Re: Replication lag

Query Execution and Reply WAL Coexistence in PostgreSQL

Wasim,

Thanks for your question.

Yes, PostgreSQL does support concurrent WAL replay and read query execution on replicas through its hot standby feature. By setting hot_standby = on, a replica can serve read-only queries while applying WAL files from the primary via streaming replication.

However, there are a few caveats:

* Read queries on the standby may be canceled if they conflict with recovery operations. This behavior can be tuned using parameters like max_standby_streaming_delay and hot_standby_feedback.
* Unlike Oracle GoldenGate, PostgreSQL’s native logical replication is more limited in terms of conflict resolution and cross-version replication, though tools like pglogical or Debezium can bridge those gaps for more complex use cases.

Best regards,

David Okeamah

DAVID OKEAMAH,DEVELOPER
________________________________
From: Wasim Devale <wasimd60(at)gmail(dot)com>
Sent: Friday, May 23, 2025 8:13:10 AM
To: pgsql-admin <pgsql-admin(at)postgresql(dot)org>; Pgsql-admin <pgsql-admin(at)lists(dot)postgresql(dot)org>
Subject: Replication lag

Hello,

Reply wal and query execution on replica can coexists?

Golden gate in oracle has this feature that they can coexists but in postgresql do we have any provision like this.

Please assist.

Thanks,
Wasim