Just an uninformed wild guess but you seem to be in
desperate search for straws:
> create table site_membership (
> id serial unique
> ,group_id int references groups(id)
> ,site_id int references someothertable(id)
> ,primary key(site_id,group_id)
> ) without oids;
Does using id as primary key and removing the multi-key
primary key constraint on (site_id, group_id) help any ?
Unlikely but you never know...
Karsten
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