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https://issues.apache.org/jira/browse/TAJO-1352?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14624349#comment-14624349
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ASF GitHub Bot commented on TAJO-1352:
--------------------------------------
Github user hyunsik commented on a diff in the pull request:
https://github.com/apache/tajo/pull/593#discussion_r34441081
--- Diff: tajo-common/src/main/java/org/apache/tajo/util/Pair.java ---
@@ -24,11 +24,20 @@
private T1 first;
private T2 second;
+ public Pair() {
--- End diff --
It is only used for JoinGraphContext::getCachedOrNewJoinEdge. It would be
better if JoinGraphContext::getCachedOrNewJoinEdge creates a new instance for
Pair instead of reusing a member variable.
> Improve the join order algorithm to consider missed cases of associative join
> operators
> ---------------------------------------------------------------------------------------
>
> Key: TAJO-1352
> URL: https://issues.apache.org/jira/browse/TAJO-1352
> Project: Tajo
> Issue Type: Improvement
> Components: planner/optimizer
> Reporter: Jihoon Son
> Assignee: Jihoon Son
> Attachments: JoinGraph.png
>
>
> TAJO-1277 fixes a bug related to the associativity of join operators, but
> there are still some missed cases that join operators are associative. This
> work should include the cases described in the following links:
> * http://stackoverflow.com/questions/20022196/are-left-outer-joins-associative
> * https://cwiki.apache.org/confluence/display/Hive/LanguageManual+Joins
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