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https://issues.apache.org/jira/browse/HIVE-11284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14631924#comment-14631924
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Jesus Camacho Rodriguez commented on HIVE-11284:
------------------------------------------------
Sure.
==
Background:
When RT is on, HiveJoinToMultiJoinRule is responsible for creating MultiJoin
operators out of Join operators (if possible). But the plan might be the
following:
{noformat}
Join(...)
Project(...)
Join(...)
...
Filter(...)
...
{noformat}
Thus, first we need to pull up the Project operator(s) through Join(s) using
HiveJoinProjectTransposeRule, to obtain:
{noformat}
Project(...)
Join(...)
Join(...)
...
Filter(...)
...
{noformat}
Then, HiveJoinToMultiJoinRule will find both Join operators and merge them.
Finally, the Project operator(s) will be pushed down again throw the tree (this
is done by HiveRelTrimmer).
==
Problem:
HIVE-11223 enabled the return path for the cbo_rp_join0.q test.
At the same time, HIVE-11252 changed the application of the rules.
- Before HIVE-11252, HiveJoinToMultiJoinRule was applied first, then
HiveJoinProjectTransposeRule + HiveJoinToMultiJoinRule. This was merging the
operators correctly, because no projects were found in between the Joins.
- After HIVE-11252, only HiveJoinToMultiJoinRule + HiveJoinProjectTransposeRule
are applied (this is correct). The problem is that 1)
HiveJoinProjectTransposeRule.LEFT and HiveJoinProjectTransposeRule.RIGHT were
not enabled, and 2) even if they were enabled, they were not working as
expected (more on this below). That's why the test failed.
==
Solution:
HiveJoinProjectTransposeRule.LEFT and HiveJoinProjectTransposeRule.RIGHT get
enabled in the patch. In addition, JoinProjectTransposeRule was only working on
inner joins, but we need it to work also on outer joins in Hive. That's why I
had to bring so much code from the Calcite superclass
(JoinProjectTransposeRule) to the Hive subclass (HiveJoinProjectTransposeRule)
to solve the issue. I plan to create a Calcite patch so we can use
JoinProjectTransposeRule with all kind of Joins.
> Fix cbo_rp_join0 failure on master
> ----------------------------------
>
> Key: HIVE-11284
> URL: https://issues.apache.org/jira/browse/HIVE-11284
> Project: Hive
> Issue Type: Bug
> Components: CBO, Query Planning
> Affects Versions: 2.0.0
> Reporter: Ashutosh Chauhan
> Assignee: Jesus Camacho Rodriguez
> Attachments: HIVE-11284.patch
>
>
> It first failed in this build :
> http://ec2-174-129-184-35.compute-1.amazonaws.com/jenkins/job/PreCommit-HIVE-TRUNK-Build/4621/
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