On Tue, Jan 23, 2007 at 07:47:26AM -0800, Subramaniam Aiylam wrote: > Hello all, > > I have a setup in which four client machines access > a Postgres database (8.1.1) running on a Linux box. > So, there are connections from each machine to the > database; hence, the Linux box has about 2 postgres > processes associated with each machine. > > I am using the JDBC driver > (postgresql-8.1-404.jdbc3.jar) to talk to the > database. I am also using the Spring framework(1.2.2) > and Hibernate (3.0.5) on top of JDBC. I use Apache's Beware of Hibernate... it likes to abuse the RDBMS... > DBCP database connection pool (1.2.1). > > Now, there is one particular update that I make from > one of the client machines - this involves a > reasonably large object graph (from the Java point of > view). It deletes a bunch of rows (around 20 rows in > all) in 4-5 tables and inserts another bunch into the > same tables. > > When I do this, I see a big spike in the CPU usage > of postgres processes that are associated with ALL the > client machines, not just the one I executed the > delete/insert operation on. The spike seems to happen > a second or two AFTER the original update completes > and last for a few seconds. > > Is it that this operation is forcibly clearing some > client cache on ALL the postgres processes? Why is > there such an interdependency? Can I set some > parameter to turn this off? No, wouldn't be clearing anything. Would the other connections be updating the same data? If so they could be waiting on locks that the graph-updating code has acquired. I suggest you turn on query logging and see what commands are actually being sent to the database. -- Jim Nasby jim@xxxxxxxxx EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)
