Release Notes
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Behavioral Changes

Behavioral changes denote a marked change in behavior from the previously released version to this version of software. In HDP 2.5.6, behavioral changes affect the following Hadoop components.

Table 1.6. Behavioral Changes

Hortonworks Bug IDApache ComponentApache JIRASummaryDetails
BUG-66121HiveHIVE-14251 Union All of different types resolves to incorrect data

Scenario: UNION result handling

Previous Behavior: queries in which union operator was used may have created an invalid output type.for example, the column type is ambigous in the following query:

select cast(1 as int) union select cast(1 as string)

Selecting the inappropriate type may cause the value to be changed to NULL.

New Behavior: The types are checked prior to execution; and the ambigous cases are rejected;

FAILED: SemanticException Schema of both sides of union should match: Column _c0 is of type int on first table and type string on second table. Cannot tell the position of null AST. (state=42000,code=40000)

The query should be clarified with explicit casts.