This is a known PostgreSQL 8.3.5 bug (#4567).

http://archives.postgresql.org/pgsql-hackers/2008-12/msg00278.php
http://archives.postgresql.org/pgsql-bugs/2008-12/msg00037.php

It looks like the there's fix for it as well.

Cheers,
Kevin


Ben Madin wrote:
G'day Vincent,

This didn't work as anticipated - in fact it appears to have truncated the table!

On 08/01/2009, at 5:01 AM, [email protected] <mailto:[email protected]> wrote:

Another and more <classic> solution (despite slower on big tables) to
keep spatially close rows together on disk is to use postgresql CLUSTER
statement.
http://www.postgresql.org/docs/8.3/static/sql-cluster.html

CLUSTER reorders data on disk using a specified index, therefore
increasing access speed when reading rows in the index order.

Example :
CREATE INDEX idx_mytable_the_geom ON mytable USING GIST(the_geom);
CLUSTER mytable USING idx_mytable_the_geom;

CLUSTER works on a normal index :

# select count(*) from gis_roads;
count -------
 89618
(1 row)

# CLUSTER gis_roads USING gis_roads_gid_key;

CLUSTER
# select count(*) from gis_roads;
count -------
 89618
(1 row)

all good!

But when I try on the gist index

# CLUSTER gis_roads USING gis_roads_gist;
CLUSTER

# select count(*) from gis_roads;
count -------
     0
(1 row)

whoops!

Is this something I missed? Is this a PostgreSQL bug... surely the cluster command shouldn't be allowed to destroy a whole table.

cheers

Ben





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Ben Madin
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[email protected] <mailto:[email protected]>



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