Shohei Okumiya created HIVE-28193:
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Summary: CBO fallback can overwrite the real error message when
EXCEPT or INTERSECT are used
Key: HIVE-28193
URL: https://issues.apache.org/jira/browse/HIVE-28193
Project: Hive
Issue Type: Improvement
Components: CBO
Affects Versions: 4.0.0
Reporter: Shohei Okumiya
Assignee: Shohei Okumiya
With `hive.cbo.fallback.strategy=CONSERVATIVE`, Hive retries to compile an SQL
without CBO when a compile error happens. We sometimes see an unkind error
message when EXCEPT or INTERSECT are used. The fallback non-CBO mode doesn't
support those operators, so Hive asked us to enable CBO.
{code:java}
0: jdbc:hive2://hive-hiveserver2:10000/defaul> select cast(0 as bigint) = '1'
EXCEPT select cast(1 as bigint) = '1';
Error: Error while compiling statement: FAILED: SemanticException EXCEPT and
INTERSECT operations are only supported with Cost Based Optimizations enabled.
Please set 'hive.cbo.enable' to true! (state=42000,code=40000)
0: jdbc:hive2://hive-hiveserver2:10000/defaul> set
hive.cbo.fallback.strategy=NEVER;
No rows affected (0.035 seconds)
0: jdbc:hive2://hive-hiveserver2:10000/defaul> select cast(0 as bigint) = '1'
EXCEPT select cast(1 as bigint) = '1';
Error: Error while compiling statement: FAILED: SemanticException Line 0:-1
Wrong arguments ''1'': Unsafe compares between different types are disabled for
safety reasons. If you know what you are doing, please set
hive.strict.checks.type.safety to false and make sure that hive.mapred.mode is
not set to 'strict' to proceed. Note that you may get errors or incorrect
results if you make a mistake while using some of the unsafe features.
(state=42000,code=40000) {code}
It is inconvenient, especially when the CBO mode fails because of
`hive.strict.checks.*`, because we can't find the true cause of an error
message.
We plan to disable the fallback behavior or deprecate the non-CBO mode.
However, we sometimes need to rely on the features at this point.
* https://issues.apache.org/jira/browse/HIVE-27831
* https://issues.apache.org/jira/browse/HIVE-27830
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