Re: about explain analyze

Teodor Sigaev <teodor@sigaev.ru> writes:
> Tom, I am afraid that I don't understand. My first example:
> wow=# explain analyze select max(click.accesses) from click;
>                                                     QUERY PLAN
> -----------------------------------------------------------------------------------------------------------------
>   Aggregate  (cost=1103.70..1103.70 rows=1 width=8) (actual 
> time=289.391..289.393 rows=1 loops=1)
>     ->  Seq Scan on click  (cost=0.00..971.36 rows=52936 width=8) (actual 
> time=0.013..133.943 rows=52936 loops=1)
>   Total runtime: 289.498 ms
> (3 rows)

> Time: 290,695 ms

> select max() returns only one row... If you mean rows in Seq Scan than
> gettimeofday was called (52936+1)*2. Huge value :(

Right, that many times at the Seq Scan plan node, and (1+1)*2 more times
at the Aggregate node.
        regards, tom lane