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

Felipe,

You need to write your own connection pool to do this.  That is why I am
saying that it takes a lot of coding to get this to all work efficiently.

--Barry

Felipe Schnack wrote:
>   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));
EXECUTEJDBC_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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