[postgis-users] ERROR: Out of memory

[Mark Cave-Ayland]

On Mon, 2007-10-08 at 10:24 +0200, Andreas Laggner wrote:
> Hi,
> 
> i tried to perform the "union approach" from Kevin 
> http://postgis.refractions.net/support/wiki/index.php?ExamplesOverlayTables
> the first query worked fine:
>  CREATE TABLE all_lines AS
>    SELECT St_ExteriorRing (the_geom) AS the_geom FROM ffhsinglerep
>    UNION ALL
>    SELECT St_ExteriorRing (the_geom) AS the_geom FROM spasinglerep;
> 
> but in the second one i get an error:
> CREATE TABLE noded_lines AS
>    SELECT St_Union(the_geom) AS the_geom
>    FROM all_lines;
> 
> ERROR: Out of memory
> SQL Status:53200
> Detail:Failed on request of size 20750552.
> 
> If anybody knows what may be behind this error......i have no idea!
> 
> Cheers      Andreas

Aggregates shouldn't run out of memory in general; the only time I have
seen this discussed is if a Hash Aggregate plan is chosen for a large
number of rows due to incorrect ANALYZE estimates. What does the output
of "EXPLAIN SELECT St_Union(the_geom) AS the_geom FROM all_lines;" show?


ATB,

Mark.

-- 
ILande - Open Source Consultancy
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