[postgis-devel] CLUSTER in 8.3

[Obe, Regina]

So I guess its probably the fix to 8.3.5

#

Fix GiST index corruption due to marking the wrong index entry "dead" after a deletion (Teodor)

This would result in index searches failing to find rows they should have found. 

That introduced this seeming race condition.


-----Original Message-----
From: postgis-devel-bounces at postgis.refractions.net on behalf of Paul Ramsey
Sent: Fri 12/5/2008 3:01 PM
To: PostGIS Development Discussion
Subject: Re: [postgis-devel] CLUSTER in 8.3
 
Works with btree.

pramsey=# create table ttt as select * from counties;
SELECT
pramsey=# create index gid_bix on ttt (gid);
CREATE INDEX
pramsey=# select count(*) from ttt;
 count
-------
  3141
(1 row)

pramsey=# cluster ttt using gid_bix;
CLUSTER
pramsey=# select count(*) from ttt;
 count
-------
  3141
(1 row)


On Fri, Dec 5, 2008 at 11:49 AM, Chris Hodgson <chodgson at refractions.net> wrote:
> Kevin Neufeld wrote:
>>
>> Mark Cave-Ayland wrote:
>>  > I think the GiST part is a red herring - there is no way that a "SELECT
>>>
>>> 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...
>
> Chris
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