Date: Mon, 24 Apr 2017 11:43:53 -0700
From: Andres Freund <andres@anarazel.de>
To: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>
Cc: pgsql-hackers@postgresql.org
Subject: Re: Cached plans and statement generalization
Message-ID: <20170424184353.u2krt2eiw2l6e2af@alap3.anarazel.de>
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Hi,

On 2017-04-24 11:46:02 +0300, Konstantin Knizhnik wrote:
> So what I am thinking now is implicit query caching. If the same query with
> different literal values is repeated many times, then we can try to
> generalize this query and replace it with prepared query with
> parameters.

That's not actuall all that easy:
- You pretty much do parse analysis to be able to do an accurate match.
  How much overhead is parse analysis vs. planning in your cases?
- The invalidation infrastructure for this, if not tied to to fully
  parse-analyzed statements, is going to be hell.
- Migrating to parameters can actually cause significant slowdowns, not
  nice if that happens implicitly.

Greetings,

Andres Freund


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