On Sun, 2002-05-19 at 06:32, Keary Suska wrote: > > The drawback to using LIMIT is that you are executing the query on every > call, and Postgres cannot optimize on a LIMIT as was mentioned, because the > entire query has to be collected before the LIMIT can be applied. However, > IIRC, Postgres does query result caching, so subsequent calls on the same > query will tend to be faster, providing there is enough memory allocated to > support it. PostgreSQL will certainly take LIMIT into account when planning queries. EXPLAIN SELECT * FROM mybigtable WHERE x = y; and EXPLAIN SELECT * FROM mybigtable WHERE x = y LIMIT n; Will regularly show different query plans. For more complex queries, however, the plans are less likely to differ by much. OTOH PostgreSQL does _not_ do result caching, unless you have applied some patches that were floating around last year some time. Regards, Andrew. -- -------------------------------------------------------------------- Andrew @ Catalyst .Net.NZ Ltd, PO Box 11-053, Manners St, Wellington WEB: http://catalyst.net.nz/ PHYS: Level 2, 150-154 Willis St DDI: +64(4)916-7201 MOB: +64(21)635-694 OFFICE: +64(4)499-2267 Are you enrolled at http://schoolreunions.co.nz/ yet?
