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From "Alex Behm (Code Review)" <ger...@cloudera.org>
Subject [Impala-CR](cdh5-trunk) IMPALA-3450: LIMITs on UNION nodes are reflected in planner cardinality estimates
Date Wed, 18 May 2016 21:27:21 GMT
Alex Behm has posted comments on this change.

Change subject: IMPALA-3450: LIMITs on UNION nodes are reflected in planner cardinality estimates
......................................................................


Patch Set 1:

(2 comments)

http://gerrit.cloudera.org:8080/#/c/3127/1/testdata/workloads/functional-planner/queries/PlannerTest/limit.test
File testdata/workloads/functional-planner/queries/PlannerTest/limit.test:

Line 1: # limits on union nodes are reflected in cardinality estimates
Prefix with IMPALA-3450


Line 2: explain select * from tpch.lineitem UNION ALL (select * from tpch.lineitem) LIMIT
1
We usually add queries without 'explain', so let's stick to that.

Please move this test to union.test, and follow the standard practice of not changing the
explain level. It is unfortunate, but it avoids test flakniess (for example the "hosts" number
can change for various reasons non-deterministically)

The test will unfortunately have to be indirect, e.g., you can test that the union + limit
is moved to the build side of a join or something like that.


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Gerrit-MessageType: comment
Gerrit-Change-Id: Ic06dcb93bbb2510c0d40151302bd817ef340b825
Gerrit-PatchSet: 1
Gerrit-Project: Impala
Gerrit-Branch: cdh5-trunk
Gerrit-Owner: Jim Apple <jbapple@cloudera.com>
Gerrit-Reviewer: Alex Behm <alex.behm@cloudera.com>
Gerrit-HasComments: Yes

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