[英]What is the best approach for caching database queries
我正在编写一个管理智能应用程序,该应用程序需要大量复杂的数据库查询,而某些查询则非常昂贵。 为了提高性能,我大量使用Memcached在内存中存储尽可能多的内容。
这导致了我代码中的大量重复,我渴望摆脱这些重复并构建更干净的数据访问解决方案。 我的很多数据访问功能最终都看起来像这样。
public int NumberOfTimeouts(DateTime date, int? applicationId)
{
var functionCacheKey = "NumberOfTimeouts";
var cacheKey = string.Format("{0}-{1}-{2}-{3}", RepositoryCacheKey, functionCacheKey, date, applicationId);
var cachedNumberTimeouts = _cache.Retrieve(cacheKey);
if (cachedNumberTimeouts != null)
{
return (int)cachedNumberTimeouts;
}
//query logic here, calculates numberOfTimeouts
UpdateCache(date, cacheKey, numberOfTimeouts);
return numberOfTimeouts;
}
我只是不太确定这是什么标准方法,它可能涉及使用自定义属性类还是类似的东西?
这是一个跨领域的问题。 Decorator
模式可能在这里适用。 我可能没有这种模式的经验,但是我会试一试
// model
public class CustomObject
{
public int Id { get; set; }
}
// interface
public interface IRepository<T>
{
IEnumerable<T> Find(Expression<Func<T, bool>> expression);
}
public interface ICacheableRepository<T>
{
IEnumerable<T> Find(Expression<Func<T, bool>> expression, Func<int> cacheKey);
}
public interface IRepositoryCacheManager<T>
{
IEnumerable<T> Get(int key);
bool Any(int key);
void Add(int key, IEnumerable<T> result);
}
// cache manager
public class RepositoryCacheManager<T> : IRepositoryCacheManager<T>
{
private Dictionary<int, IEnumerable<T>> cache = new Dictionary<int,IEnumerable<T>>();
#region IRepositoryCache<T> Members
public IEnumerable<T> Get(int key)
{
return cache[key];
}
public bool Any(int key)
{
IEnumerable<T> result = null;
return cache.TryGetValue(key, out result);
}
public void Add(int key, IEnumerable<T> result)
{
cache.Add(key, result);
}
#endregion
}
// cache repository decorator
public class CachedRepositoryDecorator<T> : IRepository<T>, ICacheableRepository<T>
{
public CachedRepositoryDecorator(IRepositoryCacheManager<T> cache
, IRepository<T> member)
{
this.member = member;
this.cache = cache;
}
private IRepository<T> member;
private IRepositoryCacheManager<T> cache;
#region IRepository<T> Members
// this is not caching
public IEnumerable<T> Find(Expression<Func<T, bool>> expression)
{
return member.Find(expression);
}
#endregion
#region ICacheableRepository<T> Members
public IEnumerable<T> Find(Expression<Func<T, bool>> expression, Func<int> cacheKey)
{
if (cache.Any(cacheKey()))
{
return cache.Get(cacheKey());
}
else
{
IEnumerable<T> result = member.Find(expression);
cache.Add(cacheKey(), result);
return result;
}
}
#endregion
}
// object repository
public class CustomObjectRepository : IRepository<CustomObject>
{
#region IRepository<CustomObject> Members
public IEnumerable<CustomObject> Find(Expression<Func<CustomObject, bool>> expression)
{
List<CustomObject> cust = new List<CustomObject>();
// retrieve data here
return cust;
}
#endregion
}
// example
public class Consumer
{
// this cache manager should be persistent, maybe can be used in static, etc
IRepositoryCacheManager<CustomObject> cache = new RepositoryCacheManager<CustomObject>();
public Consumer()
{
int id = 25;
ICacheableRepository<CustomObject> customObjectRepository =
new CachedRepositoryDecorator<CustomObject>(
cache
, new CustomObjectRepository()
);
customObjectRepository.Find(k => k.Id == id, () => { return id; });
}
}
请注意:
Find
的ICacheableRepository
重载而产生的代码味道,但是我无法使用Expression
作为Dictionary
Key
优点:
SRP
缺点:
归功于这篇文章 :)
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