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Re: [HACKERS] How embarrassing: optimization of a one-shot query doesn't work

From: Michael Paesold <mpaesold(at)gmx(dot)at>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgreSQL(dot)org, pgsql-jdbc(at)postgreSQL(dot)org
Subject: Re: [HACKERS] How embarrassing: optimization of a one-shot query doesn't work
Date: 2008-04-01 10:25:14
Message-ID: B3023355-2601-46B6-9248-A0DD6C26BD62@gmx.at (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-jdbc
Am 01.04.2008 um 01:26 schrieb Tom Lane:
> While testing the changes I was making to Pavel's EXECUTE USING patch
> to ensure that parameter values were being provided to the planner,
> it became painfully obvious that the planner wasn't actually *doing*
> anything with them.  For example
>
> 	execute 'select count(*) from foo where x like $1' into c using $1;
>
> wouldn't generate an indexscan when $1 was of the form 'prefix%'.
...
> The implication of this is that 8.3 is significantly worse than 8.2
> in optimizing unnamed statements in the extended-Query protocol;
> a feature that JDBC, at least, relies on.
>
> The fix is simple: add PlannerInfo to eval_const_expressions's
> parameter list, as was done for estimate_expression_value.  I am
> slightly hesitant to do this in a stable branch, since it would break
> any third-party code that might be calling that function.  I doubt  
> there
> is currently any production-grade code doing so, but if anyone out  
> there
> is actively using those planner hooks we put into 8.3, it's  
> conceivable
> this would affect them.
>
> Still, the performance regression here is bad enough that I think  
> there
> is little choice.  Comments/objections?

Yeah, please fix this performance regression in the 8.3 branch. This  
would affect most of the JDBC applications out there, I think.

Best Regards
Michael Paesold

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