RE: how to tell if you are getting a partition wise join

Ryan

>My expectation before running this query was:
>1. Each slave will scan a partition
>2. Then eight slaves will each do a partition wise hash join.
>3. The results will queued. The query coordinator will dequeue the results.
>
>Is this a correct interpretation?

Yes.

>I am not sure if the plan says that.
>
>This is the second plan:
> explain plan for
> select /*+ parallel (a,8) parallel (b,8) */ count(*)
> from hash_test_a partition(HASH_TEST_A01) a, hash_test_c partition(HASH_TEST_A01) b
> where a.object_id = b.object_id

A join is executed using a full partition-wise join if the partition row source appears before the join row source. According to your attachment this is your case. If you use, for example, 6 slaves, you should see a different execution plan.

>I read the partition docs and it does not give examples of partition wise join explain plans.

AFAIK the Data Warehousing Guide describes partition wise joins quite well.

HTH
Chris

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