pg_stats.avg_width differs by a factor of 4 on different machines

Hi list

We are using the PostgreSQL pg_stats view to estimate file sizes for some
geodata exports. However, the following query gives us totally different
results on different servers:

select avg_width from pg_stats where tablename='some_geodata' and attname =
> 'GEOMETRY';
>

PostgreSQL 8.3.7 on i486-pc-linux-gnu, compiled by GCC gcc-4.3.real (Ubuntu
4.3.2-1ubuntu11) 4.3.2

> 81803
>

PostgreSQL 8.2.9 on i486-pc-linux-gnu, compiled by GCC cc (GCC) 4.1.2
(Ubuntu 4.1.2-0ubuntu4)

> 20450
>

Both tables have had VACUUM FULL ANALYZE run on them and have identical
data. Note that 81803 is almost exactly 4x20450, though I don't know what
significance this has. x64/i386 makes no difference.

I couldn't find anything in the 8.3 release notes that looked relevant. Any
help appreciated.

Regards
Craig de Stigter

--
Koordinates Ltd
PO Box 1604, Shortland St, Auckland, New Zealand
Phone +64-9-966 0433 Fax +64-9-969 0045
Web http://www.koordinates.com