[jira] [Commented] (PIG-2224) Incorrect arity test in AstValidator.g with ALL and column-based grouping condition together in cogroup

["JArod Wen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PIG-2224?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13095064#comment-13095064 ] 

JArod Wen commented on PIG-2224:
--------------------------------

Thanks Alan! Your suggestion makes sense for this scenario. 

> Incorrect arity test in AstValidator.g with ALL and column-based grouping condition together in cogroup
> -------------------------------------------------------------------------------------------------------
>
>                 Key: PIG-2224
>                 URL: https://issues.apache.org/jira/browse/PIG-2224
>             Project: Pig
>          Issue Type: Bug
>          Components: grunt
>    Affects Versions: 0.9.0
>         Environment: Suse Linux 9/MacOS(10.7)
>            Reporter: JArod Wen
>              Labels: ALL, arity, astvalidator, cogroup, grunt
>             Fix For: 0.9.1
>
>         Attachments: pig-2224.diff.patch, pig-2224.diff.patch
>
>
> When ALL and column-based grouping condition are used together in COGROUP, the arity test in AstValidator.g (line 242) incorrectly sets the arity and causes exception. For example, assume we have the follow two relations:
> a = load 'A' as (col_a_0, col_a_1);
> b = load 'B' as (col_b_0, col_b_1);
> The following statement will throw an invalidation error:
> c = cogroup a by col_a_0, b ALL;
> It is because when processing a:col_a_0, the arity is set to 1; then when processing b:ALL, due to the null value in join_group_by_clause will emit arity 0 for the second relation, and arity test fails. 
> Reversing the two relations will be a work-around for this error:
> c = cogroup b ALL, a by col_a_0;
> However it is a lucky shot: when processing b:ALL, since join_group_by_clause is null, arity is still 0; then when processing a:col_a_0, arity will be initialized so no arity test is done in this case (so it passes).
> The main reason is the omission of the consideration on ALL keyword during the arity test. I attached a patch to fix this, by separating the arity test for both join_group_by_clause and ALL. The patch is tested locally and it works.

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