Re: Index on timestamp field, and now()

Denis Perchine <dyp(at)perchine(dot)com> writes:
> webmailstation=> explain select * from queue where send_date > timestamp
> 'now';
> NOTICE: QUERY PLAN:
>
> Seq Scan on queue (cost=0.00..10114.06 rows=80834 width=190)
>
> EXPLAIN
>
> queue | send_date | 0 | 8 | -1 |

> |
> |
> {"2001-12-27 21:58:24-05","2002-02-12 08:48:18.967111-05","2002-02-12
> 15:14:51.89063-05","2002-02-13 04:06:19.979181-05","2002-02-13
> 16:20:37.753221-05","2002-02-14 12:03:09.714262-05","2002-02-15
> 15:15:58.04151-05","2002-02-17 11:06:16.964311-05","2002-02-20
> 08:40:57.795043-05","2002-03-12 07:25:46-05","2003-10-28 14:58:58-05"}
> | -0.359735

According to this histogram, 90% of your table has send_date in the
future. Accordingly, seqscan is the right plan for the above query.

regards, tom lane