[postgis-devel] CLUSTER in 8.3

Chris Hodgson chodgson at refractions.net
Fri Dec 5 11:49:09 PST 2008

Kevin Neufeld wrote:
> Mark Cave-Ayland wrote:
>  > I think the GiST part is a red herring - there is no way that a 
>> COUNT(*) FROM foo" can use an index in PostgreSQL. My suspicion is 
>> that it's related to the use of ANALYZE/VACUUM/CLUSTER.
> Maybe.  You're right that "SELECT ..." doesn't use the index, but the 
> CLUSTER physically reorders the table based on the index.  If there is 
> a bizzare bug in our GiST implementation that produces an empty 
> traversal list some of the time, the table would be empty.
> Never mind, I just saw Paul's post.  This is good news for us in that 
> it's not related to our implementation of GiST ...  but it still could 
> be related to PostgreSQL's implementation, no?
Well, can anyone replicate the problem by clustering on a non-gist 
index? If so, then we should really be able to just throw this problem 
at the Postgres Devs. I'd be surprised if this was the case though, I 
can't believe no-one else would have come across this yet...


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