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Commit6054b33

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committed
Keep the list of to-be-NOTIFYed names in a plain List palloc'd in
TopTransactionContext, rather than using Dllist. This simplifies andspeeds up the code, and eliminates a former risk of coredump whenout of memory (since the old code didn't bother to check for mallocfailure). It also moves us one step closer to retiring Dllist...
1 parent1f1ca18 commit6054b33

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1 file changed

+42
-66
lines changed

1 file changed

+42
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lines changed

‎src/backend/commands/async.c

Lines changed: 42 additions & 66 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.78 2001/06/12 05:55:49 tgl Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.79 2001/06/17 22:27:15 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -82,7 +82,6 @@
8282
#include"catalog/catname.h"
8383
#include"catalog/pg_listener.h"
8484
#include"commands/async.h"
85-
#include"lib/dllist.h"
8685
#include"libpq/libpq.h"
8786
#include"libpq/pqformat.h"
8887
#include"miscadmin.h"
@@ -100,10 +99,11 @@ extern CommandDest whereToSendOutput;
10099
/*
101100
* State for outbound notifies consists of a list of all relnames NOTIFYed
102101
* in the current transaction.We do not actually perform a NOTIFY until
103-
* and unless the transaction commits.pendingNotifies is NULL if no
104-
* NOTIFYs have been done in the current transaction.
102+
* and unless the transaction commits.pendingNotifies is NIL if no
103+
* NOTIFYs have been done in the current transaction. The List nodes and
104+
* referenced strings are all palloc'd in TopTransactionContext.
105105
*/
106-
staticDllist*pendingNotifies=NULL;
106+
staticList*pendingNotifies=NIL;
107107

108108
/*
109109
* State for inbound notifies consists of two flags: one saying whether
@@ -121,16 +121,16 @@ static volatile int notifyInterruptOccurred = 0;
121121
/* True if we've registered an on_shmem_exit cleanup */
122122
staticboolunlistenExitRegistered= false;
123123

124+
boolTrace_notify= false;
125+
124126

125127
staticvoidAsync_UnlistenAll(void);
126128
staticvoidAsync_UnlistenOnExit(void);
127129
staticvoidProcessIncomingNotify(void);
128130
staticvoidNotifyMyFrontEnd(char*relname,int32listenerPID);
129-
staticintAsyncExistsPendingNotify(char*relname);
131+
staticboolAsyncExistsPendingNotify(constchar*relname);
130132
staticvoidClearPendingNotifies(void);
131133

132-
boolTrace_notify= false;
133-
134134

135135
/*
136136
*--------------------------------------------------------------
@@ -150,26 +150,23 @@ boolTrace_notify = false;
150150
void
151151
Async_Notify(char*relname)
152152
{
153-
char*notifyName;
154-
155153
if (Trace_notify)
156154
elog(DEBUG,"Async_Notify: %s",relname);
157155

158-
if (!pendingNotifies)
159-
pendingNotifies=DLNewList();
160156
/* no point in making duplicate entries in the list ... */
161-
if (!AsyncExistsPendingNotify(relname))
157+
if (!AsyncExistsPendingNotify(relname))
162158
{
163-
164159
/*
165-
* We allocate list memory from the global malloc pool to ensure
166-
* that it will live until we want to use it. This is probably
167-
* not necessary any longer, since we will use it before the end
168-
* of the transaction. DLList only knows how to use malloc()
169-
* anyway, but we could probably palloc() the strings...
160+
* The name list needs to live until end of transaction, so
161+
* store it in the top transaction context.
170162
*/
171-
notifyName=strdup(relname);
172-
DLAddHead(pendingNotifies,DLNewElem(notifyName));
163+
MemoryContextoldcontext;
164+
165+
oldcontext=MemoryContextSwitchTo(TopTransactionContext);
166+
167+
pendingNotifies=lcons(pstrdup(relname),pendingNotifies);
168+
169+
MemoryContextSwitchTo(oldcontext);
173170
}
174171
}
175172

@@ -352,7 +349,7 @@ Async_Unlisten(char *relname, int pid)
352349
*--------------------------------------------------------------
353350
*/
354351
staticvoid
355-
Async_UnlistenAll()
352+
Async_UnlistenAll(void)
356353
{
357354
RelationlRel;
358355
TupleDesctdesc;
@@ -401,7 +398,6 @@ Async_UnlistenAll()
401398
staticvoid
402399
Async_UnlistenOnExit(void)
403400
{
404-
405401
/*
406402
* We need to start/commit a transaction for the unlisten, but if
407403
* there is already an active transaction we had better abort that one
@@ -438,7 +434,7 @@ Async_UnlistenOnExit(void)
438434
*--------------------------------------------------------------
439435
*/
440436
void
441-
AtCommit_Notify()
437+
AtCommit_Notify(void)
442438
{
443439
RelationlRel;
444440
TupleDesctdesc;
@@ -449,7 +445,7 @@ AtCommit_Notify()
449445
charrepl[Natts_pg_listener],
450446
nulls[Natts_pg_listener];
451447

452-
if (!pendingNotifies)
448+
if (pendingNotifies==NIL)
453449
return;/* no NOTIFY statements in this
454450
* transaction */
455451

@@ -579,7 +575,7 @@ AtCommit_Notify()
579575
*--------------------------------------------------------------
580576
*/
581577
void
582-
AtAbort_Notify()
578+
AtAbort_Notify(void)
583579
{
584580
ClearPendingNotifies();
585581
}
@@ -601,7 +597,6 @@ AtAbort_Notify()
601597
*per above
602598
*--------------------------------------------------------------
603599
*/
604-
605600
void
606601
Async_NotifyHandler(SIGNAL_ARGS)
607602
{
@@ -671,7 +666,6 @@ Async_NotifyHandler(SIGNAL_ARGS)
671666
*PostgresMain calls this the first time.
672667
* --------------------------------------------------------------
673668
*/
674-
675669
void
676670
EnableNotifyInterrupt(void)
677671
{
@@ -729,7 +723,6 @@ EnableNotifyInterrupt(void)
729723
*is disabled until the next EnableNotifyInterrupt call.
730724
* --------------------------------------------------------------
731725
*/
732-
733726
void
734727
DisableNotifyInterrupt(void)
735728
{
@@ -848,8 +841,9 @@ ProcessIncomingNotify(void)
848841
elog(DEBUG,"ProcessIncomingNotify: done");
849842
}
850843

851-
/* Send NOTIFY message to my front end. */
852-
844+
/*
845+
* Send NOTIFY message to my front end.
846+
*/
853847
staticvoid
854848
NotifyMyFrontEnd(char*relname,int32listenerPID)
855849
{
@@ -874,50 +868,32 @@ NotifyMyFrontEnd(char *relname, int32 listenerPID)
874868
elog(NOTICE,"NOTIFY for %s",relname);
875869
}
876870

877-
/* Does pendingNotifies include the given relname?
878-
*
879-
* NB: not called unless pendingNotifies != NULL.
880-
*/
881-
882-
staticint
883-
AsyncExistsPendingNotify(char*relname)
871+
/* Does pendingNotifies include the given relname? */
872+
staticbool
873+
AsyncExistsPendingNotify(constchar*relname)
884874
{
885-
Dlelem*p;
875+
List*p;
886876

887-
for (p=DLGetHead(pendingNotifies);
888-
p!=NULL;
889-
p=DLGetSucc(p))
877+
foreach(p,pendingNotifies)
890878
{
891879
/* Use NAMEDATALEN for relname comparison. DZ - 26-08-1996 */
892-
if (strncmp((constchar*)DLE_VAL(p),relname,NAMEDATALEN)==0)
893-
return1;
880+
if (strncmp((constchar*)lfirst(p),relname,NAMEDATALEN)==0)
881+
returntrue;
894882
}
895883

896-
return0;
884+
returnfalse;
897885
}
898886

899887
/* Clear the pendingNotifies list. */
900-
901888
staticvoid
902-
ClearPendingNotifies()
889+
ClearPendingNotifies(void)
903890
{
904-
Dlelem*p;
905-
906-
if (pendingNotifies)
907-
{
908-
909-
/*
910-
* Since the referenced strings are malloc'd, we have to scan the
911-
* list and delete them individually. If we used palloc for the
912-
* strings then we could just do DLFreeList to get rid of both the
913-
* list nodes and the list base...
914-
*/
915-
while ((p=DLRemHead(pendingNotifies))!=NULL)
916-
{
917-
free(DLE_VAL(p));
918-
DLFreeElem(p);
919-
}
920-
DLFreeList(pendingNotifies);
921-
pendingNotifies=NULL;
922-
}
891+
/*
892+
* We used to have to explicitly deallocate the list members and nodes,
893+
* because they were malloc'd. Now, since we know they are palloc'd
894+
* in TopTransactionContext, we need not do that --- they'll go away
895+
* automatically at transaction exit. We need only reset the list head
896+
* pointer.
897+
*/
898+
pendingNotifies=NIL;
923899
}

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