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https://issues.apache.org/jira/browse/PIG-1618?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12965316#action_12965316
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Alan Gates commented on PIG-1618:
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There was a question on whether the default type inserter should be done as a
visitor on the AST or on the logical plan. We want to limit the number of
visitors we create on the AST since they require a definition of the grammar in
each visitor. But I think the default type inserter makes sense on the AST.
Moving this to the logical plan would most likely involve putting information
in the logical plan that shouldn't be there (like whether there was an AS
defined on this clause). Since the AST already has this information it makes
more sense to do that processing there.
> 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: antlr-3.2.jar, javadoc.patch, NewParser-1.patch,
> NewParser-2.patch, NewParser-3.patch, NewParser-3.patch, NewParser-4.patch,
> NewParser-5.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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