I am interested in giving the query planner the ability to replan (or re-rank plans) after query execution has begun, based on the progression of the query so far.
Example use case: * A LIMIT 1 query is planned using an expensive scan which the planner expects to return a large number of results, and to terminate early. The reality is the query actually produces no results, and the scan must run to completion, potentially taking thousands of times longer than expected. * If this plans costs were adjusted mid-execution to reflect the fact that the scan is producing far fewer rows than expected, then another query plan might come out ahead, which would complete far faster. Has this been done before? Are there any pitfalls to beware of? -- Sent via pgsql-performance mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance