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portalmem.c
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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 {
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 
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
105 {
106  HASHCTL ctl;
107 
108  Assert(TopPortalContext == NULL);
109 
110  TopPortalContext = AllocSetContextCreate(TopMemoryContext,
111  "TopPortalContext",
113 
115  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  PortalHashTable = hash_create("Portal hash", PORTALS_PER_USER,
122  &ctl, HASH_ELEM);
123 }
124 
125 /*
126  * GetPortalByName
127  * Returns a portal given a portal name, or NULL if name not found.
128  */
129 Portal
130 GetPortalByName(const char *name)
131 {
132  Portal portal;
133 
134  if (PointerIsValid(name))
135  PortalHashTableLookup(name, portal);
136  else
137  portal = NULL;
138 
139  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 *
152 {
153  ListCell *lc;
154 
155  foreach(lc, portal->stmts)
156  {
157  PlannedStmt *stmt = lfirst_node(PlannedStmt, lc);
158 
159  if (stmt->canSetTag)
160  return stmt;
161  }
162  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 CreatePortal(const char *name, bool allowDup, bool dupSilent)
176 {
177  Portal portal;
178 
179  AssertArg(PointerIsValid(name));
180 
181  portal = GetPortalByName(name);
182  if (PortalIsValid(portal))
183  {
184  if (!allowDup)
185  ereport(ERROR,
186  (errcode(ERRCODE_DUPLICATE_CURSOR),
187  errmsg("cursor \"%s\" already exists", name)));
188  if (!dupSilent)
190  (errcode(ERRCODE_DUPLICATE_CURSOR),
191  errmsg("closing existing cursor \"%s\"",
192  name)));
193  PortalDrop(portal, false);
194  }
195 
196  /* make new portal structure */
197  portal = (Portal) MemoryContextAllocZero(TopPortalContext, sizeof *portal);
198 
199  /* initialize portal context; typically it won't store much */
200  portal->portalContext = AllocSetContextCreate(TopPortalContext,
201  "PortalContext",
203 
204  /* create a resource owner for the portal */
206  "Portal");
207 
208  /* initialize portal fields that don't start off zero */
209  portal->status = PORTAL_NEW;
210  portal->cleanup = PortalCleanup;
212  portal->activeSubid = portal->createSubid;
213  portal->strategy = PORTAL_MULTI_QUERY;
215  portal->atStart = true;
216  portal->atEnd = true; /* disallow fetches until query is set */
217  portal->visible = true;
219 
220  /* put portal in table (sets portal->name) */
221  PortalHashTableInsert(portal, name);
222 
223  /* reuse portal->name copy */
225 
226  return portal;
227 }
228 
229 /*
230  * CreateNewPortal
231  * Create a new portal, assigning it a random nonconflicting name.
232  */
233 Portal
235 {
236  static unsigned int unnamed_portal_count = 0;
237 
239 
240  /* Select a nonconflicting name */
241  for (;;)
242  {
243  unnamed_portal_count++;
244  sprintf(portalname, "<unnamed portal %u>", unnamed_portal_count);
245  if (GetPortalByName(portalname) == NULL)
246  break;
247  }
248 
249  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
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  portal->prepStmtName = prepStmtName;
295  portal->sourceText = sourceText;
296  portal->commandTag = commandTag;
297  portal->stmts = stmts;
298  portal->cplan = cplan;
299  portal->status = PORTAL_DEFINED;
300 }
301 
302 /*
303  * PortalReleaseCachedPlan
304  * Release a portal's reference to its cached plan, if any.
305  */
306 static void
308 {
309  if (portal->cplan)
310  {
311  ReleaseCachedPlan(portal->cplan, false);
312  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  portal->stmts = NIL;
320  }
321 }
322 
323 /*
324  * PortalCreateHoldStore
325  * Create the tuplestore for a portal.
326  */
327 void
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  portal->holdContext =
341  AllocSetContextCreate(TopPortalContext,
342  "PortalHoldContext",
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  oldcxt = MemoryContextSwitchTo(portal->holdContext);
352 
353  portal->holdStore =
355  true, work_mem);
356 
357  MemoryContextSwitchTo(oldcxt);
358 }
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
369 {
370  if (portal->portalPinned)
371  elog(ERROR, "portal already pinned");
372 
373  portal->portalPinned = true;
374 }
375 
376 void
378 {
379  if (!portal->portalPinned)
380  elog(ERROR, "portal not pinned");
381 
382  portal->portalPinned = false;
383 }
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
393 {
394  /* For safety, this is a runtime test not just an Assert */
395  if (portal->status != PORTAL_READY)
396  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  portal->status = PORTAL_ACTIVE;
402 }
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
412 {
413  /* Perform the state transition */
414  Assert(portal->status == PORTAL_ACTIVE);
415  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  if (PointerIsValid(portal->cleanup))
426  {
427  portal->cleanup(portal);
428  portal->cleanup = NULL;
429  }
430 }
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
440 {
441  /* Perform the state transition */
442  Assert(portal->status != PORTAL_DONE);
443  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  if (PointerIsValid(portal->cleanup))
454  {
455  portal->cleanup(portal);
456  portal->cleanup = NULL;
457  }
458 }
459 
460 /*
461  * PortalDrop
462  * Destroy the portal.
463  */
464 void
465 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  if (portal->portalPinned)
474  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  if (portal->status == PORTAL_ACTIVE)
482  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  if (PointerIsValid(portal->cleanup))
498  {
499  portal->cleanup(portal);
500  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  PortalHashTableDelete(portal);
510 
511  /* drop cached plan reference, if any */
512  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  if (portal->holdSnapshot)
521  {
522  if (portal->resowner)
524  portal->resowner);
525  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  if (portal->resowner &&
552  (!isTopCommit || portal->status == PORTAL_FAILED))
553  {
554  bool isCommit = (portal->status != PORTAL_FAILED);
555 
558  isCommit, false);
561  isCommit, false);
564  isCommit, false);
565  ResourceOwnerDelete(portal->resowner);
566  }
567  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  if (portal->holdStore)
575  {
576  MemoryContext oldcontext;
577 
578  oldcontext = MemoryContextSwitchTo(portal->holdContext);
579  tuplestore_end(portal->holdStore);
580  MemoryContextSwitchTo(oldcontext);
581  portal->holdStore = NULL;
582  }
583 
584  /* delete tuplestore storage, if any */
585  if (portal->holdContext)
587 
588  /* release subsidiary storage */
590 
591  /* release portal struct (it's in TopPortalContext) */
592  pfree(portal);
593 }
594 
595 /*
596  * Delete all declared cursors.
597  *
598  * Used by commands: CLOSE ALL, DISCARD ALL
599  */
600 void
602 {
604  PortalHashEnt *hentry;
605 
606  if (PortalHashTable == NULL)
607  return;
608 
609  hash_seq_init(&status, PortalHashTable);
610  while ((hentry = hash_seq_search(&status)) != NULL)
611  {
612  Portal portal = hentry->portal;
613 
614  /* Can't close the active portal (the one running the command) */
615  if (portal->status == PORTAL_ACTIVE)
616  continue;
617 
618  PortalDrop(portal, false);
619 
620  /* Restart the iteration in case that led to other drops */
621  hash_seq_term(&status);
622  hash_seq_init(&status, PortalHashTable);
623  }
624 }
625 
626 /*
627  * "Hold" a portal. Prepare it for access by later transactions.
628  */
629 static void
631 {
632  /*
633  * Note that PersistHoldablePortal() must release all resources used by
634  * the portal that are local to the creating transaction.
635  */
636  PortalCreateHoldStore(portal);
637  PersistHoldablePortal(portal);
638 
639  /* drop cached plan reference, if any */
640  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  portal->resowner = NULL;
648 
649  /*
650  * Having successfully exported the holdable cursor, mark it as not
651  * belonging to this transaction.
652  */
655 }
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 PreCommit_Portals(bool isPrepare)
671 {
672  bool result = false;
674  PortalHashEnt *hentry;
675 
676  hash_seq_init(&status, PortalHashTable);
677 
678  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
679  {
680  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  if (portal->portalPinned && !portal->autoHeld)
688  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  if (portal->status == PORTAL_ACTIVE)
701  {
702  if (portal->holdSnapshot)
703  {
704  if (portal->resowner)
706  portal->resowner);
707  portal->holdSnapshot = NULL;
708  }
709  portal->resowner = NULL;
710  continue;
711  }
712 
713  /* Is it a holdable portal created in the current xact? */
714  if ((portal->cursorOptions & CURSOR_OPT_HOLD) &&
716  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  if (isPrepare)
727  ereport(ERROR,
728  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
729  errmsg("cannot PREPARE a transaction that has created a cursor WITH HOLD")));
730 
731  HoldPortal(portal);
732 
733  /* Report we changed state */
734  result = true;
735  }
736  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  continue;
743  }
744  else
745  {
746  /* Zap all non-holdable portals */
747  PortalDrop(portal, true);
748 
749  /* Report we changed state */
750  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  hash_seq_term(&status);
759  hash_seq_init(&status, PortalHashTable);
760  }
761 
762  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
773 {
775  PortalHashEnt *hentry;
776 
777  hash_seq_init(&status, PortalHashTable);
778 
779  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
780  {
781  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  if (portal->status == PORTAL_ACTIVE && shmem_exit_inprogress)
788  MarkPortalFailed(portal);
789 
790  /*
791  * Do nothing else to cursors held over from a previous transaction.
792  */
793  if (portal->createSubid == InvalidSubTransactionId)
794  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  if (portal->autoHeld)
802  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  if (portal->status == PORTAL_READY)
811  MarkPortalFailed(portal);
812 
813  /*
814  * Allow portalcmds.c to clean up the state it knows about, if we
815  * haven't already.
816  */
817  if (PointerIsValid(portal->cleanup))
818  {
819  portal->cleanup(portal);
820  portal->cleanup = NULL;
821  }
822 
823  /* drop cached plan reference, if any */
824  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  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  if (portal->status != PORTAL_ACTIVE)
841  }
842 }
843 
844 /*
845  * Post-abort cleanup for portals.
846  *
847  * Delete all portals not held over from prior transactions. */
848 void
850 {
852  PortalHashEnt *hentry;
853 
854  hash_seq_init(&status, PortalHashTable);
855 
856  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
857  {
858  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  if (portal->status == PORTAL_ACTIVE)
865  continue;
866 
867  /*
868  * Do nothing to cursors held over from a previous transaction or
869  * auto-held ones.
870  */
871  if (portal->createSubid == InvalidSubTransactionId || portal->autoHeld)
872  {
873  Assert(portal->status != PORTAL_ACTIVE);
874  Assert(portal->resowner == NULL);
875  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  if (portal->portalPinned)
884  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  if (PointerIsValid(portal->cleanup))
891  {
892  elog(WARNING, "skipping cleanup for portal \"%s\"", portal->name);
893  portal->cleanup = NULL;
894  }
895 
896  /* Zap it. */
897  PortalDrop(portal, false);
898  }
899 }
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
909 {
911  PortalHashEnt *hentry;
912 
913  hash_seq_init(&status, PortalHashTable);
914 
915  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
916  {
917  Portal portal = hentry->portal;
918 
919  if (portal->autoHeld)
920  {
921  portal->portalPinned = false;
922  PortalDrop(portal, false);
923  }
924  }
925 }
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
935  SubTransactionId parentSubid,
936  ResourceOwner parentXactOwner)
937 {
939  PortalHashEnt *hentry;
940 
941  hash_seq_init(&status, PortalHashTable);
942 
943  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
944  {
945  Portal portal = hentry->portal;
946 
947  if (portal->createSubid == mySubid)
948  {
949  portal->createSubid = parentSubid;
950  if (portal->resowner)
951  ResourceOwnerNewParent(portal->resowner, parentXactOwner);
952  }
953  if (portal->activeSubid == mySubid)
954  portal->activeSubid = parentSubid;
955  }
956 }
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
969  SubTransactionId parentSubid,
970  ResourceOwner myXactOwner,
971  ResourceOwner parentXactOwner)
972 {
974  PortalHashEnt *hentry;
975 
976  hash_seq_init(&status, PortalHashTable);
977 
978  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
979  {
980  Portal portal = hentry->portal;
981 
982  /* Was it created in this subtransaction? */
983  if (portal->createSubid != mySubid)
984  {
985  /* No, but maybe it was used in this subtransaction? */
986  if (portal->activeSubid == mySubid)
987  {
988  /* Maintain activeSubid until the portal is removed */
989  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  if (portal->status == PORTAL_ACTIVE)
1008  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  if (portal->status == PORTAL_FAILED && portal->resowner)
1021  {
1022  ResourceOwnerNewParent(portal->resowner, myXactOwner);
1023  portal->resowner = NULL;
1024  }
1025  }
1026  /* Done if it wasn't created in this subtransaction */
1027  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  if (portal->status == PORTAL_READY ||
1041  portal->status == PORTAL_ACTIVE)
1042  MarkPortalFailed(portal);
1043 
1044  /*
1045  * Allow portalcmds.c to clean up the state it knows about, if we
1046  * haven't already.
1047  */
1048  if (PointerIsValid(portal->cleanup))
1049  {
1050  portal->cleanup(portal);
1051  portal->cleanup = NULL;
1052  }
1053 
1054  /* drop cached plan reference, if any */
1055  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  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  */
1071  }
1072 }
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
1082 {
1084  PortalHashEnt *hentry;
1085 
1086  hash_seq_init(&status, PortalHashTable);
1087 
1088  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
1089  {
1090  Portal portal = hentry->portal;
1091 
1092  if (portal->createSubid != mySubid)
1093  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  if (portal->portalPinned)
1101  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  if (PointerIsValid(portal->cleanup))
1108  {
1109  elog(WARNING, "skipping cleanup for portal \"%s\"", portal->name);
1110  portal->cleanup = NULL;
1111  }
1112 
1113  /* Zap it. */
1114  PortalDrop(portal, false);
1115  }
1116 }
1117 
1118 /* Find all available cursors */
1119 Datum
1121 {
1122  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  if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
1132  ereport(ERROR,
1133  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1134  errmsg("set-valued function called in context that cannot accept a set")));
1135  if (!(rsinfo->allowedModes & SFRM_Materialize))
1136  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  per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
1143  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  tupdesc = CreateTemplateTupleDesc(6);
1150  TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
1151  TEXTOID, -1, 0);
1152  TupleDescInitEntry(tupdesc, (AttrNumber) 2, "statement",
1153  TEXTOID, -1, 0);
1154  TupleDescInitEntry(tupdesc, (AttrNumber) 3, "is_holdable",
1155  BOOLOID, -1, 0);
1156  TupleDescInitEntry(tupdesc, (AttrNumber) 4, "is_binary",
1157  BOOLOID, -1, 0);
1158  TupleDescInitEntry(tupdesc, (AttrNumber) 5, "is_scrollable",
1159  BOOLOID, -1, 0);
1160  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  tupstore =
1169  false, work_mem);
1170 
1171  /* generate junk in short-term context */
1172  MemoryContextSwitchTo(oldcontext);
1173 
1174  hash_seq_init(&hash_seq, PortalHashTable);
1175  while ((hentry = hash_seq_search(&hash_seq)) != NULL)
1176  {
1177  Portal portal = hentry->portal;
1178  Datum values[6];
1179  bool nulls[6];
1180 
1181  /* report only "visible" entries */
1182  if (!portal->visible)
1183  continue;
1184 
1185  MemSet(nulls, 0, sizeof(nulls));
1186 
1187  values[0] = CStringGetTextDatum(portal->name);
1188  values[1] = CStringGetTextDatum(portal->sourceText);
1189  values[2] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_HOLD);
1190  values[3] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_BINARY);
1191  values[4] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_SCROLL);
1192  values[5] = TimestampTzGetDatum(portal->creation_time);
1193 
1194  tuplestore_putvalues(tupstore, tupdesc, values, nulls);
1195  }
1196 
1197  /* clean up and return the tuplestore */
1198  tuplestore_donestoring(tupstore);
1199 
1200  rsinfo->returnMode = SFRM_Materialize;
1201  rsinfo->setResult = tupstore;
1202  rsinfo->setDesc = tupdesc;
1203 
1204  return (Datum) 0;
1205 }
1206 
1207 bool
1209 {
1211  PortalHashEnt *hentry;
1212 
1213  hash_seq_init(&status, PortalHashTable);
1214 
1215  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
1216  {
1217  Portal portal = hentry->portal;
1218 
1219  if (portal->status == PORTAL_READY)
1220  return false;
1221  }
1222 
1223  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
1245 {
1247  PortalHashEnt *hentry;
1248 
1249  hash_seq_init(&status, PortalHashTable);
1250 
1251  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
1252  {
1253  Portal portal = hentry->portal;
1254 
1255  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  if (portal->strategy != PORTAL_ONE_SELECT)
1267  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  if (portal->status != PORTAL_READY)
1273  elog(ERROR, "pinned portal is not ready to be auto-held");
1274 
1275  HoldPortal(portal);
1276  portal->autoHeld = true;
1277  }
1278  }
1279 }
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Definition: tuplestore.c:750
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Definition: portalmem.c:377
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Portal CreatePortal(const char *name, bool allowDup, bool dupSilent)
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Portal GetPortalByName(const char *name)
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SubTransactionId createSubid
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Definition: c.h:626
int16 AttrNumber
Definition: attnum.h:21
void hash_seq_term(HASH_SEQ_STATUS *status)
Definition: dynahash.c:1465
void AtSubCommit_Portals(SubTransactionId mySubid, SubTransactionId parentSubid, ResourceOwner parentXactOwner)
Definition: portalmem.c:934
const char * prepStmtName
Definition: portal.h:118
TimestampTz GetCurrentStatementStartTimestamp(void)
Definition: xact.c:792
ResourceOwner ResourceOwnerCreate(ResourceOwner parent, const char *name)
Definition: resowner.c:422