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