Re: Optimizer showing wrong rows in plan - Mailing list pgsql-performance

From Nikolas Everett
Subject Re: Optimizer showing wrong rows in plan
Date
Msg-id d4e11e981003290643s42bcdd68reab7006bbb3eaba6@mail.gmail.com
Whole thread Raw
In response to Re: Optimizer showing wrong rows in plan  (raghavendra t <raagavendra.rao@gmail.com>)
List pgsql-performance
See http://www.postgresql.org/docs/current/static/storage-page-layout.html for all of what is taking up the space.  Short version: 
 Per block overhead is > 24 bytes
 Per row overhead is 23 bytes + some alignment loss + the null bitmap if you have nullable columns

On Mon, Mar 29, 2010 at 8:24 AM, raghavendra t <raagavendra.rao@gmail.com> wrote:
Hi Mattew,
 
Thank you for the information.
 
Once again, I like to thank each and everyone in this thread for there ultimate support.
 
Regards
Raghavendra

On Mon, Mar 29, 2010 at 4:47 PM, Matthew Wakeling <matthew@flymine.org> wrote:
On Mon, 29 Mar 2010, Tadipathri Raghu wrote:
As per the documentation, one page is 8kb, when i create a table with int as
one column its 4 bytes. If i insert 2000 rows, it should be in one page only
as its 8kb, but its extending vastly as expected. Example shown below,
taking the previous example table test with one column.

There is more to a row than just the single int column. The space used by a column will include a column start marker (data length), transaction ids, hint bits, an oid, a description of the types of the columns, and finally your data columns. That takes a bit more space.

Matthew

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