Re: Optimizer showing wrong rows in plan

On 28/03/2010 10:07 AM, Tadipathri Raghu wrote:
> Hi All,
> I want to give some more light on this by analysing more like this
> 1. In my example I have created a table with one column as INT( which
> occupies 4 bytes)
> 2. Initially it occupies one page of space on the file that is (8kb).
> So, here is it assuming these many rows may fit in this page. Clarify
> me on this Please.

Like I said, it's just a guess. With no statistics all postgres can do
is guess, or in this case use the in-built default for a newly created
table. It could guess 1 or it could guess 10,000,000. What it does is
produce a reasonable guess in the absence of any other information.

You should read the postgres documentation for further information about
statistics and how the optimizer uses them.

Regards,
Gary.