On Nov 17, 2011, at 5:20 PM, Steve Atkins wrote: > > I don't think you want the group by in that first query.
Heh, I tried to simply the example, but in reality that = becomes an in clause of multiple values. So the group by is needed. >> >> >> postgres=# explain analyze select min(id) from delayed_jobs where >> strand='sis_batch:account:15' group by strand; >> QUERY PLAN >> -------------------------------------------------------------------------------------------------------------------------- >> GroupAggregate (cost=0.00..8918.59 rows=66 width=29) (actual >> time=226.759..226.760 rows=1 loops=1) >> -> Seq Scan on delayed_jobs (cost=0.00..8553.30 rows=72927 width=29) >> (actual time=0.014..169.941 rows=72268 loops=1) >> Filter: ((strand)::text = 'sis_batch:account:15'::text) >> Total runtime: 226.817 ms >> (4 rows) >> >> postgres=# explain analyze select id from delayed_jobs where >> strand='sis_batch:account:15' order by id limit 1; >> QUERY >> PLAN >> --------------------------------------------------------------------------------------------------------------------------------------------------------- >> Limit (cost=0.00..0.33 rows=1 width=8) (actual time=0.097..0.098 rows=1 >> loops=1) >> -> Index Scan using index_delayed_jobs_on_strand on delayed_jobs >> (cost=0.00..24181.74 rows=72927 width=8) (actual time=0.095..0.095 rows=1 >> loops=1) >> Index Cond: ((strand)::text = 'sis_batch:account:15'::text) >> Total runtime: 0.129 ms >> (4 rows) >> >> >> -- >> Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) >> To make changes to your subscription: >> http://www.postgresql.org/mailpref/pgsql-performance > > > -- > Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance
