Github user xccui commented on a diff in the pull request:
https://github.com/apache/flink/pull/6090#discussion_r196995191
--- Diff:
flink-libraries/flink-sql-client/src/main/java/org/apache/flink/table/client/config/UDFDescriptor.java
---
@@ -0,0 +1,153 @@
+/*
+ * 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.client.config;
+
+import org.apache.flink.api.common.typeinfo.BasicTypeInfo;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+import org.apache.flink.table.client.SqlClientException;
+import org.apache.flink.table.descriptors.ClassTypeDescriptor;
+import org.apache.flink.table.descriptors.ClassTypeValidator;
+import org.apache.flink.table.descriptors.DescriptorProperties;
+import org.apache.flink.table.descriptors.FunctionDescriptor;
+import org.apache.flink.table.descriptors.FunctionValidator;
+import org.apache.flink.table.descriptors.PrimitiveTypeDescriptor;
+import org.apache.flink.table.descriptors.PrimitiveTypeValidator;
+import org.apache.flink.table.typeutils.TypeStringUtils;
+
+import java.util.List;
+import java.util.Map;
+
+import static
org.apache.flink.table.client.config.UDFDescriptor.From.CLASS;
+
+/**
+ * Descriptor for user-defined functions.
+ */
+public class UDFDescriptor extends FunctionDescriptor {
--- End diff --
I'm not sure if there will be more descriptors (for other purposes) extend
`FunctionDescriptor` in the future. How about renaming it to
`UserDefinedFunction`?
---
