On Tue, 2007-05-08 at 14:52, Y Sidhu wrote:
> Does using DISTINCT in a query force PG to abandon any index search it
> might have embarked upon?
explain analyze select distinct request from businessrequestsummary
where lastflushtime between now() - interval '30 minutes' and now();
QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Unique (cost=3.04..3.04 rows=1 width=17) (actual time=110.565..162.630
rows=75 loops=1)
-> Sort (cost=3.04..3.04 rows=1 width=17) (actual
time=110.555..135.252 rows=6803 loops=1)
Sort Key: request
-> Index Scan using businessrequestsummary_lastflushtime_dx on
businessrequestsummary (cost=0.01..3.03 rows=1 width=17) (actual
time=0.063..59.674 rows=6803 loops=1)
Index Cond: ((lastflushtime >= (now() -
'00:30:00'::interval)) AND (lastflushtime <= now()))
Total runtime: 163.925 ms
(6 rows)
I'd say no.
---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
