>> Are you running a lot of full table updates?
> If you mean updates which are applied on every or almost every row of
> the table - yes, it happens with two rather small tables of max. 10
> 000 rows. But they are both not touched by the query with this big
> performance difference.
I'm not an expert, but would it help to change fillfactor to about 45%?
I'm just guessing that full table updates with fillfactor=45% could
store the rows on the same page. Maybe I'm wrong.