[jira] [Created] (PIG-4541) Skewed full outer join does not return records if any relation is empty.

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

Dipankar created PIG-4541:
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             Summary: Skewed full outer join does not return records if any relation is empty. 
                 Key: PIG-4541
                 URL: https://issues.apache.org/jira/browse/PIG-4541
             Project: Pig
          Issue Type: Bug
          Components: build
    Affects Versions: 0.14.0
         Environment: HDP 2.2.4
            Reporter: Dipankar


Test1:
Perform full join on two relation with left relation being blank and right containing records
empty_relation = FILTER a_relation by (join_column=='eliminate everything');
Test_output = JOIN empty_relation by (join_column) FULL , non_empty_relation by (join_column);
Result : Zero records returned.

Test2:
Perform full join on two relation with left relation being blank and right containing records using skewed
Test_output = JOIN empty_relation by (join_column) FULL , non_empty_relation by (join_column) using ‘skewed’;

Result : Zero records returned.

Test3:
Perform full join on two relation with left relation being blank and right containing records using parallel
Test_output = JOIN empty_relation by (join_column) FULL , non_empty_relation by (join_column) PARALLEL 10;

Result : Zero records returned.

Test4:
Perform full join on two relation with left relation being non empty  and right not containing records using parallel
Test_output = JOIN , non_empty_relation by (join_column) FULL , empty_relation by (join_column) PARALLEL 10;

Result : valid records  returned.

Observation:
1) If the either relation is blank , skewed full outer join does not return anything
2) If the non empty relation is kept on left, everything works except skewed
3) FULL OUTER will only work if the left relation is not empty
4) Skewed will only work if both relation is non empty.




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