On Mon, Nov 14, 2011 at 5:22 PM, Andrew Barnham <andrew.barnham@xxxxxxxxx> wrote: > I wonder, if it is possible and worthwhile, to setup the query planner to > recognize that because of the stats I indicate above, that a sort by partnum > is almost exactly the same as a sort by partnum+franchise. And doing a > Index scan on partnum index, and sorting results in memory will be > dramatically faster. The sort buffer only needs to be very small, will only > grow to 8 records only at most in my above example. The buffer will scan > partnum index, and as long as partnum is the same, it will sort that small > segment, as soon as the partnum increments when walking the index, the > buffer zeros out again for next sort group. This has come up before and seems worthwhile, but nobody's implemented it yet. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
