Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * portalmem.c
4 : * backend portal memory management
5 : *
6 : * Portals are objects representing the execution state of a query.
7 : * This module provides memory management services for portals, but it
8 : * doesn't actually run the executor for them.
9 : *
10 : *
11 : * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
12 : * Portions Copyright (c) 1994, Regents of the University of California
13 : *
14 : * IDENTIFICATION
15 : * src/backend/utils/mmgr/portalmem.c
16 : *
17 : *-------------------------------------------------------------------------
18 : */
19 : #include "postgres.h"
20 :
21 : #include "access/xact.h"
22 : #include "catalog/pg_type.h"
23 : #include "commands/portalcmds.h"
24 : #include "miscadmin.h"
25 : #include "storage/ipc.h"
26 : #include "utils/builtins.h"
27 : #include "utils/memutils.h"
28 : #include "utils/snapmgr.h"
29 : #include "utils/timestamp.h"
30 :
31 : /*
32 : * Estimate of the maximum number of open portals a user would have,
33 : * used in initially sizing the PortalHashTable in EnablePortalManager().
34 : * Since the hash table can expand, there's no need to make this overly
35 : * generous, and keeping it small avoids unnecessary overhead in the
36 : * hash_seq_search() calls executed during transaction end.
37 : */
38 : #define PORTALS_PER_USER 16
39 :
40 :
41 : /* ----------------
42 : * Global state
43 : * ----------------
44 : */
45 :
46 : #define MAX_PORTALNAME_LEN NAMEDATALEN
47 :
48 : typedef struct portalhashent
49 : {
50 : char portalname[MAX_PORTALNAME_LEN];
51 : Portal portal;
52 : } PortalHashEnt;
53 :
54 : static HTAB *PortalHashTable = NULL;
55 :
56 : #define PortalHashTableLookup(NAME, PORTAL) \
57 : do { \
58 : PortalHashEnt *hentry; \
59 : \
60 : hentry = (PortalHashEnt *) hash_search(PortalHashTable, \
61 : (NAME), HASH_FIND, NULL); \
62 : if (hentry) \
63 : PORTAL = hentry->portal; \
64 : else \
65 : PORTAL = NULL; \
66 : } while(0)
67 :
68 : #define PortalHashTableInsert(PORTAL, NAME) \
69 : do { \
70 : PortalHashEnt *hentry; bool found; \
71 : \
72 : hentry = (PortalHashEnt *) hash_search(PortalHashTable, \
73 : (NAME), HASH_ENTER, &found); \
74 : if (found) \
75 : elog(ERROR, "duplicate portal name"); \
76 : hentry->portal = PORTAL; \
77 : /* To avoid duplicate storage, make PORTAL->name point to htab entry */ \
78 : PORTAL->name = hentry->portalname; \
79 : } while(0)
80 :
81 : #define PortalHashTableDelete(PORTAL) \
82 : do { \
83 : PortalHashEnt *hentry; \
84 : \
85 : hentry = (PortalHashEnt *) hash_search(PortalHashTable, \
86 : PORTAL->name, HASH_REMOVE, NULL); \
87 : if (hentry == NULL) \
88 : elog(WARNING, "trying to delete portal name that does not exist"); \
89 : } while(0)
90 :
91 : static MemoryContext TopPortalContext = NULL;
92 :
93 :
94 : /* ----------------------------------------------------------------
95 : * public portal interface functions
96 : * ----------------------------------------------------------------
97 : */
98 :
99 : /*
100 : * EnablePortalManager
101 : * Enables the portal management module at backend startup.
102 : */
103 : void
104 9902 : EnablePortalManager(void)
105 : {
106 : HASHCTL ctl;
107 :
108 : Assert(TopPortalContext == NULL);
109 :
110 9902 : TopPortalContext = AllocSetContextCreate(TopMemoryContext,
111 : "TopPortalContext",
112 : ALLOCSET_DEFAULT_SIZES);
113 :
114 9902 : ctl.keysize = MAX_PORTALNAME_LEN;
115 9902 : ctl.entrysize = sizeof(PortalHashEnt);
116 :
117 : /*
118 : * use PORTALS_PER_USER as a guess of how many hash table entries to
119 : * create, initially
120 : */
121 9902 : PortalHashTable = hash_create("Portal hash", PORTALS_PER_USER,
122 : &ctl, HASH_ELEM);
123 9902 : }
124 :
125 : /*
126 : * GetPortalByName
127 : * Returns a portal given a portal name, or NULL if name not found.
128 : */
129 : Portal
130 585466 : GetPortalByName(const char *name)
131 : {
132 : Portal portal;
133 :
134 585466 : if (PointerIsValid(name))
135 585466 : PortalHashTableLookup(name, portal);
136 : else
137 0 : portal = NULL;
138 :
139 585466 : return portal;
140 : }
141 :
142 : /*
143 : * PortalGetPrimaryStmt
144 : * Get the "primary" stmt within a portal, ie, the one marked canSetTag.
145 : *
146 : * Returns NULL if no such stmt. If multiple PlannedStmt structs within the
147 : * portal are marked canSetTag, returns the first one. Neither of these
148 : * cases should occur in present usages of this function.
149 : */
150 : PlannedStmt *
151 169198 : PortalGetPrimaryStmt(Portal portal)
152 : {
153 : ListCell *lc;
154 :
155 169198 : foreach(lc, portal->stmts)
156 : {
157 169198 : PlannedStmt *stmt = lfirst_node(PlannedStmt, lc);
158 :
159 169198 : if (stmt->canSetTag)
160 169198 : return stmt;
161 : }
162 0 : return NULL;
163 : }
164 :
165 : /*
166 : * CreatePortal
167 : * Returns a new portal given a name.
168 : *
169 : * allowDup: if true, automatically drop any pre-existing portal of the
170 : * same name (if false, an error is raised).
171 : *
172 : * dupSilent: if true, don't even emit a WARNING.
173 : */
174 : Portal
175 505386 : CreatePortal(const char *name, bool allowDup, bool dupSilent)
176 : {
177 : Portal portal;
178 :
179 : AssertArg(PointerIsValid(name));
180 :
181 505386 : portal = GetPortalByName(name);
182 505386 : if (PortalIsValid(portal))
183 : {
184 5804 : if (!allowDup)
185 0 : ereport(ERROR,
186 : (errcode(ERRCODE_DUPLICATE_CURSOR),
187 : errmsg("cursor \"%s\" already exists", name)));
188 5804 : if (!dupSilent)
189 0 : ereport(WARNING,
190 : (errcode(ERRCODE_DUPLICATE_CURSOR),
191 : errmsg("closing existing cursor \"%s\"",
192 : name)));
193 5804 : PortalDrop(portal, false);
194 : }
195 :
196 : /* make new portal structure */
197 505386 : portal = (Portal) MemoryContextAllocZero(TopPortalContext, sizeof *portal);
198 :
199 : /* initialize portal context; typically it won't store much */
200 505386 : portal->portalContext = AllocSetContextCreate(TopPortalContext,
201 : "PortalContext",
202 : ALLOCSET_SMALL_SIZES);
203 :
204 : /* create a resource owner for the portal */
205 505386 : portal->resowner = ResourceOwnerCreate(CurTransactionResourceOwner,
206 : "Portal");
207 :
208 : /* initialize portal fields that don't start off zero */
209 505386 : portal->status = PORTAL_NEW;
210 505386 : portal->cleanup = PortalCleanup;
211 505386 : portal->createSubid = GetCurrentSubTransactionId();
212 505386 : portal->activeSubid = portal->createSubid;
213 505386 : portal->strategy = PORTAL_MULTI_QUERY;
214 505386 : portal->cursorOptions = CURSOR_OPT_NO_SCROLL;
215 505386 : portal->atStart = true;
216 505386 : portal->atEnd = true; /* disallow fetches until query is set */
217 505386 : portal->visible = true;
218 505386 : portal->creation_time = GetCurrentStatementStartTimestamp();
219 :
220 : /* put portal in table (sets portal->name) */
221 505386 : PortalHashTableInsert(portal, name);
222 :
223 : /* reuse portal->name copy */
224 505386 : MemoryContextSetIdentifier(portal->portalContext, portal->name);
225 :
226 505386 : return portal;
227 : }
228 :
229 : /*
230 : * CreateNewPortal
231 : * Create a new portal, assigning it a random nonconflicting name.
232 : */
233 : Portal
234 5206 : CreateNewPortal(void)
235 : {
236 : static unsigned int unnamed_portal_count = 0;
237 :
238 : char portalname[MAX_PORTALNAME_LEN];
239 :
240 : /* Select a nonconflicting name */
241 : for (;;)
242 : {
243 5206 : unnamed_portal_count++;
244 5206 : sprintf(portalname, "<unnamed portal %u>", unnamed_portal_count);
245 5206 : if (GetPortalByName(portalname) == NULL)
246 5206 : break;
247 : }
248 :
249 5206 : return CreatePortal(portalname, false, false);
250 : }
251 :
252 : /*
253 : * PortalDefineQuery
254 : * A simple subroutine to establish a portal's query.
255 : *
256 : * Notes: as of PG 8.4, caller MUST supply a sourceText string; it is not
257 : * allowed anymore to pass NULL. (If you really don't have source text,
258 : * you can pass a constant string, perhaps "(query not available)".)
259 : *
260 : * commandTag shall be NULL if and only if the original query string
261 : * (before rewriting) was an empty string. Also, the passed commandTag must
262 : * be a pointer to a constant string, since it is not copied.
263 : *
264 : * If cplan is provided, then it is a cached plan containing the stmts, and
265 : * the caller must have done GetCachedPlan(), causing a refcount increment.
266 : * The refcount will be released when the portal is destroyed.
267 : *
268 : * If cplan is NULL, then it is the caller's responsibility to ensure that
269 : * the passed plan trees have adequate lifetime. Typically this is done by
270 : * copying them into the portal's context.
271 : *
272 : * The caller is also responsible for ensuring that the passed prepStmtName
273 : * (if not NULL) and sourceText have adequate lifetime.
274 : *
275 : * NB: this function mustn't do much beyond storing the passed values; in
276 : * particular don't do anything that risks elog(ERROR). If that were to
277 : * happen here before storing the cplan reference, we'd leak the plancache
278 : * refcount that the caller is trying to hand off to us.
279 : */
280 : void
281 505366 : PortalDefineQuery(Portal portal,
282 : const char *prepStmtName,
283 : const char *sourceText,
284 : const char *commandTag,
285 : List *stmts,
286 : CachedPlan *cplan)
287 : {
288 : AssertArg(PortalIsValid(portal));
289 : AssertState(portal->status == PORTAL_NEW);
290 :
291 : AssertArg(sourceText != NULL);
292 : AssertArg(commandTag != NULL || stmts == NIL);
293 :
294 505366 : portal->prepStmtName = prepStmtName;
295 505366 : portal->sourceText = sourceText;
296 505366 : portal->commandTag = commandTag;
297 505366 : portal->stmts = stmts;
298 505366 : portal->cplan = cplan;
299 505366 : portal->status = PORTAL_DEFINED;
300 505366 : }
301 :
302 : /*
303 : * PortalReleaseCachedPlan
304 : * Release a portal's reference to its cached plan, if any.
305 : */
306 : static void
307 518008 : PortalReleaseCachedPlan(Portal portal)
308 : {
309 518008 : if (portal->cplan)
310 : {
311 28390 : ReleaseCachedPlan(portal->cplan, false);
312 28390 : portal->cplan = NULL;
313 :
314 : /*
315 : * We must also clear portal->stmts which is now a dangling reference
316 : * to the cached plan's plan list. This protects any code that might
317 : * try to examine the Portal later.
318 : */
319 28390 : portal->stmts = NIL;
320 : }
321 518008 : }
322 :
323 : /*
324 : * PortalCreateHoldStore
325 : * Create the tuplestore for a portal.
326 : */
327 : void
328 15890 : PortalCreateHoldStore(Portal portal)
329 : {
330 : MemoryContext oldcxt;
331 :
332 : Assert(portal->holdContext == NULL);
333 : Assert(portal->holdStore == NULL);
334 : Assert(portal->holdSnapshot == NULL);
335 :
336 : /*
337 : * Create the memory context that is used for storage of the tuple set.
338 : * Note this is NOT a child of the portal's portalContext.
339 : */
340 15890 : portal->holdContext =
341 15890 : AllocSetContextCreate(TopPortalContext,
342 : "PortalHoldContext",
343 : ALLOCSET_DEFAULT_SIZES);
344 :
345 : /*
346 : * Create the tuple store, selecting cross-transaction temp files, and
347 : * enabling random access only if cursor requires scrolling.
348 : *
349 : * XXX: Should maintenance_work_mem be used for the portal size?
350 : */
351 15890 : oldcxt = MemoryContextSwitchTo(portal->holdContext);
352 :
353 15890 : portal->holdStore =
354 15890 : tuplestore_begin_heap(portal->cursorOptions & CURSOR_OPT_SCROLL,
355 : true, work_mem);
356 :
357 15890 : MemoryContextSwitchTo(oldcxt);
358 15890 : }
359 :
360 : /*
361 : * PinPortal
362 : * Protect a portal from dropping.
363 : *
364 : * A pinned portal is still unpinned and dropped at transaction or
365 : * subtransaction abort.
366 : */
367 : void
368 3734 : PinPortal(Portal portal)
369 : {
370 3734 : if (portal->portalPinned)
371 0 : elog(ERROR, "portal already pinned");
372 :
373 3734 : portal->portalPinned = true;
374 3734 : }
375 :
376 : void
377 3698 : UnpinPortal(Portal portal)
378 : {
379 3698 : if (!portal->portalPinned)
380 0 : elog(ERROR, "portal not pinned");
381 :
382 3698 : portal->portalPinned = false;
383 3698 : }
384 :
385 : /*
386 : * MarkPortalActive
387 : * Transition a portal from READY to ACTIVE state.
388 : *
389 : * NOTE: never set portal->status = PORTAL_ACTIVE directly; call this instead.
390 : */
391 : void
392 511616 : MarkPortalActive(Portal portal)
393 : {
394 : /* For safety, this is a runtime test not just an Assert */
395 511616 : if (portal->status != PORTAL_READY)
396 12 : ereport(ERROR,
397 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
398 : errmsg("portal \"%s\" cannot be run", portal->name)));
399 : /* Perform the state transition */
400 511604 : portal->status = PORTAL_ACTIVE;
401 511604 : portal->activeSubid = GetCurrentSubTransactionId();
402 511604 : }
403 :
404 : /*
405 : * MarkPortalDone
406 : * Transition a portal from ACTIVE to DONE state.
407 : *
408 : * NOTE: never set portal->status = PORTAL_DONE directly; call this instead.
409 : */
410 : void
411 339216 : MarkPortalDone(Portal portal)
412 : {
413 : /* Perform the state transition */
414 : Assert(portal->status == PORTAL_ACTIVE);
415 339216 : portal->status = PORTAL_DONE;
416 :
417 : /*
418 : * Allow portalcmds.c to clean up the state it knows about. We might as
419 : * well do that now, since the portal can't be executed any more.
420 : *
421 : * In some cases involving execution of a ROLLBACK command in an already
422 : * aborted transaction, this is necessary, or we'd reach AtCleanup_Portals
423 : * with the cleanup hook still unexecuted.
424 : */
425 339216 : if (PointerIsValid(portal->cleanup))
426 : {
427 339180 : portal->cleanup(portal);
428 339180 : portal->cleanup = NULL;
429 : }
430 339216 : }
431 :
432 : /*
433 : * MarkPortalFailed
434 : * Transition a portal into FAILED state.
435 : *
436 : * NOTE: never set portal->status = PORTAL_FAILED directly; call this instead.
437 : */
438 : void
439 12416 : MarkPortalFailed(Portal portal)
440 : {
441 : /* Perform the state transition */
442 : Assert(portal->status != PORTAL_DONE);
443 12416 : portal->status = PORTAL_FAILED;
444 :
445 : /*
446 : * Allow portalcmds.c to clean up the state it knows about. We might as
447 : * well do that now, since the portal can't be executed any more.
448 : *
449 : * In some cases involving cleanup of an already aborted transaction, this
450 : * is necessary, or we'd reach AtCleanup_Portals with the cleanup hook
451 : * still unexecuted.
452 : */
453 12416 : if (PointerIsValid(portal->cleanup))
454 : {
455 12416 : portal->cleanup(portal);
456 12416 : portal->cleanup = NULL;
457 : }
458 12416 : }
459 :
460 : /*
461 : * PortalDrop
462 : * Destroy the portal.
463 : */
464 : void
465 505378 : PortalDrop(Portal portal, bool isTopCommit)
466 : {
467 : AssertArg(PortalIsValid(portal));
468 :
469 : /*
470 : * Don't allow dropping a pinned portal, it's still needed by whoever
471 : * pinned it.
472 : */
473 505378 : if (portal->portalPinned)
474 0 : ereport(ERROR,
475 : (errcode(ERRCODE_INVALID_CURSOR_STATE),
476 : errmsg("cannot drop pinned portal \"%s\"", portal->name)));
477 :
478 : /*
479 : * Not sure if the PORTAL_ACTIVE case can validly happen or not...
480 : */
481 505378 : if (portal->status == PORTAL_ACTIVE)
482 0 : ereport(ERROR,
483 : (errcode(ERRCODE_INVALID_CURSOR_STATE),
484 : errmsg("cannot drop active portal \"%s\"", portal->name)));
485 :
486 : /*
487 : * Allow portalcmds.c to clean up the state it knows about, in particular
488 : * shutting down the executor if still active. This step potentially runs
489 : * user-defined code so failure has to be expected. It's the cleanup
490 : * hook's responsibility to not try to do that more than once, in the case
491 : * that failure occurs and then we come back to drop the portal again
492 : * during transaction abort.
493 : *
494 : * Note: in most paths of control, this will have been done already in
495 : * MarkPortalDone or MarkPortalFailed. We're just making sure.
496 : */
497 505378 : if (PointerIsValid(portal->cleanup))
498 : {
499 153724 : portal->cleanup(portal);
500 153724 : portal->cleanup = NULL;
501 : }
502 :
503 : /*
504 : * Remove portal from hash table. Because we do this here, we will not
505 : * come back to try to remove the portal again if there's any error in the
506 : * subsequent steps. Better to leak a little memory than to get into an
507 : * infinite error-recovery loop.
508 : */
509 505378 : PortalHashTableDelete(portal);
510 :
511 : /* drop cached plan reference, if any */
512 505378 : PortalReleaseCachedPlan(portal);
513 :
514 : /*
515 : * If portal has a snapshot protecting its data, release that. This needs
516 : * a little care since the registration will be attached to the portal's
517 : * resowner; if the portal failed, we will already have released the
518 : * resowner (and the snapshot) during transaction abort.
519 : */
520 505378 : if (portal->holdSnapshot)
521 : {
522 11200 : if (portal->resowner)
523 11060 : UnregisterSnapshotFromOwner(portal->holdSnapshot,
524 : portal->resowner);
525 11200 : portal->holdSnapshot = NULL;
526 : }
527 :
528 : /*
529 : * Release any resources still attached to the portal. There are several
530 : * cases being covered here:
531 : *
532 : * Top transaction commit (indicated by isTopCommit): normally we should
533 : * do nothing here and let the regular end-of-transaction resource
534 : * releasing mechanism handle these resources too. However, if we have a
535 : * FAILED portal (eg, a cursor that got an error), we'd better clean up
536 : * its resources to avoid resource-leakage warning messages.
537 : *
538 : * Sub transaction commit: never comes here at all, since we don't kill
539 : * any portals in AtSubCommit_Portals().
540 : *
541 : * Main or sub transaction abort: we will do nothing here because
542 : * portal->resowner was already set NULL; the resources were already
543 : * cleaned up in transaction abort.
544 : *
545 : * Ordinary portal drop: must release resources. However, if the portal
546 : * is not FAILED then we do not release its locks. The locks become the
547 : * responsibility of the transaction's ResourceOwner (since it is the
548 : * parent of the portal's owner) and will be released when the transaction
549 : * eventually ends.
550 : */
551 993980 : if (portal->resowner &&
552 509466 : (!isTopCommit || portal->status == PORTAL_FAILED))
553 : {
554 467738 : bool isCommit = (portal->status != PORTAL_FAILED);
555 :
556 467738 : ResourceOwnerRelease(portal->resowner,
557 : RESOURCE_RELEASE_BEFORE_LOCKS,
558 : isCommit, false);
559 467738 : ResourceOwnerRelease(portal->resowner,
560 : RESOURCE_RELEASE_LOCKS,
561 : isCommit, false);
562 467738 : ResourceOwnerRelease(portal->resowner,
563 : RESOURCE_RELEASE_AFTER_LOCKS,
564 : isCommit, false);
565 467738 : ResourceOwnerDelete(portal->resowner);
566 : }
567 505378 : portal->resowner = NULL;
568 :
569 : /*
570 : * Delete tuplestore if present. We should do this even under error
571 : * conditions; since the tuplestore would have been using cross-
572 : * transaction storage, its temp files need to be explicitly deleted.
573 : */
574 505378 : if (portal->holdStore)
575 : {
576 : MemoryContext oldcontext;
577 :
578 15882 : oldcontext = MemoryContextSwitchTo(portal->holdContext);
579 15882 : tuplestore_end(portal->holdStore);
580 15882 : MemoryContextSwitchTo(oldcontext);
581 15882 : portal->holdStore = NULL;
582 : }
583 :
584 : /* delete tuplestore storage, if any */
585 505378 : if (portal->holdContext)
586 15882 : MemoryContextDelete(portal->holdContext);
587 :
588 : /* release subsidiary storage */
589 505378 : MemoryContextDelete(portal->portalContext);
590 :
591 : /* release portal struct (it's in TopPortalContext) */
592 505378 : pfree(portal);
593 505378 : }
594 :
595 : /*
596 : * Delete all declared cursors.
597 : *
598 : * Used by commands: CLOSE ALL, DISCARD ALL
599 : */
600 : void
601 12 : PortalHashTableDeleteAll(void)
602 : {
603 : HASH_SEQ_STATUS status;
604 : PortalHashEnt *hentry;
605 :
606 12 : if (PortalHashTable == NULL)
607 0 : return;
608 :
609 12 : hash_seq_init(&status, PortalHashTable);
610 60 : while ((hentry = hash_seq_search(&status)) != NULL)
611 : {
612 36 : Portal portal = hentry->portal;
613 :
614 : /* Can't close the active portal (the one running the command) */
615 36 : if (portal->status == PORTAL_ACTIVE)
616 20 : continue;
617 :
618 16 : PortalDrop(portal, false);
619 :
620 : /* Restart the iteration in case that led to other drops */
621 16 : hash_seq_term(&status);
622 16 : hash_seq_init(&status, PortalHashTable);
623 : }
624 : }
625 :
626 : /*
627 : * "Hold" a portal. Prepare it for access by later transactions.
628 : */
629 : static void
630 48 : HoldPortal(Portal portal)
631 : {
632 : /*
633 : * Note that PersistHoldablePortal() must release all resources used by
634 : * the portal that are local to the creating transaction.
635 : */
636 48 : PortalCreateHoldStore(portal);
637 48 : PersistHoldablePortal(portal);
638 :
639 : /* drop cached plan reference, if any */
640 44 : PortalReleaseCachedPlan(portal);
641 :
642 : /*
643 : * Any resources belonging to the portal will be released in the upcoming
644 : * transaction-wide cleanup; the portal will no longer have its own
645 : * resources.
646 : */
647 44 : portal->resowner = NULL;
648 :
649 : /*
650 : * Having successfully exported the holdable cursor, mark it as not
651 : * belonging to this transaction.
652 : */
653 44 : portal->createSubid = InvalidSubTransactionId;
654 44 : portal->activeSubid = InvalidSubTransactionId;
655 44 : }
656 :
657 : /*
658 : * Pre-commit processing for portals.
659 : *
660 : * Holdable cursors created in this transaction need to be converted to
661 : * materialized form, since we are going to close down the executor and
662 : * release locks. Non-holdable portals created in this transaction are
663 : * simply removed. Portals remaining from prior transactions should be
664 : * left untouched.
665 : *
666 : * Returns true if any portals changed state (possibly causing user-defined
667 : * code to be run), false if not.
668 : */
669 : bool
670 461830 : PreCommit_Portals(bool isPrepare)
671 : {
672 461830 : bool result = false;
673 : HASH_SEQ_STATUS status;
674 : PortalHashEnt *hentry;
675 :
676 461830 : hash_seq_init(&status, PortalHashTable);
677 :
678 1021972 : while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
679 : {
680 98312 : Portal portal = hentry->portal;
681 :
682 : /*
683 : * There should be no pinned portals anymore. Complain if someone
684 : * leaked one. Auto-held portals are allowed; we assume that whoever
685 : * pinned them is managing them.
686 : */
687 98312 : if (portal->portalPinned && !portal->autoHeld)
688 0 : elog(ERROR, "cannot commit while a portal is pinned");
689 :
690 : /*
691 : * Do not touch active portals --- this can only happen in the case of
692 : * a multi-transaction utility command, such as VACUUM, or a commit in
693 : * a procedure.
694 : *
695 : * Note however that any resource owner attached to such a portal is
696 : * still going to go away, so don't leave a dangling pointer. Also
697 : * unregister any snapshots held by the portal, mainly to avoid
698 : * snapshot leak warnings from ResourceOwnerRelease().
699 : */
700 98312 : if (portal->status == PORTAL_ACTIVE)
701 : {
702 77148 : if (portal->holdSnapshot)
703 : {
704 2 : if (portal->resowner)
705 2 : UnregisterSnapshotFromOwner(portal->holdSnapshot,
706 : portal->resowner);
707 2 : portal->holdSnapshot = NULL;
708 : }
709 77148 : portal->resowner = NULL;
710 77148 : continue;
711 : }
712 :
713 : /* Is it a holdable portal created in the current xact? */
714 21404 : if ((portal->cursorOptions & CURSOR_OPT_HOLD) &&
715 260 : portal->createSubid != InvalidSubTransactionId &&
716 20 : portal->status == PORTAL_READY)
717 : {
718 : /*
719 : * We are exiting the transaction that created a holdable cursor.
720 : * Instead of dropping the portal, prepare it for access by later
721 : * transactions.
722 : *
723 : * However, if this is PREPARE TRANSACTION rather than COMMIT,
724 : * refuse PREPARE, because the semantics seem pretty unclear.
725 : */
726 20 : if (isPrepare)
727 0 : ereport(ERROR,
728 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
729 : errmsg("cannot PREPARE a transaction that has created a cursor WITH HOLD")));
730 :
731 20 : HoldPortal(portal);
732 :
733 : /* Report we changed state */
734 20 : result = true;
735 : }
736 21144 : else if (portal->createSubid == InvalidSubTransactionId)
737 : {
738 : /*
739 : * Do nothing to cursors held over from a previous transaction
740 : * (including ones we just froze in a previous cycle of this loop)
741 : */
742 280 : continue;
743 : }
744 : else
745 : {
746 : /* Zap all non-holdable portals */
747 20864 : PortalDrop(portal, true);
748 :
749 : /* Report we changed state */
750 20864 : result = true;
751 : }
752 :
753 : /*
754 : * After either freezing or dropping a portal, we have to restart the
755 : * iteration, because we could have invoked user-defined code that
756 : * caused a drop of the next portal in the hash chain.
757 : */
758 20884 : hash_seq_term(&status);
759 20884 : hash_seq_init(&status, PortalHashTable);
760 : }
761 :
762 461830 : return result;
763 : }
764 :
765 : /*
766 : * Abort processing for portals.
767 : *
768 : * At this point we run the cleanup hook if present, but we can't release the
769 : * portal's memory until the cleanup call.
770 : */
771 : void
772 19156 : AtAbort_Portals(void)
773 : {
774 : HASH_SEQ_STATUS status;
775 : PortalHashEnt *hentry;
776 :
777 19156 : hash_seq_init(&status, PortalHashTable);
778 :
779 50876 : while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
780 : {
781 12564 : Portal portal = hentry->portal;
782 :
783 : /*
784 : * When elog(FATAL) is progress, we need to set the active portal to
785 : * failed, so that PortalCleanup() doesn't run the executor shutdown.
786 : */
787 12564 : if (portal->status == PORTAL_ACTIVE && shmem_exit_inprogress)
788 0 : MarkPortalFailed(portal);
789 :
790 : /*
791 : * Do nothing else to cursors held over from a previous transaction.
792 : */
793 12564 : if (portal->createSubid == InvalidSubTransactionId)
794 102 : continue;
795 :
796 : /*
797 : * Do nothing to auto-held cursors. This is similar to the case of a
798 : * cursor from a previous transaction, but it could also be that the
799 : * cursor was auto-held in this transaction, so it wants to live on.
800 : */
801 12462 : if (portal->autoHeld)
802 0 : continue;
803 :
804 : /*
805 : * If it was created in the current transaction, we can't do normal
806 : * shutdown on a READY portal either; it might refer to objects
807 : * created in the failed transaction. See comments in
808 : * AtSubAbort_Portals.
809 : */
810 12462 : if (portal->status == PORTAL_READY)
811 208 : MarkPortalFailed(portal);
812 :
813 : /*
814 : * Allow portalcmds.c to clean up the state it knows about, if we
815 : * haven't already.
816 : */
817 12462 : if (PointerIsValid(portal->cleanup))
818 : {
819 58 : portal->cleanup(portal);
820 58 : portal->cleanup = NULL;
821 : }
822 :
823 : /* drop cached plan reference, if any */
824 12462 : PortalReleaseCachedPlan(portal);
825 :
826 : /*
827 : * Any resources belonging to the portal will be released in the
828 : * upcoming transaction-wide cleanup; they will be gone before we run
829 : * PortalDrop.
830 : */
831 12462 : portal->resowner = NULL;
832 :
833 : /*
834 : * Although we can't delete the portal data structure proper, we can
835 : * release any memory in subsidiary contexts, such as executor state.
836 : * The cleanup hook was the last thing that might have needed data
837 : * there. But leave active portals alone.
838 : */
839 12462 : if (portal->status != PORTAL_ACTIVE)
840 12318 : MemoryContextDeleteChildren(portal->portalContext);
841 : }
842 19156 : }
843 :
844 : /*
845 : * Post-abort cleanup for portals.
846 : *
847 : * Delete all portals not held over from prior transactions. */
848 : void
849 19146 : AtCleanup_Portals(void)
850 : {
851 : HASH_SEQ_STATUS status;
852 : PortalHashEnt *hentry;
853 :
854 19146 : hash_seq_init(&status, PortalHashTable);
855 :
856 50084 : while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
857 : {
858 11792 : Portal portal = hentry->portal;
859 :
860 : /*
861 : * Do not touch active portals --- this can only happen in the case of
862 : * a multi-transaction command.
863 : */
864 11792 : if (portal->status == PORTAL_ACTIVE)
865 144 : continue;
866 :
867 : /*
868 : * Do nothing to cursors held over from a previous transaction or
869 : * auto-held ones.
870 : */
871 11648 : if (portal->createSubid == InvalidSubTransactionId || portal->autoHeld)
872 : {
873 : Assert(portal->status != PORTAL_ACTIVE);
874 : Assert(portal->resowner == NULL);
875 102 : continue;
876 : }
877 :
878 : /*
879 : * If a portal is still pinned, forcibly unpin it. PortalDrop will not
880 : * let us drop the portal otherwise. Whoever pinned the portal was
881 : * interrupted by the abort too and won't try to use it anymore.
882 : */
883 11546 : if (portal->portalPinned)
884 26 : portal->portalPinned = false;
885 :
886 : /*
887 : * We had better not call any user-defined code during cleanup, so if
888 : * the cleanup hook hasn't been run yet, too bad; we'll just skip it.
889 : */
890 11546 : if (PointerIsValid(portal->cleanup))
891 : {
892 0 : elog(WARNING, "skipping cleanup for portal \"%s\"", portal->name);
893 0 : portal->cleanup = NULL;
894 : }
895 :
896 : /* Zap it. */
897 11546 : PortalDrop(portal, false);
898 : }
899 19146 : }
900 :
901 : /*
902 : * Portal-related cleanup when we return to the main loop on error.
903 : *
904 : * This is different from the cleanup at transaction abort. Auto-held portals
905 : * are cleaned up on error but not on transaction abort.
906 : */
907 : void
908 17896 : PortalErrorCleanup(void)
909 : {
910 : HASH_SEQ_STATUS status;
911 : PortalHashEnt *hentry;
912 :
913 17896 : hash_seq_init(&status, PortalHashTable);
914 :
915 36854 : while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
916 : {
917 1062 : Portal portal = hentry->portal;
918 :
919 1062 : if (portal->autoHeld)
920 : {
921 4 : portal->portalPinned = false;
922 4 : PortalDrop(portal, false);
923 : }
924 : }
925 17896 : }
926 :
927 : /*
928 : * Pre-subcommit processing for portals.
929 : *
930 : * Reassign portals created or used in the current subtransaction to the
931 : * parent subtransaction.
932 : */
933 : void
934 4434 : AtSubCommit_Portals(SubTransactionId mySubid,
935 : SubTransactionId parentSubid,
936 : ResourceOwner parentXactOwner)
937 : {
938 : HASH_SEQ_STATUS status;
939 : PortalHashEnt *hentry;
940 :
941 4434 : hash_seq_init(&status, PortalHashTable);
942 :
943 13038 : while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
944 : {
945 4170 : Portal portal = hentry->portal;
946 :
947 4170 : if (portal->createSubid == mySubid)
948 : {
949 58 : portal->createSubid = parentSubid;
950 58 : if (portal->resowner)
951 58 : ResourceOwnerNewParent(portal->resowner, parentXactOwner);
952 : }
953 4170 : if (portal->activeSubid == mySubid)
954 208 : portal->activeSubid = parentSubid;
955 : }
956 4434 : }
957 :
958 : /*
959 : * Subtransaction abort handling for portals.
960 : *
961 : * Deactivate portals created or used during the failed subtransaction.
962 : * Note that per AtSubCommit_Portals, this will catch portals created/used
963 : * in descendants of the subtransaction too.
964 : *
965 : * We don't destroy any portals here; that's done in AtSubCleanup_Portals.
966 : */
967 : void
968 2928 : AtSubAbort_Portals(SubTransactionId mySubid,
969 : SubTransactionId parentSubid,
970 : ResourceOwner myXactOwner,
971 : ResourceOwner parentXactOwner)
972 : {
973 : HASH_SEQ_STATUS status;
974 : PortalHashEnt *hentry;
975 :
976 2928 : hash_seq_init(&status, PortalHashTable);
977 :
978 10758 : while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
979 : {
980 4902 : Portal portal = hentry->portal;
981 :
982 : /* Was it created in this subtransaction? */
983 4902 : if (portal->createSubid != mySubid)
984 : {
985 : /* No, but maybe it was used in this subtransaction? */
986 4778 : if (portal->activeSubid == mySubid)
987 : {
988 : /* Maintain activeSubid until the portal is removed */
989 28 : portal->activeSubid = parentSubid;
990 :
991 : /*
992 : * A MarkPortalActive() caller ran an upper-level portal in
993 : * this subtransaction and left the portal ACTIVE. This can't
994 : * happen, but force the portal into FAILED state for the same
995 : * reasons discussed below.
996 : *
997 : * We assume we can get away without forcing upper-level READY
998 : * portals to fail, even if they were run and then suspended.
999 : * In theory a suspended upper-level portal could have
1000 : * acquired some references to objects that are about to be
1001 : * destroyed, but there should be sufficient defenses against
1002 : * such cases: the portal's original query cannot contain such
1003 : * references, and any references within, say, cached plans of
1004 : * PL/pgSQL functions are not from active queries and should
1005 : * be protected by revalidation logic.
1006 : */
1007 28 : if (portal->status == PORTAL_ACTIVE)
1008 0 : MarkPortalFailed(portal);
1009 :
1010 : /*
1011 : * Also, if we failed it during the current subtransaction
1012 : * (either just above, or earlier), reattach its resource
1013 : * owner to the current subtransaction's resource owner, so
1014 : * that any resources it still holds will be released while
1015 : * cleaning up this subtransaction. This prevents some corner
1016 : * cases wherein we might get Asserts or worse while cleaning
1017 : * up objects created during the current subtransaction
1018 : * (because they're still referenced within this portal).
1019 : */
1020 28 : if (portal->status == PORTAL_FAILED && portal->resowner)
1021 : {
1022 8 : ResourceOwnerNewParent(portal->resowner, myXactOwner);
1023 8 : portal->resowner = NULL;
1024 : }
1025 : }
1026 : /* Done if it wasn't created in this subtransaction */
1027 4778 : continue;
1028 : }
1029 :
1030 : /*
1031 : * Force any live portals of my own subtransaction into FAILED state.
1032 : * We have to do this because they might refer to objects created or
1033 : * changed in the failed subtransaction, leading to crashes within
1034 : * ExecutorEnd when portalcmds.c tries to close down the portal.
1035 : * Currently, every MarkPortalActive() caller ensures it updates the
1036 : * portal status again before relinquishing control, so ACTIVE can't
1037 : * happen here. If it does happen, dispose the portal like existing
1038 : * MarkPortalActive() callers would.
1039 : */
1040 238 : if (portal->status == PORTAL_READY ||
1041 114 : portal->status == PORTAL_ACTIVE)
1042 10 : MarkPortalFailed(portal);
1043 :
1044 : /*
1045 : * Allow portalcmds.c to clean up the state it knows about, if we
1046 : * haven't already.
1047 : */
1048 124 : if (PointerIsValid(portal->cleanup))
1049 : {
1050 0 : portal->cleanup(portal);
1051 0 : portal->cleanup = NULL;
1052 : }
1053 :
1054 : /* drop cached plan reference, if any */
1055 124 : PortalReleaseCachedPlan(portal);
1056 :
1057 : /*
1058 : * Any resources belonging to the portal will be released in the
1059 : * upcoming transaction-wide cleanup; they will be gone before we run
1060 : * PortalDrop.
1061 : */
1062 124 : portal->resowner = NULL;
1063 :
1064 : /*
1065 : * Although we can't delete the portal data structure proper, we can
1066 : * release any memory in subsidiary contexts, such as executor state.
1067 : * The cleanup hook was the last thing that might have needed data
1068 : * there.
1069 : */
1070 124 : MemoryContextDeleteChildren(portal->portalContext);
1071 : }
1072 2928 : }
1073 :
1074 : /*
1075 : * Post-subabort cleanup for portals.
1076 : *
1077 : * Drop all portals created in the failed subtransaction (but note that
1078 : * we will not drop any that were reassigned to the parent above).
1079 : */
1080 : void
1081 2928 : AtSubCleanup_Portals(SubTransactionId mySubid)
1082 : {
1083 : HASH_SEQ_STATUS status;
1084 : PortalHashEnt *hentry;
1085 :
1086 2928 : hash_seq_init(&status, PortalHashTable);
1087 :
1088 10646 : while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
1089 : {
1090 4790 : Portal portal = hentry->portal;
1091 :
1092 4790 : if (portal->createSubid != mySubid)
1093 4778 : continue;
1094 :
1095 : /*
1096 : * If a portal is still pinned, forcibly unpin it. PortalDrop will not
1097 : * let us drop the portal otherwise. Whoever pinned the portal was
1098 : * interrupted by the abort too and won't try to use it anymore.
1099 : */
1100 12 : if (portal->portalPinned)
1101 6 : portal->portalPinned = false;
1102 :
1103 : /*
1104 : * We had better not call any user-defined code during cleanup, so if
1105 : * the cleanup hook hasn't been run yet, too bad; we'll just skip it.
1106 : */
1107 12 : if (PointerIsValid(portal->cleanup))
1108 : {
1109 0 : elog(WARNING, "skipping cleanup for portal \"%s\"", portal->name);
1110 0 : portal->cleanup = NULL;
1111 : }
1112 :
1113 : /* Zap it. */
1114 12 : PortalDrop(portal, false);
1115 : }
1116 2928 : }
1117 :
1118 : /* Find all available cursors */
1119 : Datum
1120 82 : pg_cursor(PG_FUNCTION_ARGS)
1121 : {
1122 82 : ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
1123 : TupleDesc tupdesc;
1124 : Tuplestorestate *tupstore;
1125 : MemoryContext per_query_ctx;
1126 : MemoryContext oldcontext;
1127 : HASH_SEQ_STATUS hash_seq;
1128 : PortalHashEnt *hentry;
1129 :
1130 : /* check to see if caller supports us returning a tuplestore */
1131 82 : if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
1132 0 : ereport(ERROR,
1133 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1134 : errmsg("set-valued function called in context that cannot accept a set")));
1135 82 : if (!(rsinfo->allowedModes & SFRM_Materialize))
1136 0 : ereport(ERROR,
1137 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1138 : errmsg("materialize mode required, but it is not " \
1139 : "allowed in this context")));
1140 :
1141 : /* need to build tuplestore in query context */
1142 82 : per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
1143 82 : oldcontext = MemoryContextSwitchTo(per_query_ctx);
1144 :
1145 : /*
1146 : * build tupdesc for result tuples. This must match the definition of the
1147 : * pg_cursors view in system_views.sql
1148 : */
1149 82 : tupdesc = CreateTemplateTupleDesc(6);
1150 82 : TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
1151 : TEXTOID, -1, 0);
1152 82 : TupleDescInitEntry(tupdesc, (AttrNumber) 2, "statement",
1153 : TEXTOID, -1, 0);
1154 82 : TupleDescInitEntry(tupdesc, (AttrNumber) 3, "is_holdable",
1155 : BOOLOID, -1, 0);
1156 82 : TupleDescInitEntry(tupdesc, (AttrNumber) 4, "is_binary",
1157 : BOOLOID, -1, 0);
1158 82 : TupleDescInitEntry(tupdesc, (AttrNumber) 5, "is_scrollable",
1159 : BOOLOID, -1, 0);
1160 82 : TupleDescInitEntry(tupdesc, (AttrNumber) 6, "creation_time",
1161 : TIMESTAMPTZOID, -1, 0);
1162 :
1163 : /*
1164 : * We put all the tuples into a tuplestore in one scan of the hashtable.
1165 : * This avoids any issue of the hashtable possibly changing between calls.
1166 : */
1167 82 : tupstore =
1168 82 : tuplestore_begin_heap(rsinfo->allowedModes & SFRM_Materialize_Random,
1169 : false, work_mem);
1170 :
1171 : /* generate junk in short-term context */
1172 82 : MemoryContextSwitchTo(oldcontext);
1173 :
1174 82 : hash_seq_init(&hash_seq, PortalHashTable);
1175 330 : while ((hentry = hash_seq_search(&hash_seq)) != NULL)
1176 : {
1177 166 : Portal portal = hentry->portal;
1178 : Datum values[6];
1179 : bool nulls[6];
1180 :
1181 : /* report only "visible" entries */
1182 166 : if (!portal->visible)
1183 86 : continue;
1184 :
1185 80 : MemSet(nulls, 0, sizeof(nulls));
1186 :
1187 80 : values[0] = CStringGetTextDatum(portal->name);
1188 80 : values[1] = CStringGetTextDatum(portal->sourceText);
1189 80 : values[2] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_HOLD);
1190 80 : values[3] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_BINARY);
1191 80 : values[4] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_SCROLL);
1192 80 : values[5] = TimestampTzGetDatum(portal->creation_time);
1193 :
1194 80 : tuplestore_putvalues(tupstore, tupdesc, values, nulls);
1195 : }
1196 :
1197 : /* clean up and return the tuplestore */
1198 : tuplestore_donestoring(tupstore);
1199 :
1200 82 : rsinfo->returnMode = SFRM_Materialize;
1201 82 : rsinfo->setResult = tupstore;
1202 82 : rsinfo->setDesc = tupdesc;
1203 :
1204 82 : return (Datum) 0;
1205 : }
1206 :
1207 : bool
1208 28 : ThereAreNoReadyPortals(void)
1209 : {
1210 : HASH_SEQ_STATUS status;
1211 : PortalHashEnt *hentry;
1212 :
1213 28 : hash_seq_init(&status, PortalHashTable);
1214 :
1215 28 : while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
1216 : {
1217 28 : Portal portal = hentry->portal;
1218 :
1219 28 : if (portal->status == PORTAL_READY)
1220 0 : return false;
1221 : }
1222 :
1223 28 : return true;
1224 : }
1225 :
1226 : /*
1227 : * Hold all pinned portals.
1228 : *
1229 : * When initiating a COMMIT or ROLLBACK inside a procedure, this must be
1230 : * called to protect internally-generated cursors from being dropped during
1231 : * the transaction shutdown. Currently, SPI calls this automatically; PLs
1232 : * that initiate COMMIT or ROLLBACK some other way are on the hook to do it
1233 : * themselves. (Note that we couldn't do this in, say, AtAbort_Portals
1234 : * because we need to run user-defined code while persisting a portal.
1235 : * It's too late to do that once transaction abort has started.)
1236 : *
1237 : * We protect such portals by converting them to held cursors. We mark them
1238 : * as "auto-held" so that exception exit knows to clean them up. (In normal,
1239 : * non-exception code paths, the PL needs to clean such portals itself, since
1240 : * transaction end won't do it anymore; but that should be normal practice
1241 : * anyway.)
1242 : */
1243 : void
1244 4330 : HoldPinnedPortals(void)
1245 : {
1246 : HASH_SEQ_STATUS status;
1247 : PortalHashEnt *hentry;
1248 :
1249 4330 : hash_seq_init(&status, PortalHashTable);
1250 :
1251 13086 : while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
1252 : {
1253 4432 : Portal portal = hentry->portal;
1254 :
1255 4432 : if (portal->portalPinned && !portal->autoHeld)
1256 : {
1257 : /*
1258 : * Doing transaction control, especially abort, inside a cursor
1259 : * loop that is not read-only, for example using UPDATE ...
1260 : * RETURNING, has weird semantics issues. Also, this
1261 : * implementation wouldn't work, because such portals cannot be
1262 : * held. (The core grammar enforces that only SELECT statements
1263 : * can drive a cursor, but for example PL/pgSQL does not restrict
1264 : * it.)
1265 : */
1266 30 : if (portal->strategy != PORTAL_ONE_SELECT)
1267 2 : ereport(ERROR,
1268 : (errcode(ERRCODE_INVALID_TRANSACTION_TERMINATION),
1269 : errmsg("cannot perform transaction commands inside a cursor loop that is not read-only")));
1270 :
1271 : /* Verify it's in a suitable state to be held */
1272 28 : if (portal->status != PORTAL_READY)
1273 0 : elog(ERROR, "pinned portal is not ready to be auto-held");
1274 :
1275 28 : HoldPortal(portal);
1276 24 : portal->autoHeld = true;
1277 : }
1278 : }
1279 4324 : }
|
