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Re: Optimizer showing wrong rows in plan

From: Nikolas Everett <nik9000(at)gmail(dot)com>
To: raghavendra t <raagavendra(dot)rao(at)gmail(dot)com>
Cc: Matthew Wakeling <matthew(at)flymine(dot)org>, Tadipathri Raghu <traghu(dot)dba(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jeremy Harris <jgh(at)wizmail(dot)org>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Optimizer showing wrong rows in plan
Date: 2010-03-29 13:43:18
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
See 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(dot)rao(at)gmail(dot)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(at)flymine(dot)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
>> --
>> If you let your happiness depend upon how somebody else feels about you,
>> now you have to control how somebody else feels about you. -- Abraham
>> Hicks
>> --
>> Sent via pgsql-performance mailing list (pgsql-performance(at)postgresql(dot)org
>> )
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Subject: Re: Optimizer showing wrong rows in plan

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