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