On Thu, Mar 1, 2018 at 6:57 AM, Amit Langote <langote_amit...@lab.ntt.co.jp> wrote: > On 2018/02/28 19:14, Ashutosh Bapat wrote: >> On Wed, Feb 28, 2018 at 6:42 AM, Amit Langote wrote: >>> BTW, should there be a relevant test in partition_join.sql? If yes, >>> attached a patch (partitionwise-join-collation-test-1.patch) to add one. >> >> A partition-wise join path will be created but discarded because of >> higher cost. This test won't see it in that case. So, please add some >> data like other tests and add command to analyze the partitioned >> tables. That kind of protects from something like that. > > Thanks for the review. > > Hmm, the added test is such that the partition collations won't match, so > partition-wise join won't be considered at all due to differing > PartitionSchemes, unless I'm missing something. >
The point is we wouldn't know whether PWJ was not selected because of PartitionScheme mismatch OR the PWJ paths were expensive compared to non-PWJ as happens with empty tables. In both the cases we will see a non-PWJ "plan" although in one case PWJ was not possible and in the other it was possible. I think what we want to test is that PWJ Is not possible with collation mismatch. -- Best Wishes, Ashutosh Bapat EnterpriseDB Corporation The Postgres Database Company
