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From "Jesus Camacho Rodriguez (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-11752) Pre-materializing complex CTE queries
Date Tue, 02 Feb 2016 09:11:39 GMT

    [ https://issues.apache.org/jira/browse/HIVE-11752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15127939#comment-15127939
] 

Jesus Camacho Rodriguez commented on HIVE-11752:
------------------------------------------------

[~navis], thanks to you, the patch was almost ready (modulo some fixes/testing). It would
be indeed a great addition.

I guess there are two reasons why views need special treatment.
First, CTE within view should not be materialized. Thus, I introduced a flag that disables
CTE materialization if we are parsing a view creation/alter statement.
Secondly, counting CTE references within views is a bit tricky (code is a bit convoluted).
The current patch skips views for counting purposes, treating them simply as tables. We can
address this issue in a follow-up JIRA.

> Pre-materializing complex CTE queries
> -------------------------------------
>
>                 Key: HIVE-11752
>                 URL: https://issues.apache.org/jira/browse/HIVE-11752
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Processor
>    Affects Versions: 2.1.0
>            Reporter: Navis
>            Assignee: Jesus Camacho Rodriguez
>            Priority: Minor
>         Attachments: HIVE-11752.03.patch, HIVE-11752.04.patch, HIVE-11752.1.patch.txt,
HIVE-11752.2.patch.txt
>
>
> Currently, hive regards CTE clauses as a simple alias to the query block, which makes
redundant works if it's used multiple times in a query. This introduces a reference threshold
for pre-materializing the CTE clause as a volatile table (which is not exists in any form
of metastore and just accessible from QB).



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