wuchong commented on a change in pull request #10500:
[FLINK-15161][table-common] Introduce TypeTransformation interface and basic
transformations
URL: https://github.com/apache/flink/pull/10500#discussion_r356960766
##########
File path:
flink-table/flink-table-common/src/main/java/org/apache/flink/table/types/utils/DataTypeUtils.java
##########
@@ -36,7 +52,101 @@ public static DataType replaceLogicalType(DataType
dataType, LogicalType replace
.bridgedTo(dataType.getConversionClass());
}
+ /**
+ * Transforms the given data type (can be nested) to a different data
type using the given
+ * transformations. The given transformations will be called in order.
+ *
+ * @param typeToTransform data type to be transformed.
+ * @param transformations the transformations to transform data type to
another type.
+ * @return the new data type,
+ */
+ public static DataType transform(DataType typeToTransform,
TypeTransformation... transformations) {
+ Preconditions.checkArgument(transformations.length > 0,
"transformations should not be empty.");
+ DataType newType = typeToTransform;
+ for (TypeTransformation transformation : transformations) {
+ newType = newType.accept(new
DataTypeTransformer(transformation));
+ }
+ return newType;
+ }
+
private DataTypeUtils() {
// no instantiation
}
+
+
+ //
------------------------------------------------------------------------------------------
+
+ private static class DataTypeTransformer implements
DataTypeVisitor<DataType> {
+
+ private final TypeTransformation transformation;
+
+ private DataTypeTransformer(TypeTransformation transformation) {
+ this.transformation = transformation;
+ }
+
+ @Override
+ public DataType visit(AtomicDataType atomicDataType) {
+ return transformation.transform(atomicDataType);
+ }
+
+ @Override
+ public DataType visit(CollectionDataType collectionDataType) {
+ DataType newElementType =
collectionDataType.getElementDataType().accept(this);
+ LogicalType logicalType =
collectionDataType.getLogicalType();
+ LogicalType newLogicalType;
+ if (logicalType instanceof ArrayType) {
+ newLogicalType = new ArrayType(
Review comment:
We have to create a new logical type, because users may transform the
original type to another logical type, e.g. `DataTypes.INT()` ->
`DataTypes.TIMESTAMP()`. From the interface of `TypeTransformation`, we didn't
stop users to do this.
For collection types,
`CollectionDataType(ArrayType(elementLogicalType), elementDataType)`, if
the `elementDataType` is changed, we have to update the corresponding
`elementLogicalType` to reflect the truth.
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