Joseph Shraibman <jks(at)selectacast(dot)net> writes:
> No, pkey is not the primary key in this case. The number of entries in u
> that have pkey 260 and not boolfield is 344706.
... and every one of those rows *must* be included in the join input,
regardless of its status value, because it might join to some d row that
has status=3. Conversely, every single row of d must be considered in
the join because it might join to some u row with status=3. So any way
you slice it, this query requires a large and expensive join operation,
no matter that there are only a few rows with the right status values in
the other table.
I'd rewrite the query if I were you.
regards, tom lane