using System;
using System.Collections.Generic;
using System.Linq;
using NewLife;
using XCode.Configuration;
namespace XCode.Shards
{
/// <summary>时间分表策略</summary>
public class TimeShardPolicy : IShardPolicy
{
#region 属性
/// <summary>实体工厂</summary>
public IEntityFactory Factory { get; set; }
/// <summary>字段</summary>
public FieldItem Field { get; set; }
/// <summary>连接名策略。格式化字符串，0位基础连接名，1位时间，如{0}_{1:yyyy}</summary>
public String ConnPolicy { get; set; }
/// <summary>表名策略。格式化字符串，0位基础表名，1位时间，如{0}_{1:yyyyMM}</summary>
public String TablePolicy { get; set; }
/// <summary>时间区间步进。遇到时间区间需要扫描多张表时的时间步进，默认1天</summary>
public TimeSpan Step { get; set; } = TimeSpan.FromDays(1);
private readonly String _fieldName;
#endregion
#region 构造
/// <summary>实例化</summary>
public TimeShardPolicy() { }
/// <summary>指定字段实例化分表策略</summary>
/// <param name="field"></param>
/// <param name="factory"></param>
public TimeShardPolicy(FieldItem field, IEntityFactory factory = null)
{
Field = field;
Factory = factory ?? field.Factory;
}
/// <summary>指定字段名和工厂实例化分表策略</summary>
/// <param name="fieldName"></param>
/// <param name="factory"></param>
public TimeShardPolicy(String fieldName, IEntityFactory factory)
{
_fieldName = fieldName;
Factory = factory;
}
private FieldItem GetField() => Field ??= Factory.Table.FindByName(_fieldName);
#endregion
/// <summary>为实体对象、时间、雪花Id等计算分表分库</summary>
/// <param name="value"></param>
/// <returns></returns>
public virtual ShardModel Shard(Object value)
{
if (value is IEntity entity) return Shard(entity);
if (value is DateTime dt) return Shard(dt);
if (value is Int64 id)
{
if (!Factory.Snow.TryParse(id, out var time, out _, out _)) throw new XCodeException("雪花Id解析时间失败，无法用于分表");
return Shard(time);
}
throw new XCodeException($"分表策略无法识别数据[{value}]");
}
/// <summary>为实体对象计算分表分库</summary>
/// <param name="entity"></param>
/// <returns></returns>
public virtual ShardModel Shard(IEntity entity)
{
var fi = GetField();
if (fi == null) throw new XCodeException("分表策略要求指定时间字段！");
if (fi.Type == typeof(DateTime))
{
var time = entity[fi.Name].ToDateTime();
if (time.Year <= 1) throw new XCodeException("实体对象时间字段为空，无法用于分表");
return Shard(time);
}
else if (fi.Type == typeof(Int64))
{
var id = entity[fi.Name].ToLong();
if (!Factory.Snow.TryParse(id, out var time, out _, out _)) throw new XCodeException("雪花Id解析时间失败，无法用于分表");
return Shard(time);
}
throw new XCodeException($"时间分表策略不支持[{fi.Type.FullName}]类型字段");
}
/// <summary>为时间计算分表分库</summary>
/// <param name="time"></param>
/// <returns></returns>
public virtual ShardModel Shard(DateTime time)
{
if (time.Year <= 1) throw new ArgumentNullException(nameof(time), "分表策略要求指定时间！");
var fi = GetField();
if (fi == null) throw new XCodeException("分表策略要求指定时间字段！");
if (ConnPolicy.IsNullOrEmpty() && TablePolicy.IsNullOrEmpty()) return null;
var table = Factory.Table;
var model = new ShardModel();
if (!ConnPolicy.IsNullOrEmpty()) model.ConnName = String.Format(ConnPolicy, table.ConnName, time);
if (!TablePolicy.IsNullOrEmpty()) model.TableName = String.Format(TablePolicy, table.TableName, time);
return model;
}
/// <summary>从时间区间中计算多个分表分库，支持倒序。步进由Step指定，默认1天</summary>
/// <param name="start"></param>
/// <param name="end"></param>
/// <returns></returns>
public virtual ShardModel[] Shards(DateTime start, DateTime end)
{
if (start.Year <= 1) throw new ArgumentNullException(nameof(start), "分表策略要求指定时间！");
if (end.Year <= 1) throw new ArgumentNullException(nameof(end), "分表策略要求指定时间！");
if (start <= end) return GetModels(start, end);
var arr = GetModels(end, start);
Array.Reverse(arr);
return arr;
}
/// <summary>从查询表达式中计算多个分表分库</summary>
/// <param name="expression"></param>
/// <returns></returns>
public virtual ShardModel[] Shards(Expression expression)
{
//if (expression is not WhereExpression where) return null;
// 时间范围查询，用户可能自己写分表查询
var fi = GetField();
var exps = new List<FieldExpression>();
if (expression is WhereExpression where)
exps = where.Where(e => e is FieldExpression fe && fe.Field == fi).Cast<FieldExpression>().ToList();
else if (expression is FieldExpression fieldExpression && fieldExpression.Field == fi)
exps.Add(fieldExpression);
//if (exps.Count == 0) throw new XCodeException($"分表策略要求查询条件包括[{fi}]字段！");
if (exps.Count == 0) return null;
if (fi.Type == typeof(DateTime))
{
var sf = exps.FirstOrDefault(e => e.Action is ">" or ">=");
var ef = exps.FirstOrDefault(e => e.Action is "<" or "<=");
if (sf != null)
{
var start = sf.Value.ToDateTime();
if (start.Year > 1)
{
var end = DateTime.Now;
if (ef != null)
{
var time = ef.Value.ToDateTime();
if (time.Year > 1) end = time;
}
return GetModels(start, end);
}
}
}
else if (fi.Type == typeof(Int64))
{
var sf = exps.FirstOrDefault(e => e.Action is ">" or ">=");
var ef = exps.FirstOrDefault(e => e.Action is "<" or "<=");
if (sf != null)
{
var id = sf.Value.ToLong();
if (Factory.Snow.TryParse(id, out var time, out _, out _))
{
var start = time;
var end = DateTime.Now;
if (ef != null && Factory.Snow.TryParse(ef.Value.ToLong(), out var time2, out _, out _))
{
end = time2;
}
return GetModels(start, end);
}
}
var eq = exps.FirstOrDefault(e => e.Action == "=");
if (eq != null)
{
var id = eq.Value.ToLong();
if (Factory.Snow.TryParse(id, out var time, out _, out _))
return new[] { Shard(time) };
}
}
throw new XCodeException("分表策略因条件不足无法执行分表查询操作！");
}
private ShardModel[] GetModels(DateTime start, DateTime end)
{
var models = new List<ShardModel>();
var hash = new HashSet<String>();
for (var dt = start; dt < end; dt = dt.Add(Step))
{
var model = Shard(dt);
var key = $"{model.ConnName}#{model.TableName}";
if (key != "#" && !hash.Contains(key))
{
models.Add(model);
hash.Add(key);
}
}
// 标准时间区间 start <= @fi < end ，但是要考虑到end有一部分落入新的分片，减一秒判断
{
var model = Shard(end.AddSeconds(1));
var key = $"{model.ConnName}#{model.TableName}";
if (key != "#" && !hash.Contains(key))
{
models.Add(model);
hash.Add(key);
}
}
return models.ToArray();
}
}
}
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