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Re: Patch to fix bug #6293 - regression in driver performance with regards to ResultSetMetaData-heavy workloads

From: Dave Cramer <pg(at)fastcrypt(dot)com>
To: Steven Schlansker <steven(at)likeness(dot)com>
Cc: pgsql-jdbc(at)postgresql(dot)org
Subject: Re: Patch to fix bug #6293 - regression in driver performance with regards to ResultSetMetaData-heavy workloads
Date: 2012-02-10 02:59:23
Message-ID: CADK3HHJgR_sDBTvmAmkyEM9RxE9x2QGA1Ukb+mnsooZQd+NULQ@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-jdbc
Steven,

I think this http://www.javaworld.com/javaworld/jw-02-2001/jw-0209-double.html
applies to your implementation ?

Dave Cramer

dave.cramer(at)credativ(dot)ca
http://www.credativ.ca



On Thu, Feb 9, 2012 at 7:01 PM, Steven Schlansker <steven(at)likeness(dot)com> wrote:
> Hi,
>
> There is a bug report and associated mailing list thread
> [JDBC] [BUGS] BUG #6293: JDBC driver performance, dated Nov 15 2011
>
>>>>
>>>> The following bug has been logged online:
>>>>
>>>> Bug reference:      6293
>>>> PostgreSQL version: 9.1
>>>> Description:        JDBC driver performance
>>>> Details:
>>>
>>> The 9.1 JDBC driver was changed to try and fetch all metadata for the
>>> entire resultset in one query instead of potentially issuing multiple
>>> queries for each column.  So this change was supposed to improve things.
>>>
>>> Looking at the code, the caching pattern has changed slightly, so now it's
>>> important to hold onto the same ResultSetMetaData instance.  That is you
>>> need to do:
>
> I have a proposed fix available as a pull request on GitHub.  The commit itself is here:
> https://github.com/NessComputing/pgjdbc/commit/15dee25198c0a7a4d3bdeca2193a003d552fac2f
>
> and the pull request complete with an in-progress discussion is here:
> https://github.com/pgjdbc/pgjdbc/pull/1
>
> I requested guidance on the mailing list last week on the best way to approach this problem,
> but there were no responses, so I have changed the ResultSet to cache the MetaData instances.
>
> As best as I can tell the MetaData is immutable, so hopefully there will be no ill effects from
> caching instances.
>
> I saw some discussion about licensing re: GitHub on the mailing list the other day, so to be
> perfectly clear I am releasing this code to the pgsql-jdbc project under whatever terms they
> so choose, or the public domain if that is the appropriate choice.
>
> I hope this will be an example of how moving to GitHub pull requests can be a positive change :-)
>
>
> I believe this fixes the referenced bug, and I've asked the original submitter to test out my change
> to see if it fixes it for him.
>
> Regards,
> Steven Schlansker
> Ness Computing
>
>
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Next:From: Steven SchlanskerDate: 2012-02-10 03:32:26
Subject: Re: Patch to fix bug #6293 - regression in driver performance with regards to ResultSetMetaData-heavy workloads
Previous:From: Dave CramerDate: 2012-02-10 00:50:13
Subject: Fwd: [pgjdbc] Change Jdbc4ResultSet to cache Jdbc4ResultSetMetaData instances (#1)

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