org.apache.hadoop.hive.ql.udf.generic.GenericUDFCase 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;
import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorUtils;
/**
* GenericUDF Class for SQL construct "CASE a WHEN b THEN c [ELSE f] END".
*
* NOTES: 1. a and b should be compatible, or an exception will be
* thrown. 2. c and f should be compatible types, or an exception will be
* thrown.
*/
@Description(
name = "case",
value = "CASE a WHEN b THEN c [WHEN d THEN e]* [ELSE f] END - "
+ "When a = b, returns c; when a = d, return e; else return f",
extended = "Example:\n "
+ "SELECT\n"
+ " CASE deptno\n"
+ " WHEN 1 THEN Engineering\n"
+ " WHEN 2 THEN Finance\n"
+ " ELSE admin\n"
+ " END,\n"
+ " CASE zone\n"
+ " WHEN 7 THEN Americas\n"
+ " ELSE Asia-Pac\n"
+ " END\n"
+ " FROM emp_details")
public class GenericUDFCase extends GenericUDF {
private transient ObjectInspector[] argumentOIs;
private transient GenericUDFUtils.ReturnObjectInspectorResolver returnOIResolver;
private transient GenericUDFUtils.ReturnObjectInspectorResolver caseOIResolver;
@Override
public ObjectInspector initialize(ObjectInspector[] arguments) throws UDFArgumentTypeException {
argumentOIs = arguments;
caseOIResolver = new GenericUDFUtils.ReturnObjectInspectorResolver(true);
returnOIResolver = new GenericUDFUtils.ReturnObjectInspectorResolver(true);
boolean r = caseOIResolver.update(arguments[0]);
assert (r);
for (int i = 1; i + 1 < arguments.length; i += 2) {
if (!caseOIResolver.update(arguments[i])) {
throw new UDFArgumentTypeException(i,
"The expressions after WHEN should have the same type with that after CASE: \""
+ caseOIResolver.get().getTypeName() + "\" is expected 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 == 0) {
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 {
Object exprValue = arguments[0].get();
for (int i = 1; i + 1 < arguments.length; i += 2) {
Object caseKey = arguments[i].get();
// May need to convert to common type to compare
PrimitiveObjectInspector caseOI = (PrimitiveObjectInspector) caseOIResolver.get();
if (PrimitiveObjectInspectorUtils.comparePrimitiveObjects(
caseOIResolver.convertIfNecessary(exprValue, argumentOIs[0]), caseOI,
caseOIResolver.convertIfNecessary(caseKey, argumentOIs[i], false), caseOI)) {
Object caseValue = arguments[i + 1].get();
return returnOIResolver.convertIfNecessary(caseValue, argumentOIs[i + 1]);
}
}
// Process else statement
if (arguments.length % 2 == 0) {
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 >= 3);
StringBuilder sb = new StringBuilder();
sb.append("CASE (");
sb.append(children[0]);
sb.append(")");
for (int i = 1; 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 == 0) {
sb.append(" ELSE (");
sb.append(children[children.length - 1]);
sb.append(")");
}
sb.append(" END");
return sb.toString();
}
}