Re: IN list processing performance (yet again)

Dave Tenny <tenny@attbi.com>

From: Dave Tenny <tenny@attbi.com>
To: Shridhar Daithankar <shridhar_daithankar@persistent.co.in>
Cc: pgsql-performance@postgresql.org
Date: 2003-05-28T17:58:14Z
Lists: pgsql-performance
A join isn't an option, these elements come a a selection of entity ID's 
that are specific to some client context.
Some other people suggested joins too. 

Consider it something like this, say there's a database that represents 
the entire file system content
of a set of machines, hundreds of thousands of files.  A single user 
wants to do something
related to the ID's of 3000 files.  The requests for those 3000 files 
can be built up in a number of ways,
not all of which rely on data in the database.  So I need to retrieve 
data on those 3000 files using IN lists or some alternative.

Dave

Shridhar Daithankar wrote:

>On Wednesday 28 May 2003 18:21, Dave Tenny wrote:
>  
>
>>Having grepped the web, it's clear that this isn't the first or last
>>time this issue will be raised.
>>
>>My application relies heavily on IN lists.  The lists are primarily
>>constant integers, so queries look like:
>>
>>SELECT val FROM table WHERE id IN (43, 49, 1001, 100002, ...)
>>    
>>
>
>How do you derive this list of number? If it is from same database, can you 
>rewrite the query using a join statement?
>
>HTH
>
> Shridhar
>
>
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