[HIVE-14251] Union All of different types resolves to incorrect data - ASF JIRA

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Details

Type: Bug
Status: Closed
Priority: Major
Resolution: Fixed
Affects Version/s: 2.0.0
Fix Version/s: 2.2.0
Component/s: Query Planning
Labels:
None

Target Version/s:

1.3.0, 2.0.2
Release Note:

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With this change, Hive will only perform implicit conversion within each type groups including string group, number group or date group, not across groups. So in order to union a string type with a date type, a explicit cast from string to date or from date to string is needed.

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With this change, Hive will only perform implicit conversion within each type groups including string group, number group or date group, not across groups. So in order to union a string type with a date type, a explicit cast from string to date or from date to string is needed.

Description

create table src(c1 date, c2 int, c3 double);
insert into src values ('2016-01-01',5,1.25);
select * from
(select c1 from src union all
select c2 from src union all
select c3 from src) t;

It will return NULL for the c1 values. Seems the common data type is resolved to the last c3 which is double.