com.mysql.fabric.RangeShardMapping Maven / Gradle / Ivy

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MySQL JDBC Type 4 driver
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/*
  Copyright (c) 2013, 2014, Oracle and/or its affiliates. All rights reserved.

  The MySQL Connector/J is licensed under the terms of the GPLv2
  , like most MySQL Connectors.
  There are special exceptions to the terms and conditions of the GPLv2 as it is applied to
  this software, see the FOSS License Exception
  .

  This program is free software; you can redistribute it and/or modify it under the terms
  of the GNU General Public License as published by the Free Software Foundation; version 2
  of the License.

  This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  See the GNU General Public License for more details.

  You should have received a copy of the GNU General Public License along with this
  program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth
  Floor, Boston, MA 02110-1301  USA

 */

package com.mysql.fabric;

import java.util.Comparator;
import java.util.Set;
import java.util.TreeSet;

/**
 * A shard mapping that partitions data by ranges.
 */
public class RangeShardMapping extends ShardMapping {
    /**
     * A sorter that sorts shard indices from highest to lowest based on the integer
     * value of their bounds. For a range shard mapping, the bound is a lowest bound.
     */
    private static class RangeShardIndexSorter implements Comparator {
        public int compare(ShardIndex i1, ShardIndex i2) {
            Integer bound1, bound2;
            bound1 = Integer.parseInt(i1.getBound());
            bound2 = Integer.parseInt(i2.getBound());
            return bound2.compareTo(bound1); // this reverses it
        }

        // singleton instance
        public static final RangeShardIndexSorter instance = new RangeShardIndexSorter();
    }

    public RangeShardMapping(int mappingId, ShardingType shardingType, String globalGroupName, Set shardTables, Set shardIndices) {
        // sort shard indices eagerly so {@link getShardIndexForKey} has them in the necessary order
        super(mappingId, shardingType, globalGroupName, shardTables, new TreeSet(RangeShardIndexSorter.instance));
        this.shardIndices.addAll(shardIndices);
    }

    /**
     * Search through the shard indicies to find the shard holding this key. Range-based sharding
     * defines a lower bound for each partition with the upper bound being one less than the lower bound
     * of the next highest shard. There is no upper bound for the shard with the highest lower bound.
     */
    @Override
    protected ShardIndex getShardIndexForKey(String stringKey) {
        Integer key = -1;
        key = Integer.parseInt(stringKey);
        for (ShardIndex i : this.shardIndices) {
            Integer lowerBound = Integer.valueOf(i.getBound());
            if (key >= lowerBound) {
                return i;
            }
        }
        return null;
    }
}