org.apache.hadoop.hive.ql.udf.generic.GenericUDFWhen 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.serde.serdeConstants;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.BooleanObjectInspector;
/**
* GenericUDF Class for SQL construct
* "CASE WHEN a THEN b WHEN c THEN d [ELSE f] END".
*
* NOTES: 1. a and c should be boolean, or an exception will be thrown. 2. b, d
* and f should be common types, or an exception will be thrown.
*/
@Description(
name = "when",
value = "CASE WHEN a THEN b [WHEN c THEN d]* [ELSE e] END - "
+ "When a = true, returns b; when c = true, return d; else return e",
extended = "Example:\n "
+ "SELECT\n"
+ " CASE\n"
+ " WHEN deptno=1 THEN Engineering\n"
+ " WHEN deptno=2 THEN Finance\n"
+ " ELSE admin\n"
+ " END,\n"
+ " CASE\n"
+ " WHEN zone=7 THEN Americas\n"
+ " ELSE Asia-Pac\n"
+ " END\n"
+ " FROM emp_details")
public class GenericUDFWhen 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 + 1 < arguments.length; i += 2) {
if (!arguments[i].getTypeName().equals(serdeConstants.BOOLEAN_TYPE_NAME)) {
throw new UDFArgumentTypeException(i, "\""
+ serdeConstants.BOOLEAN_TYPE_NAME + "\" is expected after WHEN, "
+ "but \"" + arguments[i].getTypeName() + "\" is found");
}
if (!returnOIResolver.update(arguments[i + 1])) {
throw new UDFArgumentTypeException(i + 1,
"The expressions after THEN should have the same type: \""
+ returnOIResolver.get().getTypeName()
+ "\" is expected but \"" + arguments[i + 1].getTypeName()
+ "\" is found");
}
}
if (arguments.length % 2 == 1) {
int i = arguments.length - 2;
if (!returnOIResolver.update(arguments[i + 1])) {
throw new UDFArgumentTypeException(i + 1,
"The expression after ELSE should have the same type as those after THEN: \""
+ returnOIResolver.get().getTypeName()
+ "\" is expected but \"" + arguments[i + 1].getTypeName()
+ "\" is found");
}
}
return returnOIResolver.get();
}
@Override
public Object evaluate(DeferredObject[] arguments) throws HiveException {
for (int i = 0; i + 1 < arguments.length; i += 2) {
Object caseKey = arguments[i].get();
if (caseKey != null
&& ((BooleanObjectInspector) argumentOIs[i]).get(caseKey)) {
Object caseValue = arguments[i + 1].get();
return returnOIResolver.convertIfNecessary(caseValue,
argumentOIs[i + 1]);
}
}
// Process else statement
if (arguments.length % 2 == 1) {
int i = arguments.length - 2;
Object elseValue = arguments[i + 1].get();
return returnOIResolver.convertIfNecessary(elseValue, argumentOIs[i + 1]);
}
return null;
}
@Override
public String getDisplayString(String[] children) {
assert (children.length >= 2);
StringBuilder sb = new StringBuilder();
sb.append("CASE");
for (int i = 0; i + 1 < children.length; i += 2) {
sb.append(" WHEN (");
sb.append(children[i]);
sb.append(") THEN (");
sb.append(children[i + 1]);
sb.append(")");
}
if (children.length % 2 == 1) {
sb.append(" ELSE (");
sb.append(children[children.length - 1]);
sb.append(")");
}
sb.append(" END");
return sb.toString();
}
}