On Wed, Apr 14, 2010 at 7:10 PM, Craig Ringer <craig@xxxxxxxxxxxxxxxxxxxxx> 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 is partially true. The driver uses an unnamed prepared statement on the server. > 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. This is a limitation of the server, not the driver -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
