[GitHub] [flink] twalthr commented on a change in pull request #12900: [FLINK-18537][table] Remove RowDataTypeInfo

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twalthr commented on a change in pull request #12900:
URL: https://github.com/apache/flink/pull/12900#discussion_r454506847



##########
File path: flink-table/flink-table-common/src/main/java/org/apache/flink/table/types/DataTypeQueryable.java
##########
@@ -0,0 +1,30 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.types;
+
+import org.apache.flink.annotation.PublicEvolving;
+
+/**
+ * Indicates that a {@link DataType} can be retrieved from a class that implements this interfaces.
+ */
+@PublicEvolving
+public interface DataTypeQueryable {

Review comment:
       I thought about this as well and decided for keeping `WrapperTypeInfo` in the runtime package. The reason for this is to keep the serializers close to this utility class in the same package. `WrapperTypeInfo` is not needed in `table-common` because it is internal. Actually the constructor of `WrappenTypeInfo` should even be private but this is not possible due to other failing tests so far. We can mark `DataTypeQueryable` internal if that helps, but the past around `TypeInformation` has shown that you need such a simple interface over and over again. It will be more useful in the future once we introduce a "converter type serializer" where the return data type is not of internal data structure.




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