As I commented two days ago:

I had written:

> >2) there are good indexes on the right side (relative to the left side of
> >the join in each respective join) to use for the WHERE search..I'd want to
> >look at foreign key indexes to make sure they are decently selective and,
> >if not, I'd add an OR to avoid using that index

You replied:

>Yes, the fields on the right side are all foreign key constraint against
>left side.

Some foreign key indexes are terribly unselective. Try running gstat
against the FK indexes used by the plan, to observe a) their selectivity
and b) the length of the longest duplicated chain (Max Dup).

./helen