[jira] [Created] (CALCITE-5046) SqlTypeFactorylmpl#leastRestrictiveByCast incorrect results with MAP types

["Francesco Guardiani (Jira)" <ji...@apache.org>]

Francesco Guardiani created CALCITE-5046:
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             Summary: SqlTypeFactorylmpl#leastRestrictiveByCast incorrect results with MAP types
                 Key: CALCITE-5046
                 URL: https://issues.apache.org/jira/browse/CALCITE-5046
             Project: Calcite
          Issue Type: Bug
    Affects Versions: 1.26.0
            Reporter: Francesco Guardiani


SqlTypeFactorylmpl#leastRestrictiveByCast returns incorrect results when the two input types are maps, with key and value types castable.

For example, trying with this input:

{code:sql}
(CHAR(1), VARCHAR(6)) MAP
(VARCHAR(2147483647), VARCHAR(2147483647)) MAP
(CHAR(1), CHAR(1)) MAP
{code}

Returns the type {{(CHAR(1), CHAR(1)) MAP}}, which is incorrect as i would expect {{(VARCHAR(2147483647), VARCHAR(2147483647)) MAP}} as result.

My analysis is that this is caused by {{SqlTypeUtil#canCastFrom}} which doesn't properly support MAP types, in particular when coerce = false. Adding this chunk of code here https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/sql/type/SqlTypeUtil.java#L877:

{code:java}
        if (fromTypeName == toTypeName && fromTypeName == SqlTypeName.MAP) {
            return canCastFrom(toType.getKeyType(), fromType.getKeyType(), coerce)
                    && canCastFrom(toType.getValueType(), fromType.getValueType(), coerce);
        }
{code}

Solves the issue, as now the MAP type casting check is not falling back to {{SqlTypeMappingRule}} anymore.

I tested with 1.26, but looking on master, it sounds like the problem applies to later versions as well https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/sql/type/SqlTypeUtil.java#L814



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