Shant Hovsepian created IMPALA-9973:
---------------------------------------
Summary: Perform distinct elimination with constraint information
Key: IMPALA-9973
URL: https://issues.apache.org/jira/browse/IMPALA-9973
Project: IMPALA
Issue Type: Sub-task
Components: Frontend
Reporter: Shant Hovsepian
Table constraints (primary key, unique key) or reference integrity constraint
information can be used to remove unnecessary DISTINCT aggregation.
T1 (A, B, C)
T2 (X, Y, Z)
Given the constraints:
primary key (T1.A)
primary key (T2.X, T2.Y)
T1 foreign key references T2
T1.B -> T2.X
T1.C -> T2.Y
Distinct can be removed:
SELECT DISTINCT T1.A, T1.B FROM T1;
SELECT DISTINCT T2.X, T2.Y FROM T2;
SELECT DISTINCT T1.A, T2.X, T2.Y, T2.Z FROM T1 INNER JOIN T2 ON (T1.B=T2.X and
T1.C = T2.Y)
Distinct can't be removed:
SELECT DISTINCT T2.X, T2.Z FROM T2;
SELECT DISTINCT T1.A, T2.X, T2.Z FROM T1 INNER JOIN T2 ON (T1.B=T2.X and T1.C =
T2.Y)
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
