Tom Lane <[EMAIL PROTECTED]> writes: > > Partition Elimination relies upon being able to prove at execution time > > You mean plan time.
Fwiw, both are possible. In oracle there are (at least) three different cases: 1. For queries like "select * from tab" the plan shows a multiple partition scan. 2. For queries like "select * from tab where partition_key = 1" the plan shows the partition that the planner proved would suffice. 3. For queries like select * from tab where partition_key = ?" the plan shows a single partition scan of a partition to be determined at run-time. This last case can be very important for joins as well. For queries like select * from tab,tab2 where tab1.partition_key = tab2.fk" the planner can prove that each nested loop iteration will only require a single btree lookup. This is important since if it can't prove this the nested loop has to do multiple index lookups making it look very poor compared to a merge join or hash join. There are also cases where Oracle knows that the plan node will involve reading multiple partitions but not all. -- greg ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
