[jira] Commented: (PIG-847) Setting twoLevelAccessRequired field in a bag schema should not be required to access fields in the tuples of the bag

["Richard Ding (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PIG-847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12991539#comment-12991539 ] 

Richard Ding commented on PIG-847:
----------------------------------

+1.

Notice schema display change between 0.8 and 0.9 for group/cogroup:

0.8:

{code}
b: {group: int,a: {a0: int,a1: int,a2: int}}
{code}

0.9:

{code}
b: {group: int,a: {(a0: int,a1: int,a2: int)}}
{code}


> Setting twoLevelAccessRequired field in a bag schema should not be required to access fields in the tuples of the bag
> ---------------------------------------------------------------------------------------------------------------------
>
>                 Key: PIG-847
>                 URL: https://issues.apache.org/jira/browse/PIG-847
>             Project: Pig
>          Issue Type: Improvement
>    Affects Versions: 0.3.0
>            Reporter: Pradeep Kamath
>            Assignee: Daniel Dai
>             Fix For: 0.9.0
>
>         Attachments: PIG-847-1.patch
>
>
> Currently Pig interprets the result type of a relation as a bag. However the schema of the relation directly contains the schema describing the fields in the tuples for the relation. However when a udf wants to return a bag or if there is a bag in input data or if the user creates a bag constant, the schema of the bag has one field schema which is that of the tuple. The Tuple's schema has the types of the fields. To be able to access the fields from the bag directly in such a case by using something like <bagname>.<fieldname> or <bag>.<fieldposition>, the schema of the bag should have the twoLevelAccess set to true so that pig's type system can get traverse the tuple schema and get to the field in question. This is confusing - we should try and see if we can avoid needing this extra flag. A possible solution is to treat bags the same way - whether they represent relations or real bags. Another way is to introduce a special "relation" datatype for the result type of a relation and bag type would be used only for true bags. In this case, we would always need bag schema to have a tuple schema which would describe the fields. 

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