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https://issues.apache.org/jira/browse/PIG-1618?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13003588#comment-13003588
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Thejas M Nair commented on PIG-1618:
------------------------------------
The new parser changes also fixes one behavior seen in earlier versions
including 0.8 .
With the changes in trunk - flatten of bag with null schema will result in a
null schema.
For example,
in 0.8 -
{code}
grunt> describe g;
g: {group: bytearray,a: {null}}
grunt> f = foreach g generate $0 , flatten(a);
grunt> describe f;
f: {group: bytearray,bytearray}
{code}
in trunk with new parser changes -
{code}
grunt> describe g;
g: {group: bytearray,a: {(null)}}
grunt> f = foreach g generate $0 , flatten(a);
grunt> describe f;
Schema for f unknown.
{code}
> 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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