Re: [HACKERS] Cached plans and statement generalization

From: Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>
To: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Cc: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] Cached plans and statement generalization
Date: 2019-08-05 17:02:09
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On 01.08.2019 19:56, Konstantin Knizhnik wrote:
> On 31.07.2019 19:56, Heikki Linnakangas wrote:
>> On 09/07/2019 23:59, Konstantin Knizhnik wrote:
>>> Fixed patch version of the path is attached.
>> Much of the patch and the discussion has been around the raw parsing,
>> and guessing which literals are actually parameters that have been
>> inlined into the SQL text. Do we really need to do that, though? The
>> documentation mentions pgbouncer and other connection poolers, where
>> you don't have session state, as a use case for this. But such
>> connection poolers could and should still be using the extended query
>> protocol, with Parse+Bind messages and query parameters, even if they
>> don't use named prepared statements. I'd want to encourage
>> applications and middleware to use out-of-band query parameters, to
>> avoid SQL injection attacks, regardless of whether they use prepared
>> statements or cache query plans. So how about dropping all the raw
>> parse tree stuff, and doing the automatic caching of plans based on
>> the SQL string, somewhere in the exec_parse_message? Check the
>> autoprepare cache in exec_parse_message(), if it was an "unnamed"
>> prepared statement, i.e. if the prepared statement name is an empty
>> string.
>> (I'm actually not sure if exec_parse/bind_message is the right place
>> for this, but I saw that your current patch did it in
>> exec_simple_query, and exec_parse/bind_message are the equivalent of
>> that for the extended query protocol).
>> - Heikki
> I decided to implement your proposal. Much simple version of
> autoprepare patch is attached.
> At my computer I got the following results:
>  pgbench -M simple -S         22495 TPS
>  pgbench -M extended -S    47633 TPS
>  pgbench -M prepared -S    47683 TPS
> So autoprepare speedup execution of queries sent using extended
> protocol more than twice and it is almost the same as with explicitly
> prepared statements.
> I failed to create regression test for it because I do not know how to
> force psql to use extended protocol. Any advice is welcome.

Slightly improved and rebased version of the patch.

Konstantin Knizhnik
Postgres Professional:
The Russian Postgres Company

Attachment Content-Type Size
autoprepare-extended-2.patch text/x-patch 25.3 KB

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