From: Dave Crooke <dcrooke@gmail.com>
To: Craig Ringer <craig@postnewspapers.com.au>
Cc: pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: JDBC question for PG 8.3.9
Date: Wed, 14 Apr 2010 22:03:09 -0500
Message-ID: <x2lca24673e1004142003w31b01a9ercab43cb566b64075@mail.gmail.com> (raw)
In-Reply-To: <4BC64B64.5070608@postnewspapers.com.au>
References: <y2xca24673e1004141349l531c9710i5ed197a258d6ca8d@mail.gmail.com>
<4BC64B64.5070608@postnewspapers.com.au>
Mine is a single record INSERT, so no issues with plans :-) Little Java ETL
job.
Is there any setting I'd need to tweak assuming I'm using 150-200 of these
at once?
Cheers
Dave
On Wed, Apr 14, 2010 at 6:10 PM, Craig Ringer
<craig@postnewspapers.com.au>wrote:
> On 15/04/10 04:49, Dave Crooke wrote:
>
>> Hi foilks
>>
>> I am using PG 8.3 from Java. I am considering a performance tweak which
>> will involve holding about 150 java.sql.PreparedStatment objects open
>> against a single PGSQL connection. Is this safe?
>>
>> I know that MySQL does not support prepared statements /per se/, and so
>> their implementation of PreparedStatement is nothing more than some
>> client-side convenience code that knows how to escape and format
>> constants for you. Is this the case for PG, or does the PG JDBC driver
>> do the real thing?
>>
>
> Pg supports real server-side prepared statements, as does the JDBC driver.
>
> IIRC (and I can't say this with 100% certainty without checking the sources
> or a good look at TFM) the PostgreSQL JDBC driver initially does only a
> client-side prepare. However, if the PreparedStatement is re-used more than
> a certain number of times (five by default?) it switches to server-side
> prepared statements.
>
> This has actually caused a bunch of performance complaints on the jdbc
> list, because the query plan may change at that switch-over point, since
> with a server-side prepared statement Pg no longer has a specific value for
> each parameter and may pick a more generic plan.
>
> Again only IIRC there's a configurable threshold for prepared statement
> switch-over. I thought all this was in the PgJDBC documentation and/or
> javadoc - if it's not, it needs to be.
>
> --
> Craig Ringer
>
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To: pgsql-performance@postgresql.org
Cc: dcrooke@gmail.com, craig@postnewspapers.com.au
Subject: Re: JDBC question for PG 8.3.9
In-Reply-To: <x2lca24673e1004142003w31b01a9ercab43cb566b64075@mail.gmail.com>
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