From: | Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Pull up aggregate subquery |
Date: | 2011-05-25 14:35:53 |
Message-ID: | BANLkTik3M-K8sc2hhHmyT-mpVD6rSB2acQ@mail.gmail.com |
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Lists: | pgsql-hackers |
2011/5/25 Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>:
> So I'm still
> thinking which of pulling up and parameterized scan is better.
After more investigation I came up with third idea, pushing down
RangeTblEntry to aggregate subquery. This sounds like a crazy idea,
but it seems to me like it is slightly easier than pulling up
agg-subquery. The main point is that when you want to pull up, you
must care if the final output would be correct with other join
relations than the aggregate-related one. In contrast, when pushing
down the target relation to agg-subquery it is simple to ensure the
result.
I'm looking around pull_up_subqueries() in subquery_planner() to add
the pushing down logic. It could be possible to do it around
make_one_rel() but I bet query structure changes are doable against
Query, not PlannerInfo.
I appreciate any comments.
Regards,
--
Hitoshi Harada
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