=?iso-8859-1?Q?Ga=EBtan_Allart?= <gallart(at)free(dot)fr> writes:
> I'm experiencing an interesting issue with PostgreSQL 8.4.2-r2.
> I was running a pretty big database on another server (8.3) pretty fine.
> When I moved it to this new server, behaviour changed.
Did you ANALYZE the database after loading it? Are you sure you
have all the parameters set similarly to what you used in the 8.3
installation?
(The described behavior sounds suspiciously like work_mem is not
large enough to allow a hashagg to be chosen.)
regards, tom lane