Re: [BUGS] Bad mis-costing of Merge Left Join in 8.0.1

#1

Andrew - Supernews <andrew+nonews (AT) supernews (DOT) com> writes:

Quote:

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

---------------------------(end of broadcast)---------------------------
TIP 7: don't forget to increase your free space map settings

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Re: [BUGS] Bad mis-costing of Merge Left Join in 8.0.1

mailing.database.pgsql-bugs mailing.database.pgsql-bugs

Re: [BUGS] Bad mis-costing of Merge Left Join in 8.0.1 - 04-03-2005 , 08:13 PM