[postgis-users] Transform Performance

Charlie Savage cfis at interserv.com
Tue Oct 25 16:14:45 PDT 2005

Just curious about the performance of transform - if what I am seeing is 

Setup - Postgis Head version, Postgresql 8.1beta3, running on SUSE 10 
(client machine is Windows XP):

I have a table with a POINT geometry in it, and it has approximately 
500,000 records.

This query takes 1 second:

create temp table t1 as
select ogc_fid, wkb_geometry as wkb_geometry
from my_table;

This query takes 1.3 seconds:

create temp table t2 as
select ogc_fid, noop(wkb_geometry) as wkb_geometry
from my_table;

This query, with a transform, takes 34 seconds:

create temp table t3 as
select ogc_fid, Transform(wkb_geometry, 4326) as wkb_geometry
from my_table;

Should it be expected that doing a transform causes such a large 
performance degradation?



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