Setting twoLevelAccessRequired field in a bag schema should not be required to
access fields in the tuples of the bag
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Key: PIG-847
URL: https://issues.apache.org/jira/browse/PIG-847
Project: Pig
Issue Type: Improvement
Affects Versions: 0.2.1
Reporter: Pradeep Kamath
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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