Re: CVS JDBC driver will try to use server-side-prepare on - Mailing list pgsql-jdbc

I can't understand. How can I "cache" my Statements? As far as I know after I return my connection to tomcat's
connectionpooling my statement becomes pratically unusable, isn't it? 

On Fri, 15 Aug 2003 09:55:02 -0700
Barry Lind <blind@xythos.com> wrote:

> Oliver,
>
> See my comments below.
>
> Oliver Jowett wrote:
> > It looks like the driver is trying to use server-side prepare on SQL that it
> > won't work on:
> >
> > Aug 16 00:05:40 flood postgres[12989]: [12-1] LOG:  query: PREPARE JDBC_STATEMENT_4 AS CREATE TABLE
"testBigDB/persisted_testBigDB/persisted_one"( pk         BYTEA   NOT 
> > Aug 16 00:05:40 flood postgres[12989]: [12-2]  NULL,  generation INT8    NOT NULL,  data       BYTEA   NOT NULL,
CONSTRAINT
> > Aug 16 00:05:40 flood postgres[12989]: [12-3]  "pkey_testBigDB/persisted_testBigDB/persisted_one" PRIMARY KEY
(pk));EXECUTE JDBC_STATEMENT_4 
> > Aug 16 00:05:40 flood postgres[12989]: [13] ERROR:  parser: parse error at or near "CREATE" at character 29
> >
> > This then turns up as a SQLException on the java side.
> >
> > Yes, I know, "don't do that then!", but isn't the plan to default to
> > server-side prepare eventually?
>
> Yes and no.  The plan is to convert fully over to the new V3 protocol
> which will better handle cases like this and a lot of other things.  So
> yes the plan is to move fully to server side prepared statements, but
> via a different mechanism.  And conversly the plan isn't to move the
> current mechanism forward as it has many limitations (as you are finding
> out).  One of the big reasons for the new functionality in the V3
> protocol is to provide better support for these type of opperations
> efficiently.
>
> However a workaround for this specific problem would be to only use
> server side prepared statements in the current implementation for
> executeQuery calls, not for executeUpdate or for plain execute.
>
> >
> > Should we only be doing PREPARE on queries that are known to be safe (e.g.
> > single-statement SELECTs), or is it better to try to catch the errors and
> > abandon the prepare? (more general, but sounds a bit hairy).
> >
> > The reason that this came up is I'm modifying the driver to allow
> > server-side prepare to be toggled at the connection- and datasource- level.
> > Patches for that to follow once I've sorted this problem out.
> >
>
> I would rather see you invest your time in implementing the V3 protocol
> to do this correctly.  I am reluctant to commit patches along the lines
> of what you are describing (check the archives for previous discussions
> on this).  But in short the reason is, that in general using the current
> prepared implementation will be *slower* than not using it, unless you
> are reusing the statement a number of times.  Therefore unless you have
> some sort of complex application layer that is caching Statement objects
> and reusing them, this feature will nagatively impact performance, and
> IMHO will lead to problems because people will assume that something
> like this should be used and complain when it makes things slower.
> Since in order to be useful you need application logic to cache and
> reuse the Statement objects, it isn't that difficult to have that logic
> also turn on server side prepare using the current methods.
>
> Finally, if you do want to pursue your current course, I would like to
> see some sort of benchmarks that show these changes actually on average
> help.
>
> thanks,
> --Barry
>
>
> > -O
> >
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> >
>
>
>
>
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