org.apache.pig.builtin.RollupDimensions.java Source code

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Here is the source code for org.apache.pig.builtin.RollupDimensions.java

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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.pig.builtin;

import java.io.IOException;
import java.util.List;

import org.apache.pig.EvalFunc;
import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.data.BagFactory;
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;
import org.apache.pig.impl.logicalLayer.schema.Schema.FieldSchema;

import com.google.common.collect.Lists;

/**
 * Produces a DataBag with hierarchy of values (from the most detailed level of
 * aggregation to most general level of aggregation) of the specified dimensions
 * For example, (a, b, c) will produce the following bag:
 * 
 * <pre>
 * { (a, b, c), (a, b, null), (a, null, null), (null, null, null) }
 * </pre>
 */
public class RollupDimensions extends EvalFunc<DataBag> {

    private static BagFactory bf = BagFactory.getInstance();
    private static TupleFactory tf = TupleFactory.getInstance();
    private final String allMarker;

    public RollupDimensions() {
        this(null);
    }

    public RollupDimensions(String allMarker) {
        super();
        this.allMarker = allMarker;
    }

    @Override
    public DataBag exec(Tuple tuple) throws IOException {
        List<Tuple> result = Lists.newArrayListWithCapacity(tuple.size() + 1);
        CubeDimensions.convertNullToUnknown(tuple);
        result.add(tuple);
        iterativelyRollup(result, tuple);
        return bf.newDefaultBag(result);
    }

    private void iterativelyRollup(List<Tuple> result, Tuple input) throws ExecException {
        Tuple tempTup = tf.newTuple(input.getAll());
        for (int i = input.size() - 1; i >= 0; i--) {
            tempTup.set(i, allMarker);
            result.add(tf.newTuple(tempTup.getAll()));
        }
    }

    @Override
    public Schema outputSchema(Schema input) {
        // "dimensions" string is the default namespace assigned to the output
        // schema. this can be overridden by specifying user defined schema
        // names in foreach operator. if user defined schema names are not
        // specified then the output schema of foreach operator using this UDF
        // will have "dimensions::" namespace for all fields in the tuple
        try {
            return new Schema(new FieldSchema("dimensions", input, DataType.BAG));
        } catch (FrontendException e) {
            // we are specifying BAG explicitly, so this should not happen.
            throw new RuntimeException(e);
        }
    }

    @Override
    public boolean allowCompileTimeCalculation() {
        return true;
    }
}