[jira] [Created] (FLINK-4242) Improve validation exception messages

[Shang Yuanchun (Jira)]

Till Rohrmann created FLINK-4242:
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             Summary: Improve validation exception messages
                 Key: FLINK-4242
                 URL: https://issues.apache.org/jira/browse/FLINK-4242
             Project: Flink
          Issue Type: Improvement
          Components: Table API & SQL
    Affects Versions: 1.1.0
            Reporter: Till Rohrmann
            Priority: Minor


The Table API's validation exceptions could be improved to be more meaningful for users. For example, the following code snippet:

{code}
Table inputTable = tableEnv.fromDataStream(env.fromElements(
                Tuple3.of(1, "a", 1.0),
                Tuple3.of(2, "b", 2.0),
                Tuple3.of(3, "c", 3.0)), "a, b, c");
inputTable.select("a").where("!a");
{code}

fails correctly. However, the validation exception message says "Expression !('a) failed on input check: Not only accepts child of Boolean Type, get Integer". I think it could be changed such that it says: "The not operator requires a boolean input but "a" is of type integer." or something similar.



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