[IMPALA-1987] Wrong results when query has an outer join, inline views and null-generating functions like coalesce

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: Impala 2.2
• Fix Version/s: Impala 2.2.7, Impala 2.3.0
• Labels: correctness impala
• Target Version: Impala 2.2.7, Impala 2.3.0
• Assignee: Dimitris Tsirogiannis
• Reporter: Dimitris Tsirogiannis
• Created: 08/May/15 22:04
• Updated: 20/Dec/15 00:05
• Resolved: 11/Jun/15 18:05

Description

Steps to reproduce:

create table tt1 (a int, b int);
insert into tt1 values ((1,1), (2,2));
create table tt2 (a int, b int);
insert into tt2 values ((1,1), (2,2));
create function identity(int) returns int location '/test-warehouse/libTestUdfs.so' symbol='Identity';

The following query returns nulls in the columns of the outer joined table.

select * from tt1 left outer join (select coalesce(identity(a), 1) as b from tt2) tt3 on tt1.a = tt3.b;

The issue also appears when no UDFs are used in the coalesce expression, as follows:

select * from tt1 left outer join (select coalesce(a, 1) as b from tt2) tt3 on tt1.a = tt3.b;