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From "Lianhui Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-3561) Build a full SQL-compliant parser for Hive
Date Wed, 10 Oct 2012 12:07:04 GMT

    [ https://issues.apache.org/jira/browse/HIVE-3561?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13473167#comment-13473167
] 

Lianhui Wang commented on HIVE-3561:
------------------------------------

for the first approach,there is a problem. standardSQL can not support the HiveQL writting
in historical.
because there is a big difference in some operators. example:join.
so that maybe spent a lot of time to transfering using hivesql to standardSQL.
in my opinion,in short time,both maybe co-exist.

 
                
> Build a full SQL-compliant parser for Hive
> ------------------------------------------
>
>                 Key: HIVE-3561
>                 URL: https://issues.apache.org/jira/browse/HIVE-3561
>             Project: Hive
>          Issue Type: Sub-task
>          Components: Query Processor
>    Affects Versions: 0.10.0
>            Reporter: Shengsheng Huang
>
> To build a full SQL compliant engine on Hive, we'll need a full SQL complant parser.
The current Hive parser missed a lot of grammar units from standard SQL. To support full SQL
there're possibly four approaches:
> 1.Extend the existing Hive parser to support full SQL constructs. We need to modify the
current Hive.g and add any missing grammar units and resolve conflicts. 
> 2.Reuse an existing open source SQL compliant parser and extend it to support Hive extensions.
We may need to adapt Semantic Analyzers to the new AST structure.  
> 3.Reuse an existing SQL compliant parser and make it co-exist with the existing Hive
parser. Both parsers share the same CliDriver interface. Use a query mode configuration to
switch the query mode between SQL and HQL (this is the approach we're now using in the 0.9.0
demo project)
> 4.Reuse an existing SQL compliant parser and make it co-exist with the existing Hive
parser. Use a separate xxxCliDriver interface for standard SQL.  
> Let's discuss which is the best approach. 

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