org.apache.hadoop.hive.ql.udf.generic.GenericUDFCoalesce Maven / Gradle / Ivy
/**
* 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.hadoop.hive.ql.udf.generic;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDFArgumentTypeException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
/**
* GenericUDF Class for SQL construct "COALESCE(a, b, c)".
*
* NOTES: 1. a, b and c should have the same TypeInfo, or an exception will be
* thrown.
*/
@Description(name = "coalesce",
value = "_FUNC_(a1, a2, ...) - Returns the first non-null argument",
extended = "Example:\n"
+ " > SELECT _FUNC_(NULL, 1, NULL) FROM src LIMIT 1;\n" + " 1")
public class GenericUDFCoalesce extends GenericUDF {
private transient ObjectInspector[] argumentOIs;
private transient GenericUDFUtils.ReturnObjectInspectorResolver returnOIResolver;
@Override
public ObjectInspector initialize(ObjectInspector[] arguments) throws UDFArgumentTypeException {
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 expressions after COALESCE should all have the same type: \""
+ returnOIResolver.get().getTypeName()
+ "\" is expected but \"" + arguments[i].getTypeName()
+ "\" is found");
}
}
return returnOIResolver.get();
}
@Override
public Object evaluate(DeferredObject[] arguments) throws HiveException {
for (int i = 0; i < arguments.length; i++) {
Object ai = arguments[i].get();
if (ai == null) {
continue;
}
return returnOIResolver.convertIfNecessary(ai, argumentOIs[i]);
}
return null;
}
@Override
public String getDisplayString(String[] children) {
return getStandardDisplayString("COALESCE", children, ",");
}
}