1 /*-------------------------------------------------------------------------
4 * Asynchronous notification: NOTIFY, LISTEN, UNLISTEN
6 * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
7 * Portions Copyright (c) 1994, Regents of the University of California
10 * $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.100 2003/09/15 23:33:39 tgl Exp $
12 *-------------------------------------------------------------------------
15 /*-------------------------------------------------------------------------
16 * New Async Notification Model:
17 * 1. Multiple backends on same machine. Multiple backends listening on
18 * one relation. (Note: "listening on a relation" is not really the
19 * right way to think about it, since the notify names need not have
20 * anything to do with the names of relations actually in the database.
21 * But this terminology is all over the code and docs, and I don't feel
22 * like trying to replace it.)
24 * 2. There is a tuple in relation "pg_listener" for each active LISTEN,
25 * ie, each relname/listenerPID pair. The "notification" field of the
26 * tuple is zero when no NOTIFY is pending for that listener, or the PID
27 * of the originating backend when a cross-backend NOTIFY is pending.
28 * (We skip writing to pg_listener when doing a self-NOTIFY, so the
29 * notification field should never be equal to the listenerPID field.)
31 * 3. The NOTIFY statement itself (routine Async_Notify) just adds the target
32 * relname to a list of outstanding NOTIFY requests. Actual processing
33 * happens if and only if we reach transaction commit. At that time (in
34 * routine AtCommit_Notify) we scan pg_listener for matching relnames.
35 * If the listenerPID in a matching tuple is ours, we just send a notify
36 * message to our own front end. If it is not ours, and "notification"
37 * is not already nonzero, we set notification to our own PID and send a
38 * SIGUSR2 signal to the receiving process (indicated by listenerPID).
39 * BTW: if the signal operation fails, we presume that the listener backend
40 * crashed without removing this tuple, and remove the tuple for it.
42 * 4. Upon receipt of a SIGUSR2 signal, the signal handler can call inbound-
43 * notify processing immediately if this backend is idle (ie, it is
44 * waiting for a frontend command and is not within a transaction block).
45 * Otherwise the handler may only set a flag, which will cause the
46 * processing to occur just before we next go idle.
48 * 5. Inbound-notify processing consists of scanning pg_listener for tuples
49 * matching our own listenerPID and having nonzero notification fields.
50 * For each such tuple, we send a message to our frontend and clear the
51 * notification field. BTW: this routine has to start/commit its own
52 * transaction, since by assumption it is only called from outside any
55 * Although we grab AccessExclusiveLock on pg_listener for any operation,
56 * the lock is never held very long, so it shouldn't cause too much of
57 * a performance problem.
59 * An application that listens on the same relname it notifies will get
60 * NOTIFY messages for its own NOTIFYs. These can be ignored, if not useful,
61 * by comparing be_pid in the NOTIFY message to the application's own backend's
62 * PID. (As of FE/BE protocol 2.0, the backend's PID is provided to the
63 * frontend during startup.) The above design guarantees that notifies from
64 * other backends will never be missed by ignoring self-notifies. Note,
65 * however, that we do *not* guarantee that a separate frontend message will
66 * be sent for every outside NOTIFY. Since there is only room for one
67 * originating PID in pg_listener, outside notifies occurring at about the
68 * same time may be collapsed into a single message bearing the PID of the
69 * first outside backend to perform the NOTIFY.
70 *-------------------------------------------------------------------------
78 #include <netinet/in.h>
80 #include "access/heapam.h"
81 #include "catalog/catname.h"
82 #include "catalog/pg_listener.h"
83 #include "commands/async.h"
84 #include "libpq/libpq.h"
85 #include "libpq/pqformat.h"
86 #include "miscadmin.h"
87 #include "storage/ipc.h"
88 #include "tcop/tcopprot.h"
89 #include "utils/fmgroids.h"
90 #include "utils/ps_status.h"
91 #include "utils/syscache.h"
94 /* stuff that we really ought not be touching directly :-( */
95 extern TransactionState CurrentTransactionState;
99 * State for outbound notifies consists of a list of all relnames NOTIFYed
100 * in the current transaction. We do not actually perform a NOTIFY until
101 * and unless the transaction commits. pendingNotifies is NIL if no
102 * NOTIFYs have been done in the current transaction. The List nodes and
103 * referenced strings are all palloc'd in TopTransactionContext.
105 static List *pendingNotifies = NIL;
108 * State for inbound notifies consists of two flags: one saying whether
109 * the signal handler is currently allowed to call ProcessIncomingNotify
110 * directly, and one saying whether the signal has occurred but the handler
111 * was not allowed to call ProcessIncomingNotify at the time.
113 * NB: the "volatile" on these declarations is critical! If your compiler
114 * does not grok "volatile", you'd be best advised to compile this file
115 * with all optimization turned off.
117 static volatile int notifyInterruptEnabled = 0;
118 static volatile int notifyInterruptOccurred = 0;
120 /* True if we've registered an on_shmem_exit cleanup */
121 static bool unlistenExitRegistered = false;
123 bool Trace_notify = false;
126 static void Async_UnlistenAll(void);
127 static void Async_UnlistenOnExit(void);
128 static void ProcessIncomingNotify(void);
129 static void NotifyMyFrontEnd(char *relname, int32 listenerPID);
130 static bool AsyncExistsPendingNotify(const char *relname);
131 static void ClearPendingNotifies(void);
135 *--------------------------------------------------------------
138 * This is executed by the SQL notify command.
140 * Adds the relation to the list of pending notifies.
141 * Actual notification happens during transaction commit.
142 * ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
147 *--------------------------------------------------------------
150 Async_Notify(char *relname)
153 elog(DEBUG1, "Async_Notify(%s)", relname);
155 /* no point in making duplicate entries in the list ... */
156 if (!AsyncExistsPendingNotify(relname))
159 * The name list needs to live until end of transaction, so store
160 * it in the top transaction context.
162 MemoryContext oldcontext;
164 oldcontext = MemoryContextSwitchTo(TopTransactionContext);
166 pendingNotifies = lcons(pstrdup(relname), pendingNotifies);
168 MemoryContextSwitchTo(oldcontext);
173 *--------------------------------------------------------------
176 * This is executed by the SQL listen command.
178 * Register a backend (identified by its Unix PID) as listening
179 * on the specified relation.
185 * pg_listener is updated.
187 *--------------------------------------------------------------
190 Async_Listen(char *relname, int pid)
195 Datum values[Natts_pg_listener];
196 char nulls[Natts_pg_listener];
198 bool alreadyListener = false;
201 elog(DEBUG1, "Async_Listen(%s,%d)", relname, pid);
203 lRel = heap_openr(ListenerRelationName, AccessExclusiveLock);
205 /* Detect whether we are already listening on this relname */
206 scan = heap_beginscan(lRel, SnapshotNow, 0, (ScanKey) NULL);
207 while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
209 Form_pg_listener listener = (Form_pg_listener) GETSTRUCT(tuple);
211 if (listener->listenerpid == pid &&
212 strncmp(NameStr(listener->relname), relname, NAMEDATALEN) == 0)
214 alreadyListener = true;
215 /* No need to scan the rest of the table */
223 heap_close(lRel, AccessExclusiveLock);
228 * OK to insert a new tuple
231 for (i = 0; i < Natts_pg_listener; i++)
234 values[i] = PointerGetDatum(NULL);
238 values[i++] = (Datum) relname;
239 values[i++] = (Datum) pid;
240 values[i++] = (Datum) 0; /* no notifies pending */
242 tuple = heap_formtuple(RelationGetDescr(lRel), values, nulls);
243 simple_heap_insert(lRel, tuple);
245 #ifdef NOT_USED /* currently there are no indexes */
246 CatalogUpdateIndexes(lRel, tuple);
249 heap_freetuple(tuple);
251 heap_close(lRel, AccessExclusiveLock);
254 * now that we are listening, make sure we will unlisten before dying.
256 if (!unlistenExitRegistered)
258 on_shmem_exit(Async_UnlistenOnExit, 0);
259 unlistenExitRegistered = true;
264 *--------------------------------------------------------------
267 * This is executed by the SQL unlisten command.
269 * Remove the backend from the list of listening backends
270 * for the specified relation.
276 * pg_listener is updated.
278 *--------------------------------------------------------------
281 Async_Unlisten(char *relname, int pid)
287 /* Handle specially the `unlisten "*"' command */
288 if ((!relname) || (*relname == '\0') || (strcmp(relname, "*") == 0))
295 elog(DEBUG1, "Async_Unlisten(%s,%d)", relname, pid);
297 lRel = heap_openr(ListenerRelationName, AccessExclusiveLock);
299 scan = heap_beginscan(lRel, SnapshotNow, 0, (ScanKey) NULL);
300 while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
302 Form_pg_listener listener = (Form_pg_listener) GETSTRUCT(tuple);
304 if (listener->listenerpid == pid &&
305 strncmp(NameStr(listener->relname), relname, NAMEDATALEN) == 0)
307 /* Found the matching tuple, delete it */
308 simple_heap_delete(lRel, &tuple->t_self);
311 * We assume there can be only one match, so no need to scan
312 * the rest of the table
319 heap_close(lRel, AccessExclusiveLock);
322 * We do not complain about unlistening something not being listened;
328 *--------------------------------------------------------------
331 * Unlisten all relations for this backend.
333 * This is invoked by UNLISTEN "*" command, and also at backend exit.
339 * pg_listener is updated.
341 *--------------------------------------------------------------
344 Async_UnlistenAll(void)
353 elog(DEBUG1, "Async_UnlistenAll");
355 lRel = heap_openr(ListenerRelationName, AccessExclusiveLock);
356 tdesc = RelationGetDescr(lRel);
358 /* Find and delete all entries with my listenerPID */
359 ScanKeyEntryInitialize(&key[0], 0,
360 Anum_pg_listener_pid,
362 Int32GetDatum(MyProcPid));
363 scan = heap_beginscan(lRel, SnapshotNow, 1, key);
365 while ((lTuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
366 simple_heap_delete(lRel, &lTuple->t_self);
369 heap_close(lRel, AccessExclusiveLock);
373 *--------------------------------------------------------------
374 * Async_UnlistenOnExit
376 * Clean up the pg_listener table at backend exit.
378 * This is executed if we have done any LISTENs in this backend.
379 * It might not be necessary anymore, if the user UNLISTENed everything,
380 * but we don't try to detect that case.
386 * pg_listener is updated if necessary.
388 *--------------------------------------------------------------
391 Async_UnlistenOnExit(void)
394 * We need to start/commit a transaction for the unlisten, but if
395 * there is already an active transaction we had better abort that one
396 * first. Otherwise we'd end up committing changes that probably
397 * ought to be discarded.
399 AbortOutOfAnyTransaction();
400 /* Now we can do the unlisten */
401 StartTransactionCommand();
403 CommitTransactionCommand();
407 *--------------------------------------------------------------
410 * This is called at transaction commit.
412 * If there are outbound notify requests in the pendingNotifies list,
413 * scan pg_listener for matching tuples, and either signal the other
414 * backend or send a message to our own frontend.
416 * NOTE: we are still inside the current transaction, therefore can
417 * piggyback on its committing of changes.
423 * Tuples in pg_listener that have matching relnames and other peoples'
424 * listenerPIDs are updated with a nonzero notification field.
426 *--------------------------------------------------------------
429 AtCommit_Notify(void)
436 Datum value[Natts_pg_listener];
437 char repl[Natts_pg_listener],
438 nulls[Natts_pg_listener];
440 if (pendingNotifies == NIL)
441 return; /* no NOTIFY statements in this
445 * NOTIFY is disabled if not normal processing mode. This test used to
446 * be in xact.c, but it seems cleaner to do it here.
448 if (!IsNormalProcessingMode())
450 ClearPendingNotifies();
455 elog(DEBUG1, "AtCommit_Notify");
457 /* preset data to update notify column to MyProcPid */
458 nulls[0] = nulls[1] = nulls[2] = ' ';
459 repl[0] = repl[1] = repl[2] = ' ';
460 repl[Anum_pg_listener_notify - 1] = 'r';
461 value[0] = value[1] = value[2] = (Datum) 0;
462 value[Anum_pg_listener_notify - 1] = Int32GetDatum(MyProcPid);
464 lRel = heap_openr(ListenerRelationName, AccessExclusiveLock);
465 tdesc = RelationGetDescr(lRel);
466 scan = heap_beginscan(lRel, SnapshotNow, 0, (ScanKey) NULL);
468 while ((lTuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
470 Form_pg_listener listener = (Form_pg_listener) GETSTRUCT(lTuple);
471 char *relname = NameStr(listener->relname);
472 int32 listenerPID = listener->listenerpid;
474 if (!AsyncExistsPendingNotify(relname))
477 if (listenerPID == MyProcPid)
480 * Self-notify: no need to bother with table update. Indeed,
481 * we *must not* clear the notification field in this path, or
482 * we could lose an outside notify, which'd be bad for
483 * applications that ignore self-notify messages.
487 elog(DEBUG1, "AtCommit_Notify: notifying self");
489 NotifyMyFrontEnd(relname, listenerPID);
494 elog(DEBUG1, "AtCommit_Notify: notifying pid %d",
498 * If someone has already notified this listener, we don't
499 * bother modifying the table, but we do still send a SIGUSR2
500 * signal, just in case that backend missed the earlier signal
501 * for some reason. It's OK to send the signal first, because
502 * the other guy can't read pg_listener until we unlock it.
504 if (kill(listenerPID, SIGUSR2) < 0)
507 * Get rid of pg_listener entry if it refers to a PID that
508 * no longer exists. Presumably, that backend crashed
509 * without deleting its pg_listener entries. This code
510 * used to only delete the entry if errno==ESRCH, but as
511 * far as I can see we should just do it for any failure
512 * (certainly at least for EPERM too...)
514 simple_heap_delete(lRel, &lTuple->t_self);
516 else if (listener->notification == 0)
518 ItemPointerData ctid;
521 rTuple = heap_modifytuple(lTuple, lRel,
524 * We cannot use simple_heap_update here because the tuple
525 * could have been modified by an uncommitted transaction;
526 * specifically, since UNLISTEN releases exclusive lock on
527 * the table before commit, the other guy could already have
528 * tried to unlisten. There are no other cases where we
529 * should be able to see an uncommitted update or delete.
530 * Therefore, our response to a HeapTupleBeingUpdated result
531 * is just to ignore it. We do *not* wait for the other
532 * guy to commit --- that would risk deadlock, and we don't
533 * want to block while holding the table lock anyway for
534 * performance reasons. We also ignore HeapTupleUpdated,
535 * which could occur if the other guy commits between our
536 * heap_getnext and heap_update calls.
538 result = heap_update(lRel, &lTuple->t_self, rTuple,
540 GetCurrentCommandId(),
541 false /* no wait for commit */);
544 case HeapTupleSelfUpdated:
545 /* Tuple was already updated in current command? */
546 elog(ERROR, "tuple already updated by self");
549 case HeapTupleMayBeUpdated:
550 /* done successfully */
552 #ifdef NOT_USED /* currently there are no indexes */
553 CatalogUpdateIndexes(lRel, rTuple);
557 case HeapTupleBeingUpdated:
558 /* ignore uncommitted tuples */
561 case HeapTupleUpdated:
562 /* ignore just-committed tuples */
566 elog(ERROR, "unrecognized heap_update status: %u",
577 * We do NOT release the lock on pg_listener here; we need to hold it
578 * until end of transaction (which is about to happen, anyway) to
579 * ensure that notified backends see our tuple updates when they look.
580 * Else they might disregard the signal, which would make the
581 * application programmer very unhappy.
583 heap_close(lRel, NoLock);
585 ClearPendingNotifies();
588 elog(DEBUG1, "AtCommit_Notify: done");
592 *--------------------------------------------------------------
595 * This is called at transaction abort.
597 * Gets rid of pending outbound notifies that we would have executed
598 * if the transaction got committed.
603 *--------------------------------------------------------------
608 ClearPendingNotifies();
612 *--------------------------------------------------------------
613 * Async_NotifyHandler
615 * This is the signal handler for SIGUSR2.
617 * If we are idle (notifyInterruptEnabled is set), we can safely invoke
618 * ProcessIncomingNotify directly. Otherwise, just set a flag
626 *--------------------------------------------------------------
629 Async_NotifyHandler(SIGNAL_ARGS)
631 int save_errno = errno;
634 * Note: this is a SIGNAL HANDLER. You must be very wary what you do
635 * here. Some helpful soul had this routine sprinkled with TPRINTFs,
636 * which would likely lead to corruption of stdio buffers if they were
640 /* Don't joggle the elbow of proc_exit */
641 if (proc_exit_inprogress)
644 if (notifyInterruptEnabled)
646 bool save_ImmediateInterruptOK = ImmediateInterruptOK;
649 * We may be called while ImmediateInterruptOK is true; turn it
650 * off while messing with the NOTIFY state. (We would have to
651 * save and restore it anyway, because PGSemaphore operations
652 * inside ProcessIncomingNotify() might reset it.)
654 ImmediateInterruptOK = false;
657 * I'm not sure whether some flavors of Unix might allow another
658 * SIGUSR2 occurrence to recursively interrupt this routine. To
659 * cope with the possibility, we do the same sort of dance that
660 * EnableNotifyInterrupt must do --- see that routine for
663 notifyInterruptEnabled = 0; /* disable any recursive signal */
664 notifyInterruptOccurred = 1; /* do at least one iteration */
667 notifyInterruptEnabled = 1;
668 if (!notifyInterruptOccurred)
670 notifyInterruptEnabled = 0;
671 if (notifyInterruptOccurred)
673 /* Here, it is finally safe to do stuff. */
675 elog(DEBUG1, "Async_NotifyHandler: perform async notify");
677 ProcessIncomingNotify();
680 elog(DEBUG1, "Async_NotifyHandler: done");
685 * Restore ImmediateInterruptOK, and check for interrupts if
688 ImmediateInterruptOK = save_ImmediateInterruptOK;
689 if (save_ImmediateInterruptOK)
690 CHECK_FOR_INTERRUPTS();
695 * In this path it is NOT SAFE to do much of anything, except
698 notifyInterruptOccurred = 1;
705 * --------------------------------------------------------------
706 * EnableNotifyInterrupt
708 * This is called by the PostgresMain main loop just before waiting
709 * for a frontend command. If we are truly idle (ie, *not* inside
710 * a transaction block), then process any pending inbound notifies,
711 * and enable the signal handler to process future notifies directly.
713 * NOTE: the signal handler starts out disabled, and stays so until
714 * PostgresMain calls this the first time.
715 * --------------------------------------------------------------
718 EnableNotifyInterrupt(void)
720 if (CurrentTransactionState->blockState != TRANS_DEFAULT)
721 return; /* not really idle */
724 * This code is tricky because we are communicating with a signal
725 * handler that could interrupt us at any point. If we just checked
726 * notifyInterruptOccurred and then set notifyInterruptEnabled, we
727 * could fail to respond promptly to a signal that happens in between
728 * those two steps. (A very small time window, perhaps, but Murphy's
729 * Law says you can hit it...) Instead, we first set the enable flag,
730 * then test the occurred flag. If we see an unserviced interrupt has
731 * occurred, we re-clear the enable flag before going off to do the
732 * service work. (That prevents re-entrant invocation of
733 * ProcessIncomingNotify() if another interrupt occurs.) If an
734 * interrupt comes in between the setting and clearing of
735 * notifyInterruptEnabled, then it will have done the service work and
736 * left notifyInterruptOccurred zero, so we have to check again after
737 * clearing enable. The whole thing has to be in a loop in case
738 * another interrupt occurs while we're servicing the first. Once we
739 * get out of the loop, enable is set and we know there is no
740 * unserviced interrupt.
742 * NB: an overenthusiastic optimizing compiler could easily break this
743 * code. Hopefully, they all understand what "volatile" means these
748 notifyInterruptEnabled = 1;
749 if (!notifyInterruptOccurred)
751 notifyInterruptEnabled = 0;
752 if (notifyInterruptOccurred)
755 elog(DEBUG1, "EnableNotifyInterrupt: perform async notify");
757 ProcessIncomingNotify();
760 elog(DEBUG1, "EnableNotifyInterrupt: done");
766 * --------------------------------------------------------------
767 * DisableNotifyInterrupt
769 * This is called by the PostgresMain main loop just after receiving
770 * a frontend command. Signal handler execution of inbound notifies
771 * is disabled until the next EnableNotifyInterrupt call.
772 * --------------------------------------------------------------
775 DisableNotifyInterrupt(void)
777 notifyInterruptEnabled = 0;
781 * --------------------------------------------------------------
782 * ProcessIncomingNotify
784 * Deal with arriving NOTIFYs from other backends.
785 * This is called either directly from the SIGUSR2 signal handler,
786 * or the next time control reaches the outer idle loop.
787 * Scan pg_listener for arriving notifies, report them to my front end,
788 * and clear the notification field in pg_listener until next time.
790 * NOTE: since we are outside any transaction, we must create our own.
795 * --------------------------------------------------------------
798 ProcessIncomingNotify(void)
806 Datum value[Natts_pg_listener];
807 char repl[Natts_pg_listener],
808 nulls[Natts_pg_listener];
811 elog(DEBUG1, "ProcessIncomingNotify");
813 set_ps_display("async_notify");
815 notifyInterruptOccurred = 0;
817 StartTransactionCommand();
819 lRel = heap_openr(ListenerRelationName, AccessExclusiveLock);
820 tdesc = RelationGetDescr(lRel);
822 /* Scan only entries with my listenerPID */
823 ScanKeyEntryInitialize(&key[0], 0,
824 Anum_pg_listener_pid,
826 Int32GetDatum(MyProcPid));
827 scan = heap_beginscan(lRel, SnapshotNow, 1, key);
829 /* Prepare data for rewriting 0 into notification field */
830 nulls[0] = nulls[1] = nulls[2] = ' ';
831 repl[0] = repl[1] = repl[2] = ' ';
832 repl[Anum_pg_listener_notify - 1] = 'r';
833 value[0] = value[1] = value[2] = (Datum) 0;
834 value[Anum_pg_listener_notify - 1] = Int32GetDatum(0);
836 while ((lTuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
838 Form_pg_listener listener = (Form_pg_listener) GETSTRUCT(lTuple);
839 char *relname = NameStr(listener->relname);
840 int32 sourcePID = listener->notification;
844 /* Notify the frontend */
847 elog(DEBUG1, "ProcessIncomingNotify: received %s from %d",
848 relname, (int) sourcePID);
850 NotifyMyFrontEnd(relname, sourcePID);
852 * Rewrite the tuple with 0 in notification column.
854 * simple_heap_update is safe here because no one else would
855 * have tried to UNLISTEN us, so there can be no uncommitted
858 rTuple = heap_modifytuple(lTuple, lRel, value, nulls, repl);
859 simple_heap_update(lRel, &lTuple->t_self, rTuple);
861 #ifdef NOT_USED /* currently there are no indexes */
862 CatalogUpdateIndexes(lRel, rTuple);
869 * We do NOT release the lock on pg_listener here; we need to hold it
870 * until end of transaction (which is about to happen, anyway) to
871 * ensure that other backends see our tuple updates when they look.
872 * Otherwise, a transaction started after this one might mistakenly
873 * think it doesn't need to send this backend a new NOTIFY.
875 heap_close(lRel, NoLock);
877 CommitTransactionCommand();
880 * Must flush the notify messages to ensure frontend gets them
885 set_ps_display("idle");
888 elog(DEBUG1, "ProcessIncomingNotify: done");
892 * Send NOTIFY message to my front end.
895 NotifyMyFrontEnd(char *relname, int32 listenerPID)
897 if (whereToSendOutput == Remote)
901 pq_beginmessage(&buf, 'A');
902 pq_sendint(&buf, listenerPID, sizeof(int32));
903 pq_sendstring(&buf, relname);
904 if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
906 /* XXX Add parameter string here later */
907 pq_sendstring(&buf, "");
912 * NOTE: we do not do pq_flush() here. For a self-notify, it will
913 * happen at the end of the transaction, and for incoming notifies
914 * ProcessIncomingNotify will do it after finding all the
919 elog(INFO, "NOTIFY for %s", relname);
922 /* Does pendingNotifies include the given relname? */
924 AsyncExistsPendingNotify(const char *relname)
928 foreach(p, pendingNotifies)
930 /* Use NAMEDATALEN for relname comparison. DZ - 26-08-1996 */
931 if (strncmp((const char *) lfirst(p), relname, NAMEDATALEN) == 0)
938 /* Clear the pendingNotifies list. */
940 ClearPendingNotifies(void)
943 * We used to have to explicitly deallocate the list members and
944 * nodes, because they were malloc'd. Now, since we know they are
945 * palloc'd in TopTransactionContext, we need not do that --- they'll
946 * go away automatically at transaction exit. We need only reset the
949 pendingNotifies = NIL;