From: | Daniel Gustafsson <daniel(at)yesql(dot)se> |
---|---|
To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, David Steele <david(at)pgmasters(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> |
Subject: | Re: PoC plpgsql - possibility to force custom or generic plan |
Date: | 2017-09-08 19:21:52 |
Message-ID: | 6C2B395D-64BA-46F2-A6B3-864EBCB37143@yesql.se |
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Lists: | pgsql-hackers |
> On 08 Sep 2017, at 19:14, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>
> On 6 September 2017 at 07:43, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
>> LET custom_plan_tries = 0 IN SELECT ...
>
> Tom has pointed me at this proposal, since on another thread I asked
> for something very similar. (No need to reprise that discussion, but I
> wanted prepared queries to be able to do SET work_mem = X; SELECT).
> This idea looks a good way forward to me.
>
> Since we're all in roughly the same place, I'd like to propose that we
> proceed with the following syntax... whether or not this precisely
> solves OP's issue on this thread.
>
> 1. Allow SET to set multiple parameters...
> SET guc1 = x, guc2 = y
> This looks fairly straightforward
>
> 2. Allow a SET to apply only for a single statement
> SET guc1 = x, guc2 = y FOR stmt
> e.g. SET max_parallel_workers = 4 FOR SELECT count(*) FROM bigtable
> Internally a GUC setting already exists for a single use, via
> GUC_ACTION_SAVE, so we just need to invoke it.
This syntax proposal makes sense, +1. My immediate thought was that the
per-statement GUCs were sort of like options, and most options in our syntax
are enclosed with (), like: SET (guc1 = x, guc2 = y) FOR SELECT ..;
cheers ./daniel
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