Mycat2 分片策略

分片算法概述

Mycat2 支持可插拔的分片算法框架，以下为内置分片算法：

1. 取模分片

{
  "function": {
    "clazz": "io.mycat.router.function.PartitionByMod",
    "properties": {
      "count": 4
    }
  },
  "shardingFunc": {
    "function": { "clazz": "...PartitionByMod", "properties": {"count": 4} },
    "tableMatcher": "db1.travelrecord",
    "columnName": "id",
    "version": "1"
  }
}

2. 一致性哈希 (MurmurHash)

{
  "function": {
    "clazz": "io.mycat.router.function.PartitionByMurmurHash",
    "properties": {
      "seed": 0,
      "count": 4,
      "virtualBucketTimes": 160
    }
  }
}

3. 日期分片

{
  "function": {
    "clazz": "io.mycat.router.function.PartitionByDate",
    "properties": {
      "dateFormat": "yyyy-MM-dd",
      "sBeginDate": "2026-01-01",
      "sEndDate": "2026-12-31",
      "sPartionDay": 30
    }
  }
}

4. 范围取模分片

{
  "function": {
    "clazz": "io.mycat.router.function.PartitionByRangeMod",
    "properties": {
      "defaultNode": 0,
      "mapFile": "partition-range-mod.txt"
    }
  }
}

# partition-range-mod.txt
0-2000=0
2001-4000=1
4001-6000=2

5. 枚举分片

{
  "function": {
    "clazz": "io.mycat.router.function.PartitionByFileMap",
    "properties": {
      "type": "Integer",
      "defaultNode": -1,
      "mapFile": "sharding-by-enum.txt"
    }
  }
}

# sharding-by-enum.txt
10000=0
10010=1

6. CRC32 预分槽算法

{
  "function": {
    "clazz": "io.mycat.router.function.PartitionByCRC32PreSlot",
    "properties": {
      "count": 1024
    }
  }
}

自定义分片算法

实现 io.mycat.router.function.ShardingFunction 接口即可：

public class MyShardingFunction implements ShardingFunction {
    @Override
    public int calculate(String columnValue) {
        // 自定义分片逻辑
        int hash = Math.abs(columnValue.hashCode());
        return hash % nodeCount;
    }

    @Override
    public void init(Properties properties) {
        // 读取配置参数
    }
}

负载均衡算法