/*
* 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.pig.builtin;
import java.io.IOException;
import org.apache.pig.EvalFunc;
import org.apache.pig.PigException;
import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.data.DataBag;
import org.apache.pig.data.DataType;
import org.apache.pig.data.Tuple;
import org.apache.pig.data.TupleFactory;
import org.apache.pig.impl.logicalLayer.FrontendException;
import org.apache.pig.impl.logicalLayer.schema.Schema;
/**
* Flatten a bag into a tuple. This UDF performs only flattening at the first level,
* it doesn't recursively flatten nested bags.
*
* Example: {(a),(b),(c)} --> (a,b,c)
* {(a,b), (c,d), (e,f)} --> (a,b,c,d,e,f);
*
* If input bag is null, this UDF will return null;
*
*/
public class BagToTuple extends EvalFunc<Tuple> {
@Override
public Tuple exec(Tuple inputTuple) throws IOException {
if (inputTuple.size() != 1) {
throw new ExecException("Expecting 1 input, found " + inputTuple.size(), PigException.INPUT);
}
if (inputTuple.get(0) == null) {
return null;
}
if (!(inputTuple.get(0) instanceof DataBag)) {
throw new ExecException("Usage BagToTuple(DataBag)", PigException.INPUT);
}
DataBag inputBag = (DataBag) (inputTuple.get(0));
try {
Tuple outputTuple = null;
long outputTupleSize = getOuputTupleSize(inputBag);
// TupleFactory.newTuple(int size) can only support up to Integer.MAX_VALUE
if (outputTupleSize > Integer.MAX_VALUE) {
throw new ExecException("Input bag is too large", 105, PigException.INPUT);
}
TupleFactory tupleFactory = TupleFactory.getInstance();
outputTuple = tupleFactory.newTuple((int) outputTupleSize);
int fieldNum = 0;
for (Tuple t : inputBag) {
if (t != null) {
for (int i = 0; i < t.size(); i++) {
outputTuple.set(fieldNum++, t.get(i));
}
}
}
return outputTuple;
} catch (Exception e) {
String msg = "Encourntered error while flattening a bag to tuple"
+ this.getClass().getSimpleName();
throw new ExecException(msg, PigException.BUG, e);
}
}
/**
* Calculate the size of the output tuple based on the sum
* of the size of each tuple in the input bag
*
* @param bag
* @return total # of data elements in a tab
*/
private long getOuputTupleSize(DataBag bag) {
long size = 0;
if (bag != null) {
for (Tuple t : bag) {
size = size + t.size();
}
}
return size;
}
@Override
public Schema outputSchema(Schema inputSchema) {
try {
if ((inputSchema == null) || inputSchema.size() != 1) {
throw new RuntimeException("Expecting 1 input, found " +
((inputSchema == null) ? 0 : inputSchema.size()));
}
Schema.FieldSchema inputFieldSchema = inputSchema.getField(0);
if (inputFieldSchema.type != DataType.BAG) {
throw new RuntimeException("Expecting a bag of tuples: {()}");
}
// first field in the bag schema
Schema.FieldSchema firstFieldSchema = inputFieldSchema.schema.getField(0);
if ((firstFieldSchema == null) || (firstFieldSchema.schema == null)
|| firstFieldSchema.schema.size() < 1) {
throw new RuntimeException("Expecting a bag of tuples: {()}, found: " + inputSchema);
}
if (firstFieldSchema.type != DataType.TUPLE) {
throw new RuntimeException("Expecting a bag of tuples: {()}, found: " + inputSchema);
}
// now for output schema
Schema tupleOutputSchema = new Schema();
for (int i = 0; i < firstFieldSchema.schema.size(); ++i) {
tupleOutputSchema.add(firstFieldSchema.schema.getField(i));
}
return new Schema(new Schema.FieldSchema(getSchemaName(this
.getClass().getName().toLowerCase(), inputSchema), tupleOutputSchema,
DataType.TUPLE));
} catch (FrontendException e) {
e.printStackTrace();
return null;
}
}
@Override
public boolean allowCompileTimeCalculation() {
return true;
}
}