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分库分表策略

根据订单ID分库分表，M库N表，orderId 落到哪张表的算法：

• 表ID = 订单ID后六位 % (库数量 * 每库表数量)
• 库ID = 表ID / 每库表数量

表ID范围 0 到 (M*N-1)，库ID范围 0 到 （M-1）

Code:

/**
 * MySQL 分库分表策略
 */
public class TableShardingStrategy {

    public record ShardingLocation(int dbId, int tableId) {
    }

    private final int dbNums;
    private final int tableNums;

    public TableShardingStrategy(int dbNums, int tableNums) {
        if (dbNums <= 0) {
            throw new IllegalArgumentException("dbNums must > 0");
        }
        if (tableNums <= 0) {
            throw new IllegalArgumentException("tableNums must > 0");
        }
        this.dbNums = dbNums; 
        this.tableNums = tableNums;
    }

    public ShardingLocation getShardingLocation(long primaryId) {
        int shardingId = (int) (primaryId % 1000_000);
        int tableId = shardingId % (dbNums * tableNums);
        int dbId = tableId / tableNums;
        return new ShardingLocation(dbId, tableId);
    }
}