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From "Tianyi Wang (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-4794: Grouping distinct agg plan robust to data skew
Date Mon, 14 Aug 2017 22:11:08 GMT
Tianyi Wang has posted comments on this change.

Change subject: IMPALA-4794: Grouping distinct agg plan robust to data skew
......................................................................


Patch Set 4:

(5 comments)

http://gerrit.cloudera.org:8080/#/c/7643/3//COMMIT_MSG
Commit Message:

Line 11: plan partitions data between phase-1 and phase-2 by the grouping exprs.
> the grouping exprs
Done


Line 12: Under this strategy the data skewness on the grouping exprs directly
> make this statement about skew a separate sentence
Done


Line 13: impacts performance. The new plan partitions data by both the grouping
> by both the grouping and distinct agg exprs
Done


Line 14: exprs and distinct agg exprs, then adds one more aggregation and
> Try to avoid descriptions like "supposed to be". We should test and underst
Done


Line 19: sufficient coverage. The pattern is that the distinct agg exprs are
> the first exchange node
Done


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Gerrit-MessageType: comment
Gerrit-Change-Id: I7bdada0e328b555900c7b7ff8aabc8eb15ae8fa9
Gerrit-PatchSet: 4
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Tianyi Wang <twang@cloudera.com>
Gerrit-Reviewer: Alex Behm <alex.behm@cloudera.com>
Gerrit-Reviewer: Tianyi Wang <twang@cloudera.com>
Gerrit-HasComments: Yes

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