Re: Postgres 8.3 only uses seq scan

On Tue, Nov 25, 2008 at 10:22 PM, Clemens Schwaighofer
<clemens(dot)schwaighofer(at)tequila(dot)jp> wrote:
> On 11/26/2008 02:15 PM, Scott Marlowe wrote:
>>
>> Are there more rows in the 8.2 table you're testing on? Or is the
>> whole table small enough to fit on a few pages?
>
> I highly doubt that. I have right now in one of the DBs I transfered
> tables from ~100.000 down to ~40.000 rows that all join together. I
> somehow really doubt that fit in a few pages.

Right, with more rows, and choosing fewer, pgsql will go for an index
scan. if choosing a good %, the seq scan.

> So, I am fine when I trust the Postgresql planner :) Because speed wise
> I see no difference that 8.3 would be slower than 8.2

Well, the planner's not perfect. Some off corner cases can catch it
out, or if your database isn't analyzed after a lot of changes it may
make an uninformed decision. But most the time it makes the right, or
close enough, decision.