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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