[jira] Created: (PIG-1277) Pig should give error message when cogroup on tuple keys of different inner type

[Daniel Dai (JIRA)]

Pig should give error message when cogroup on tuple keys of different inner type
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                 Key: PIG-1277
                 URL: https://issues.apache.org/jira/browse/PIG-1277
             Project: Pig
          Issue Type: Bug
          Components: impl
    Affects Versions: 0.6.0
            Reporter: Daniel Dai


When we cogroup on a tuple, if the inner type of tuple does not match, we treat 
them as different keys. This is confusing. It is desirable to give 
error/warnings when it happens.

Here is one example:
UDF:
{code}
public class MapGenerate extends EvalFunc<Map> {
    @Override
    public Map exec(Tuple input) throws IOException {
        // TODO Auto-generated method stub
        Map m = new HashMap();
        m.put("key", new Integer(input.size()));
        return m;
    }
    
    @Override
    public Schema outputSchema(Schema input) {
        return new Schema(new Schema.FieldSchema(null, DataType.MAP));
    }
}
{code}

Pig script: 
{code}
a = load '1.txt' as (a0);
b = foreach a generate a0, MapGenerate(*) as m:map[];
c = foreach b generate a0, m#'key' as key;
d = load '2.txt' as (c0, c1);
e = cogroup c by (a0, key), d by (c0, c1);
dump e;
{code}

1.txt
{code}
1
{code}

2.txt
{code}
1 1
{code}

User expected result (which is not right):
{code}
((1,1),{(1,1)},{(1,1)})
{code}

Real result:
{code}
((1,1),{(1,1)},{})
((1,1),{},{(1,1)})
{code}

We shall give user the message that we can not merge the key due to the type 
mismatch.

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