Re: Why should such a simple query over indexed columns be so slow?
| От | Fernando Hevia |
|---|---|
| Тема | Re: Why should such a simple query over indexed columns be so slow? |
| Дата | |
| Msg-id | CAGYT1XR+ztEYV-P2EpFZ8z826CoRNQTzmYk2yy=QUBaaaZPXbw@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Why should such a simple query over indexed columns be so slow? (Alessandro Gagliardi <alessandro@path.com>) |
| Ответы |
Re: Why should such a simple query over indexed columns be
so slow?
|
| Список | pgsql-performance |
On Mon, Jan 30, 2012 at 17:35, Alessandro Gagliardi <alessandro@path.com> wrote:
Well that was a lot faster:"HashAggregate (cost=156301.82..156301.83 rows=2 width=26) (actual time=2692.806..2692.807 rows=2 loops=1)"" -> Bitmap Heap Scan on blocks (cost=14810.54..155828.95 rows=472871 width=26) (actual time=289.828..1593.893 rows=575186 loops=1)"" Recheck Cond: (created > '2012-01-29 00:00:00+00'::timestamp with time zone)"" Filter: (shared IS FALSE)"" -> Bitmap Index Scan on blocks_created_idx (cost=0.00..14786.89 rows=550404 width=0) (actual time=277.407..277.407 rows=706663 loops=1)"" Index Cond: (created > '2012-01-29 00:00:00+00'::timestamp with time zone)""Total runtime: 2693.107 ms"
U sure the new timing isn't owed to cached data? If I am reading it correctly, from the latest explain you posted the Index Scan shouldn't have made a difference as it is reporting pretty much all rows in the table have created > 'yesterday'.
If the number of rows with created < 'yesterday' isn't significant (~ over 25% with default config) a full scan will be chosen and it will probably be the better choice too.
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