative costs.
775 */
776
777 plansource->is_valid = true;
778
779 /* Return transient copy of querytrees for possible use in planning */
780 return tlist;
781}
782
783/*
784 * CheckCachedPlan: see if the CachedPlanSource's generic plan is valid.
785 *
786 * Caller must have already called RevalidateCachedQuery to verify that the
787 * querytree is up to date.
788 *
789 * On a "true" return, we have acquired the locks needed to run the plan.
790 * (We must do this for the "true" result to be race-condition-free.)
791 */
792static bool
793CheckCachedPlan(CachedPlanSource *plansource)
794{
795 CachedPlan *plan = plansource->gplan;
796
797 /* Assert that caller checked the querytree */
798 Assert(plansource->is_valid);
799
800 /* If there's no generic plan, just say "false" */
801 if (!plan)
802 return false;
803
804 Assert(plan->magic == CACHEDPLAN_MAGIC);
805 /* Generic plans are never one-shot */
806 Assert(!plan->is_oneshot);
807
808 /*
809 * If plan isn't valid for current role, we can't use it.
810 */
811 if (plan->is_valid && plan->dependsOnRole &&
812 plan->planRoleId != GetUserId())
813 plan->is_valid = false;
814
815 /*
816 * If it appears valid, acquire locks and recheck; this is much the same
817 * logic as in RevalidateCachedQuery, but for a plan.
818 */
819 if (plan->is_valid)
820 {
821 /*
822 * Plan must have positive refcount because it is referenced by
823 * plansource; so no need to fear it disappears under us here.
824 */
825 Assert(plan->refcount > 0);
826
827 AcquireExecutorLocks(plan->stmt_list, true);
828
829 /*
830 * If plan was transient, check to see if TransactionXmin has
831 * advanced, and if so invalidate it.
832 */
833 if (plan->is_valid &&
834 TransactionIdIsValid(plan->saved_xmin) &&
835 !TransactionIdEquals(plan->saved_xmin, TransactionXmin))
836 plan->is_valid = false;
837
838 /*
839 * By now, if any invalidation has happened, the inval callback
840 * functions will have marked the plan invalid.
841 */
842 if (plan->is_valid)
843 {
844 /* Successfully revalidated and locked the query. */
845 return true;
846 }
847
848 /* Oops, the race case happened. Release useless locks. */
849 AcquireExecutorLocks(plan->stmt_list, false);
850 }
851
852 /*
853 * Plan has been invalidated, so unlink it from the parent and release it.
854 */
855 ReleaseGenericPlan(plansource);
856
857 return false;
858}
859
860/*
861 * BuildCachedPlan: construct a new CachedPlan from a CachedPlanSource.
862 *
863 * qlist should be the result value from a previous RevalidateCachedQuery,
864 * or it can be set to NIL if we need to re-copy the plansource's query_list.
865 *
866 * To build a generic, parameter-value-independent plan, pass NULL for
867 * boundParams. To build a custom plan, pass the actual parameter values via
868 * boundParams. For best effect, the PARAM_FLAG_CONST flag should be set on
869 * each parameter value; otherwise the planner will treat the value as a
870 * hint rather than a hard constant.
871 *
872 * Planning work is done in the caller's memory context. The finished plan
873 * is in a child memory context, which typically should get reparented
874 * (unless this is a one-shot plan, in which case we don't copy the plan).
875 */
876static CachedPlan *
877BuildCachedPlan(CachedPlanSource *plansource, List *qlist,
878 ParamListInfo boundParams, QueryEnvironment *queryEnv)
879{
880 CachedPlan *plan;
881 List *plist;
882 bool snapshot_set;
883 bool is_transient;
884 MemoryContext plan_context;
885 MemoryContext oldcxt = CurrentMemoryContext;
886 ListCell *lc;
887
888 /*
889 * Normally the querytree should be valid already, but if it's not,
890 * rebuild it.
891 *
892 * NOTE: GetCachedPlan should have called RevalidateCachedQuery first, so
893 * we ought to be holding sufficient locks to prevent any invalidation.
894 * However, if we're building a custom plan after having built and
895 * rejected a generic plan, it's possible to reach here with is_valid
896 * false due to an invalidation while making the generic plan. In theory
897 * the invalidation must be a false positive, perhaps a consequence of an
898 * sinval reset event or the CLOBBER_CACHE_ALWAYS debug code. But for
899 * safety, let's treat it as real and redo the RevalidateCachedQuery call.
900 */
901 if (!plansource->is_valid)
902 qlist = RevalidateCachedQuery(plansource, queryEnv);
903
904 /*
905 * If we don't already have a copy of the querytree list that can be
906 * scribbled on by the planner, make one. For a one-shot plan, we assume
907 * it's okay to scribble on the original query_list.
908 */
909 if (qlist == NIL)
910 {
911 if (!plansource->is_oneshot)
912 qlist = copyObject(plansource->query_list);
913 else
914 qlist = plansource->query_list;
915 }
916
917 /*
918 * If a snapshot is already set (the normal case), we can just use that
919 * for planning. But if it isn't, and we need one, install one.
920 */
921 snapshot_set = false;
922 if (!ActiveSnapshotSet() &&
923 plansource->raw_parse_tree &&
924 analyze_requires_snapshot(plansource->raw_parse_tree))
925 {
926 PushActiveSnapshot(GetTransactionSnapshot());
927 snapshot_set = true;
928 }
929
930 /*
931 * Generate the plan.
932 */
933 plist = pg_plan_queries(qlist, plansource->cursor_options, boundParams);
934
935 /* Release snapshot if we got one */
936 if (snapshot_set)
937 PopActiveSnapshot();
938
939 /*
940 * Normally we make a dedicated memory context for the CachedPlan and its
941 * subsidiary data. (It's probably not going to be large, but just in
942 * case, allow it to grow large. It's transient for the moment.) But for
943 * a one-shot plan, we just leave it in the caller's memory context.
944 */
945 if (!plansource->is_oneshot)
946 {
947 plan_context = AllocSetContextCreate(CurrentMemoryContext,
948 "CachedPlan",
949 ALLOCSET_START_SMALL_SIZES);
950 MemoryContextCopyAndSetIdentifier(plan_context, plansource->query_string);
951
952 /*
953 * Copy plan into the new context.
954 */
955 MemoryContextSwitchTo(plan_context);
956
957 plist = copyObject(plist);
958 }
959 else
960 plan_context = CurrentMemoryContext;
961
962 /*
963 * Create and fill the CachedPlan struct within the new context.
964 */
965 plan = (CachedPlan *) palloc(sizeof(CachedPlan));
966 plan->magic = CACHEDPLAN_MAGIC;
967 plan->stmt_list = plist;
968
969 /*
970 * CachedPlan is dependent on role either if RLS affected the rewrite
971 * phase or if a role dependency was injected during planning. And it's
972 * transient if any plan is marked so.
973 */
974 plan->planRoleId = GetUserId();
975 plan->dependsOnRole = plansource->dependsOnRLS;
976 is_transient = false;
977 foreach(lc, plist)
978 {
979 PlannedStmt *plannedstmt = lfirst_node(PlannedStmt, lc);
980
981 if (plannedstmt->commandType == CMD_UTILITY)
982 continue; /* Ignore utility statements */
983
984 if (plannedstmt->transientPlan)
985 is_transient = true;
986 if (plannedstmt->dependsOnRole)
987 plan->dependsOnRole = true;
988 }
989 if (is_transient)
990 {
991 Assert(TransactionIdIsNormal(TransactionXmin));
992 plan->saved_xmin = TransactionXmin;
993 }
994 else
995 plan->saved_xmin = InvalidTransactionId;
996 plan->refcount = 0;
997 plan->context = plan_context;
998 plan->is_oneshot = plansource->is_oneshot;
999 plan->is_saved = false;
1000 plan->is_valid = true;
1001
1002 /* assign generation number to new plan */
1003 plan->generation = ++(plansource->generation);
1004
1005 MemoryContextSwitchTo(oldcxt);
1006
1007 return plan;
1008}
1009
1010/*
1011 * choose_custom_plan: choose whether to use custom or generic plan
1012 *
1013 * This defines the policy followed by GetCachedPlan.
1014 */
1015static bool
1016choose_custom_plan(CachedPlanSource *plansource, ParamListInfo boundParams)
1017{
1018 double avg_custom_cost;
1019
1020 /* One-shot plans will always be considered custom */
1021 if (plansource->is_oneshot)
1022 return true;
1023
1024 /* Otherwise, never any point in a custom plan if there's no parameters */
1025 if (boundParams == NULL)
1026 return false;
1027 /* ... nor for transaction control statements */
1028 if (IsTransactionStmtPlan(plansource))
1029 return false;
1030
1031 /* Let settings force the decision */
1032 if (plan_cache_mode == PLAN_CACHE_MODE_FORCE_GENERIC_PLAN)
1033 return false;
1034 if (plan_cache_mode == PLAN_CACHE_MODE_FORCE_CUSTOM_PLAN)
1035 return true;
1036
1037 /* See if caller wants to force the decision */
1038 if (plansource->cursor_options & CURSOR_OPT_GENERIC_PLAN)
1039 return false;
1040 if (plansource->cursor_options & CURSOR_OPT_CUSTOM_PLAN)
1041 return true;
1042
1043 /* Generate custom plans until we have done at least 5 (arbitrary) */
1044 if (plansource->num_custom_plans < 5)
1045 return true;
1046
1047 avg_custom_cost = plansource->total_custom_cost / plansource->num_custom_plans;
1048
1049 /*
1050 * Prefer generic plan if it's less expensive than the average custom
1051 * plan. (Because we include a charge for cost of planning in the
1052 * custom-plan costs, this means the generic plan only has to be less
1053 * expensive than the execution cost plus replan cost of the custom
1054 * plans.)
1055 *
1056 * Note that if generic_cost is -1 (indicating we've not yet determined
1057 * the generic plan cost), we'll always prefer generic at this point.
1058 */
1059 if (plansource->generic_cost < avg_custom_cost)
1060 return false;
1061
1062 return true;
1063}
1064
1065/*
1066 * cached_plan_cost: calculate estimated cost of a plan
1067 *
1068 * If include_planner is true, also include the estimated cost of constructing
1069 * the plan. (We must factor that into the cost of using a custom plan, but
1070 * we don't count it for a generic plan.)
1071 */
1072static double
1073cached_plan_cost(CachedPlan *plan, bool include_planner)
1074{
1075 double result = 0;
1076 ListCell *lc;
1077
1078 foreach(lc, plan->stmt_list)
1079 {
1080 PlannedStmt *plannedstmt = lfirst_node(PlannedStmt, lc);
1081
1082 if (plannedstmt->commandType == CMD_UTILITY)
1083 continue; /* Ignore utility statements */
1084
1085 result += plannedstmt->planTree->total_cost;
1086
1087 if (include_planner)
1088 {
1089 /*
1090 * Currently we use a very crude estimate of planning effort based
1091 * on the number of relations in the finished plan's rangetable.
1092 * Join planning effort actually scales much worse than linearly
1093 * in the number of relations --- but only until the join collapse
1094 * limits kick in. Also, while inheritance child relations surely
1095 * add to planning effort, they don't make the join situation
1096 * worse. So the actual shape of the planning cost curve versus
1097 * number of relations isn't all that obvious. It will take
1098 * considerable work to arrive at a less crude estimate, and for
1099 * now it's not clear that's worth doing.
1100 *
1101 * The other big difficulty here is that we don't have any very
1102 * good model of how planning cost compares to execution costs.
1103 * The current multiplier of 1000 * cpu_operator_cost is probably
1104 * on the low side, but we'll try this for awhile before making a
1105 * more aggressive correction.
1106 *
1107 * If we ever do write a more complicated estimator, it should
1108 * probably live in src/backend/optimizer/ not here.
1109 */
1110 int nrelations = list_length(plannedstmt->rtable);
1111
1112 result += 1000.0 * cpu_operator_cost * (nrelations + 1);
1113 }
1114 }
1115
1116 return result;
1117}
1118
1119/*
1120 * GetCachedPlan: get a cached plan from a CachedPlanSource.
1121 *
1122 * This function hides the logic that decides whether to use a generic
1123 * plan or a custom plan for the given parameters: the caller does not know
1124 * which it will get.
1125 *
1126 * On return, the plan is valid and we have sufficient locks to begin
1127 * execution.
1128 *
1129 * On return, the refcount of the plan has been incremented; a later
1130 * ReleaseCachedPlan() call is expected. The refcount has been reported
1131 * to the CurrentResourceOwner if useResOwner is true (note that that must
1132 * only be true if it's a "saved" CachedPlanSource).
1133 *
1134 * Note: if any replanning activity is required, the caller's memory context
1135 * is used for that work.
1136 */
1137CachedPlan *
1138GetCachedPlan(CachedPlanSource *plansource, ParamListInfo boundParams,
1139 bool useResOwner, QueryEnvironment *queryEnv)
1140{
1141 CachedPlan *plan = NULL;
1142 List *qlist;
1143 bool customplan;
1144
1145 /* Assert caller is doing things in a sane order */
1146 Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
1147 Assert(plansource->is_complete);
1148 /* This seems worth a real test, though */
1149 if (useResOwner && !plansource->is_saved)
1150 elog(ERROR, "cannot apply ResourceOwner to non-saved cached plan");
1151
1152 /* Make sure the querytree list is valid and we have parse-time locks */
1153 qlist = RevalidateCachedQuery(plansource, queryEnv);
1154
1155 /* Decide whether to use a custom plan */
1156 customplan = choose_custom_plan(plansource, boundParams);
1157
1158 if (!customplan)
1159 {
1160 if (CheckCachedPlan(plansource))
1161 {
1162 /* We want a generic plan, and we already have a valid one */
1163 plan = plansource->gplan;
1164 Assert(plan->magic == CACHEDPLAN_MAGIC);
1165 }
1166 else
1167 {
1168 /* Build a new generic plan */
1169 plan = BuildCachedPlan(plansource, qlist, NULL, queryEnv);
1170 /* Just make real sure plansource->gplan is clear */
1171 ReleaseGenericPlan(plansource);
1172 /* Link the new generic plan into the plansource */
1173 plansource->gplan = plan;
1174 plan->refcount++;
1175 /* Immediately reparent into appropriate context */
1176 if (plansource->is_saved)
1177 {
1178 /* saved plans all live under CacheMemoryContext */
1179 MemoryContextSetParent(plan->context, CacheMemoryContext);
1180 plan->is_saved = true;
1181 }
1182 else
1183 {
1184 /* otherwise, it should be a sibling of the plansource */
1185 MemoryContextSetParent(plan->context,
1186 MemoryContextGetParent(plansource->context));
1187 }
1188 /* Update generic_cost whenever we make a new generic plan */
1189 plansource->generic_cost = cached_plan_cost(plan, false);
1190
1191 /*
1192 * If, based on the now-known value of generic_cost, we'd not have
1193 * chosen to use a generic plan, then forget it and make a custom
1194 * plan. This is a bit of a wart but is necessary to avoid a
1195 * glitch in behavior when the custom plans are consistently big
1196 * winners; at some point we'll experiment with a generic plan and
1197 * find it's a loser, but we don't want to actually execute that
1198 * plan.
1199 */
1200 customplan = choose_custom_plan(plansource, boundParams);
1201
1202 /*
1203 * If we choose to plan again, we need to re-copy the query_list,
1204 * since the planner probably scribbled on it. We can force
1205 * BuildCachedPlan to do that by passing NIL.
1206 */
1207 qlist = NIL;
1208 }
1209 }
1210
1211 if (customplan)
1212 {
1213 /* Build a custom plan */
1214 plan = BuildCachedPlan(plansource, qlist, boundParams, queryEnv);
1215 /* Accumulate total costs of custom plans, but 'ware overflow */
1216 if (plansource->num_custom_plans < INT_MAX)
1217 {
1218 plansource->total_custom_cost += cached_plan_cost(plan, true);
1219 plansource->num_custom_plans++;
1220 }
1221 }
1222
1223 Assert(plan != NULL);
1224
1225 /* Flag the plan as in use by caller */
1226 if (useResOwner)
1227 ResourceOwnerEnlargePlanCacheRefs(CurrentResourceOwner);
1228 plan->refcount++;
1229 if (useResOwner)
1230 ResourceOwnerRememberPlanCacheRef(CurrentResourceOwner, plan);
1231
1232 /*
1233 * Saved plans should be under CacheMemoryContext so they will not go away
1234 * until their reference count goes to zero. In the generic-plan cases we
1235 * already took care of that, but for a custom plan, do it as soon as we
1236 * have created a reference-counted link.
1237 */
1238 if (customplan && plansource->is_saved)
1239 {
1240 MemoryContextSetParent(plan->context, CacheMemoryContext);
1241 plan->is_saved = true;
1242 }
1243
1244 return plan;
1245}
1246
1247/*
1248 * ReleaseCachedPlan: release active use of a cached plan.
1249 *
1250 * This decrements the reference count, and frees the plan if the count
1251 * has thereby gone to zero. If useResOwner is true, it is assumed that
1252 * the reference count is managed by the CurrentResourceOwner.
1253 *
1254 * Note: useResOwner = false is used for releasing references that are in
1255 * persistent data structures, such as the parent CachedPlanSource or a
1256 * Portal. Transient references should be protected by a resource owner.
1257 */
1258void
1259ReleaseCachedPlan(CachedPlan *plan, bool useResOwner)
1260{
1261 Assert(plan->magic == CACHEDPLAN_MAGIC);
1262 if (useResOwner)
1263 {
1264 Assert(plan->is_saved);
1265 ResourceOwnerForgetPlanCacheRef(CurrentResourceOwner, plan);
1266 }
1267 Assert(plan->refcount > 0);
1268 plan->refcount--;
1269 if (plan->refcount == 0)
1270 {
1271 /* Mark it no longer valid */
1272 plan->magic = 0;
1273
1274 /* One-shot plans do not own their context, so we can't free them */
1275 if (!plan->is_oneshot)
1276 MemoryContextDelete(plan->context);
1277 }
1278}
1279
1280/*
1281 * CachedPlanSetParentContext: move a CachedPlanSource to a new memory context
1282 *
1283 * This can only be applied to unsaved plans; once saved, a plan always
1284 * lives underneath CacheMemoryContext.
1285 */
1286void
1287CachedPlanSetParentContext(CachedPlanSource *plansource,
1288 MemoryContext newcontext)
1289{
1290 /* Assert caller is doing things in a sane order */
1291 Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
1292 Assert(plansource->is_complete);
1293
1294 /* These seem worth real tests, though */
1295 if (plansource->is_saved)
1296 elog(ERROR, "cannot move a saved cached plan to another context");
1297 if (plansource->is_oneshot)
1298 elog(ERROR, "cannot move a one-shot cached plan to another context");
1299
1300 /* OK, let the caller keep the plan where he wishes */
1301 MemoryContextSetParent(plansource->context, newcontext);
1302
1303 /*
1304 * The query_context needs no special handling, since it's a child of
1305 * plansource->context. But if there's a generic plan, it should be
1306 * maintained as a sibling of plansource->context.
1307 */
1308 if (plansource->gplan)
1309 {
1310 Assert(plansource->gplan->magic == CACHEDPLAN_MAGIC);
1311 MemoryContextSetParent(plansource->gplan->context, newcontext);
1312 }
1313}
1314
1315/*
1316 * CopyCachedPlan: make a copy of a CachedPlanSource
1317 *
1318 * This is a convenience routine that does the equivalent of
1319 * CreateCachedPlan + CompleteCachedPlan, using the data stored in the
1320 * input CachedPlanSource. The result is therefore "unsaved" (regardless
1321 * of the state of the source), and we don't copy any generic plan either.
1322 * The result will be currently valid, or not, the same as the source.
1323 */
1324CachedPlanSource *
1325CopyCachedPlan(CachedPlanSource *plansource)
1326{
1327 CachedPlanSource *newsource;
1328 MemoryContext source_context;
1329 MemoryContext querytree_context;
1330 MemoryContext oldcxt;
1331
1332 Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
1333 Assert(plansource->is_complete);
1334
1335 /*
1336 * One-shot plans can't be copied, because we haven't taken care that
1337 * parsing/planning didn't scribble on the raw parse tree or querytrees.
1338 */
1339 if (plansource->is_oneshot)
1340 elog(ERROR, "cannot copy a one-shot cached plan");
1341
1342 source_context = AllocSetContextCreate(CurrentMemoryContext,
1343 "CachedPlanSource",
1344 ALLOCSET_START_SMALL_SIZES);
1345
1346 oldcxt = MemoryContextSwitchTo(source_context);
1347
1348 newsource = (CachedPlanSource *) palloc0(sizeof(CachedPlanSource));
1349 newsource->magic = CACHEDPLANSOURCE_MAGIC;
1350 newsource->raw_parse_tree = copyObject(plansource->raw_parse_tree);
1351 newsource->query_string = pstrdup(plansource->query_string);
1352 MemoryContextSetIdentifier(source_context, newsource->query_string);
1353 newsource->commandTag = plansource->commandTag;
1354 if (plansource->num_params > 0)
1355 {
1356 newsource->param_types = (Oid *)
1357 palloc(plansource->num_params * sizeof(Oid));
1358 memcpy(newsource->param_types, plansource->param_types,
1359 plansource->num_params * sizeof(Oid));
1360 }
1361 else
1362 newsource->param_types = NULL;
1363 newsource->num_params = plansource->num_params;
1364 newsource->parserSetup = plansource->parserSetup;
1365 newsource->parserSetupArg = plansource->parserSetupArg;
1366 newsource->cursor_options = plansource->cursor_options;
1367 newsource->fixed_result = plansource->fixed_result;
1368 if (plansource->resultDesc)
1369 newsource->resultDesc = CreateTupleDescCopy(plansource->resultDesc);
1370 else
1371 newsource->resultDesc = NULL;
1372 newsource->context = source_context;
1373
1374 querytree_context = AllocSetContextCreate(source_context,
1375 "CachedPlanQuery",
1376 ALLOCSET_START_SMALL_SIZES);
1377 MemoryContextSwitchTo(querytree_context);
1378 newsource->query_list = copyObject(plansource->query_list);
1379 newsource->relationOids = copyObject(plansource->relationOids);
1380 newsource->invalItems = copyObject(plansource->invalItems);
1381 if (plansource->search_path)
1382 newsource->search_path = CopyOverrideSearchPath(plansource->search_path);
1383 newsource->query_context = querytree_context;
1384 newsource->rewriteRoleId = plansource->rewriteRoleId;
1385 newsource->rewriteRowSecurity = plansource->rewriteRowSecurity;
1386 newsource->dependsOnRLS = plansource->dependsOnRLS;
1387
1388 newsource->gplan = NULL;
1389
1390 newsource->is_oneshot = false;
1391 newsource->is_complete = true;
1392 newsource->is_saved = false;
1393 newsource->is_valid = plansource->is_valid;
1394 newsource->generation = plansource->generation;
1395
1396 /* We may as well copy any acquired cost knowledge */
1397 newsource->generic_cost = plansource->generic_cost;
1398 newsource->total_custom_cost = plansource->total_custom_cost;
1399 newsource->num_custom_plans = plansource->num_custom_plans;
1400
1401 MemoryContextSwitchTo(oldcxt);
1402
1403 return newsource;
1404}
1405
1406/*
1407 * CachedPlanIsValid: test whether the rewritten querytree within a
1408 * CachedPlanSource is currently valid (that is, not marked as being in need
1409 * of revalidation).
1410 *
1411 * This result is only trustworthy (ie, free from race conditions) if
1412 * the caller has acquired locks on all the relations used in the plan.
1413 */
1414bool
1415CachedPlanIsValid(CachedPlanSource *plansource)
1416{
1417 Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
1418 return plansource->is_valid;
1419}
1420
1421/*
1422 * CachedPlanGetTargetList: return tlist, if any, describing plan's output
1423 *
1424 * The result is guaranteed up-to-date. However, it is local storage
1425 * within the cached plan, and may disappear next time the plan is updated.
1426 */
1427List *
1428CachedPlanGetTargetList(CachedPlanSource *plansource,
1429 QueryEnvironment *queryEnv)
1430{
1431 Query *pstmt;
1432
1433 /* Assert caller is doing things in a sane order */
1434 Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
1435 Assert(plansource->is_complete);
1436
1437 /*
1438 * No work needed if statement doesn't return tuples (we assume this
1439 * feature cannot be changed by an invalidation)
1440 */
1441 if (plansource->resultDesc == NULL)
1442 return NIL;
1443
1444 /* Make sure the querytree list is valid and we have parse-time locks */
1445 RevalidateCachedQuery(plansource, queryEnv);
1446
1447 /* Get the primary statement and find out what it returns */
1448 pstmt = QueryListGetPrimaryStmt(plansource->query_list);
1449
1450 return FetchStatementTargetList((Node *) pstmt);
1451}
1452
1453/*
1454 * GetCachedExpression: construct a CachedExpression for an expression.
1455 *
1456 * This performs the same transformations on the expression as
1457 * expression_planner(), ie, convert an expression as emitted by parse
1458 * analysis to be ready to pass to the executor.
1459 *
1460 * The result is stashed in a private, long-lived memory context.
1461 * (Note that this might leak a good deal of memory in the caller's
1462 * context before that.) The passed-in expr tree is not modified.
1463 */
1464CachedExpression *
1465GetCachedExpression(Node *expr)
1466{
1467 CachedExpression *cexpr;
1468 List *relationOids;
1469 List *invalItems;
1470 MemoryContext cexpr_context;
1471 MemoryContext oldcxt;
1472
1473 /*
1474 * Pass the expression through the planner, and collect dependencies.
1475 * Everything built here is leaked in the caller's context; that's
1476 * intentional to minimize the size of the permanent data structure.
1477 */
1478 expr = (Node *) expression_planner_with_deps((Expr *) expr,
1479 &relationOids,
1480 &invalItems);
1481
1482 /*
1483 * Make a private memory context, and copy what we need into that. To
1484 * avoid leaking a long-lived context if we fail while copying data, we
1485 * initially make the context under the caller's context.
1486 */
1487 cexpr_context = AllocSetContextCreate(CurrentMemoryContext,
1488 "CachedExpression",
1489 ALLOCSET_SMALL_SIZES);
1490
1491 oldcxt = MemoryContextSwitchTo(cexpr_context);
1492
1493 cexpr = (CachedExpression *) palloc(sizeof(CachedExpression));
1494 cexpr->magic = CACHEDEXPR_MAGIC;
1495 cexpr->expr = copyObject(expr);
1496 cexpr->is_valid = true;
1497 cexpr->relationOids = copyObject(relationOids);
1498 cexpr->invalItems = copyObject(invalItems);
1499 cexpr->context = cexpr_context;
1500
1501 MemoryContextSwitchTo(oldcxt);
1502
1503 /*
1504 * Reparent the expr's memory context under CacheMemoryContext so that it
1505 * will live indefinitely.
1506 */
1507 MemoryContextSetParent(cexpr_context, CacheMemoryContext);
1508
1509 /*
1510 * Add the entry to the global list of cached expressions.
1511 */
1512 dlist_push_tail(&cached_expression_list, &cexpr->node);
1513
1514 return cexpr;
1515}
1516
1517/*
1518 * FreeCachedExpression
1519 * Delete a CachedExpression.
1520 */
1521void
1522FreeCachedExpression(CachedExpression *cexpr)
1523{
1524 /* Sanity check */
1525 Assert(cexpr->magic == CACHEDEXPR_MAGIC);
1526 /* Unlink from global list */
1527 dlist_delete(&cexpr->node);
1528 /* Free all storage associated with CachedExpression */
1529 MemoryContextDelete(cexpr->context);
1530}
1531
1532/*
1533 * QueryListGetPrimaryStmt
1534 * Get the "primary" stmt within a list, ie, the one marked canSetTag.
1535 *
1536 * Returns NULL if no such stmt. If multiple queries within the list are
1537 * marked canSetTag, returns the first one. Neither of these cases should
1538 * occur in present usages of this function.
1539 */
1540static Query *
1541QueryListGetPrimaryStmt(List *stmts)
1542{
1543 ListCell *lc;
1544
1545 foreach(lc, stmts)
1546 {
1547 Query *stmt = lfirst_node(Query, lc);
1548
1549 if (stmt->canSetTag)
1550 return stmt;
1551 }
1552 return NULL;
1553}
1554
1555/*
1556 * AcquireExecutorLocks: acquire locks needed for execution of a cached plan;
1557 * or release them if acquire is false.
1558 */
1559static void
1560AcquireExecutorLocks(List *stmt_list, bool acquire)
1561{
1562 ListCell *lc1;
1563
1564 foreach(lc1, stmt_list)
1565 {
1566 PlannedStmt *plannedstmt = lfirst_node(PlannedStmt, lc1);
1567 ListCell *lc2;
1568
1569 if (plannedstmt->commandType == CMD_UTILITY)
1570 {
1571 /*
1572 * Ignore utility statements, except those (such as EXPLAIN) that
1573 * contain a parsed-but-not-planned query. Note: it's okay to use
1574 * ScanQueryForLocks, even though the query hasn't been through
1575 * rule rewriting, because rewriting doesn't change the query
1576 * representation.
1577 */
1578 Query *query = UtilityContainsQuery(plannedstmt->utilityStmt);
1579
1580 if (query)
1581 ScanQueryForLocks(query, acquire);
1582 continue;
1583 }
1584
1585 foreach(lc2, plannedstmt->rtable)
1586 {
1587 RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc2);
1588
1589 if (rte->rtekind != RTE_RELATION)
1590 continue;
1591
1592 /*
1593 * Acquire the appropriate type of lock on each relation OID. Note
1594 * that we don't actually try to open the rel, and hence will not
1595 * fail if it's been dropped entirely --- we'll just transiently
1596 * acquire a non-conflicting lock.
1597 */
1598 if (acquire)
1599 LockRelationOid(rte->relid, rte->rellockmode);
1600 else
1601 UnlockRelationOid(rte->relid, rte->rellockmode);
1602 }
1603 }
1604}
1605
1606/*
1607 * AcquirePlannerLocks: acquire locks needed for planning of a querytree list;
1608 * or release them if acquire is false.
1609 *
1610 * Note that we don't actually try to open the relations, and hence will not
1611 * fail if one has been dropped entirely --- we'll just transiently acquire
1612 * a non-conflicting lock.
1613 */
1614static void
1615AcquirePlannerLocks(List *stmt_list, bool acquire)
1616{
1617 ListCell *lc;
1618
1619 foreach(lc, stmt_list)
1620 {
1621 Query *query = lfirst_node(Query, lc);
1622
1623 if (query->commandType == CMD_UTILITY)
1624 {
1625 /* Ignore utility statements, unless they contain a Query */
1626 query = UtilityContainsQuery(query->utilityStmt);
1627 if (query)
1628 ScanQueryForLocks(query, acquire);
1629 continue;
1630 }
1631
1632 ScanQueryForLocks(query, acquire);
1633 }
1634}
1635
1636/*
1637 * ScanQueryForLocks: recursively scan one Query for AcquirePlannerLocks.
1638 */
1639static void
1640ScanQueryForLocks(Query *parsetree, bool acquire)
1641{
1642 ListCell *lc;
1643
1644 /* Shouldn't get called on utility commands */
1645 Assert(parsetree->commandType != CMD_UTILITY);
1646
1647 /*
1648 * First, process RTEs of the current query level.
1649 */
1650 foreach(lc, parsetree->rtable)
1651 {
1652 RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
1653
1654 switch (rte->rtekind)
1655 {
1656 case RTE_RELATION:
1657 /* Acquire or release the appropriate type of lock */
1658 if (acquire)
1659 LockRelationOid(rte->relid, rte->rellockmode);
1660 else
1661 UnlockRelationOid(rte->relid, rte->rellockmode);
1662 break;
1663
1664 case RTE_SUBQUERY:
1665 /* Recurse into subquery-in-FROM */
1666 ScanQueryForLocks(rte->subquery, acquire);
1667 break;
1668
1669 default:
1670 /* ignore other types of RTEs */
1671 break;
1672 }
1673 }
1674
1675 /* Recurse into subquery-in-WITH */
1676 foreach(lc, parsetree->cteList)
1677 {
1678 CommonTableExpr *cte = lfirst_node(CommonTableExpr, lc);
1679
1680 ScanQueryForLocks(castNode(Query, cte->ctequery), acquire);
1681 }
1682
1683 /*
1684 * Recurse into sublink subqueries, too. But we already did the ones in
1685 * the rtable and cteList.
1686 */
1687 if (parsetree->hasSubLinks)
1688 {
1689 query_tree_walker(parsetree, ScanQueryWalker,
1690 (void *) &acquire,
1691 QTW_IGNORE_RC_SUBQUERIES);
1692 }
1693}
1694
1695/*
1696 * Walker to find sublink subqueries for ScanQueryForLocks
1697 */
1698static bool
1699ScanQueryWalker(Node *node, bool *acquire)
1700{
1701 if (node == NULL)
1702 return false;
1703 if (IsA(node, SubLink))
1704 {
1705 SubLink *sub = (SubLink *) node;
1706
1707 /* Do what we came for */
1708 ScanQueryForLocks(castNode(Query, sub->subselect), *acquire);
1709 /* Fall through to process lefthand args of SubLink */
1710 }
1711
1712 /*
1713 * Do NOT recurse into Query nodes, because ScanQueryForLocks already
1714 * processed subselects of subselects for us.
1715 */
1716 return expression_tree_walker(node, ScanQueryWalker,
1717 (void *) acquire);
1718}
1719
1720/*
1721 * PlanCacheComputeResultDesc: given a list of analyzed-and-rewritten Queries,
1722 * determine the result tupledesc it will produce. Returns NULL if the
1723 * execution will not return tuples.
1724 *
1725 * Note: the result is created or copied into current memory context.
1726 */
1727static TupleDesc
1728PlanCacheComputeResultDesc(List *stmt_list)
1729{
1730 Query *query;
1731
1732 switch (ChoosePortalStrategy(stmt_list))
1733 {
1734 case PORTAL_ONE_SELECT:
1735 case PORTAL_ONE_MOD_WITH:
1736 query = linitial_node(Query, stmt_list);
1737 return ExecCleanTypeFromTL(query->targetList);
1738
1739 case PORTAL_ONE_RETURNING:
1740 query = QueryListGetPrimaryStmt(stmt_list);
1741 Assert(query->returningList);
1742 return ExecCleanTypeFromTL(query->returningList);
1743
1744 case PORTAL_UTIL_SELECT:
1745 query = linitial_node(Query, stmt_list);
1746 Assert(query->utilityStmt);
1747 return UtilityTupleDescriptor(query->utilityStmt);
1748
1749 case PORTAL_MULTI_QUERY:
1750 /* will not return tuples */
1751 break;
1752 }
1753 return NULL;
1754}
1755
1756/*
1757 * PlanCacheRelCallback
1758 * Relcache inval callback function
1759 *
1760 * Invalidate all plans mentioning the given rel, or all plans mentioning
1761 * any rel at all if relid == InvalidOid.
1762 */
1763static void
1764PlanCacheRelCallback(Datum arg, Oid relid)
1765{
1766 dlist_iter iter;
1767
1768 dlist_foreach(iter, &saved_plan_list)
1769 {
1770 CachedPlanSource *plansource = dlist_container(CachedPlanSource,
1771 node, iter.cur);
1772
1773 Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
1774
1775 /* No work if it's already invalidated */
1776 if (!plansource->is_valid)
1777 continue;
1778
1779 /* Never invalidate transaction control commands */
1780 if (IsTransactionStmtPlan(plansource))
1781 continue;
1782
1783 /*
1784 * Check the dependency list for the rewritten querytree.
1785 */
1786 if ((relid == InvalidOid) ? plansource->relationOids != NIL :
1787 list_member_oid(plansource->relationOids, relid))
1788 {
1789 /* Invalidate the querytree and generic plan */
1790 plansource->is_valid = false;
1791 if (plansource->gplan)
1792 plansource->gplan->is_valid = false;
1793 }
1794
1795 /*
1796 * The generic plan, if any, could have more dependencies than the
1797 * querytree does, so we have to check it too.
1798 */
1799 if (plansource->gplan && plansource->gplan->is_valid)
1800 {
1801 ListCell *lc;
1802
1803 foreach(lc, plansource->gplan->stmt_list)
1804 {
1805 PlannedStmt *plannedstmt = lfirst_node(PlannedStmt, lc);
1806
1807 if (plannedstmt->commandType == CMD_UTILITY)
1808 continue; /* Ignore utility statements */
1809 if ((relid == InvalidOid) ? plannedstmt->relationOids != NIL :
1810 list_member_oid(plannedstmt->relationOids, relid))
1811 {
1812 /* Invalidate the generic plan only */
1813 plansource->gplan->is_valid = false;
1814 break; /* out of stmt_list scan */
1815 }
1816 }
1817 }
1818 }
1819
1820 /* Likewise check cached expressions */
1821 dlist_foreach(iter, &cached_expression_list)
1822 {
1823 CachedExpression *cexpr = dlist_container(CachedExpression,
1824 node, iter.cur);
1825
1826 Assert(cexpr->magic == CACHEDEXPR_MAGIC);
1827
1828 /* No work if it's already invalidated */
1829 if (!cexpr->is_valid)
1830 continue;
1831
1832 if ((relid == InvalidOid) ? cexpr->relationOids != NIL :
1833 list_member_oid(cexpr->relationOids, relid))
1834 {
1835 cexpr->is_valid = false;
1836 }
1837 }
1838}
1839
1840/*
1841 * PlanCacheObjectCallback
1842 * Syscache inval callback function for PROCOID and TYPEOID caches
1843 *
1844 * Invalidate all plans mentioning the object with the specified hash value,
1845 * or all plans mentioning any member of this cache if hashvalue == 0.
1846 */
1847static void
1848PlanCacheObjectCallback(Datum arg, int cacheid, uint32 hashvalue)
1849{
1850 dlist_iter iter;
1851
1852 dlist_foreach(iter, &saved_plan_list)
1853 {
1854 CachedPlanSource *plansource = dlist_container(CachedPlanSource,
1855 node, iter.cur);
1856 ListCell *lc;
1857
1858 Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
1859
1860 /* No work if it's already invalidated */
1861 if (!plansource->is_valid)
1862 continue;
1863
1864 /* Never invalidate transaction control commands */
1865 if (IsTransactionStmtPlan(plansource))
1866 continue;
1867
1868 /*
1869 * Check the dependency list for the rewritten querytree.
1870 */
1871 foreach(lc, plansource->invalItems)
1872 {
1873 PlanInvalItem *item = (PlanInvalItem *) lfirst(lc);
1874
1875 if (item->cacheId != cacheid)
1876 continue;
1877 if (hashvalue == 0 ||
1878 item->hashValue == hashvalue)
1879 {
1880 /* Invalidate the querytree and generic plan */
1881 plansource->is_valid = false;
1882 if (plansource->gplan)
1883 plansource->gplan->is_valid = false;
1884 break;
1885 }
1886 }
1887
1888 /*
1889 * The generic plan, if any, could have more dependencies than the
1890 * querytree does, so we have to check it too.
1891 */
1892 if (plansource->gplan && plansource->gplan->is_valid)
1893 {
1894 foreach(lc, plansource->gplan->stmt_list)
1895 {
1896 PlannedStmt *plannedstmt = lfirst_node(PlannedStmt, lc);
1897 ListCell *lc3;
1898
1899 if (plannedstmt->commandType == CMD_UTILITY)
1900 continue; /* Ignore utility statements */
1901 foreach(lc3, plannedstmt->invalItems)
1902 {
1903 PlanInvalItem *item = (PlanInvalItem *) lfirst(lc3);
1904
1905 if (item->cacheId != cacheid)
1906 continue;
1907 if (hashvalue == 0 ||
1908 item->hashValue == hashvalue)
1909 {
1910 /* Invalidate the generic plan only */
1911 plansource->gplan->is_valid = false;
1912 break; /* out of invalItems scan */
1913 }
1914 }
1915 if (!plansource->gplan->is_valid)
1916 break; /* out of stmt_list scan */
1917 }
1918 }
1919 }
1920
1921 /* Likewise check cached expressions */
1922 dlist_foreach(iter, &cached_expression_list)
1923 {
1924 CachedExpression *cexpr = dlist_container(CachedExpression,
1925 node, iter.cur);
1926 ListCell *lc;
1927
1928 Assert(cexpr->magic == CACHEDEXPR_MAGIC);
1929
1930 /* No work if it's already invalidated */
1931 if (!cexpr->is_valid)
1932 continue;
1933
1934 foreach(lc, cexpr->invalItems)
1935 {
1936 PlanInvalItem *item = (PlanInvalItem *) lfirst(lc);
1937
1938 if (item->cacheId != cacheid)
1939 continue;
1940 if (hashvalue == 0 ||
1941 item->hashValue == hashvalue)
1942 {
1943 cexpr->is_valid = false;
1944 break;
1945 }
1946 }
1947 }
1948}
1949
1950/*
1951 * PlanCacheSysCallback
1952 * Syscache inval callback function for other caches
1953 *
1954 * Just invalidate everything...
1955 */
1956static void
1957PlanCacheSysCallback(Datum arg, int cacheid, uint32 hashvalue)
1958{
1959 ResetPlanCache();
1960}
1961
1962/*
1963 * ResetPlanCache: invalidate all cached plans.
1964 */
1965void
1966ResetPlanCache(void)
1967{
1968 dlist_iter iter;
1969
1970 dlist_foreach(iter, &saved_plan_list)
1971 {
1972 CachedPlanSource *plansource = dlist_container(CachedPlanSource,
1973 node, iter.cur);
1974 ListCell *lc;
1975
1976 Assert(plansource->magic == CACHEDPLANSOURCE_MAGIC);
1977
1978 /* No work if it's already invalidated */
1979 if (!plansource->is_valid)
1980 continue;
1981
1982 /*
1983 * We *must not* mark transaction control statements as invalid,
1984 * particularly not ROLLBACK, because they may need to be executed in
1985 * aborted transactions when we can't revalidate them (cf bug #5269).
1986 */
1987 if (IsTransactionStmtPlan(plansource))
1988 continue;
1989
1990 /*
1991 * In general there is no point in invalidating utility statements
1992 * since they have no plans anyway. So invalidate it only if it
1993 * contains at least one non-utility statement, or contains a utility
1994 * statement that contains a pre-analyzed query (which could have
1995 * dependencies.)
1996 */
1997 foreach(lc, plansource->query_list)
1998 {
1999 Query *query = lfirst_node(Query, lc);
2000
2001 if (query->commandType != CMD_UTILITY ||
2002 UtilityContainsQuery(query->utilityStmt))
2003 {
2004 /* non-utility statement, so invalidate */
2005 plansource->is_valid = false;
2006 if (plansource->gplan)
2007 plansource->gplan->is_valid = false;
2008 /* no need to look further */
2009 break;
2010 }
2011 }
2012 }
2013
2014 /* Likewise invalidate cached expressions */
2015 dlist_foreach(iter, &cached_expression_list)
2016 {
2017 CachedExpression *cexpr = dlist_container(CachedExpression,
2018 node, iter.cur);
2019
2020 Assert(cexpr->magic == CACHEDEXPR_MAGIC);
2021
2022 cexpr->is_valid = false;
2023 }
2024}
2025