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From "Xuefu Zhang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-1618) Switch to new parser generator technology
Date Mon, 07 Mar 2011 22:33:59 GMT

    [ https://issues.apache.org/jira/browse/PIG-1618?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13003663#comment-13003663
] 

Xuefu Zhang commented on PIG-1618:
----------------------------------

I think the behavior change was largely due to the way we interpret the schema, probably having
nothing to do with parser.

It's basically a question of how we treat a schema partially known (unknown). It doesn't seem
easy to correctly address the issue. However, treating a schema partially known as unknown
seems fine: user can always use $0 instead of "group" to access the known field.

On the other hand, treating flattan( a ) as one field of byte array seems misleading.

> Switch to new parser generator technology
> -----------------------------------------
>
>                 Key: PIG-1618
>                 URL: https://issues.apache.org/jira/browse/PIG-1618
>             Project: Pig
>          Issue Type: Improvement
>    Affects Versions: 0.8.0
>            Reporter: Alan Gates
>            Assignee: Xuefu Zhang
>             Fix For: 0.9.0
>
>         Attachments: NewParser-1.patch, NewParser-10.patch, NewParser-11.patch, NewParser-12.patch,
NewParser-13.2.patch, NewParser-13.patch, NewParser-14.patch, NewParser-15.patch, NewParser-18.patch,
NewParser-19.3.patch, NewParser-19.patch, NewParser-2.patch, NewParser-3.patch, NewParser-3.patch,
NewParser-4.patch, NewParser-5.patch, NewParser-6.patch, NewParser-7.patch, NewParser-8.patches,
NewParser-9.patch, antlr-3.2.jar, javadoc.patch
>
>
> There are many bugs in Pig related to the parser, particularly to bad error messages.
 After review of Java CC we feel these will be difficult to address using that tool.  Also,
the .jjt files used by JavaCC are hard to understand and maintain.  
> ANTLR is being reviewed as the most likely choice to move to, but other parsers will
be reviewed as well.
> This JIRA will act as an umbrella issue for other parser issues.

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