com.bah.culvert.constraints.join.IndexedJoin.java Source code

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Here is the source code for com.bah.culvert.constraints.join.IndexedJoin.java

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/**
 * Copyright 2011 Booz Allen Hamilton.
 * 
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership. Booz Allen Hamilton
 * 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 com.bah.culvert.constraints.join;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.ObjectWritable;

import com.bah.culvert.adapter.DatabaseAdapter;
import com.bah.culvert.adapter.TableAdapter;
import com.bah.culvert.constraints.Constraint;
import com.bah.culvert.constraints.Join;
import com.bah.culvert.data.CColumn;
import com.bah.culvert.data.index.Index;
import com.bah.culvert.util.Bytes;

/**
 * Do an Indexed Join. The left constraint is first applied to the table in
 * {@link #getResultIterator()}, and the the specified column in
 * {@link #leftColumn} are used to extract the desired columns from the 'left'
 * side of the join. The {@link IndexedJoinOp} is then used remotely on the
 * output table to retrieve matching values from the Index on the "right" side
 * of the join.
 */
public class IndexedJoin extends Join {

    private Index rightIndex;

    /**
     * Nullary constructor - for use with {@link #readFields(DataInput)}
     */
    public IndexedJoin() {

    }

    /**
     * Create an index based join.
     * @param db Database to use when creating the temporary table
     * @param leftTable
     * @param left
     * @param leftColumn
     * @param rightIndex Index to use when looking up values for the join. This
     *        should be an index over the VALUEs of the rows in the primary table
     *        where the columns match the specified columns.
     */
    public IndexedJoin(DatabaseAdapter db, TableAdapter leftTable, Constraint left, CColumn leftColumn,
            Index rightIndex) {
        super(db, leftTable, left, leftColumn, rightIndex.getPrimaryTable().getTableName());
        this.rightIndex = rightIndex;
    }

    @Override
    protected void doRemoteOperation(TableAdapter outputTable, byte[] rightOutputColumn) {
        Object[] args = new Object[4];
        args[0] = outputTable;
        args[1] = rightOutputColumn;
        args[2] = this.rightIndex;
        outputTable.remoteExec(Bytes.START_END_KEY, Bytes.START_END_KEY, IndexedJoinOp.class, args);

    }

    @Override
    public void readFields(DataInput in) throws IOException {
        super.readFields(in);
        ObjectWritable ow = new ObjectWritable();
        Configuration conf = new Configuration();
        ow.setConf(conf);
        ow.readFields(in);
        this.rightIndex = (Index) ow.get();
    }

    @Override
    public void write(DataOutput out) throws IOException {
        super.write(out);
        new ObjectWritable(this.rightIndex).write(out);
    }

}