Andrew - Supernews <andrew+nonews@supernews.com> writes:
> The cost for the Merge Left Join is clearly preposterous, since the join
> cost can't be lower than the cost of the left branch, as it is an outer
> join and therefore that branch must be run to completion. I do not fully
> understand the cost estimation code for the merge join, but it appears to
> be reducing its total cost estimate below that of the child nodes on the
> assumption that the join can be aborted early, which is clearly not the
> case for outer joins.
Yeah, you're right ... it needs to consider whether the join is OUTER.
This bug has been there for a long time ...
regards, tom lane