henk de wit wrote: > I'm using Postgres 9.1 on Debian Lenny and via a Java server (JBoss AS 6.1) I'm executing a simple > "select ... for update" query: > > > SELECT > > importing > > FROM > > customer > > WHERE > > id = :customer_id > > FOR UPDATE NOWAIT > > > Once every 10 to 20 times Postgres fails to obtain the lock for no apparent reason: > > 18:22:18,285 WARN [org.hibernate.util.JDBCExceptionReporter] SQL Error: 0, SQLState: 55P03 > 18:22:18,285 ERROR [org.hibernate.util.JDBCExceptionReporter] ERROR: could not obtain lock on row in > relation "customer" > > > I'm "pretty" sure there's really no other process that has the lock, as I'm the only one on a test DB. > If I execute the query immediately again, it does succeed in obtaining the lock. I can however not > reproduce this via e.g. PGAdmin. > > > Is it possible or perhaps even known that PG has this behavior, or should I look for the cause in the > Java code? (I'm using Java EE"s entity manager to execute a native query inside an EJB bean that lets > a JDBC connection from a pool join a JTA transaction.) There must be at least a second database connection that holds locks on the objects you need. Look in pg_stat_activity if you see other connections. It is probably a race condition of some kind. Turn on logging og connections and disconnections. Set log_statement='all' That way you should be able to see from the log entries who issues what queries concurrently with you. Yours, Laurenz Albe -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
