Re: postgresql shared buffers

On Fri, 8 Sep 2006, Heikki Linnakangas wrote:

> Date: Fri, 08 Sep 2006 15:22:19 +0100
> From: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
> To: Praveen Kumar N <praveen_n(at)students(dot)iiit(dot)net>
> Cc: pgsql-hackers(at)postgresql(dot)org
> Subject: Re: [HACKERS] postgresql shared buffers
>
> Praveen Kumar N wrote:
>>
>> Following is the output of query i have executed.
>
> Looks like Alvaro guessed right. It reads both relations in sequence, sorts
> them in temporary storage, outside bufmgr, and then does a merge join on the
> sorted inputs.

could you tell me how can we trace that? I mean which functions shall I
checkout for that.

>
> If you want to see the behavior you expected, I think you need to define
> indexes on a2 and b2, if you don't have them already, and coerce the planner
> to choose a nested loop join. I'd suggest using "SET enable_seqscan=false;
> SET enable_bitmapscan=false;" and see if that gets you a nested loop join.
>
>

--
N Praveen Kumar
Btech-IV CSE
IIIT,Hyd
AP,India

Imagination is more important than knowledge...
--Albert Einstein