Re: Slow SELECT with distinct, in a TIMESTAMP type column

On 24 Jun 2002, Marcos Garcia wrote:

>
> When i make the set enable_seqscan = off the result is:
>
> dbname=# set enable_seqscan = off;
> SET VARIABLE
> dbname=# explain analyze SELECT distinct(smsdate) FROM send_total;
>
> NOTICE: QUERY PLAN:
>
> Unique (cost=0.00..31084.39 rows=1232 width=8) (actual
> time=108.60..195210.91 rows=6676 loops=1)
> -> Index Scan using send_total_smsdate_idx on send_total
> (cost=0.00..31053.60 rows=12315 width=8) (actual time=108.59..195145.43
> rows=12087 loops=1)
> Total runtime: 195226.24 msec

Well the plan choice makes sense (since it's about 3.5x faster as
a sequence scan over the index scan).
It looks like most of the time is taken up by the actual scan (is
"select smsdate from send_total" pretty much as slow?).