Re: pgsql: Avoid incrementing the CommandCounter when

Added to TODO:

* Consider if CommandCounterIncrement() can avoid its
AcceptInvalidationMessages() call

http://archives.postgresql.org/pgsql-committers/2007-11/msg00585.php

---------------------------------------------------------------------------

Tom Lane wrote:
> Log Message:
> -----------
> 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.
>
> Modified Files:
> --------------
> pgsql/contrib/pgrowlocks:
> pgrowlocks.c (r1.7 -> r1.8)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pgrowlocks/pgrowlocks.c?r1=1.7&r2=1.8)
> pgsql/src/backend/access/heap:
> heapam.c (r1.245 -> r1.246)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/heap/heapam.c?r1=1.245&r2=1.246)
> tuptoaster.c (r1.79 -> r1.80)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/heap/tuptoaster.c?r1=1.79&r2=1.80)
> pgsql/src/backend/access/transam:
> xact.c (r1.253 -> r1.254)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xact.c?r1=1.253&r2=1.254)
> pgsql/src/backend/commands:
> async.c (r1.136 -> r1.137)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/async.c?r1=1.136&r2=1.137)
> copy.c (r1.288 -> r1.289)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/copy.c?r1=1.288&r2=1.289)
> explain.c (r1.167 -> r1.168)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/explain.c?r1=1.167&r2=1.168)
> trigger.c (r1.224 -> r1.225)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/trigger.c?r1=1.224&r2=1.225)
> pgsql/src/backend/executor:
> execMain.c (r1.300 -> r1.301)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execMain.c?r1=1.300&r2=1.301)
> execUtils.c (r1.152 -> r1.153)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execUtils.c?r1=1.152&r2=1.153)
> spi.c (r1.185 -> r1.186)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/spi.c?r1=1.185&r2=1.186)
> pgsql/src/backend/storage/ipc:
> procarray.c (r1.37 -> r1.38)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/ipc/procarray.c?r1=1.37&r2=1.38)
> pgsql/src/backend/utils/cache:
> inval.c (r1.81 -> r1.82)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/cache/inval.c?r1=1.81&r2=1.82)
> pgsql/src/backend/utils/time:
> tqual.c (r1.107 -> r1.108)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/time/tqual.c?r1=1.107&r2=1.108)
> pgsql/src/include/access:
> xact.h (r1.91 -> r1.92)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/access/xact.h?r1=1.91&r2=1.92)
> pgsql/src/include/commands:
> trigger.h (r1.63 -> r1.64)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/commands/trigger.h?r1=1.63&r2=1.64)
> pgsql/src/include/executor:
> executor.h (r1.144 -> r1.145)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/executor/executor.h?r1=1.144&r2=1.145)
> pgsql/src/include/nodes:
> execnodes.h (r1.181 -> r1.182)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/execnodes.h?r1=1.181&r2=1.182)
> pgsql/src/test/regress/expected:
> combocid.out (r1.1 -> r1.2)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/combocid.out?r1=1.1&r2=1.2)
> pgsql/src/test/regress/sql:
> combocid.sql (r1.1 -> r1.2)
> (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/combocid.sql?r1=1.1&r2=1.2)
>
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