Re: pgsql: Avoid incrementing the CommandCounter when - Mailing list pgsql-committers

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)
>
> ---------------------------(end of broadcast)---------------------------
> TIP 6: explain analyze is your friend

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://postgres.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +