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https://issues.apache.org/jira/browse/PIG-3144?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13592030#comment-13592030
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Cheolsoo Park commented on PIG-3144:
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Hi Jonathan,
Can you update the comment in {{LogicalRelationalOperator.fixDuplicateUids()}}?
{code}
/**
* In the case of a join it is possible for multiple columns to have been
derived from the same
* column and thus have duplicate UID's. This detects that case and resets the
uid.
* See PIG-3022 and PIG-3093 for more information.
* @param fss a list of LogicalFieldSchemas to check the uids of
*/
{code}
# This is not a join-specific issue, so "in the case of a join" should be
removed.
# PIG-3022 should be replaced with PIG-3020.
Otherwise, the patch looks good to me. I will run unit tests.
> Erroneous map entry alias resolution leading to "Duplicate schema alias"
> errors
> -------------------------------------------------------------------------------
>
> Key: PIG-3144
> URL: https://issues.apache.org/jira/browse/PIG-3144
> Project: Pig
> Issue Type: Bug
> Affects Versions: 0.11, 0.10.1
> Reporter: Kai Londenberg
> Assignee: Jonathan Coveney
> Fix For: 0.12
>
> Attachments: PIG-3144-0.patch
>
>
> The following code illustrates a problem concerning alias resolution in pig
> The schema of D2 will incorrectly be described as containing two "age"
> fields. And the last step in the following script will lead to a "Duplicate
> schema alias" error message.
> I only encountered this bug when using aliases for map fields.
> {code}
> DATA = LOAD 'file:///whatever' as (a:map[chararray], b:chararray);
> D1 = FOREACH DATA GENERATE a#'name' as name, a#'age' as age, b;
> D2 = FOREACH D1 GENERATE name, age, b;
> DESCRIBE D2;
> {code}
> Output:
> {code}
> D2: {
> age: chararray,
> age: chararray,
> b: chararray
> }
> {code}
> {code}
> D3 = FOREACH D2 GENERATE *;
> DESCRIBE D3;
> {code}
> Output:
> {code}
> <file file:///.../pig-bug-example.pig, line 20, column 16> Duplicate schema
> alias: age
> {code}
> This error occurs in this form in Apache Pig version 0.11.0-SNAPSHOT (r6408).
> A less severe variant of this bug is also present in pig 0.10.1. In 0.10.1,
> the "Duplicate schema alias" error message won't occur, but the schema of D2
> (see above) will still have wrong duplicate alias entries.
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