Postgres - ERROR: prepared statement “S_1” already exists

Question

When executing batch queries via JDBC to pgbouncer, I get the following error:

org.postgresql.util.PSQLException: ERROR: prepared statement \"S_1\" already e         


        

Answer 1

This turned out to be a pgBouncer issue that occurs when using anything other than session pooling. We were using transaction pooling, which apparently can't support prepared statements. By switching to session pooling, we got around the issue.

Unfortunately, this isn't a good fix for our use case. We have two separate uses for pgBouncer: one part of our system does bulk updates which are most efficient as prepared statements, and another part needs many connections in very rapid succession. Since pgBouncer doesn't allow switching back and forth between session pooling and transaction pooling, we're forced to either run two separate instances on different ports just to support our needs, or to implement this patch. Preliminary testing shows it to work well, but time will tell if it proves to be safe and effective.