pgsql: Optimize commit_siblings in two ways to improve group commit.

Optimize commit_siblings in two ways to improve group commit.
First, avoid scanning the whole ProcArray once we know there
are at least commit_siblings active; second, skip the check
altogether if commit_siblings = 0.

Greg Smith

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=e620ee35b249b0af255ef788003d1c9edb815a35

Modified Files
--------------
doc/src/sgml/config.sgml            |   17 ++++++++++++-----
src/backend/access/transam/xact.c   |    2 +-
src/backend/storage/ipc/procarray.c |   17 ++++++++++++-----
src/backend/utils/misc/guc.c        |    2 +-
src/include/storage/procarray.h     |    2 +-
5 files changed, 27 insertions(+), 13 deletions(-)