Friday, November 24

Trade-offs in Hot Standby Deployments

Greg's PlanetPostgreSQL, PostgreSQL
The new Hot Standby feature in the upcoming PostgreSQL 9.0 allows running queries against standby nodes that previously did nothing but execute a recovery process. Two common expectations I've heard from users anticipating this feature is that it will allow either distributing short queries across both nodes, or allow running long reports against the standby without using resources on the master. These are both possible to do right now, but unless you understand the trade-offs involved in how Hot Standby works there can be some unanticipated behavior here. Standard Long-running Queries One of the traditional problems in a database using MVCC, like PostgreSQL, is that a long-running query has to keep open a resource--referred to as a snapshot in the current Postgres implementation--to (more…)