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Re: Array performance

From: Ruben Rubio Rey <ruben(at)rentalia(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Array performance
Date: 2006-03-24 13:01:29
Message-ID: 4423EDA9.3090502@rentalia.com (view raw or flat)
Thread:
Lists: pgsql-performance
Jim C. Nasby wrote:

>On Fri, Mar 24, 2006 at 01:41:50PM +0100, Ruben Rubio Rey wrote:
>  
>
>>Hi,
>>
>>I have a select like
>>
>>SELECT (array[20]+array[21]+ ... +array[50]+array[51]) as total
>>FROM table
>>WHERE
>>(array[20]+array[21]+ ... +array[50]+array[51])<5000
>>    
>>
>
>http://www.varlena.com/GeneralBits/109.php might provide some useful
>insights. I also recall seeing something about sum operators for arrays,
>but I can't recall where.
>  
>
I ll check it out, seems to be very useful
Is faster create a function to sum the array?

>  
>
>>AND array[20]<>0
>>AND array[21]<>0
>>...
>>AND array[50]<>0
>>AND array[51])<>0
>>    
>>
>
>Uhm... please don't tell me that you're using 0 in place of NULL...
>  
>
mmm ... i have read in postgres documentation that null values on arrays 
are not supported ...

>You might be able to greatly simplify that by use of ANY; you'd need to
>ditch elements 1-19 though:
>
>... WHERE NOT ANY(array) = 0
>  
>
Yep this is much better.

>See http://www.postgresql.org/docs/8.1/interactive/arrays.html
>  
>



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