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From "Alex Behm (Code Review)" <>
Subject [Impala-ASF-CR] IMPALA-5003: Constant propagation in scan nodes
Date Thu, 06 Apr 2017 21:27:23 GMT
Alex Behm has posted comments on this change.

Change subject: IMPALA-5003: Constant propagation in scan nodes

Patch Set 18:


Basically done, final nits
Commit Message:

Line 7: IMPALA-5003: Constant propagation in scan nodes
Constant propagation in scan conjuncts

Line 9: When conjuncts are pushed into table refs from inline views, they can
Wording is slightly confusing because we don't "push conjuncts into table refs", we have specific
terms for those things. How about saying something like (amend as you see fit obviously):

Implements constant propagation within a list of conjuncts and applies the optimization to
scan conjuncts. The optimization is applied during planning to take the complete list of applicable
conjuncts into account. In particular, we want to simplify conjuncts to enable partition pruning....
File fe/src/main/java/org/apache/impala/analysis/

Line 922:   // Arbitrary cost bound for propagation
How about:

// Arbitrary max number of exprs considered during constant propagation to limit the cost
due to the O(N^2) complexity.

Line 923:   private final static int CONST_PROPAGATION_LIMIT = 200;

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Gerrit-MessageType: comment
Gerrit-Change-Id: I79750a8edb945effee2a519fa3b8192b77042cb4
Gerrit-PatchSet: 18
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Zach Amsden <>
Gerrit-Reviewer: Alex Behm <>
Gerrit-Reviewer: Dan Hecht <>
Gerrit-Reviewer: Marcel Kornacker <>
Gerrit-Reviewer: Zach Amsden <>
Gerrit-HasComments: Yes

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