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Date: Sat, 7 Jan 2017 21:29:24 +0000
From: "Marcel Kornacker (Code Review)" <gerrit@cloudera.org>
To: Thomas Tauber-Marshall <tmarshall@cloudera.com>, impala-cr@cloudera.com,
        reviews@impala.incubator.apache.org
CC: Alex Behm <alex.behm@cloudera.com>
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Subject: =?UTF-8?Q?=5BImpala-ASF-CR=5D_IMPALA-1861=3A_Simplify_conditionals_with_constant_conditions=0A?=
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archived-at: Sat, 07 Jan 2017 21:29:33 -0000

Marcel Kornacker has posted comments on this change.

Change subject: IMPALA-1861: Simplify conditionals with constant conditions
......................................................................


Patch Set 3:

(5 comments)

http://gerrit.cloudera.org:8080/#/c/5585/3/fe/src/main/java/org/apache/impala/rewrite/SimplifyConditionalsRule.java
File fe/src/main/java/org/apache/impala/rewrite/SimplifyConditionalsRule.java:

Line 133:     boolean foundFalseExpr = false;
briefly explain why this is needed (indicates that case can be simplified)


Line 140:         if (caseExpr.isLiteral() && expr.getChild(i).isLiteral()) {
> it looks like expr.hasCaseExpr() && !caseExpr.isLiteral() means you'll neve
one more thing: for 'case [<expr>]' you can remove all 'when null' branches. this applies even to non-literal case exprs (which won't trigger l159).


Line 144:           whenExpr = analyzer.getConstantFolder().rewrite(pred, analyzer);
> this is a roundabout way to get a boolean value. use FeSupport.evalPredicat
never mind, you need this for the non-const case.


http://gerrit.cloudera.org:8080/#/c/5585/3/fe/src/test/java/org/apache/impala/analysis/ExprRewriteRulesTest.java
File fe/src/test/java/org/apache/impala/analysis/ExprRewriteRulesTest.java:

Line 239:   public void TestSimplifyConditionalsRule() throws AnalysisException {
for each conditional, also add a test case that doesn't allow any rewrites.


Line 262:     RewritesOk("case 3 when 0 then id when 1 then id + 1 end", rule, "NULL");
> add 'case null'
also add statement with multiple matches.


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Gerrit-MessageType: comment
Gerrit-Change-Id: Id70aaf9fd99f64bd98175b7e2dbba28f350e7d3b
Gerrit-PatchSet: 3
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Thomas Tauber-Marshall <tmarshall@cloudera.com>
Gerrit-Reviewer: Alex Behm <alex.behm@cloudera.com>
Gerrit-Reviewer: Marcel Kornacker <marcel@cloudera.com>
Gerrit-Reviewer: Thomas Tauber-Marshall <tmarshall@cloudera.com>
Gerrit-HasComments: Yes