From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Limiting the number of parameterized indexpaths created |
Date: | 2012-10-31 19:58:52 |
Message-ID: | CA+U5nMKb5jo_OM0sjwA8RH5ne-gvjhCUgFTa2W5+uKZEberpGA@mail.gmail.com |
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Lists: | pgsql-hackers |
On 31 October 2012 19:44, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Before 9.2, we didn't have this problem in this guise because we didn't
> generate parameterized paths bottom-up; instead, given that we had
> already decided to join t2 and t3 for some reason, we would look to see
> what indexpaths we could make for t1 using values from t2 and/or t3.
> However, that approach had big problems of its own: it couldn't find
> plans that involved pushing parameters down through an intervening join.
Given that most joins patterns are repeated consistently across
multiple SQL statements, is it possible to pre-calculate paths at
ANALYZE time, or perhaps cache them (persistently?) when first
generated? That way we just look up best paths, which would make join
planning much faster.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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