Header And Logo
|
#include "fmgr.h"
Go to the source code of this file.
Defines | |
| #define | NUM_ASYNC_BUFFERS 8 |
Functions | |
| Size | AsyncShmemSize (void) |
| void | AsyncShmemInit (void) |
| void | Async_Notify (const char *channel, const char *payload) |
| void | Async_Listen (const char *channel) |
| void | Async_Unlisten (const char *channel) |
| void | Async_UnlistenAll (void) |
| Datum | pg_listening_channels (PG_FUNCTION_ARGS) |
| Datum | pg_notify (PG_FUNCTION_ARGS) |
| void | PreCommit_Notify (void) |
| void | AtCommit_Notify (void) |
| void | AtAbort_Notify (void) |
| void | AtSubStart_Notify (void) |
| void | AtSubCommit_Notify (void) |
| void | AtSubAbort_Notify (void) |
| void | AtPrepare_Notify (void) |
| void | ProcessCompletedNotifies (void) |
| void | HandleNotifyInterrupt (void) |
| void | EnableNotifyInterrupt (void) |
| bool | DisableNotifyInterrupt (void) |
Variables | |
| bool | Trace_notify |
| #define NUM_ASYNC_BUFFERS 8 |
Definition at line 21 of file async.h.
Referenced by AsyncShmemInit(), and AsyncShmemSize().
| void Async_Listen | ( | const char * | channel | ) |
Definition at line 625 of file async.c.
References DEBUG1, elog, LISTEN_LISTEN, MyProcPid, queue_listen(), and Trace_notify.
Referenced by standard_ProcessUtility().
{
if (Trace_notify)
elog(DEBUG1, "Async_Listen(%s,%d)", channel, MyProcPid);
queue_listen(LISTEN_LISTEN, channel);
}
| void Async_Notify | ( | const char * | channel, | |
| const char * | payload | |||
| ) |
Definition at line 534 of file async.c.
References AsyncExistsPendingNotify(), Notification::channel, CurTransactionContext, DEBUG1, elog, ereport, errcode(), errmsg(), ERROR, lappend(), MemoryContextSwitchTo(), NAMEDATALEN, NOTIFY_PAYLOAD_MAX_LENGTH, palloc(), Notification::payload, pstrdup(), and Trace_notify.
Referenced by pg_notify(), standard_ProcessUtility(), and triggered_change_notification().
{
Notification *n;
MemoryContext oldcontext;
if (Trace_notify)
elog(DEBUG1, "Async_Notify(%s)", channel);
/* a channel name must be specified */
if (!channel || !strlen(channel))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("channel name cannot be empty")));
if (strlen(channel) >= NAMEDATALEN)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("channel name too long")));
if (payload)
{
if (strlen(payload) >= NOTIFY_PAYLOAD_MAX_LENGTH)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("payload string too long")));
}
/* no point in making duplicate entries in the list ... */
if (AsyncExistsPendingNotify(channel, payload))
return;
/*
* The notification list needs to live until end of transaction, so store
* it in the transaction context.
*/
oldcontext = MemoryContextSwitchTo(CurTransactionContext);
n = (Notification *) palloc(sizeof(Notification));
n->channel = pstrdup(channel);
if (payload)
n->payload = pstrdup(payload);
else
n->payload = "";
/*
* We want to preserve the order so we need to append every notification.
* See comments at AsyncExistsPendingNotify().
*/
pendingNotifies = lappend(pendingNotifies, n);
MemoryContextSwitchTo(oldcontext);
}
| void Async_Unlisten | ( | const char * | channel | ) |
Definition at line 639 of file async.c.
References DEBUG1, elog, LISTEN_UNLISTEN, MyProcPid, NIL, queue_listen(), Trace_notify, and unlistenExitRegistered.
Referenced by standard_ProcessUtility().
{
if (Trace_notify)
elog(DEBUG1, "Async_Unlisten(%s,%d)", channel, MyProcPid);
/* If we couldn't possibly be listening, no need to queue anything */
if (pendingActions == NIL && !unlistenExitRegistered)
return;
queue_listen(LISTEN_UNLISTEN, channel);
}
| void Async_UnlistenAll | ( | void | ) |
Definition at line 657 of file async.c.
References DEBUG1, elog, LISTEN_UNLISTEN_ALL, MyProcPid, NIL, queue_listen(), Trace_notify, and unlistenExitRegistered.
Referenced by DiscardAll(), and standard_ProcessUtility().
{
if (Trace_notify)
elog(DEBUG1, "Async_UnlistenAll(%d)", MyProcPid);
/* If we couldn't possibly be listening, no need to queue anything */
if (pendingActions == NIL && !unlistenExitRegistered)
return;
queue_listen(LISTEN_UNLISTEN_ALL, "");
}
| void AsyncShmemInit | ( | void | ) |
Definition at line 434 of file async.c.
References add_size(), AsyncCtl, AsyncCtlLock, i, AsyncQueueControl::lastQueueFillWarn, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), MaxBackends, mul_size(), NULL, NUM_ASYNC_BUFFERS, QUEUE_BACKEND_PID, QUEUE_BACKEND_POS, QUEUE_HEAD, QUEUE_POS_PAGE, QUEUE_TAIL, SET_QUEUE_POS, ShmemInitStruct(), SimpleLruInit(), SimpleLruWritePage(), SimpleLruZeroPage(), SlruScanDirCbDeleteAll(), and SlruScanDirectory().
Referenced by CreateSharedMemoryAndSemaphores().
{
bool found;
int slotno;
Size size;
/*
* Create or attach to the AsyncQueueControl structure.
*
* The used entries in the backend[] array run from 1 to MaxBackends.
* sizeof(AsyncQueueControl) already includes space for the unused zero'th
* entry, but we need to add on space for the used entries.
*/
size = mul_size(MaxBackends, sizeof(QueueBackendStatus));
size = add_size(size, sizeof(AsyncQueueControl));
asyncQueueControl = (AsyncQueueControl *)
ShmemInitStruct("Async Queue Control", size, &found);
if (!found)
{
/* First time through, so initialize it */
int i;
SET_QUEUE_POS(QUEUE_HEAD, 0, 0);
SET_QUEUE_POS(QUEUE_TAIL, 0, 0);
asyncQueueControl->lastQueueFillWarn = 0;
/* zero'th entry won't be used, but let's initialize it anyway */
for (i = 0; i <= MaxBackends; i++)
{
QUEUE_BACKEND_PID(i) = InvalidPid;
SET_QUEUE_POS(QUEUE_BACKEND_POS(i), 0, 0);
}
}
/*
* Set up SLRU management of the pg_notify data.
*/
AsyncCtl->PagePrecedes = asyncQueuePagePrecedes;
SimpleLruInit(AsyncCtl, "Async Ctl", NUM_ASYNC_BUFFERS, 0,
AsyncCtlLock, "pg_notify");
/* Override default assumption that writes should be fsync'd */
AsyncCtl->do_fsync = false;
if (!found)
{
/*
* During start or reboot, clean out the pg_notify directory.
*/
(void) SlruScanDirectory(AsyncCtl, SlruScanDirCbDeleteAll, NULL);
/* Now initialize page zero to empty */
LWLockAcquire(AsyncCtlLock, LW_EXCLUSIVE);
slotno = SimpleLruZeroPage(AsyncCtl, QUEUE_POS_PAGE(QUEUE_HEAD));
/* This write is just to verify that pg_notify/ is writable */
SimpleLruWritePage(AsyncCtl, slotno);
LWLockRelease(AsyncCtlLock);
}
}
| Size AsyncShmemSize | ( | void | ) |
Definition at line 417 of file async.c.
References add_size(), MaxBackends, mul_size(), NUM_ASYNC_BUFFERS, and SimpleLruShmemSize().
Referenced by CreateSharedMemoryAndSemaphores().
{
Size size;
/* This had better match AsyncShmemInit */
size = mul_size(MaxBackends, sizeof(QueueBackendStatus));
size = add_size(size, sizeof(AsyncQueueControl));
size = add_size(size, SimpleLruShmemSize(NUM_ASYNC_BUFFERS, 0));
return size;
}
| void AtAbort_Notify | ( | void | ) |
Definition at line 1517 of file async.c.
References amRegisteredListener, asyncQueueUnregister(), ClearPendingActionsAndNotifies(), and NIL.
Referenced by AbortTransaction().
{
/*
* If we LISTEN but then roll back the transaction after PreCommit_Notify,
* we have registered as a listener but have not made any entry in
* listenChannels. In that case, deregister again.
*/
if (amRegisteredListener && listenChannels == NIL)
asyncQueueUnregister();
/* And clean up */
ClearPendingActionsAndNotifies();
}
| void AtCommit_Notify | ( | void | ) |
Definition at line 861 of file async.c.
References ListenAction::action, amRegisteredListener, asyncQueueUnregister(), ListenAction::channel, ClearPendingActionsAndNotifies(), DEBUG1, elog, Exec_ListenCommit(), Exec_UnlistenAllCommit(), Exec_UnlistenCommit(), lfirst, LISTEN_LISTEN, LISTEN_UNLISTEN, LISTEN_UNLISTEN_ALL, NIL, and Trace_notify.
Referenced by CommitTransaction().
{
ListCell *p;
/*
* Allow transactions that have not executed LISTEN/UNLISTEN/NOTIFY to
* return as soon as possible
*/
if (!pendingActions && !pendingNotifies)
return;
if (Trace_notify)
elog(DEBUG1, "AtCommit_Notify");
/* Perform any pending listen/unlisten actions */
foreach(p, pendingActions)
{
ListenAction *actrec = (ListenAction *) lfirst(p);
switch (actrec->action)
{
case LISTEN_LISTEN:
Exec_ListenCommit(actrec->channel);
break;
case LISTEN_UNLISTEN:
Exec_UnlistenCommit(actrec->channel);
break;
case LISTEN_UNLISTEN_ALL:
Exec_UnlistenAllCommit();
break;
}
}
/* If no longer listening to anything, get out of listener array */
if (amRegisteredListener && listenChannels == NIL)
asyncQueueUnregister();
/* And clean up */
ClearPendingActionsAndNotifies();
}
| void AtPrepare_Notify | ( | void | ) |
Definition at line 737 of file async.c.
References ereport, errcode(), errmsg(), and ERROR.
Referenced by PrepareTransaction().
{
/* It's not allowed to have any pending LISTEN/UNLISTEN/NOTIFY actions */
if (pendingActions || pendingNotifies)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot PREPARE a transaction that has executed LISTEN, UNLISTEN, or NOTIFY")));
}
| void AtSubAbort_Notify | ( | void | ) |
Definition at line 1599 of file async.c.
References GetCurrentTransactionNestLevel(), linitial, list_delete_first(), and list_length().
Referenced by AbortSubTransaction().
{
int my_level = GetCurrentTransactionNestLevel();
/*
* All we have to do is pop the stack --- the actions/notifies made in
* this subxact are no longer interesting, and the space will be freed
* when CurTransactionContext is recycled.
*
* This routine could be called more than once at a given nesting level if
* there is trouble during subxact abort. Avoid dumping core by using
* GetCurrentTransactionNestLevel as the indicator of how far we need to
* prune the list.
*/
while (list_length(upperPendingActions) > my_level - 2)
{
pendingActions = (List *) linitial(upperPendingActions);
upperPendingActions = list_delete_first(upperPendingActions);
}
while (list_length(upperPendingNotifies) > my_level - 2)
{
pendingNotifies = (List *) linitial(upperPendingNotifies);
upperPendingNotifies = list_delete_first(upperPendingNotifies);
}
}
| void AtSubCommit_Notify | ( | void | ) |
Definition at line 1567 of file async.c.
References Assert, GetCurrentTransactionNestLevel(), linitial, list_concat(), list_delete_first(), and list_length().
Referenced by CommitSubTransaction().
{
List *parentPendingActions;
List *parentPendingNotifies;
parentPendingActions = (List *) linitial(upperPendingActions);
upperPendingActions = list_delete_first(upperPendingActions);
Assert(list_length(upperPendingActions) ==
GetCurrentTransactionNestLevel() - 2);
/*
* Mustn't try to eliminate duplicates here --- see queue_listen()
*/
pendingActions = list_concat(parentPendingActions, pendingActions);
parentPendingNotifies = (List *) linitial(upperPendingNotifies);
upperPendingNotifies = list_delete_first(upperPendingNotifies);
Assert(list_length(upperPendingNotifies) ==
GetCurrentTransactionNestLevel() - 2);
/*
* We could try to eliminate duplicates here, but it seems not worthwhile.
*/
pendingNotifies = list_concat(parentPendingNotifies, pendingNotifies);
}
| void AtSubStart_Notify | ( | void | ) |
Definition at line 1537 of file async.c.
References Assert, GetCurrentTransactionNestLevel(), lcons(), list_length(), MemoryContextSwitchTo(), and TopTransactionContext.
Referenced by StartSubTransaction().
{
MemoryContext old_cxt;
/* Keep the list-of-lists in TopTransactionContext for simplicity */
old_cxt = MemoryContextSwitchTo(TopTransactionContext);
upperPendingActions = lcons(pendingActions, upperPendingActions);
Assert(list_length(upperPendingActions) ==
GetCurrentTransactionNestLevel() - 1);
pendingActions = NIL;
upperPendingNotifies = lcons(pendingNotifies, upperPendingNotifies);
Assert(list_length(upperPendingNotifies) ==
GetCurrentTransactionNestLevel() - 1);
pendingNotifies = NIL;
MemoryContextSwitchTo(old_cxt);
}
| bool DisableNotifyInterrupt | ( | void | ) |
Definition at line 1773 of file async.c.
References notifyInterruptEnabled.
Referenced by client_read_ended(), die(), PostgresMain(), ProcessCatchupEvent(), ProcessInterrupts(), RecoveryConflictInterrupt(), and StatementCancelHandler().
{
bool result = (notifyInterruptEnabled != 0);
notifyInterruptEnabled = 0;
return result;
}
| void EnableNotifyInterrupt | ( | void | ) |
Definition at line 1716 of file async.c.
References DEBUG1, elog, IsTransactionOrTransactionBlock(), notifyInterruptEnabled, notifyInterruptOccurred, ProcessIncomingNotify(), and Trace_notify.
Referenced by prepare_for_client_read(), and ProcessCatchupEvent().
{
if (IsTransactionOrTransactionBlock())
return; /* not really idle */
/*
* This code is tricky because we are communicating with a signal handler
* that could interrupt us at any point. If we just checked
* notifyInterruptOccurred and then set notifyInterruptEnabled, we could
* fail to respond promptly to a signal that happens in between those two
* steps. (A very small time window, perhaps, but Murphy's Law says you
* can hit it...) Instead, we first set the enable flag, then test the
* occurred flag. If we see an unserviced interrupt has occurred, we
* re-clear the enable flag before going off to do the service work. (That
* prevents re-entrant invocation of ProcessIncomingNotify() if another
* interrupt occurs.) If an interrupt comes in between the setting and
* clearing of notifyInterruptEnabled, then it will have done the service
* work and left notifyInterruptOccurred zero, so we have to check again
* after clearing enable. The whole thing has to be in a loop in case
* another interrupt occurs while we're servicing the first. Once we get
* out of the loop, enable is set and we know there is no unserviced
* interrupt.
*
* NB: an overenthusiastic optimizing compiler could easily break this
* code. Hopefully, they all understand what "volatile" means these days.
*/
for (;;)
{
notifyInterruptEnabled = 1;
if (!notifyInterruptOccurred)
break;
notifyInterruptEnabled = 0;
if (notifyInterruptOccurred)
{
if (Trace_notify)
elog(DEBUG1, "EnableNotifyInterrupt: perform async notify");
ProcessIncomingNotify();
if (Trace_notify)
elog(DEBUG1, "EnableNotifyInterrupt: done");
}
}
}
| void HandleNotifyInterrupt | ( | void | ) |
Definition at line 1636 of file async.c.
References CHECK_FOR_INTERRUPTS, DEBUG1, elog, ImmediateInterruptOK, notifyInterruptEnabled, notifyInterruptOccurred, proc_exit_inprogress, ProcessIncomingNotify(), and Trace_notify.
Referenced by procsignal_sigusr1_handler().
{
/*
* Note: this is called by a SIGNAL HANDLER. You must be very wary what
* you do here. Some helpful soul had this routine sprinkled with
* TPRINTFs, which would likely lead to corruption of stdio buffers if
* they were ever turned on.
*/
/* Don't joggle the elbow of proc_exit */
if (proc_exit_inprogress)
return;
if (notifyInterruptEnabled)
{
bool save_ImmediateInterruptOK = ImmediateInterruptOK;
/*
* We may be called while ImmediateInterruptOK is true; turn it off
* while messing with the NOTIFY state. (We would have to save and
* restore it anyway, because PGSemaphore operations inside
* ProcessIncomingNotify() might reset it.)
*/
ImmediateInterruptOK = false;
/*
* I'm not sure whether some flavors of Unix might allow another
* SIGUSR1 occurrence to recursively interrupt this routine. To cope
* with the possibility, we do the same sort of dance that
* EnableNotifyInterrupt must do --- see that routine for comments.
*/
notifyInterruptEnabled = 0; /* disable any recursive signal */
notifyInterruptOccurred = 1; /* do at least one iteration */
for (;;)
{
notifyInterruptEnabled = 1;
if (!notifyInterruptOccurred)
break;
notifyInterruptEnabled = 0;
if (notifyInterruptOccurred)
{
/* Here, it is finally safe to do stuff. */
if (Trace_notify)
elog(DEBUG1, "HandleNotifyInterrupt: perform async notify");
ProcessIncomingNotify();
if (Trace_notify)
elog(DEBUG1, "HandleNotifyInterrupt: done");
}
}
/*
* Restore ImmediateInterruptOK, and check for interrupts if needed.
*/
ImmediateInterruptOK = save_ImmediateInterruptOK;
if (save_ImmediateInterruptOK)
CHECK_FOR_INTERRUPTS();
}
else
{
/*
* In this path it is NOT SAFE to do much of anything, except this:
*/
notifyInterruptOccurred = 1;
}
}
| Datum pg_listening_channels | ( | PG_FUNCTION_ARGS | ) |
Definition at line 677 of file async.c.
References CStringGetTextDatum, lfirst, list_head(), lnext, MemoryContextSwitchTo(), FuncCallContext::multi_call_memory_ctx, NULL, palloc(), SRF_FIRSTCALL_INIT, SRF_IS_FIRSTCALL, SRF_PERCALL_SETUP, SRF_RETURN_DONE, SRF_RETURN_NEXT, and FuncCallContext::user_fctx.
{
FuncCallContext *funcctx;
ListCell **lcp;
/* stuff done only on the first call of the function */
if (SRF_IS_FIRSTCALL())
{
MemoryContext oldcontext;
/* create a function context for cross-call persistence */
funcctx = SRF_FIRSTCALL_INIT();
/* switch to memory context appropriate for multiple function calls */
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
/* allocate memory for user context */
lcp = (ListCell **) palloc(sizeof(ListCell *));
*lcp = list_head(listenChannels);
funcctx->user_fctx = (void *) lcp;
MemoryContextSwitchTo(oldcontext);
}
/* stuff done on every call of the function */
funcctx = SRF_PERCALL_SETUP();
lcp = (ListCell **) funcctx->user_fctx;
while (*lcp != NULL)
{
char *channel = (char *) lfirst(*lcp);
*lcp = lnext(*lcp);
SRF_RETURN_NEXT(funcctx, CStringGetTextDatum(channel));
}
SRF_RETURN_DONE(funcctx);
}
| Datum pg_notify | ( | PG_FUNCTION_ARGS | ) |
Definition at line 500 of file async.c.
References Async_Notify(), PG_ARGISNULL, PG_GETARG_TEXT_PP, PG_RETURN_VOID, PreventCommandDuringRecovery(), and text_to_cstring().
{
const char *channel;
const char *payload;
if (PG_ARGISNULL(0))
channel = "";
else
channel = text_to_cstring(PG_GETARG_TEXT_PP(0));
if (PG_ARGISNULL(1))
payload = "";
else
payload = text_to_cstring(PG_GETARG_TEXT_PP(1));
/* For NOTIFY as a statement, this is checked in ProcessUtility */
PreventCommandDuringRecovery("NOTIFY");
Async_Notify(channel, payload);
PG_RETURN_VOID();
}
| void PreCommit_Notify | ( | void | ) |
Definition at line 762 of file async.c.
References AccessExclusiveLock, ListenAction::action, asyncQueueAddEntries(), asyncQueueFillWarning(), asyncQueueIsFull(), AsyncQueueLock, backendHasSentNotifications, DatabaseRelationId, DEBUG1, elog, ereport, errcode(), errmsg(), ERROR, Exec_ListenPreCommit(), GetCurrentTransactionId(), InvalidOid, lfirst, list_head(), LISTEN_LISTEN, LISTEN_UNLISTEN, LISTEN_UNLISTEN_ALL, LockSharedObject(), LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), NIL, NULL, and Trace_notify.
Referenced by CommitTransaction().
{
ListCell *p;
if (pendingActions == NIL && pendingNotifies == NIL)
return; /* no relevant statements in this xact */
if (Trace_notify)
elog(DEBUG1, "PreCommit_Notify");
/* Preflight for any pending listen/unlisten actions */
foreach(p, pendingActions)
{
ListenAction *actrec = (ListenAction *) lfirst(p);
switch (actrec->action)
{
case LISTEN_LISTEN:
Exec_ListenPreCommit();
break;
case LISTEN_UNLISTEN:
/* there is no Exec_UnlistenPreCommit() */
break;
case LISTEN_UNLISTEN_ALL:
/* there is no Exec_UnlistenAllPreCommit() */
break;
}
}
/* Queue any pending notifies */
if (pendingNotifies)
{
ListCell *nextNotify;
/*
* Make sure that we have an XID assigned to the current transaction.
* GetCurrentTransactionId is cheap if we already have an XID, but not
* so cheap if we don't, and we'd prefer not to do that work while
* holding AsyncQueueLock.
*/
(void) GetCurrentTransactionId();
/*
* Serialize writers by acquiring a special lock that we hold till
* after commit. This ensures that queue entries appear in commit
* order, and in particular that there are never uncommitted queue
* entries ahead of committed ones, so an uncommitted transaction
* can't block delivery of deliverable notifications.
*
* We use a heavyweight lock so that it'll automatically be released
* after either commit or abort. This also allows deadlocks to be
* detected, though really a deadlock shouldn't be possible here.
*
* The lock is on "database 0", which is pretty ugly but it doesn't
* seem worth inventing a special locktag category just for this.
* (Historical note: before PG 9.0, a similar lock on "database 0" was
* used by the flatfiles mechanism.)
*/
LockSharedObject(DatabaseRelationId, InvalidOid, 0,
AccessExclusiveLock);
/* Now push the notifications into the queue */
backendHasSentNotifications = true;
nextNotify = list_head(pendingNotifies);
while (nextNotify != NULL)
{
/*
* Add the pending notifications to the queue. We acquire and
* release AsyncQueueLock once per page, which might be overkill
* but it does allow readers to get in while we're doing this.
*
* A full queue is very uncommon and should really not happen,
* given that we have so much space available in the SLRU pages.
* Nevertheless we need to deal with this possibility. Note that
* when we get here we are in the process of committing our
* transaction, but we have not yet committed to clog, so at this
* point in time we can still roll the transaction back.
*/
LWLockAcquire(AsyncQueueLock, LW_EXCLUSIVE);
asyncQueueFillWarning();
if (asyncQueueIsFull())
ereport(ERROR,
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
errmsg("too many notifications in the NOTIFY queue")));
nextNotify = asyncQueueAddEntries(nextNotify);
LWLockRelease(AsyncQueueLock);
}
}
}
| void ProcessCompletedNotifies | ( | void | ) |
Definition at line 1057 of file async.c.
References asyncQueueAdvanceTail(), asyncQueueReadAllNotifications(), backendHasSentNotifications, CommitTransactionCommand(), CurrentMemoryContext, DEBUG1, elog, MemoryContextSwitchTo(), NIL, SignalBackends(), StartTransactionCommand(), and Trace_notify.
Referenced by PostgresMain().
{
MemoryContext caller_context;
bool signalled;
/* Nothing to do if we didn't send any notifications */
if (!backendHasSentNotifications)
return;
/*
* We reset the flag immediately; otherwise, if any sort of error occurs
* below, we'd be locked up in an infinite loop, because control will come
* right back here after error cleanup.
*/
backendHasSentNotifications = false;
/*
* We must preserve the caller's memory context (probably MessageContext)
* across the transaction we do here.
*/
caller_context = CurrentMemoryContext;
if (Trace_notify)
elog(DEBUG1, "ProcessCompletedNotifies");
/*
* We must run asyncQueueReadAllNotifications inside a transaction, else
* bad things happen if it gets an error.
*/
StartTransactionCommand();
/* Send signals to other backends */
signalled = SignalBackends();
if (listenChannels != NIL)
{
/* Read the queue ourselves, and send relevant stuff to the frontend */
asyncQueueReadAllNotifications();
}
else if (!signalled)
{
/*
* If we found no other listening backends, and we aren't listening
* ourselves, then we must execute asyncQueueAdvanceTail to flush the
* queue, because ain't nobody else gonna do it. This prevents queue
* overflow when we're sending useless notifies to nobody. (A new
* listener could have joined since we looked, but if so this is
* harmless.)
*/
asyncQueueAdvanceTail();
}
CommitTransactionCommand();
MemoryContextSwitchTo(caller_context);
/* We don't need pq_flush() here since postgres.c will do one shortly */
}
Definition at line 360 of file async.c.
Referenced by Async_Listen(), Async_Notify(), Async_Unlisten(), Async_UnlistenAll(), AtCommit_Notify(), EnableNotifyInterrupt(), Exec_ListenPreCommit(), Exec_UnlistenAllCommit(), Exec_UnlistenCommit(), HandleNotifyInterrupt(), PreCommit_Notify(), ProcessCompletedNotifies(), and ProcessIncomingNotify().
1.7.1