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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2007-11-30 21:22:54 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2007-11-30 21:22:54 +0000 |
| commit | 895a94de6dffa71741586a2228275f66db03f8ca (patch) | |
| tree | 55ec3c2629305d83b35f98956c3c3bee449d86bb /src/backend/commands/async.c | |
| parent | f0f18c7087e04a60e2612151401b07df87e51d96 (diff) | |
| download | postgresql-895a94de6dffa71741586a2228275f66db03f8ca.tar.gz postgresql-895a94de6dffa71741586a2228275f66db03f8ca.zip | |
Avoid incrementing the CommandCounter when CommandCounterIncrement is called
but no database changes have been made since the last CommandCounterIncrement.
This should result in a significant improvement in the number of "commands"
that can typically be performed within a transaction before hitting the 2^32
CommandId size limit. In particular this buys back (and more) the possible
adverse consequences of my previous patch to fix plan caching behavior.
The implementation requires tracking whether the current CommandCounter
value has been "used" to mark any tuples. CommandCounter values stored into
snapshots are presumed not to be used for this purpose. This requires some
small executor changes, since the executor used to conflate the curcid of
the snapshot it was using with the command ID to mark output tuples with.
Separating these concepts allows some small simplifications in executor APIs.
Something for the TODO list: look into having CommandCounterIncrement not do
AcceptInvalidationMessages. It seems fairly bogus to be doing it there,
but exactly where to do it instead isn't clear, and I'm disinclined to mess
with asynchronous behavior during late beta.
Diffstat (limited to 'src/backend/commands/async.c')
| -rw-r--r-- | src/backend/commands/async.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c index 55b99f8c922..c32dd2b19fc 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 1.136 2007/04/12 06:53:46 neilc Exp $ + * $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.137 2007/11/30 21:22:53 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -562,7 +562,8 @@ AtCommit_Notify(void) */ result = heap_update(lRel, &lTuple->t_self, rTuple, &update_ctid, &update_xmax, - GetCurrentCommandId(), InvalidSnapshot, + GetCurrentCommandId(true), + InvalidSnapshot, false /* no wait for commit */ ); switch (result) { |