[GitHub] [flink] xuefuz commented on a change in pull request #8700: [FLINK-12657][hive] Integrate Flink with Hive UDF

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xuefuz commented on a change in pull request #8700: [FLINK-12657][hive] Integrate Flink with Hive UDF
URL: https://github.com/apache/flink/pull/8700#discussion_r293066789
 
 

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 File path: flink-connectors/flink-connector-hive/src/main/java/org/apache/flink/table/functions/hive/HiveFunction.java
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 @@ -0,0 +1,62 @@
+/*
+ * 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.functions.hive;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.table.types.DataType;
+
+/**
+ * Interface for Hive simple udf, generic udf, and generic udtf.
+ * TODO: Note: this is only a temporary interface for workaround when Flink type system and udf system
+ * 	rework is not finished. Should adapt to Flink type system and Flink UDF framework later on.
+ */
+@Internal
+public interface HiveFunction {
+
+	/**
+	 * Set arguments and argTypes for Function instance.
+	 * In this way, the correct method can be really deduced by the function instance.
+	 *
+	 * <p>Framework should guarantee that this is always called
+	 * before {@link #getHiveResultType(Object[] constantArguments, DataType[] argTypes)}.
+	 *
+	 * @param constantArguments arguments of a function call (only literal arguments
+	 *                  are passed, nulls for non-literal ones)
+	 * @param argTypes types of arguments
+	 */
+	void setArgumentTypesAndConstants(Object[] constantArguments, DataType[] argTypes);
+
+	/**
+	 * Get result type by arguments and argTypes.
+	 *
+	 * <p>We can't use getResultType(Object[], Class[]). The Class[] is the classes of what
+	 * is defined in eval(), for example, if eval() is "public Integer eval(Double)", the
+	 * argTypes would be Class[Double]. However, in our wrapper, the signature of eval() is
+	 * "public Object eval(Object... args)", which means we cannot get any info from the interface.
+	 *
+	 * <p>Framework should guarantee that this is always called
+	 * 	 after {@link #setArgumentTypesAndConstants(Object[] constantArguments, DataType[] argTypes)}.
+	 *
+	 * @param constantArguments arguments of a function call (only literal arguments
+	 *                  are passed, nulls for non-literal ones)
+	 * @param argTypes types of arguments
+	 * @return result type.
+	 */
+	DataType getHiveResultType(Object[] constantArguments, DataType[] argTypes);
 
 Review comment:
   Just curious, if setArgumentTypesAndConstants() is called before this one is called with the same arguments, why do we need those arguments again?

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