[postgis-users] Understanding speed issues

[John Abraham]

Hello postgis friends.  I'm doing a simple update query on a table of 
138000 records.  The update query is
update Parcels
set pecastype=' ', pecassqft=0, yearbuilt=1993;

It takes over 10000s.  Why might that be ? 

I've been googling a bit, and I understand that because of the 
transaction nature of the postgresql system, each of these updates would 
be an "delete" and an "insert".  That, I suppose, *might* explain the 
slowness.  But how to get around it?  Are there database config 
setttings or options in the query that might help?

PostGIS relevance:  It has a GIST index, but I'm not changing the 
geometry at all.  But if it's a delete and an insert, maybe it has to 
keep rebuilding the GIST index, which could be slow?

Thanks in advance for any help,

PS also my hard drive is almost full; I'm working on that problem but I 
can't see how it could be too relevant.

--
John Abraham
jabraham at ucalgary.ca