Adding LEAST UDF

README.md

@@ -35,6 +35,7 @@ Apache licensed.
     hive> CREATE TEMPORARY FUNCTION chr AS 'com.nexr.platform.hive.udf.UDFChr';
     hive> CREATE TEMPORARY FUNCTION last_day AS 'com.nexr.platform.hive.udf.UDFLastDay';
     hive> CREATE TEMPORARY FUNCTION greatest AS 'com.nexr.platform.hive.udf.GenericUDFGreatest';
+    hive> CREATE TEMPORARY FUNCTION least AS 'com.nexr.platform.hive.udf.GenericUDFLeast';
     hive> CREATE TEMPORARY FUNCTION to_number AS 'com.nexr.platform.hive.udf.GenericUDFToNumber';
     hive> CREATE TEMPORARY FUNCTION trunc AS 'com.nexr.platform.hive.udf.GenericUDFTrunc';
     hive> CREATE TEMPORARY FUNCTION rank AS 'com.nexr.platform.hive.udf.GenericUDFRank';

src/main/java/com/nexr/platform/hive/udf/GenericUDFLeast.java

@@ -0,0 +1,110 @@
+/**
+ * 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 com.nexr.platform.hive.udf;
+
+import org.apache.hadoop.hive.ql.exec.Description;
+import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
+import org.apache.hadoop.hive.ql.exec.UDFArgumentTypeException;
+import org.apache.hadoop.hive.ql.metadata.HiveException;
+import org.apache.hadoop.hive.ql.udf.generic.GenericUDF;
+import org.apache.hadoop.hive.ql.udf.generic.GenericUDFUtils;
+import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
+import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorUtils;
+import org.apache.hive.pdk.HivePdkUnitTest;
+import org.apache.hive.pdk.HivePdkUnitTests;
+
+/**
+ * GenericUDF Class for SQL construct "least(value1, value2, value3, ....)". 
+ * 
+ */
+@Description(name = "least", value = "_FUNC_(value1, value2, value3, ....) " +
+		"- Returns the least value in the list.", 
+		extended = "Example:\n" + " > SELECT _FUNC_(2, 5, 12, 3) FROM src;\n 2")
+@HivePdkUnitTests(setup = "create table dual_data (i int); "
+		+ "insert overwrite table dual_data select 1 from dual limit 1;", 
+		cleanup = "drop table if exists dual_data;", 
+		cases = {
+		@HivePdkUnitTest(query = "SELECT nexr_least(2, 5, 12, 3) " +
+				"FROM dual_data;", result = "2"),
+		@HivePdkUnitTest(query = "SELECT nexr_least('2', '5', '12', '3') " +
+				"FROM dual_data;", result = "12"),
+		@HivePdkUnitTest(query = "SELECT nexr_least('apples', 'oranges', 'bananas') " +
+				"FROM dual_data;", result = "apples") })
+public class GenericUDFLeast extends GenericUDF {
+
+	private ObjectInspector[] argumentOIs;
+	private GenericUDFUtils.ReturnObjectInspectorResolver returnOIResolver;
+
+	@Override
+	public ObjectInspector initialize(ObjectInspector[] arguments) throws UDFArgumentException {
+
+		for (int i = 0; i < arguments.length; i++) {
+			if (arguments[i].getCategory() != ObjectInspector.Category.PRIMITIVE) {
+				throw new UDFArgumentTypeException(i, "Only primitive type arguments are accepted but "
+						+ arguments[i].getTypeName() + " is passed.");
+			}
+		}
+
+		argumentOIs = arguments;
+		returnOIResolver = new GenericUDFUtils.ReturnObjectInspectorResolver(true);
+		for (int i = 0; i < arguments.length; i++) {
+			if (!returnOIResolver.update(arguments[i])) {
+				throw new UDFArgumentTypeException(i, "The value of return should have the same type: \""
+						+ returnOIResolver.get().getTypeName() + 
+						"\" is expected but \"" + arguments[i].getTypeName()
+						+ "\" is found");
+			}
+		}
+
+		return returnOIResolver.get();
+	}
+
+	@Override
+	public Object evaluate(DeferredObject[] fields) throws HiveException {
+		Object leastObject = null;
+		ObjectInspector leastOI = null;
+
+		for (int i = 0; i < fields.length; i++) {
+			Object fieldObject = fields[i].get();
+			if (leastObject == null) {
+				leastObject = fieldObject;
+				leastOI = argumentOIs[i];
+				continue;
+			}
+
+			if (ObjectInspectorUtils.compare(leastObject, leastOI, fieldObject, argumentOIs[i]) >= 0) {
+				leastObject = fieldObject;
+				leastOI = argumentOIs[i];
+			}
+		}
+
+		return returnOIResolver.convertIfNecessary(leastObject, leastOI);
+	}
+
+	@Override
+	public String getDisplayString(String[] children) {
+		StringBuilder sb = new StringBuilder();
+		sb.append("least (");
+		for (int i = 0; i < children.length - 1; i++) {
+			sb.append(children[i]).append(", ");
+		}
+		sb.append(children[children.length - 1]).append(")");
+		return sb.toString();
+	}
+
+}