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 <cr...@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 >