[英]Repository Pattern and Local Caching
我有以下接口/類:
public interface IUnitOfWork : IDisposable
{
event EventHandler<EventArgs> Saved;
DbSet<T> Set<T>() where T : class;
DbEntityEntry<T> Entry<T>(T entity) where T : class;
void Commit();
}
以及存儲庫的實現:
public class CachedSqlRepository<T, TKey, TContext> : ICacheRepository<T, TKey, TContext>
where T : class
where TContext : DbContext, IDisposable, new()
{
//A list of the Navigation Properties to include
private readonly Expression<Func<T, object>>[] _NavigationProperties;
public CachedSqlRepository(params Expression<Func<T, object>>[] navigationProperties)
{
_NavigationProperties = navigationProperties;
using (TContext dbContext = new TContext()) //Fetch the List of Entities
{
RefreshCache(dbContext);
}
}
/// <summary>
/// The Collection of Items in the database
/// Note this is a Cache, but should replicate whats in the DB
/// </summary>
public IList<T> Items { get; private set; }
public bool Any(Func<T, bool> predicate)
{
return Items.Any(predicate);
}
public void RefreshCache(DbContext context)
{
switch (_NavigationProperties.Length)
{
case 0:
Items = context.Set<T>().ToList();
break;
case 1:
Items = context.Set<T>().Include(_NavigationProperties[0]).ToList();
break;
//more here
}
}
/// <summary>
/// Refresh the internal cache
/// </summary>
public void RefreshCache()
{
using (TContext dbContext = new TContext())
{
RefreshCache(dbContext);
}
}
public IEnumerable<T> FilterBy(Func<T, bool> predicate)
{
return Items.Where(predicate);
}
public T Add(T entity)
{
T newEntity;
using (TContext dbContext = new TContext())
{
newEntity = dbContext.Set<T>().Add(entity);
if (dbContext.SaveChanges() == 1) //1 change was made
Items.Add(newEntity);
}
return newEntity;
}
public void Delete(TKey id)
{
using (TContext dbContext = new TContext())
{
var attachedEntry = dbContext.Set<T>().Find(id);
if (attachedEntry == null) return; //it doesnt exist anyway!
dbContext.Set<T>().Remove(attachedEntry);
dbContext.SaveChanges();
RefreshCache(dbContext);
}
}
public void Update(T entity, TKey id)
{
if (entity == null) throw new ArgumentException("Cannot update a null entity.");
using (TContext dbContext = new TContext())
{
var entry = dbContext.Entry(entity);
if (entry.State != EntityState.Detached) return;
T attachedEntity = dbContext.Set<T>().Find(id);
if (attachedEntity != null)
{
var attachedEntry = dbContext.Entry(attachedEntity);
attachedEntry.CurrentValues.SetValues(entity);
}
else
{
entry.State = EntityState.Modified; // This should attach entity
}
dbContext.SaveChanges();
RefreshCache(dbContext);
}
}
#region Transaction Methods
public IUnitOfWork StartTransaction()
{
return new EFUnitOfWork(new TContext());
}
public T TransactionAdd(T entity, IUnitOfWork context)
{
context.Saved += OnSave;
return context.Set<T>().Add(entity);
}
public void TransactionDelete(TKey id, IUnitOfWork context)
{
var attachedEntry = context.Set<T>().Find(id);
if (attachedEntry == null) return; //it doesnt exist anyway
context.Saved += OnSave;
context.Set<T>().Remove(attachedEntry);
}
public void TransactionUpdate(T entity, TKey id, IUnitOfWork context)
{
if (entity == null) throw new ArgumentException("Cannot update a null entity.");
var entry = context.Entry(entity);
if (entry.State != EntityState.Detached) return;
T attachedEntity = context.Set<T>().Find(id);
if (attachedEntity != null)
{
var attachedEntry = context.Entry(attachedEntity);
attachedEntry.CurrentValues.SetValues(entity);
}
else
{
entry.State = EntityState.Modified; // This should attach entity
}
context.Saved += OnSave;
}
private void OnSave(object sender, EventArgs e)
{
RefreshCache();
}
#endregion
}
它改編自網上的各種圖案。 我不認為這對於具有數十萬行的表有用,但對於查找表等 - 我並不總是打到數據庫。
它可以工作,但有些東西不是很干凈,例如我刷新緩存 - 有時我必須再次拉取所有數據(目前正在進行中)。
這個聲音設計? 還是我在這里重新發明輪子?
一個有趣的問題+1。 在我看來,上下文內容緩存是最好的,或者單獨使用。 並使用DB緩存。
為什么:
在各種環境中研究了這個主題,而不僅僅是EF / .NET / SQL Server,我得出的結論是,除非數據庫服務器已成為或者趨向於成為CPU瓶頸並且無法輕松擴展,否則它是為DB提供內存並讓它在構建或嘗試緩存條目之前緩存100sMB的一種非常合理的方法。 在使用WebServer上的app knots進行編碼之前,我寧願在SQL Server中拋出GB或RAM。
當每微秒計數時,或者您的數據庫在網絡范圍內與延遲/吞吐量問題分離,並且您的數據是非易失性的,並且不需要緩存到期/並發管理。 然后繼續實施緩存。
仔細考慮內存使用,緩存構建時間和內存持久性模型。
查看一些用於緩存創意和潛在解決方案的工具。 例如企業緩存塊。
祝好運。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.