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From "Cheng Lian (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-16576) Move plan SQL generation code from SQLBuilder into logical operators
Date Mon, 18 Jul 2016 09:25:20 GMT

    [ https://issues.apache.org/jira/browse/SPARK-16576?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15381969#comment-15381969
] 

Cheng Lian commented on SPARK-16576:
------------------------------------

[~rxin] I wrote the first version of the {{SQLBuilder}}. The reason why the {{toSQL}} method
isn't implemented as a method of individual logical plan classes is that a single node may
be mapped to different SQL fragments according to its parent and/or children. But now we can
have the canonicalizer to do all the preprocessing, and it's possible to split this method
into individual logical plan classes.

> Move plan SQL generation code from SQLBuilder into logical operators
> --------------------------------------------------------------------
>
>                 Key: SPARK-16576
>                 URL: https://issues.apache.org/jira/browse/SPARK-16576
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Reynold Xin
>
> We currently handle all SQL query generation in a single class (SQLBuilder). This has
many disadvantages:
> 1. It is not extensible, i.e. it is not possible to introduce a new logical operator,
even just for experimentation purpose, without modifying Spark.
> 2. It is very fragile. When we introduce a new logical operator, it is very likely that
we forget to update SQLBuilder and then the use of that new logical operator would fail view
definition.
> We should move the SQL definition part into logical operators themselves, so this becomes
more robust and scalable.



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