Alessandro Solimando created HIVE-26722:
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Summary: HiveFilterSetOpTransposeRule incorrectly prune UNION ALL
operands
Key: HIVE-26722
URL: https://issues.apache.org/jira/browse/HIVE-26722
Project: Hive
Issue Type: Bug
Components: CBO
Affects Versions: 4.0.0-alpha-1
Reporter: Alessandro Solimando
Assignee: Alessandro Solimando
Consider the following query:
{code:java}
set hive.cbo.rule.exclusion.regex=ReduceExpressionsRule\(Project\);
CREATE EXTERNAL TABLE t (a string, b string);
INSERT INTO t VALUES ('1000', 'b1');
INSERT INTO t VALUES ('2000', 'b2');
SELECT * FROM (
SELECT
a,
b
FROM t
UNION ALL
SELECT
a,
CAST(NULL AS string)
FROM t) AS t2
WHERE a = 1000;EXPLAIN CBO
SELECT * FROM (
SELECT
a,
b
FROM t
UNION ALL
SELECT
a,
CAST(NULL AS string)
FROM t) AS t2
WHERE a = 1000; {code}
The expected result is:
{code:java}
1000 b1
1000 NULL{code}
An example of correct plan is as follows:
{noformat}
CBO PLAN:
HiveUnion(all=[true])
HiveProject(a=[$0], b=[$1])
HiveFilter(condition=[=(CAST($0):DOUBLE, 1000)])
HiveTableScan(table=[[default, t]], table:alias=[t])
HiveProject(a=[$0], _o__c1=[null:VARCHAR(2147483647) CHARACTER SET
"UTF-16LE"])
HiveFilter(condition=[=(CAST($0):DOUBLE, 1000)])
HiveTableScan(table=[[default, t]], table:alias=[t]){noformat}
Consider now a scenario where expression reduction in projections is disabled
by setting the following property{_}:{_}
{noformat}
set hive.cbo.rule.exclusion.regex=ReduceExpressionsRule\(Project\);
{noformat}
In this case, the simplification of _CAST(NULL)_ into _NULL_ does not happen,
and we get the following (invalid) result:
1000 b1
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