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

From: Dave Cramer <pg(at)fastcrypt(dot)com>
To: Michael Paesold <mpaesold(at)gmx(dot)at>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, 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 11:14:34
Message-ID: 5E59B144-3024-44AA-8C98-FDFE1BFE060E@fastcrypt.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-jdbc
On 1-Apr-08, at 6:25 AM, Michael Paesold wrote:

>
> 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.
>
Was the driver ever changed to take advantage of the above strategy?


Dave
> Best Regards
> Michael Paesold
>
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