diff --git a/doc/src/sgml/ref/prepare_transaction.sgml b/doc/src/sgml/ref/prepare_transaction.sgml
index 5874b7993033990ecd45999569fab20e342e2153..41f06e5932cfe81b6d0071c673d5b0fc68671a30 100644
--- a/doc/src/sgml/ref/prepare_transaction.sgml
+++ b/doc/src/sgml/ref/prepare_transaction.sgml
@@ -1,5 +1,5 @@
<!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/prepare_transaction.sgml,v 1.6 2007/09/11 00:06:41 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/prepare_transaction.sgml,v 1.7 2008/03/12 20:11:45 tgl Exp $
PostgreSQL documentation
-->
@@ -88,8 +88,10 @@ PREPARE TRANSACTION <replaceable class="PARAMETER">transaction_id</replaceable>
<para>
It is not currently allowed to <command>PREPARE</> a transaction that
- has executed any operations involving temporary tables or
- created any cursors <literal>WITH HOLD</>. Those features are too tightly
+ has executed any operations involving temporary tables,
+ created any cursors <literal>WITH HOLD</>, or executed
+ <command>LISTEN</> or <command>UNLISTEN</>.
+ Those features are too tightly
tied to the current session to be useful in a transaction to be prepared.
</para>
diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c
index b42a278d9f0f7d6fbaf6f29798f58e859367063e..bf967679c7c1115df90a8030da052e699bf8d58a 100644
--- a/src/backend/commands/async.c
+++ b/src/backend/commands/async.c
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.138 2008/01/01 19:45:48 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.139 2008/03/12 20:11:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -52,6 +52,16 @@
* transaction, since by assumption it is only called from outside any
* transaction.
*
+ * Like NOTIFY, LISTEN and UNLISTEN just add the desired action to a list
+ * of pending actions. If we reach transaction commit, the changes are
+ * applied to pg_listener just before executing any pending NOTIFYs. This
+ * method is necessary because to avoid race conditions, we must hold lock
+ * on pg_listener from when we insert a new listener tuple until we commit.
+ * To do that and not create undue hazard of deadlock, we don't want to
+ * touch pg_listener until we are otherwise done with the transaction;
+ * in particular it'd be uncool to still be taking user-commanded locks
+ * while holding the pg_listener lock.
+ *
* Although we grab ExclusiveLock on pg_listener for any operation,
* the lock is never held very long, so it shouldn't cause too much of
* a performance problem. (Previously we used AccessExclusiveLock, but
@@ -75,7 +85,6 @@
#include <unistd.h>
#include <signal.h>
-#include <netinet/in.h>
#include "access/heapam.h"
#include "access/twophase_rmgr.h"
@@ -88,11 +97,39 @@
#include "storage/ipc.h"
#include "storage/sinval.h"
#include "tcop/tcopprot.h"
+#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/memutils.h"
#include "utils/ps_status.h"
+/*
+ * State for pending LISTEN/UNLISTEN actions consists of an ordered list of
+ * all actions requested in the current transaction. As explained above,
+ * we don't actually modify pg_listener until we reach transaction commit.
+ *
+ * The list is kept in CurTransactionContext. In subtransactions, each
+ * subtransaction has its own list in its own CurTransactionContext, but
+ * successful subtransactions attach their lists to their parent's list.
+ * Failed subtransactions simply discard their lists.
+ */
+typedef enum
+{
+ LISTEN_LISTEN,
+ LISTEN_UNLISTEN,
+ LISTEN_UNLISTEN_ALL
+} ListenActionKind;
+
+typedef struct
+{
+ ListenActionKind action;
+ char condname[1]; /* actually, as long as needed */
+} ListenAction;
+
+static List *pendingActions = NIL; /* list of ListenAction */
+
+static List *upperPendingActions = NIL; /* list of upper-xact lists */
+
/*
* State for outbound notifies consists of a list of all relnames NOTIFYed
* in the current transaction. We do not actually perform a NOTIFY until
@@ -103,8 +140,13 @@
* subtransaction has its own list in its own CurTransactionContext, but
* successful subtransactions attach their lists to their parent's list.
* Failed subtransactions simply discard their lists.
+ *
+ * Note: the action and notify lists do not interact within a transaction.
+ * In particular, if a transaction does NOTIFY and then LISTEN on the same
+ * condition name, it will get a self-notify at commit. This is a bit odd
+ * but is consistent with our historical behavior.
*/
-static List *pendingNotifies = NIL;
+static List *pendingNotifies = NIL; /* list of C strings */
static List *upperPendingNotifies = NIL; /* list of upper-xact lists */
@@ -118,8 +160,8 @@ static List *upperPendingNotifies = NIL; /* list of upper-xact lists */
* does not grok "volatile", you'd be best advised to compile this file
* with all optimization turned off.
*/
-static volatile int notifyInterruptEnabled = 0;
-static volatile int notifyInterruptOccurred = 0;
+static volatile sig_atomic_t notifyInterruptEnabled = 0;
+static volatile sig_atomic_t notifyInterruptOccurred = 0;
/* True if we've registered an on_shmem_exit cleanup */
static bool unlistenExitRegistered = false;
@@ -127,15 +169,19 @@ static bool unlistenExitRegistered = false;
bool Trace_notify = false;
+static void queue_listen(ListenActionKind action, const char *condname);
static void Async_UnlistenOnExit(int code, Datum arg);
+static void Exec_Listen(Relation lRel, const char *relname);
+static void Exec_Unlisten(Relation lRel, const char *relname);
+static void Exec_UnlistenAll(Relation lRel);
+static void Send_Notify(Relation lRel);
static void ProcessIncomingNotify(void);
static void NotifyMyFrontEnd(char *relname, int32 listenerPID);
static bool AsyncExistsPendingNotify(const char *relname);
-static void ClearPendingNotifies(void);
+static void ClearPendingActionsAndNotifies(void);
/*
- *--------------------------------------------------------------
* Async_Notify
*
* This is executed by the SQL notify command.
@@ -143,8 +189,6 @@ static void ClearPendingNotifies(void);
* Adds the relation to the list of pending notifies.
* Actual notification happens during transaction commit.
* ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- *
- *--------------------------------------------------------------
*/
void
Async_Notify(const char *relname)
@@ -163,6 +207,12 @@ Async_Notify(const char *relname)
oldcontext = MemoryContextSwitchTo(CurTransactionContext);
+ /*
+ * Ordering of the list isn't important. We choose to put new
+ * entries on the front, as this might make duplicate-elimination
+ * a tad faster when the same condition is signaled many times in
+ * a row.
+ */
pendingNotifies = lcons(pstrdup(relname), pendingNotifies);
MemoryContextSwitchTo(oldcontext);
@@ -170,34 +220,245 @@ Async_Notify(const char *relname)
}
/*
- *--------------------------------------------------------------
+ * queue_listen
+ * Common code for listen, unlisten, unlisten all commands.
+ *
+ * Adds the request to the list of pending actions.
+ * Actual update of pg_listener happens during transaction commit.
+ * ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ */
+static void
+queue_listen(ListenActionKind action, const char *condname)
+{
+ MemoryContext oldcontext;
+ ListenAction *actrec;
+
+ /*
+ * Unlike Async_Notify, we don't try to collapse out duplicates.
+ * It would be too complicated to ensure we get the right interactions
+ * of conflicting LISTEN/UNLISTEN/UNLISTEN_ALL, and it's unlikely that
+ * there would be any performance benefit anyway in sane applications.
+ */
+ oldcontext = MemoryContextSwitchTo(CurTransactionContext);
+
+ /* space for terminating null is included in sizeof(ListenAction) */
+ actrec = (ListenAction *) palloc(sizeof(ListenAction) + strlen(condname));
+ actrec->action = action;
+ strcpy(actrec->condname, condname);
+
+ pendingActions = lappend(pendingActions, actrec);
+
+ MemoryContextSwitchTo(oldcontext);
+}
+
+/*
* Async_Listen
*
* This is executed by the SQL listen command.
+ */
+void
+Async_Listen(const char *relname)
+{
+ if (Trace_notify)
+ elog(DEBUG1, "Async_Listen(%s,%d)", relname, MyProcPid);
+
+ queue_listen(LISTEN_LISTEN, relname);
+}
+
+/*
+ * Async_Unlisten
+ *
+ * This is executed by the SQL unlisten command.
+ */
+void
+Async_Unlisten(const char *relname)
+{
+ /* Handle specially the `unlisten "*"' command */
+ if ((!relname) || (*relname == '\0') || (strcmp(relname, "*") == 0))
+ {
+ Async_UnlistenAll();
+ }
+ else
+ {
+ if (Trace_notify)
+ elog(DEBUG1, "Async_Unlisten(%s,%d)", relname, MyProcPid);
+
+ queue_listen(LISTEN_UNLISTEN, relname);
+ }
+}
+
+/*
+ * Async_UnlistenAll
+ *
+ * This is invoked by UNLISTEN "*" command, and also at backend exit.
+ */
+void
+Async_UnlistenAll(void)
+{
+ if (Trace_notify)
+ elog(DEBUG1, "Async_UnlistenAll(%d)", MyProcPid);
+
+ queue_listen(LISTEN_UNLISTEN_ALL, "");
+}
+
+/*
+ * Async_UnlistenOnExit
+ *
+ * Clean up the pg_listener table at backend exit.
+ *
+ * This is executed if we have done any LISTENs in this backend.
+ * It might not be necessary anymore, if the user UNLISTENed everything,
+ * but we don't try to detect that case.
+ */
+static void
+Async_UnlistenOnExit(int code, Datum arg)
+{
+ /*
+ * We need to start/commit a transaction for the unlisten, but if there is
+ * already an active transaction we had better abort that one first.
+ * Otherwise we'd end up committing changes that probably ought to be
+ * discarded.
+ */
+ AbortOutOfAnyTransaction();
+ /* Now we can do the unlisten */
+ StartTransactionCommand();
+ Async_UnlistenAll();
+ CommitTransactionCommand();
+}
+
+/*
+ * AtPrepare_Notify
*
- * Register the current backend as listening on the specified
- * relation.
+ * This is called at the prepare phase of a two-phase
+ * transaction. Save the state for possible commit later.
+ */
+void
+AtPrepare_Notify(void)
+{
+ ListCell *p;
+
+ /* It's not sensible to have any pending LISTEN/UNLISTEN actions */
+ if (pendingActions)
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("cannot PREPARE a transaction that has executed LISTEN or UNLISTEN")));
+
+ /* We can deal with pending NOTIFY though */
+ foreach(p, pendingNotifies)
+ {
+ const char *relname = (const char *) lfirst(p);
+
+ RegisterTwoPhaseRecord(TWOPHASE_RM_NOTIFY_ID, 0,
+ relname, strlen(relname) + 1);
+ }
+
+ /*
+ * We can clear the state immediately, rather than needing a separate
+ * PostPrepare call, because if the transaction fails we'd just discard
+ * the state anyway.
+ */
+ ClearPendingActionsAndNotifies();
+}
+
+/*
+ * AtCommit_Notify
*
- * Side effects:
- * pg_listener is updated.
+ * This is called at transaction commit.
+ *
+ * If there are pending LISTEN/UNLISTEN actions, insert or delete
+ * tuples in pg_listener accordingly.
+ *
+ * If there are outbound notify requests in the pendingNotifies list,
+ * scan pg_listener for matching tuples, and either signal the other
+ * backend or send a message to our own frontend.
*
- *--------------------------------------------------------------
+ * NOTE: we are still inside the current transaction, therefore can
+ * piggyback on its committing of changes.
*/
void
-Async_Listen(const char *relname)
+AtCommit_Notify(void)
{
Relation lRel;
+ ListCell *p;
+
+ if (pendingActions == NIL && pendingNotifies == NIL)
+ return; /* no relevant statements in this xact */
+
+ /*
+ * NOTIFY is disabled if not normal processing mode. This test used to be
+ * in xact.c, but it seems cleaner to do it here.
+ */
+ if (!IsNormalProcessingMode())
+ {
+ ClearPendingActionsAndNotifies();
+ return;
+ }
+
+ if (Trace_notify)
+ elog(DEBUG1, "AtCommit_Notify");
+
+ /* Acquire ExclusiveLock on pg_listener */
+ lRel = heap_open(ListenerRelationId, ExclusiveLock);
+
+ /* Perform any pending listen/unlisten actions */
+ foreach(p, pendingActions)
+ {
+ ListenAction *actrec = (ListenAction *) lfirst(p);
+
+ switch (actrec->action)
+ {
+ case LISTEN_LISTEN:
+ Exec_Listen(lRel, actrec->condname);
+ break;
+ case LISTEN_UNLISTEN:
+ Exec_Unlisten(lRel, actrec->condname);
+ break;
+ case LISTEN_UNLISTEN_ALL:
+ Exec_UnlistenAll(lRel);
+ break;
+ }
+
+ /* We must CCI after each action in case of conflicting actions */
+ CommandCounterIncrement();
+ }
+
+ /* Perform any pending notifies */
+ if (pendingNotifies)
+ Send_Notify(lRel);
+
+ /*
+ * We do NOT release the lock on pg_listener here; we need to hold it
+ * until end of transaction (which is about to happen, anyway) to ensure
+ * that notified backends see our tuple updates when they look. Else they
+ * might disregard the signal, which would make the application programmer
+ * very unhappy. Also, this prevents race conditions when we have just
+ * inserted a listening tuple.
+ */
+ heap_close(lRel, NoLock);
+
+ ClearPendingActionsAndNotifies();
+
+ if (Trace_notify)
+ elog(DEBUG1, "AtCommit_Notify: done");
+}
+
+/*
+ * Exec_Listen --- subroutine for AtCommit_Notify
+ *
+ * Register the current backend as listening on the specified relation.
+ */
+static void
+Exec_Listen(Relation lRel, const char *relname)
+{
HeapScanDesc scan;
HeapTuple tuple;
Datum values[Natts_pg_listener];
char nulls[Natts_pg_listener];
- int i;
+ NameData condname;
bool alreadyListener = false;
if (Trace_notify)
- elog(DEBUG1, "Async_Listen(%s,%d)", relname, MyProcPid);
-
- lRel = heap_open(ListenerRelationId, ExclusiveLock);
+ elog(DEBUG1, "Exec_Listen(%s,%d)", relname, MyProcPid);
/* Detect whether we are already listening on this relname */
scan = heap_beginscan(lRel, SnapshotNow, 0, NULL);
@@ -216,27 +477,20 @@ Async_Listen(const char *relname)
heap_endscan(scan);
if (alreadyListener)
- {
- heap_close(lRel, ExclusiveLock);
return;
- }
/*
* OK to insert a new tuple
*/
+ memset(nulls, ' ', sizeof(nulls));
- for (i = 0; i < Natts_pg_listener; i++)
- {
- nulls[i] = ' ';
- values[i] = PointerGetDatum(NULL);
- }
-
- i = 0;
- values[i++] = (Datum) relname;
- values[i++] = (Datum) MyProcPid;
- values[i++] = (Datum) 0; /* no notifies pending */
+ namestrcpy(&condname, relname);
+ values[Anum_pg_listener_relname - 1] = NameGetDatum(&condname);
+ values[Anum_pg_listener_pid - 1] = Int32GetDatum(MyProcPid);
+ values[Anum_pg_listener_notify - 1] = Int32GetDatum(0); /* no notifies pending */
tuple = heap_formtuple(RelationGetDescr(lRel), values, nulls);
+
simple_heap_insert(lRel, tuple);
#ifdef NOT_USED /* currently there are no indexes */
@@ -245,8 +499,6 @@ Async_Listen(const char *relname)
heap_freetuple(tuple);
- heap_close(lRel, ExclusiveLock);
-
/*
* now that we are listening, make sure we will unlisten before dying.
*/
@@ -258,37 +510,19 @@ Async_Listen(const char *relname)
}
/*
- *--------------------------------------------------------------
- * Async_Unlisten
- *
- * This is executed by the SQL unlisten command.
+ * Exec_Unlisten --- subroutine for AtCommit_Notify
*
* Remove the current backend from the list of listening backends
* for the specified relation.
- *
- * Side effects:
- * pg_listener is updated.
- *
- *--------------------------------------------------------------
*/
-void
-Async_Unlisten(const char *relname)
+static void
+Exec_Unlisten(Relation lRel, const char *relname)
{
- Relation lRel;
HeapScanDesc scan;
HeapTuple tuple;
- /* Handle specially the `unlisten "*"' command */
- if ((!relname) || (*relname == '\0') || (strcmp(relname, "*") == 0))
- {
- Async_UnlistenAll();
- return;
- }
-
if (Trace_notify)
- elog(DEBUG1, "Async_Unlisten(%s,%d)", relname, MyProcPid);
-
- lRel = heap_open(ListenerRelationId, ExclusiveLock);
+ elog(DEBUG1, "Exec_Unlisten(%s,%d)", relname, MyProcPid);
scan = heap_beginscan(lRel, SnapshotNow, 0, NULL);
while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
@@ -310,8 +544,6 @@ Async_Unlisten(const char *relname)
}
heap_endscan(scan);
- heap_close(lRel, ExclusiveLock);
-
/*
* We do not complain about unlistening something not being listened;
* should we?
@@ -319,35 +551,19 @@ Async_Unlisten(const char *relname)
}
/*
- *--------------------------------------------------------------
- * Async_UnlistenAll
- *
- * Unlisten all relations for this backend.
- *
- * This is invoked by UNLISTEN "*" command, and also at backend exit.
- *
- * Results:
- * XXX
- *
- * Side effects:
- * pg_listener is updated.
+ * Exec_UnlistenAll --- subroutine for AtCommit_Notify
*
- *--------------------------------------------------------------
+ * Update pg_listener to unlisten all relations for this backend.
*/
-void
-Async_UnlistenAll(void)
+static void
+Exec_UnlistenAll(Relation lRel)
{
- Relation lRel;
- TupleDesc tdesc;
HeapScanDesc scan;
HeapTuple lTuple;
ScanKeyData key[1];
if (Trace_notify)
- elog(DEBUG1, "Async_UnlistenAll");
-
- lRel = heap_open(ListenerRelationId, ExclusiveLock);
- tdesc = RelationGetDescr(lRel);
+ elog(DEBUG1, "Exec_UnlistenAll");
/* Find and delete all entries with my listenerPID */
ScanKeyInit(&key[0],
@@ -360,100 +576,18 @@ Async_UnlistenAll(void)
simple_heap_delete(lRel, &lTuple->t_self);
heap_endscan(scan);
- heap_close(lRel, ExclusiveLock);
}
/*
- *--------------------------------------------------------------
- * Async_UnlistenOnExit
- *
- * Clean up the pg_listener table at backend exit.
+ * Send_Notify --- subroutine for AtCommit_Notify
*
- * This is executed if we have done any LISTENs in this backend.
- * It might not be necessary anymore, if the user UNLISTENed everything,
- * but we don't try to detect that case.
- *
- * Results:
- * XXX
- *
- * Side effects:
- * pg_listener is updated if necessary.
- *
- *--------------------------------------------------------------
+ * Scan pg_listener for tuples matching our pending notifies, and
+ * either signal the other backend or send a message to our own frontend.
*/
static void
-Async_UnlistenOnExit(int code, Datum arg)
-{
- /*
- * We need to start/commit a transaction for the unlisten, but if there is
- * already an active transaction we had better abort that one first.
- * Otherwise we'd end up committing changes that probably ought to be
- * discarded.
- */
- AbortOutOfAnyTransaction();
- /* Now we can do the unlisten */
- StartTransactionCommand();
- Async_UnlistenAll();
- CommitTransactionCommand();
-}
-
-
-/*
- *--------------------------------------------------------------
- * AtPrepare_Notify
- *
- * This is called at the prepare phase of a two-phase
- * transaction. Save the state for possible commit later.
- *--------------------------------------------------------------
- */
-void
-AtPrepare_Notify(void)
-{
- ListCell *p;
-
- foreach(p, pendingNotifies)
- {
- const char *relname = (const char *) lfirst(p);
-
- RegisterTwoPhaseRecord(TWOPHASE_RM_NOTIFY_ID, 0,
- relname, strlen(relname) + 1);
- }
-
- /*
- * We can clear the state immediately, rather than needing a separate
- * PostPrepare call, because if the transaction fails we'd just discard
- * the state anyway.
- */
- ClearPendingNotifies();
-}
-
-/*
- *--------------------------------------------------------------
- * AtCommit_Notify
- *
- * This is called at transaction commit.
- *
- * If there are outbound notify requests in the pendingNotifies list,
- * scan pg_listener for matching tuples, and either signal the other
- * backend or send a message to our own frontend.
- *
- * NOTE: we are still inside the current transaction, therefore can
- * piggyback on its committing of changes.
- *
- * Results:
- * XXX
- *
- * Side effects:
- * Tuples in pg_listener that have matching relnames and other peoples'
- * listenerPIDs are updated with a nonzero notification field.
- *
- *--------------------------------------------------------------
- */
-void
-AtCommit_Notify(void)
+Send_Notify(Relation lRel)
{
- Relation lRel;
- TupleDesc tdesc;
+ TupleDesc tdesc = RelationGetDescr(lRel);
HeapScanDesc scan;
HeapTuple lTuple,
rTuple;
@@ -461,22 +595,6 @@ AtCommit_Notify(void)
char repl[Natts_pg_listener],
nulls[Natts_pg_listener];
- if (pendingNotifies == NIL)
- return; /* no NOTIFY statements in this transaction */
-
- /*
- * NOTIFY is disabled if not normal processing mode. This test used to be
- * in xact.c, but it seems cleaner to do it here.
- */
- if (!IsNormalProcessingMode())
- {
- ClearPendingNotifies();
- return;
- }
-
- if (Trace_notify)
- elog(DEBUG1, "AtCommit_Notify");
-
/* preset data to update notify column to MyProcPid */
nulls[0] = nulls[1] = nulls[2] = ' ';
repl[0] = repl[1] = repl[2] = ' ';
@@ -484,8 +602,6 @@ AtCommit_Notify(void)
value[0] = value[1] = value[2] = (Datum) 0;
value[Anum_pg_listener_notify - 1] = Int32GetDatum(MyProcPid);
- lRel = heap_open(ListenerRelationId, ExclusiveLock);
- tdesc = RelationGetDescr(lRel);
scan = heap_beginscan(lRel, SnapshotNow, 0, NULL);
while ((lTuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
@@ -505,7 +621,6 @@ AtCommit_Notify(void)
* could lose an outside notify, which'd be bad for applications
* that ignore self-notify messages.
*/
-
if (Trace_notify)
elog(DEBUG1, "AtCommit_Notify: notifying self");
@@ -538,99 +653,32 @@ AtCommit_Notify(void)
}
else if (listener->notification == 0)
{
- HTSU_Result result;
- ItemPointerData update_ctid;
- TransactionId update_xmax;
-
- rTuple = heap_modifytuple(lTuple, tdesc,
- value, nulls, repl);
+ /* Rewrite the tuple with my PID in notification column */
+ rTuple = heap_modifytuple(lTuple, tdesc, value, nulls, repl);
+ simple_heap_update(lRel, &lTuple->t_self, rTuple);
- /*
- * We cannot use simple_heap_update here because the tuple
- * could have been modified by an uncommitted transaction;
- * specifically, since UNLISTEN releases exclusive lock on the
- * table before commit, the other guy could already have tried
- * to unlisten. There are no other cases where we should be
- * able to see an uncommitted update or delete. Therefore, our
- * response to a HeapTupleBeingUpdated result is just to
- * ignore it. We do *not* wait for the other guy to commit
- * --- that would risk deadlock, and we don't want to block
- * while holding the table lock anyway for performance
- * reasons. We also ignore HeapTupleUpdated, which could occur
- * if the other guy commits between our heap_getnext and
- * heap_update calls.
- */
- result = heap_update(lRel, &lTuple->t_self, rTuple,
- &update_ctid, &update_xmax,
- GetCurrentCommandId(true),
- InvalidSnapshot,
- false /* no wait for commit */ );
- switch (result)
- {
- case HeapTupleSelfUpdated:
- /* Tuple was already updated in current command? */
- elog(ERROR, "tuple already updated by self");
- break;
-
- case HeapTupleMayBeUpdated:
- /* done successfully */
#ifdef NOT_USED /* currently there are no indexes */
- CatalogUpdateIndexes(lRel, rTuple);
+ CatalogUpdateIndexes(lRel, rTuple);
#endif
- break;
-
- case HeapTupleBeingUpdated:
- /* ignore uncommitted tuples */
- break;
-
- case HeapTupleUpdated:
- /* ignore just-committed tuples */
- break;
-
- default:
- elog(ERROR, "unrecognized heap_update status: %u",
- result);
- break;
- }
}
}
}
heap_endscan(scan);
-
- /*
- * We do NOT release the lock on pg_listener here; we need to hold it
- * until end of transaction (which is about to happen, anyway) to ensure
- * that notified backends see our tuple updates when they look. Else they
- * might disregard the signal, which would make the application programmer
- * very unhappy.
- */
- heap_close(lRel, NoLock);
-
- ClearPendingNotifies();
-
- if (Trace_notify)
- elog(DEBUG1, "AtCommit_Notify: done");
}
/*
- *--------------------------------------------------------------
* AtAbort_Notify
*
* This is called at transaction abort.
*
- * Gets rid of pending outbound notifies that we would have executed
- * if the transaction got committed.
- *
- * Results:
- * XXX
- *
- *--------------------------------------------------------------
+ * Gets rid of pending actions and outbound notifies that we would have
+ * executed if the transaction got committed.
*/
void
AtAbort_Notify(void)
{
- ClearPendingNotifies();
+ ClearPendingActionsAndNotifies();
}
/*
@@ -646,6 +694,13 @@ AtSubStart_Notify(void)
/* 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) ==
@@ -659,13 +714,25 @@ AtSubStart_Notify(void)
/*
* AtSubCommit_Notify() --- Take care of subtransaction commit.
*
- * Reassign all items in the pending notifies list to the parent transaction.
+ * Reassign all items in the pending lists to the parent transaction.
*/
void
AtSubCommit_Notify(void)
{
+ 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);
@@ -687,7 +754,7 @@ AtSubAbort_Notify(void)
int my_level = GetCurrentTransactionNestLevel();
/*
- * All we have to do is pop the stack --- the notifies made in this
+ * 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.
*
@@ -696,6 +763,12 @@ AtSubAbort_Notify(void)
* 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);
@@ -704,7 +777,6 @@ AtSubAbort_Notify(void)
}
/*
- *--------------------------------------------------------------
* NotifyInterruptHandler
*
* This is the signal handler for SIGUSR2.
@@ -712,13 +784,6 @@ AtSubAbort_Notify(void)
* If we are idle (notifyInterruptEnabled is set), we can safely invoke
* ProcessIncomingNotify directly. Otherwise, just set a flag
* to do it later.
- *
- * Results:
- * none
- *
- * Side effects:
- * per above
- *--------------------------------------------------------------
*/
void
NotifyInterruptHandler(SIGNAL_ARGS)
@@ -794,7 +859,6 @@ NotifyInterruptHandler(SIGNAL_ARGS)
}
/*
- * --------------------------------------------------------------
* EnableNotifyInterrupt
*
* This is called by the PostgresMain main loop just before waiting
@@ -804,7 +868,6 @@ NotifyInterruptHandler(SIGNAL_ARGS)
*
* NOTE: the signal handler starts out disabled, and stays so until
* PostgresMain calls this the first time.
- * --------------------------------------------------------------
*/
void
EnableNotifyInterrupt(void)
@@ -853,7 +916,6 @@ EnableNotifyInterrupt(void)
}
/*
- * --------------------------------------------------------------
* DisableNotifyInterrupt
*
* This is called by the PostgresMain main loop just after receiving
@@ -863,7 +925,6 @@ EnableNotifyInterrupt(void)
* The SIGUSR1 signal handler also needs to call this, so as to
* prevent conflicts if one signal interrupts the other. So we
* must return the previous state of the flag.
- * --------------------------------------------------------------
*/
bool
DisableNotifyInterrupt(void)
@@ -876,7 +937,6 @@ DisableNotifyInterrupt(void)
}
/*
- * --------------------------------------------------------------
* ProcessIncomingNotify
*
* Deal with arriving NOTIFYs from other backends.
@@ -886,7 +946,6 @@ DisableNotifyInterrupt(void)
* and clear the notification field in pg_listener until next time.
*
* NOTE: since we are outside any transaction, we must create our own.
- * --------------------------------------------------------------
*/
static void
ProcessIncomingNotify(void)
@@ -949,9 +1008,6 @@ ProcessIncomingNotify(void)
/*
* Rewrite the tuple with 0 in notification column.
- *
- * simple_heap_update is safe here because no one else would have
- * tried to UNLISTEN us, so there can be no uncommitted changes.
*/
rTuple = heap_modifytuple(lTuple, tdesc, value, nulls, repl);
simple_heap_update(lRel, &lTuple->t_self, rTuple);
@@ -1035,17 +1091,18 @@ AsyncExistsPendingNotify(const char *relname)
return false;
}
-/* Clear the pendingNotifies list. */
+/* Clear the pendingActions and pendingNotifies lists. */
static void
-ClearPendingNotifies(void)
+ClearPendingActionsAndNotifies(void)
{
/*
* We used to have to explicitly deallocate the list members and nodes,
* because they were malloc'd. Now, since we know they are palloc'd in
* CurTransactionContext, we need not do that --- they'll go away
* automatically at transaction exit. We need only reset the list head
- * pointer.
+ * pointers.
*/
+ pendingActions = NIL;
pendingNotifies = NIL;
}