Greg Stark <stark@xxxxxxx> writes: > On 19 Sep 2014 19:40, "Josh Berkus" <josh@xxxxxxxxxxxx> wrote: >> Yeah, here's an example of the canonical case: >> >> Table t1 ( a, b, c ) >> >> - "b" is low-cardinality >> - "c" is high-cardinality >> - There are separate indexes on both b and c. >> >> SELECT a, b, c FROM t1 >> WHERE b = 2 >> ORDER BY c LIMIT 1; > You badly want a partial index on c WHERE b=2 for each value of 2 which > appears in your queries. Well, if it's *only* b = 2 that you ever search for, then maybe a partial index would be a good answer. Personally I'd use a plain btree index on (b, c). The planner's been able to match this type of query to multicolumn indexes for a long time. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
