[IMPALA-2811] UNION will translated to UNION ALL in Jdbc

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: Impala 2.2.9
• Component/s: Clients
• Labels: correctness downgraded driver jdbc
• Target Version: Impala 2.6.0
• Assignee: Syed A. Hashmi
• Reporter: Afshin Moazami
• Created: 05/Jan/16 20:33
• Updated: 20/May/16 20:29
• Resolved: 20/May/16 20:29

Description

If the UseNativeQuery=0, the UNION will be translated to UNION ALL instead of UNION DISTINCT if there are duplicates in one side of the union.

For example Q1 will return set A where there are two records of X, and Q2 will return set B where there is one record of X.
Q1 UNION Q2 should be equal to Q1 UNION DISTINCT Q2 where we have one record of X.
But, using the impala jdbc driver (2.5.28) it behaves as Q1 UNION ALL Q2 if UseNativeQuery=0