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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) 1996-2020, 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  CommandTag 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 != CMDTAG_UNKNOWN || stmts == NIL);
293 
294  portal->prepStmtName = prepStmtName;
295  portal->sourceText = sourceText;
296  portal->qc.commandTag = commandTag;
297  portal->qc.nprocessed = 0;
298  portal->commandTag = commandTag;
299  portal->stmts = stmts;
300  portal->cplan = cplan;
301  portal->status = PORTAL_DEFINED;
302 }
303 
304 /*
305  * PortalReleaseCachedPlan
306  * Release a portal's reference to its cached plan, if any.
307  */
308 static void
310 {
311  if (portal->cplan)
312  {
313  ReleaseCachedPlan(portal->cplan, false);
314  portal->cplan = NULL;
315 
316  /*
317  * We must also clear portal->stmts which is now a dangling reference
318  * to the cached plan's plan list. This protects any code that might
319  * try to examine the Portal later.
320  */
321  portal->stmts = NIL;
322  }
323 }
324 
325 /*
326  * PortalCreateHoldStore
327  * Create the tuplestore for a portal.
328  */
329 void
331 {
332  MemoryContext oldcxt;
333 
334  Assert(portal->holdContext == NULL);
335  Assert(portal->holdStore == NULL);
336  Assert(portal->holdSnapshot == NULL);
337 
338  /*
339  * Create the memory context that is used for storage of the tuple set.
340  * Note this is NOT a child of the portal's portalContext.
341  */
342  portal->holdContext =
343  AllocSetContextCreate(TopPortalContext,
344  "PortalHoldContext",
346 
347  /*
348  * Create the tuple store, selecting cross-transaction temp files, and
349  * enabling random access only if cursor requires scrolling.
350  *
351  * XXX: Should maintenance_work_mem be used for the portal size?
352  */
353  oldcxt = MemoryContextSwitchTo(portal->holdContext);
354 
355  portal->holdStore =
357  true, work_mem);
358 
359  MemoryContextSwitchTo(oldcxt);
360 }
361 
362 /*
363  * PinPortal
364  * Protect a portal from dropping.
365  *
366  * A pinned portal is still unpinned and dropped at transaction or
367  * subtransaction abort.
368  */
369 void
371 {
372  if (portal->portalPinned)
373  elog(ERROR, "portal already pinned");
374 
375  portal->portalPinned = true;
376 }
377 
378 void
380 {
381  if (!portal->portalPinned)
382  elog(ERROR, "portal not pinned");
383 
384  portal->portalPinned = false;
385 }
386 
387 /*
388  * MarkPortalActive
389  * Transition a portal from READY to ACTIVE state.
390  *
391  * NOTE: never set portal->status = PORTAL_ACTIVE directly; call this instead.
392  */
393 void
395 {
396  /* For safety, this is a runtime test not just an Assert */
397  if (portal->status != PORTAL_READY)
398  ereport(ERROR,
399  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
400  errmsg("portal \"%s\" cannot be run", portal->name)));
401  /* Perform the state transition */
402  portal->status = PORTAL_ACTIVE;
404 }
405 
406 /*
407  * MarkPortalDone
408  * Transition a portal from ACTIVE to DONE state.
409  *
410  * NOTE: never set portal->status = PORTAL_DONE directly; call this instead.
411  */
412 void
414 {
415  /* Perform the state transition */
416  Assert(portal->status == PORTAL_ACTIVE);
417  portal->status = PORTAL_DONE;
418 
419  /*
420  * Allow portalcmds.c to clean up the state it knows about. We might as
421  * well do that now, since the portal can't be executed any more.
422  *
423  * In some cases involving execution of a ROLLBACK command in an already
424  * aborted transaction, this is necessary, or we'd reach AtCleanup_Portals
425  * with the cleanup hook still unexecuted.
426  */
427  if (PointerIsValid(portal->cleanup))
428  {
429  portal->cleanup(portal);
430  portal->cleanup = NULL;
431  }
432 }
433 
434 /*
435  * MarkPortalFailed
436  * Transition a portal into FAILED state.
437  *
438  * NOTE: never set portal->status = PORTAL_FAILED directly; call this instead.
439  */
440 void
442 {
443  /* Perform the state transition */
444  Assert(portal->status != PORTAL_DONE);
445  portal->status = PORTAL_FAILED;
446 
447  /*
448  * Allow portalcmds.c to clean up the state it knows about. We might as
449  * well do that now, since the portal can't be executed any more.
450  *
451  * In some cases involving cleanup of an already aborted transaction, this
452  * is necessary, or we'd reach AtCleanup_Portals with the cleanup hook
453  * still unexecuted.
454  */
455  if (PointerIsValid(portal->cleanup))
456  {
457  portal->cleanup(portal);
458  portal->cleanup = NULL;
459  }
460 }
461 
462 /*
463  * PortalDrop
464  * Destroy the portal.
465  */
466 void
467 PortalDrop(Portal portal, bool isTopCommit)
468 {
469  AssertArg(PortalIsValid(portal));
470 
471  /*
472  * Don't allow dropping a pinned portal, it's still needed by whoever
473  * pinned it.
474  */
475  if (portal->portalPinned)
476  ereport(ERROR,
477  (errcode(ERRCODE_INVALID_CURSOR_STATE),
478  errmsg("cannot drop pinned portal \"%s\"", portal->name)));
479 
480  /*
481  * Not sure if the PORTAL_ACTIVE case can validly happen or not...
482  */
483  if (portal->status == PORTAL_ACTIVE)
484  ereport(ERROR,
485  (errcode(ERRCODE_INVALID_CURSOR_STATE),
486  errmsg("cannot drop active portal \"%s\"", portal->name)));
487 
488  /*
489  * Allow portalcmds.c to clean up the state it knows about, in particular
490  * shutting down the executor if still active. This step potentially runs
491  * user-defined code so failure has to be expected. It's the cleanup
492  * hook's responsibility to not try to do that more than once, in the case
493  * that failure occurs and then we come back to drop the portal again
494  * during transaction abort.
495  *
496  * Note: in most paths of control, this will have been done already in
497  * MarkPortalDone or MarkPortalFailed. We're just making sure.
498  */
499  if (PointerIsValid(portal->cleanup))
500  {
501  portal->cleanup(portal);
502  portal->cleanup = NULL;
503  }
504 
505  /*
506  * Remove portal from hash table. Because we do this here, we will not
507  * come back to try to remove the portal again if there's any error in the
508  * subsequent steps. Better to leak a little memory than to get into an
509  * infinite error-recovery loop.
510  */
511  PortalHashTableDelete(portal);
512 
513  /* drop cached plan reference, if any */
514  PortalReleaseCachedPlan(portal);
515 
516  /*
517  * If portal has a snapshot protecting its data, release that. This needs
518  * a little care since the registration will be attached to the portal's
519  * resowner; if the portal failed, we will already have released the
520  * resowner (and the snapshot) during transaction abort.
521  */
522  if (portal->holdSnapshot)
523  {
524  if (portal->resowner)
526  portal->resowner);
527  portal->holdSnapshot = NULL;
528  }
529 
530  /*
531  * Release any resources still attached to the portal. There are several
532  * cases being covered here:
533  *
534  * Top transaction commit (indicated by isTopCommit): normally we should
535  * do nothing here and let the regular end-of-transaction resource
536  * releasing mechanism handle these resources too. However, if we have a
537  * FAILED portal (eg, a cursor that got an error), we'd better clean up
538  * its resources to avoid resource-leakage warning messages.
539  *
540  * Sub transaction commit: never comes here at all, since we don't kill
541  * any portals in AtSubCommit_Portals().
542  *
543  * Main or sub transaction abort: we will do nothing here because
544  * portal->resowner was already set NULL; the resources were already
545  * cleaned up in transaction abort.
546  *
547  * Ordinary portal drop: must release resources. However, if the portal
548  * is not FAILED then we do not release its locks. The locks become the
549  * responsibility of the transaction's ResourceOwner (since it is the
550  * parent of the portal's owner) and will be released when the transaction
551  * eventually ends.
552  */
553  if (portal->resowner &&
554  (!isTopCommit || portal->status == PORTAL_FAILED))
555  {
556  bool isCommit = (portal->status != PORTAL_FAILED);
557 
560  isCommit, false);
563  isCommit, false);
566  isCommit, false);
567  ResourceOwnerDelete(portal->resowner);
568  }
569  portal->resowner = NULL;
570 
571  /*
572  * Delete tuplestore if present. We should do this even under error
573  * conditions; since the tuplestore would have been using cross-
574  * transaction storage, its temp files need to be explicitly deleted.
575  */
576  if (portal->holdStore)
577  {
578  MemoryContext oldcontext;
579 
580  oldcontext = MemoryContextSwitchTo(portal->holdContext);
581  tuplestore_end(portal->holdStore);
582  MemoryContextSwitchTo(oldcontext);
583  portal->holdStore = NULL;
584  }
585 
586  /* delete tuplestore storage, if any */
587  if (portal->holdContext)
589 
590  /* release subsidiary storage */
592 
593  /* release portal struct (it's in TopPortalContext) */
594  pfree(portal);
595 }
596 
597 /*
598  * Delete all declared cursors.
599  *
600  * Used by commands: CLOSE ALL, DISCARD ALL
601  */
602 void
604 {
606  PortalHashEnt *hentry;
607 
608  if (PortalHashTable == NULL)
609  return;
610 
611  hash_seq_init(&status, PortalHashTable);
612  while ((hentry = hash_seq_search(&status)) != NULL)
613  {
614  Portal portal = hentry->portal;
615 
616  /* Can't close the active portal (the one running the command) */
617  if (portal->status == PORTAL_ACTIVE)
618  continue;
619 
620  PortalDrop(portal, false);
621 
622  /* Restart the iteration in case that led to other drops */
623  hash_seq_term(&status);
624  hash_seq_init(&status, PortalHashTable);
625  }
626 }
627 
628 /*
629  * "Hold" a portal. Prepare it for access by later transactions.
630  */
631 static void
633 {
634  /*
635  * Note that PersistHoldablePortal() must release all resources used by
636  * the portal that are local to the creating transaction.
637  */
638  PortalCreateHoldStore(portal);
639  PersistHoldablePortal(portal);
640 
641  /* drop cached plan reference, if any */
642  PortalReleaseCachedPlan(portal);
643 
644  /*
645  * Any resources belonging to the portal will be released in the upcoming
646  * transaction-wide cleanup; the portal will no longer have its own
647  * resources.
648  */
649  portal->resowner = NULL;
650 
651  /*
652  * Having successfully exported the holdable cursor, mark it as not
653  * belonging to this transaction.
654  */
657 }
658 
659 /*
660  * Pre-commit processing for portals.
661  *
662  * Holdable cursors created in this transaction need to be converted to
663  * materialized form, since we are going to close down the executor and
664  * release locks. Non-holdable portals created in this transaction are
665  * simply removed. Portals remaining from prior transactions should be
666  * left untouched.
667  *
668  * Returns true if any portals changed state (possibly causing user-defined
669  * code to be run), false if not.
670  */
671 bool
672 PreCommit_Portals(bool isPrepare)
673 {
674  bool result = false;
676  PortalHashEnt *hentry;
677 
678  hash_seq_init(&status, PortalHashTable);
679 
680  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
681  {
682  Portal portal = hentry->portal;
683 
684  /*
685  * There should be no pinned portals anymore. Complain if someone
686  * leaked one. Auto-held portals are allowed; we assume that whoever
687  * pinned them is managing them.
688  */
689  if (portal->portalPinned && !portal->autoHeld)
690  elog(ERROR, "cannot commit while a portal is pinned");
691 
692  /*
693  * Do not touch active portals --- this can only happen in the case of
694  * a multi-transaction utility command, such as VACUUM, or a commit in
695  * a procedure.
696  *
697  * Note however that any resource owner attached to such a portal is
698  * still going to go away, so don't leave a dangling pointer. Also
699  * unregister any snapshots held by the portal, mainly to avoid
700  * snapshot leak warnings from ResourceOwnerRelease().
701  */
702  if (portal->status == PORTAL_ACTIVE)
703  {
704  if (portal->holdSnapshot)
705  {
706  if (portal->resowner)
708  portal->resowner);
709  portal->holdSnapshot = NULL;
710  }
711  portal->resowner = NULL;
712  continue;
713  }
714 
715  /* Is it a holdable portal created in the current xact? */
716  if ((portal->cursorOptions & CURSOR_OPT_HOLD) &&
718  portal->status == PORTAL_READY)
719  {
720  /*
721  * We are exiting the transaction that created a holdable cursor.
722  * Instead of dropping the portal, prepare it for access by later
723  * transactions.
724  *
725  * However, if this is PREPARE TRANSACTION rather than COMMIT,
726  * refuse PREPARE, because the semantics seem pretty unclear.
727  */
728  if (isPrepare)
729  ereport(ERROR,
730  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
731  errmsg("cannot PREPARE a transaction that has created a cursor WITH HOLD")));
732 
733  HoldPortal(portal);
734 
735  /* Report we changed state */
736  result = true;
737  }
738  else if (portal->createSubid == InvalidSubTransactionId)
739  {
740  /*
741  * Do nothing to cursors held over from a previous transaction
742  * (including ones we just froze in a previous cycle of this loop)
743  */
744  continue;
745  }
746  else
747  {
748  /* Zap all non-holdable portals */
749  PortalDrop(portal, true);
750 
751  /* Report we changed state */
752  result = true;
753  }
754 
755  /*
756  * After either freezing or dropping a portal, we have to restart the
757  * iteration, because we could have invoked user-defined code that
758  * caused a drop of the next portal in the hash chain.
759  */
760  hash_seq_term(&status);
761  hash_seq_init(&status, PortalHashTable);
762  }
763 
764  return result;
765 }
766 
767 /*
768  * Abort processing for portals.
769  *
770  * At this point we run the cleanup hook if present, but we can't release the
771  * portal's memory until the cleanup call.
772  */
773 void
775 {
777  PortalHashEnt *hentry;
778 
779  hash_seq_init(&status, PortalHashTable);
780 
781  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
782  {
783  Portal portal = hentry->portal;
784 
785  /*
786  * When elog(FATAL) is progress, we need to set the active portal to
787  * failed, so that PortalCleanup() doesn't run the executor shutdown.
788  */
789  if (portal->status == PORTAL_ACTIVE && shmem_exit_inprogress)
790  MarkPortalFailed(portal);
791 
792  /*
793  * Do nothing else to cursors held over from a previous transaction.
794  */
795  if (portal->createSubid == InvalidSubTransactionId)
796  continue;
797 
798  /*
799  * Do nothing to auto-held cursors. This is similar to the case of a
800  * cursor from a previous transaction, but it could also be that the
801  * cursor was auto-held in this transaction, so it wants to live on.
802  */
803  if (portal->autoHeld)
804  continue;
805 
806  /*
807  * If it was created in the current transaction, we can't do normal
808  * shutdown on a READY portal either; it might refer to objects
809  * created in the failed transaction. See comments in
810  * AtSubAbort_Portals.
811  */
812  if (portal->status == PORTAL_READY)
813  MarkPortalFailed(portal);
814 
815  /*
816  * Allow portalcmds.c to clean up the state it knows about, if we
817  * haven't already.
818  */
819  if (PointerIsValid(portal->cleanup))
820  {
821  portal->cleanup(portal);
822  portal->cleanup = NULL;
823  }
824 
825  /* drop cached plan reference, if any */
826  PortalReleaseCachedPlan(portal);
827 
828  /*
829  * Any resources belonging to the portal will be released in the
830  * upcoming transaction-wide cleanup; they will be gone before we run
831  * PortalDrop.
832  */
833  portal->resowner = NULL;
834 
835  /*
836  * Although we can't delete the portal data structure proper, we can
837  * release any memory in subsidiary contexts, such as executor state.
838  * The cleanup hook was the last thing that might have needed data
839  * there. But leave active portals alone.
840  */
841  if (portal->status != PORTAL_ACTIVE)
843  }
844 }
845 
846 /*
847  * Post-abort cleanup for portals.
848  *
849  * Delete all portals not held over from prior transactions. */
850 void
852 {
854  PortalHashEnt *hentry;
855 
856  hash_seq_init(&status, PortalHashTable);
857 
858  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
859  {
860  Portal portal = hentry->portal;
861 
862  /*
863  * Do not touch active portals --- this can only happen in the case of
864  * a multi-transaction command.
865  */
866  if (portal->status == PORTAL_ACTIVE)
867  continue;
868 
869  /*
870  * Do nothing to cursors held over from a previous transaction or
871  * auto-held ones.
872  */
873  if (portal->createSubid == InvalidSubTransactionId || portal->autoHeld)
874  {
875  Assert(portal->status != PORTAL_ACTIVE);
876  Assert(portal->resowner == NULL);
877  continue;
878  }
879 
880  /*
881  * If a portal is still pinned, forcibly unpin it. PortalDrop will not
882  * let us drop the portal otherwise. Whoever pinned the portal was
883  * interrupted by the abort too and won't try to use it anymore.
884  */
885  if (portal->portalPinned)
886  portal->portalPinned = false;
887 
888  /*
889  * We had better not call any user-defined code during cleanup, so if
890  * the cleanup hook hasn't been run yet, too bad; we'll just skip it.
891  */
892  if (PointerIsValid(portal->cleanup))
893  {
894  elog(WARNING, "skipping cleanup for portal \"%s\"", portal->name);
895  portal->cleanup = NULL;
896  }
897 
898  /* Zap it. */
899  PortalDrop(portal, false);
900  }
901 }
902 
903 /*
904  * Portal-related cleanup when we return to the main loop on error.
905  *
906  * This is different from the cleanup at transaction abort. Auto-held portals
907  * are cleaned up on error but not on transaction abort.
908  */
909 void
911 {
913  PortalHashEnt *hentry;
914 
915  hash_seq_init(&status, PortalHashTable);
916 
917  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
918  {
919  Portal portal = hentry->portal;
920 
921  if (portal->autoHeld)
922  {
923  portal->portalPinned = false;
924  PortalDrop(portal, false);
925  }
926  }
927 }
928 
929 /*
930  * Pre-subcommit processing for portals.
931  *
932  * Reassign portals created or used in the current subtransaction to the
933  * parent subtransaction.
934  */
935 void
937  SubTransactionId parentSubid,
938  ResourceOwner parentXactOwner)
939 {
941  PortalHashEnt *hentry;
942 
943  hash_seq_init(&status, PortalHashTable);
944 
945  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
946  {
947  Portal portal = hentry->portal;
948 
949  if (portal->createSubid == mySubid)
950  {
951  portal->createSubid = parentSubid;
952  if (portal->resowner)
953  ResourceOwnerNewParent(portal->resowner, parentXactOwner);
954  }
955  if (portal->activeSubid == mySubid)
956  portal->activeSubid = parentSubid;
957  }
958 }
959 
960 /*
961  * Subtransaction abort handling for portals.
962  *
963  * Deactivate portals created or used during the failed subtransaction.
964  * Note that per AtSubCommit_Portals, this will catch portals created/used
965  * in descendants of the subtransaction too.
966  *
967  * We don't destroy any portals here; that's done in AtSubCleanup_Portals.
968  */
969 void
971  SubTransactionId parentSubid,
972  ResourceOwner myXactOwner,
973  ResourceOwner parentXactOwner)
974 {
976  PortalHashEnt *hentry;
977 
978  hash_seq_init(&status, PortalHashTable);
979 
980  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
981  {
982  Portal portal = hentry->portal;
983 
984  /* Was it created in this subtransaction? */
985  if (portal->createSubid != mySubid)
986  {
987  /* No, but maybe it was used in this subtransaction? */
988  if (portal->activeSubid == mySubid)
989  {
990  /* Maintain activeSubid until the portal is removed */
991  portal->activeSubid = parentSubid;
992 
993  /*
994  * A MarkPortalActive() caller ran an upper-level portal in
995  * this subtransaction and left the portal ACTIVE. This can't
996  * happen, but force the portal into FAILED state for the same
997  * reasons discussed below.
998  *
999  * We assume we can get away without forcing upper-level READY
1000  * portals to fail, even if they were run and then suspended.
1001  * In theory a suspended upper-level portal could have
1002  * acquired some references to objects that are about to be
1003  * destroyed, but there should be sufficient defenses against
1004  * such cases: the portal's original query cannot contain such
1005  * references, and any references within, say, cached plans of
1006  * PL/pgSQL functions are not from active queries and should
1007  * be protected by revalidation logic.
1008  */
1009  if (portal->status == PORTAL_ACTIVE)
1010  MarkPortalFailed(portal);
1011 
1012  /*
1013  * Also, if we failed it during the current subtransaction
1014  * (either just above, or earlier), reattach its resource
1015  * owner to the current subtransaction's resource owner, so
1016  * that any resources it still holds will be released while
1017  * cleaning up this subtransaction. This prevents some corner
1018  * cases wherein we might get Asserts or worse while cleaning
1019  * up objects created during the current subtransaction
1020  * (because they're still referenced within this portal).
1021  */
1022  if (portal->status == PORTAL_FAILED && portal->resowner)
1023  {
1024  ResourceOwnerNewParent(portal->resowner, myXactOwner);
1025  portal->resowner = NULL;
1026  }
1027  }
1028  /* Done if it wasn't created in this subtransaction */
1029  continue;
1030  }
1031 
1032  /*
1033  * Force any live portals of my own subtransaction into FAILED state.
1034  * We have to do this because they might refer to objects created or
1035  * changed in the failed subtransaction, leading to crashes within
1036  * ExecutorEnd when portalcmds.c tries to close down the portal.
1037  * Currently, every MarkPortalActive() caller ensures it updates the
1038  * portal status again before relinquishing control, so ACTIVE can't
1039  * happen here. If it does happen, dispose the portal like existing
1040  * MarkPortalActive() callers would.
1041  */
1042  if (portal->status == PORTAL_READY ||
1043  portal->status == PORTAL_ACTIVE)
1044  MarkPortalFailed(portal);
1045 
1046  /*
1047  * Allow portalcmds.c to clean up the state it knows about, if we
1048  * haven't already.
1049  */
1050  if (PointerIsValid(portal->cleanup))
1051  {
1052  portal->cleanup(portal);
1053  portal->cleanup = NULL;
1054  }
1055 
1056  /* drop cached plan reference, if any */
1057  PortalReleaseCachedPlan(portal);
1058 
1059  /*
1060  * Any resources belonging to the portal will be released in the
1061  * upcoming transaction-wide cleanup; they will be gone before we run
1062  * PortalDrop.
1063  */
1064  portal->resowner = NULL;
1065 
1066  /*
1067  * Although we can't delete the portal data structure proper, we can
1068  * release any memory in subsidiary contexts, such as executor state.
1069  * The cleanup hook was the last thing that might have needed data
1070  * there.
1071  */
1073  }
1074 }
1075 
1076 /*
1077  * Post-subabort cleanup for portals.
1078  *
1079  * Drop all portals created in the failed subtransaction (but note that
1080  * we will not drop any that were reassigned to the parent above).
1081  */
1082 void
1084 {
1086  PortalHashEnt *hentry;
1087 
1088  hash_seq_init(&status, PortalHashTable);
1089 
1090  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
1091  {
1092  Portal portal = hentry->portal;
1093 
1094  if (portal->createSubid != mySubid)
1095  continue;
1096 
1097  /*
1098  * If a portal is still pinned, forcibly unpin it. PortalDrop will not
1099  * let us drop the portal otherwise. Whoever pinned the portal was
1100  * interrupted by the abort too and won't try to use it anymore.
1101  */
1102  if (portal->portalPinned)
1103  portal->portalPinned = false;
1104 
1105  /*
1106  * We had better not call any user-defined code during cleanup, so if
1107  * the cleanup hook hasn't been run yet, too bad; we'll just skip it.
1108  */
1109  if (PointerIsValid(portal->cleanup))
1110  {
1111  elog(WARNING, "skipping cleanup for portal \"%s\"", portal->name);
1112  portal->cleanup = NULL;
1113  }
1114 
1115  /* Zap it. */
1116  PortalDrop(portal, false);
1117  }
1118 }
1119 
1120 /* Find all available cursors */
1121 Datum
1123 {
1124  ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
1125  TupleDesc tupdesc;
1126  Tuplestorestate *tupstore;
1127  MemoryContext per_query_ctx;
1128  MemoryContext oldcontext;
1129  HASH_SEQ_STATUS hash_seq;
1130  PortalHashEnt *hentry;
1131 
1132  /* check to see if caller supports us returning a tuplestore */
1133  if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
1134  ereport(ERROR,
1135  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1136  errmsg("set-valued function called in context that cannot accept a set")));
1137  if (!(rsinfo->allowedModes & SFRM_Materialize))
1138  ereport(ERROR,
1139  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1140  errmsg("materialize mode required, but it is not allowed in this context")));
1141 
1142  /* need to build tuplestore in query context */
1143  per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
1144  oldcontext = MemoryContextSwitchTo(per_query_ctx);
1145 
1146  /*
1147  * build tupdesc for result tuples. This must match the definition of the
1148  * pg_cursors view in system_views.sql
1149  */
1150  tupdesc = CreateTemplateTupleDesc(6);
1151  TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
1152  TEXTOID, -1, 0);
1153  TupleDescInitEntry(tupdesc, (AttrNumber) 2, "statement",
1154  TEXTOID, -1, 0);
1155  TupleDescInitEntry(tupdesc, (AttrNumber) 3, "is_holdable",
1156  BOOLOID, -1, 0);
1157  TupleDescInitEntry(tupdesc, (AttrNumber) 4, "is_binary",
1158  BOOLOID, -1, 0);
1159  TupleDescInitEntry(tupdesc, (AttrNumber) 5, "is_scrollable",
1160  BOOLOID, -1, 0);
1161  TupleDescInitEntry(tupdesc, (AttrNumber) 6, "creation_time",
1162  TIMESTAMPTZOID, -1, 0);
1163 
1164  /*
1165  * We put all the tuples into a tuplestore in one scan of the hashtable.
1166  * This avoids any issue of the hashtable possibly changing between calls.
1167  */
1168  tupstore =
1170  false, work_mem);
1171 
1172  /* generate junk in short-term context */
1173  MemoryContextSwitchTo(oldcontext);
1174 
1175  hash_seq_init(&hash_seq, PortalHashTable);
1176  while ((hentry = hash_seq_search(&hash_seq)) != NULL)
1177  {
1178  Portal portal = hentry->portal;
1179  Datum values[6];
1180  bool nulls[6];
1181 
1182  /* report only "visible" entries */
1183  if (!portal->visible)
1184  continue;
1185 
1186  MemSet(nulls, 0, sizeof(nulls));
1187 
1188  values[0] = CStringGetTextDatum(portal->name);
1189  values[1] = CStringGetTextDatum(portal->sourceText);
1190  values[2] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_HOLD);
1191  values[3] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_BINARY);
1192  values[4] = BoolGetDatum(portal->cursorOptions & CURSOR_OPT_SCROLL);
1193  values[5] = TimestampTzGetDatum(portal->creation_time);
1194 
1195  tuplestore_putvalues(tupstore, tupdesc, values, nulls);
1196  }
1197 
1198  /* clean up and return the tuplestore */
1199  tuplestore_donestoring(tupstore);
1200 
1201  rsinfo->returnMode = SFRM_Materialize;
1202  rsinfo->setResult = tupstore;
1203  rsinfo->setDesc = tupdesc;
1204 
1205  return (Datum) 0;
1206 }
1207 
1208 bool
1210 {
1212  PortalHashEnt *hentry;
1213 
1214  hash_seq_init(&status, PortalHashTable);
1215 
1216  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
1217  {
1218  Portal portal = hentry->portal;
1219 
1220  if (portal->status == PORTAL_READY)
1221  return false;
1222  }
1223 
1224  return true;
1225 }
1226 
1227 /*
1228  * Hold all pinned portals.
1229  *
1230  * When initiating a COMMIT or ROLLBACK inside a procedure, this must be
1231  * called to protect internally-generated cursors from being dropped during
1232  * the transaction shutdown. Currently, SPI calls this automatically; PLs
1233  * that initiate COMMIT or ROLLBACK some other way are on the hook to do it
1234  * themselves. (Note that we couldn't do this in, say, AtAbort_Portals
1235  * because we need to run user-defined code while persisting a portal.
1236  * It's too late to do that once transaction abort has started.)
1237  *
1238  * We protect such portals by converting them to held cursors. We mark them
1239  * as "auto-held" so that exception exit knows to clean them up. (In normal,
1240  * non-exception code paths, the PL needs to clean such portals itself, since
1241  * transaction end won't do it anymore; but that should be normal practice
1242  * anyway.)
1243  */
1244 void
1246 {
1248  PortalHashEnt *hentry;
1249 
1250  hash_seq_init(&status, PortalHashTable);
1251 
1252  while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
1253  {
1254  Portal portal = hentry->portal;
1255 
1256  if (portal->portalPinned && !portal->autoHeld)
1257  {
1258  /*
1259  * Doing transaction control, especially abort, inside a cursor
1260  * loop that is not read-only, for example using UPDATE ...
1261  * RETURNING, has weird semantics issues. Also, this
1262  * implementation wouldn't work, because such portals cannot be
1263  * held. (The core grammar enforces that only SELECT statements
1264  * can drive a cursor, but for example PL/pgSQL does not restrict
1265  * it.)
1266  */
1267  if (portal->strategy != PORTAL_ONE_SELECT)
1268  ereport(ERROR,
1269  (errcode(ERRCODE_INVALID_TRANSACTION_TERMINATION),
1270  errmsg("cannot perform transaction commands inside a cursor loop that is not read-only")));
1271 
1272  /* Verify it's in a suitable state to be held */
1273  if (portal->status != PORTAL_READY)
1274  elog(ERROR, "pinned portal is not ready to be auto-held");
1275 
1276  HoldPortal(portal);
1277  portal->autoHeld = true;
1278  }
1279  }
1280 }
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Definition: tuplestore.c:750
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Definition: portalmem.c:379
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Portal CreatePortal(const char *name, bool allowDup, bool dupSilent)
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Portal portal
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static void static void status(const char *fmt,...) pg_attribute_printf(1
Definition: pg_regress.c:225
#define PortalHashTableLookup(NAME, PORTAL)
Definition: portalmem.c:56
#define PortalHashTableInsert(PORTAL, NAME)
Definition: portalmem.c:68
Definition: pg_list.h:50
#define PointerIsValid(pointer)
Definition: c.h:639
int16 AttrNumber
Definition: attnum.h:21
void hash_seq_term(HASH_SEQ_STATUS *status)
Definition: dynahash.c:1486
void AtSubCommit_Portals(SubTransactionId mySubid, SubTransactionId parentSubid, ResourceOwner parentXactOwner)
Definition: portalmem.c:936
const char * prepStmtName
Definition: portal.h:119
TimestampTz GetCurrentStatementStartTimestamp(void)
Definition: xact.c:807
ResourceOwner ResourceOwnerCreate(ResourceOwner parent, const char *name)
Definition: resowner.c:422