From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | pgsql-committers(at)postgresql(dot)org |
Subject: | pgsql: Save a few cycles in advance_transition_function(). |
Date: | 2014-01-08 18:59:20 |
Message-ID: | E1W0yLY-00054T-7s@gemulon.postgresql.org |
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Lists: | pgsql-committers |
Save a few cycles in advance_transition_function().
Keep a pre-initialized FunctionCallInfoData in AggStatePerAggData, and
re-use that at each row instead of doing InitFunctionCallInfoData each
time. This saves only half a dozen assignments and maybe some stack
manipulation, and yet that seems to be good for a percent or two of the
overall query run time for simple aggregates such as count(*). The cost
is that the FunctionCallInfoData (which is about a kilobyte, on 64-bit
machines) stays allocated for the duration of the query instead of being
short-lived stack data. But we're already paying an equivalent space cost
for each regular FuncExpr or OpExpr node, so I don't feel bad about paying
it for aggregate functions. The code seems a little cleaner this way too,
since the number of things passed to advance_transition_function decreases.
Branch
------
master
Details
-------
http://git.postgresql.org/pg/commitdiff/e6336b8b5772b9856d65ef967e0b9f748f0f7b0b
Modified Files
--------------
src/backend/executor/nodeAgg.c | 65 +++++++++++++++++++++++-----------------
1 file changed, 38 insertions(+), 27 deletions(-)
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