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Performance penalty of visibility info in indexes?

From: Jim Nasby <decibel(at)decibel(dot)org>
To: PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org>
Subject: Performance penalty of visibility info in indexes?
Date: 2007-02-02 05:57:41
Message-ID: (view raw or whole thread)
Lists: pgsql-hackers
Has anyone actually measured the performance overhead of storing  
visibility info in indexes? I know the space overhead sounds  
daunting, but even if it doubled the size of the index in many cases  
that'd still be a huge win over having to scan the heap as well as  
the index (esp. for things like count(*)). There would also be  
overhead from having to update the old index tuple, but for the case  
of updates you're likely to need that page for the new index tuple  

I know this wouldn't work for all cases, but ISTM there are many  
cases where it would be a win.
Jim Nasby                                            jim(at)nasby(dot)net
EnterpriseDB      512.569.9461 (cell)


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