Dimitris Tsirogiannis has posted comments on this change.

Change subject: IMPALA-4309: Introduce Expr rewrite phase and supporting 
classes.
......................................................................


Patch Set 4:

(2 comments)

http://gerrit.cloudera.org:8080/#/c/4746/4/fe/src/main/java/org/apache/impala/analysis/AnalysisContext.java
File fe/src/main/java/org/apache/impala/analysis/AnalysisContext.java:

PS4, Line 378: rewriter_.reset();
             :         analysisResult_.stmt_.rewriteExprs(rewriter_);
             :         reAnalyze = rewriter_.changed();
> Don't really agree.
I understand what you're saying. However, as is now, you have a class that 
keeps track of modifications to other classes it acts upon. So now you have to 
make sure that you reset the state of the rewriter before you apply it to a 
different entity. Re #2, I believe there is a way to have each class track 
modifications to its own state but it will probably require some kind of 
visitor pattern. Let me think about it and maybe I can suggest something more 
concrete.


http://gerrit.cloudera.org:8080/#/c/4746/4/fe/src/main/java/org/apache/impala/analysis/Analyzer.java
File fe/src/main/java/org/apache/impala/analysis/Analyzer.java:

PS4, Line 60: rewrite
> Sorry, missed this.
ha, correct. I was thinking of the action. But rewriter is not ambiguous :)


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Gerrit-MessageType: comment
Gerrit-Change-Id: I2279dc984bcf7742db4fa3b1aa67283ecbb05e6e
Gerrit-PatchSet: 4
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Alex Behm <alex.b...@cloudera.com>
Gerrit-Reviewer: Alex Behm <alex.b...@cloudera.com>
Gerrit-Reviewer: Bharath Vissapragada <bhara...@cloudera.com>
Gerrit-Reviewer: Dimitris Tsirogiannis <dtsirogian...@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <tarmstr...@cloudera.com>
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