diff options
Diffstat (limited to 'src/backend/commands/async.c')
| -rw-r--r-- | src/backend/commands/async.c | 59 |
1 files changed, 55 insertions, 4 deletions
diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c index 8ceac36cf4a..95c83c2372e 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 - * $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.99 2003/09/15 00:26:31 petere Exp $ + * $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.100 2003/09/15 23:33:39 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -515,13 +515,58 @@ AtCommit_Notify(void) } else if (listener->notification == 0) { + ItemPointerData ctid; + int result; + rTuple = heap_modifytuple(lTuple, lRel, 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, + &ctid, + GetCurrentCommandId(), + 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; + } } } } @@ -803,7 +848,13 @@ ProcessIncomingNotify(void) relname, (int) sourcePID); NotifyMyFrontEnd(relname, sourcePID); - /* Rewrite the tuple with 0 in notification column */ + /* + * 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, lRel, value, nulls, repl); simple_heap_update(lRel, &lTuple->t_self, rTuple); |