PostgreSQL subtransactions (nested transactions) may cause multiple performance and scalability issues: higher rates of XID growth and higher risks of transaction ID wraparound, performance degradation when more than PGPROC_MAX_CACHED_SUBXIDS (64) are used in a session, drastic performance slowdowns when subtransactions are combined with SELECT .. FOR UPDATE, and finally, brief downtime on standbys when subtranasctions used on the primary in paralell with long-running transactions or just slo...|
1. Introduction As an experienced PostgreSQL user, you may have a lot of experience in setting up streaming replication in your database clusters to make multiple backups of your data. But have you wondered how the standby is able to correctly determine if a tuple sent from the primary should be visible to the user| Highgo Software Inc. - Enterprise PostgreSQL Solutions