org.apache.hadoop.hive.ql.udf.generic.GenericUDTF Maven / Gradle / Ivy
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* 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 java.util.List;
import org.apache.hadoop.hive.ql.exec.MapredContext;
import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.StructField;
import org.apache.hadoop.hive.serde2.objectinspector.StructObjectInspector;
/**
* A Generic User-defined Table Generating Function (UDTF)
*
* Generates a variable number of output rows for a single input row. Useful for
* explode(array)...
*/
public abstract class GenericUDTF {
Collector collector = null;
/**
* Additionally setup GenericUDTF with MapredContext before initializing.
* This is only called in runtime of MapRedTask.
*
* @param context context
*/
public void configure(MapredContext mapredContext) {
}
public StructObjectInspector initialize(StructObjectInspector argOIs)
throws UDFArgumentException {
List inputFields = argOIs.getAllStructFieldRefs();
ObjectInspector[] udtfInputOIs = new ObjectInspector[inputFields.size()];
for (int i = 0; i < inputFields.size(); i++) {
udtfInputOIs[i] = inputFields.get(i).getFieldObjectInspector();
}
return initialize(udtfInputOIs);
}
/**
* Initialize this GenericUDTF. This will be called only once per instance.
*
* @param argOIs
* An array of ObjectInspectors for the arguments
* @return A StructObjectInspector for output. The output struct represents a
* row of the table where the fields of the stuct are the columns. The
* field names are unimportant as they will be overridden by user
* supplied column aliases.
*/
@Deprecated
public StructObjectInspector initialize(ObjectInspector[] argOIs)
throws UDFArgumentException {
throw new IllegalStateException("Should not be called directly");
}
/**
* Give a set of arguments for the UDTF to process.
*
* @param args
* object array of arguments
*/
public abstract void process(Object[] args) throws HiveException;
/**
* Called to notify the UDTF that there are no more rows to process.
* Clean up code or additional forward() calls can be made here.
*/
public abstract void close() throws HiveException;
/**
* Associates a collector with this UDTF. Can't be specified in the
* constructor as the UDTF may be initialized before the collector has been
* constructed.
*
* @param collector
*/
public final void setCollector(Collector collector) {
this.collector = collector;
}
/**
* Passes an output row to the collector.
*
* @param o
* @throws HiveException
*/
protected final void forward(Object o) throws HiveException {
collector.collect(o);
}
}