Mike Christensen <mike@kitchenpc.com> writes:
> I'm curious under what circumstances Postgres will cache an execution
> plan for a query.
If you're writing raw SQL, never. The assumption is that the
application knows its usage pattern a lot better than the server does,
and if the application is going to re-execute the same/similar statement
a lot of times, the app ought to make use of a prepared statement for
that.
Some client-side code (such as the JDBC driver) will make use of
prepared statements under the hood, so a lot depends on context.
But sending plain SQL with PQexec() does not result in any cached plan.
regards, tom lane
