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From "Zoltan Haindrich (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-20255) Review LevelOrderWalker.java
Date Mon, 27 Aug 2018 09:11:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-20255?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16593364#comment-16593364
] 

Zoltan Haindrich commented on HIVE-20255:
-----------------------------------------

[~belugabehr] this patch makes the apidoc unreadable:
{code}
 /**
- * This is a level-wise walker implementation which dispatches the node in the order
- * that the node will only get dispatched after all the parents are dispatched.
+ * This is a level-wise walker implementation which dispatches the node in the
+ * order that the node will only get dispatched after all the parents are
+ * dispatched.
  *
  * Each node will be accessed once while it could be dispatched multiple times.
  * e.g., for a lineage generator with operator tree, 2 levels of current node's
- * ancestors need to keep in the operator stack.
- *                  FIL(2) FIL(4)
- *                      |    |
- *                    RS(3) RS(5)
- *                       \  /
- *                      JOIN(7)
- * The join lineage needs to be called twice for JOIN(7) node with different operator
- * ancestors.
+ * ancestors need to keep in the operator stack. FIL(2) FIL(4) | | RS(3) RS(5) \
+ * / JOIN(7) The join lineage needs to be called twice for JOIN(7) node with
+ * different operator ancestors.
{code}


> Review LevelOrderWalker.java
> ----------------------------
>
>                 Key: HIVE-20255
>                 URL: https://issues.apache.org/jira/browse/HIVE-20255
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Planning
>    Affects Versions: 3.0.0, 4.0.0
>            Reporter: BELUGA BEHR
>            Assignee: BELUGA BEHR
>            Priority: Minor
>         Attachments: HIVE-20255.1.patch, HIVE-20255.2.patch, HIVE-20255.3.patch
>
>
> https://github.com/apache/hive/blob/6d890faf22fd1ede3658a5eed097476eab3c67e9/ql/src/java/org/apache/hadoop/hive/ql/lib/LevelOrderWalker.java
> * Make code more concise
> * Fix some check style issues
> {code}
>       if (toWalk.get(index).getChildren() != null) {
>         for(Node child : toWalk.get(index).getChildren()) {
> {code}
> Actually, the underlying implementation of {{getChildren()}} has to do some real work,
so do not throw away the work after checking for null.  Simply call once and store the results.



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