bchapuis commented on code in PR #3668:
URL: https://github.com/apache/calcite/pull/3668#discussion_r2423457982
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core/src/main/java/org/apache/calcite/rel/type/RelDataTypeFactory.java:
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@@ -65,6 +65,15 @@ public interface RelDataTypeFactory {
*/
RelDataType createJavaType(Class clazz);
+ /**
+ * Creates a type that corresponds to a Java class, with a given family.
+ *
+ * @param clazz the Java class used to define the type
+ * @param family The family of the type, or null to infer
+ * @return canonical Java type descriptor
+ */
+ RelDataType createJavaType(Class clazz, @Nullable RelDataTypeFamily family);
Review Comment:
This change comes from a suggestion made by @julianhyde in
https://github.com/apache/calcite/commit/da8494213c3810584a75064d5fadf52ac1f95d12
> Add annotation Parameter.sqlType
The annotation allows you to define the SQL type of a
parameter, for cases where it cannot be deduced automatically
from the Java type. This is especially useful for GEOMETRY
values, for which Calcite has no built-in Java type. (JTS
Geometry is widely used in Calcite, but it is an
implementation, and we do not want it to become the
specification.)
>
> This commit is incomplete, but illustrates the general idea.
>
> A related change is to add a 'family' parameter to
the `TypeFactory.createJavaType` method. It is nullable, and
if null, the type becomes its own family. In JavaType, we
should add a `family` field.
>
> When this change is complete we should be able to remove JTS
Geometry from RelDataTypeFactoryImpl.CLASS_FAMILIES.
In my understanding this proposition was an API change (possibly major) that
would allow to define the SQL type of a parameter more explicitly. As the
family parameter is nullable, it effectively allows the cosumers to continue
working as before. I acknoledge that I probably don't get all the possible
ramifications of this.
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