com.cloudera.fts.pig.ProjectedProtobufTupleFactory.java Source code

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Here is the source code for com.cloudera.fts.pig.ProjectedProtobufTupleFactory.java

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/**
 * Copyright (c) 2012, Cloudera, Inc. All Rights Reserved.
 *
 * Cloudera, Inc. 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
 *
 * This software 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 com.cloudera.fts.pig;

import java.util.List;

import org.apache.pig.LoadPushDown.RequiredField;
import org.apache.pig.LoadPushDown.RequiredFieldList;
import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.data.Tuple;
import org.apache.pig.data.TupleFactory;

import com.google.common.collect.Lists;
import com.google.protobuf.Descriptors.FieldDescriptor;
import com.google.protobuf.Message;

/**
 * A tuple factory to create protobuf tuples where
 * only a subset of fields are required.
 */
public class ProjectedProtobufTupleFactory {

    private static TupleFactory tf = TupleFactory.getInstance();

    private final List<FieldDescriptor> requiredFields;
    private final ProtobufToPig protoConv;

    public ProjectedProtobufTupleFactory(Message protoInstance, RequiredFieldList requiredFieldList) {

        List<FieldDescriptor> protoFields = protoInstance.getDescriptorForType().getFields();
        protoConv = new ProtobufToPig();

        if (requiredFieldList != null) {
            List<RequiredField> tupleFields = requiredFieldList.getFields();
            requiredFields = Lists.newArrayListWithCapacity(tupleFields.size());

            // should we handle nested projections?
            for (RequiredField f : tupleFields) {
                requiredFields.add(protoFields.get(f.getIndex()));
            }
        } else {
            requiredFields = protoFields;
        }
    }

    public Tuple newTuple(Message msg) throws ExecException {
        int size = requiredFields.size();
        Tuple tuple = tf.newTuple(size);

        for (int i = 0; i < size; i++) {
            FieldDescriptor fdesc = requiredFields.get(i);
            Object value = msg.getField(fdesc);
            tuple.set(i, protoConv.fieldToPig(fdesc, value));
        }
        return tuple;
    }
}