Does anyone have any suggestions for my problem? (I have to wonder if
I'm somehow just not getting peoples attention or what. This is my
second question this week on a public mailing list that has gotten
exactly 0 replies)
Jonathan
On 7/5/2011 8:18 PM, Jonathan wrote:
I have a query that uses ORDER BY and LIMIT to get a set of image data
rows that match a given tag. When both ORDER BY and LIMIT are included
for some reason the planner chooses a very slow query plan. Dropping one
or the other results in a much faster query going from 4+ seconds -> 30
ms. Database schema, EXPLAIN ANALYZE and other information can be found
at http://pgsql.privatepaste.com/31113c27bf Is there a way to convince
the planner to use the faster plan when doing both ORDER BY and LIMIT
without using SET options or will I need to disable the slow plan
options to force the planner to use the fast plan?
I found some stuff in the mailing list archives that looks related but I
didn't see any fixes. Apparently the planner hopes the merge join will
find the LIMIT # of rows fairly quickly but instead it winds up scanning
almost the entire table.
--
Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance
