Re: Horrific time for getting 1 record from an index?

On Mon, Nov 11, 2013 at 1:48 PM, Jim Nasby <jnasby@enova.com> wrote:
> Postgres 9.1.9.
>
> explain analyze select min(insert_time) from cnu_stats.page_hits_raw ;
>
> QUERY PLAN
>
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
>  Result  (cost=0.12..0.13 rows=1 width=0) (actual
> time=257545.835..257545.836 rows=1 loops=1)
>    InitPlan 1 (returns $0)
>      ->  Limit  (cost=0.00..0.12 rows=1 width=8) (actual
> time=257545.828..257545.829 rows=1 loops=1)
>            ->  Index Scan using page_hits_raw_pkey on page_hits_raw
> (cost=0.00..5445004.65 rows=47165480 width=8) (actual
> time=257545.826..257545.826 rows=1 loops=1)
>                  Index Cond: (insert_time IS NOT NULL)
>  Total runtime: 257545.881 ms
> (6 rows)
>
>
> I checked and there were no un-granted locks... but I have a hard time
> believing it actually too 257 seconds to get 2 pages (one index, one heap)
> back from our SAN.

Try adding EXPLAIN (ANALYZE, BUFFERS).  I am wondering if you are
reading through a lot of pages addressing tuples not visible to the
transaction.