On 12.11.2012 12:07, Kyotaro HORIGUCHI wrote:
Hello, This is new version of identity projection patch.
Reverted projectionInfo and ExecBuildProjectionInfo. Identity
projection is recognized directly in ExecGroup, ExecResult, and
ExecWindowAgg. nodeAgg is reverted because I couldn't make it
sane..
The following is the result of performance test posted before in
order to show the source of the gain.
Hmm, this reminds me of the discussion on removing useless Limit nodes:
http://archives.postgresql.org/pgsql-performance/2012-12/msg00127.php.
The optimization on Group, WindowAgg and Agg nodes doesn't seem that
important, the cost of doing the aggregation/grouping is likely
overwhelming the projection cost, and usually you do projection in
grouping/aggregation anyway. But makes sense for Result.
For Result, I think you should aim to remove the useless Result node
from the plan altogether. And do the same for useless Limit nodes.
- Heikki
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