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Re: IN list processing performance (yet again)

From: Dave Tenny <tenny(at)attbi(dot)com>
To: Shridhar Daithankar <shridhar_daithankar(at)persistent(dot)co(dot)in>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: IN list processing performance (yet again)
Date: 2003-05-28 17:58:14
Message-ID: (view raw, whole thread or download thread mbox)
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.


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?
> Shridhar
>---------------------------(end of broadcast)---------------------------
>TIP 4: Don't 'kill -9' the postmaster

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