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Re: BUG #3225: BitmapOr plan node does not show currect row count

From: Russell Smith <mr-russ(at)pws(dot)com(dot)au>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Jens-Wolfhard Schicke <j(dot)schicke(at)asco(dot)de>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #3225: BitmapOr plan node does not show currect row count
Date: 2007-04-14 01:02:40
Message-ID: 46202830.5030909@pws.com.au (view raw or flat)
Thread:
Lists: pgsql-bugs
Tom Lane wrote:
> "Jens-Wolfhard Schicke" <j(dot)schicke(at)asco(dot)de> writes:
>   
>> I an explain analyze I saw recently, a BitmapOr node of 5 Bitmap Index Scan
>> looked like this:
>> BitmapOr  (cost=43.57..43.57 rows=1833 width=0) (actual time=0.146..0.146
>> rows=0 loops=1)
>>     
>
>   
Can we do better than just saying 0?  something indicating not 
calculated, or the fact we can't calculate it?

> BitmapOr and BitmapAnd don't attempt to count their result rows --- doing
> so would involve an extra scan over the bitmap, and what would you do
> for lossy pages?
>
> 			regards, tom lane
>
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>   


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