Shengsheng Huang created HIVE-3561:
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             Summary: 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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