[IMPALA-7045] CTAS doesn't allow NULL values

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: Frontend
• Labels: newbie ramp-up
• Environment: impalad version 2.7.0-cdh5.10.0 RELEASE (build 785a073cd07e2540d521ecebb8b38161ccbd2aa2) ; Built on Fri Jan 20 12:03:56 PST 2017
• Epic Color: ghx-label-9
• Assignee: Unassigned
• Reporter: Pavel Grafkin
• Created: 17/May/18 16:34
• Updated: 22/Dec/20 21:10

Description

When I run following:

{{CREATE TABLE temp_test AS SELECT CAST(null AS bigint) as nullable_int }}

with the error:

Unsupported type 'null_type' in column 'nullable_int' of table 'temp_test'

The reason for this, I assume, is following. In the INSERT statements data types of result set's columns are retrieved from the resulting values:
https://github.com/apache/impala/blob/789c5aac23480acc6e18c057b767b65fdd791c97/fe/src/main/java/org/apache/impala/analysis/InsertStmt.java#L275

Whereas in CTAS they are calculated via base table of the column (and there is no base table for NULL):
https://github.com/apache/impala/blob/ba84ad03cb83d7f7aed8524fcfbb0e2cdc9fdd53/fe/src/main/java/org/apache/impala/analysis/CreateTableAsSelectStmt.java#L171