如何緩存編譯的LINQ查詢（不是結果）？

Question

它看起來每個I查詢一些與LINQ NHibernate的時間一樣從頭開始構建該查詢：

代碼看起來像

session.Query<User>().Where(x => ids.Contains(x.Id)).ToFuture(); 

是否有可能避免重新編譯呢？

關於緩存QueryOver/Criteria查詢的相同問題（不是很重要，但它可能仍然適合範圍）。

Answer 1

特別是這種情況下被接入到IDS（int[]）造成這裏

session.Query<User>().Where(x => ids.Contains(x.Id)).ToFuture(); 

轉化MemberAccessExpression（不ConstantExpression）和NHibernate不得不對其進行評估。儘管ids從未被更改過，但它仍被捕獲到一個關閉生成的類中（如DisplayClass<>.ids）。

我通過製作PartialEvaluatingExpressionTreeVisitor我自己的版本優化，這種情況下：

protected Expression EvaluateSubtree(Expression subtree) 
    { 
     ArgumentUtility.CheckNotNull(nameof(subtree), subtree); 
     var memberExpression = subtree as MemberExpression; 
     if (memberExpression != null) 
     { 
      Expression constant; 
      if (TryEvaluateMember(memberExpression, out constant)) return constant; 
     } 

     if (subtree.NodeType != ExpressionType.Constant) 
      throw new NHibernateExpressionOptimizerException(subtree); 
     ConstantExpression constantExpression = (ConstantExpression)subtree; 
     IQueryable queryable = constantExpression.Value as IQueryable; 
     if (queryable != null && queryable.Expression != constantExpression) 
      return queryable.Expression; 
     return constantExpression; 
    } 

    bool TryEvaluateMember(MemberExpression memberExpression, out Expression constant) 
    { 
     constant = null; 
     ConstantExpression c = memberExpression.Expression == null ? Expression.Constant(null) : EvaluateSubtree(memberExpression.Expression) as ConstantExpression; 
     if (c == null) return false; 
     var fieldInfo = memberExpression.Member as FieldInfo; 
     if (fieldInfo != null) 
     { 
      constant = Expression.Constant(ReflectorReadFieldDelegate(fieldInfo, c.Value)); 
      return true; 
     } 

     var propertyInfo = memberExpression.Member as PropertyInfo; 
     if (propertyInfo != null) 
     { 
      constant = Expression.Constant(ReflectorReadPropertyDelegate(propertyInfo, c.Value)); 
      return true; 
     } 
     return false; 
    } 

反射器代表使用一種緩存Reflection.Emit的魔力。