public static Expression Find(Expression expression)
{
RootQueryableFinder finder = new RootQueryableFinder();
finder.Visit(expression);
return(finder.root);
}
internal void Compile(params object[] args)
{
if (this.fnQuery == null)
{
// first identify the query provider being used
Expression body = this.query.Body;
ConstantExpression root = RootQueryableFinder.Find(body) as ConstantExpression;
if (root == null && args != null && args.Length > 0)
{
Expression replaced = ExpressionReplacer.ReplaceAll(
body,
this.query.Parameters.ToArray(),
args.Select((a, i) => Expression.Constant(a, this.query.Parameters[i].Type)).ToArray()
);
body = PartialEvaluator.Eval(replaced);
root = RootQueryableFinder.Find(body) as ConstantExpression;
}
if (root == null)
{
throw new InvalidOperationException("Could not find query provider");
}
// ask the query provider to compile the query by 'executing' the lambda expression
IQueryProvider provider = ((IQueryable)root.Value).Provider;
Delegate result = (Delegate)provider.Execute(this.query);
System.Threading.Interlocked.CompareExchange(ref this.fnQuery, result, null);
}
}
/// <summary>
/// Convert the query expression into an execution plan
/// </summary>
/// <param name="expression"></param>
/// <returns></returns>
protected virtual Expression GetExecutionPlan(Expression expression)
{
// strip off lambda for now
LambdaExpression lambda = expression as LambdaExpression;
if (lambda != null)
{
expression = lambda.Body;
}
// translate query into client and server parts
ProjectionExpression projection = Translate(expression);
Expression rootQueryable = RootQueryableFinder.Find(expression);
Expression provider = Expression.Convert(
Expression.Property(rootQueryable, typeof(IQueryable).GetProperty("Provider")),
typeof(DbQueryProvider)
);
return(policy.BuildExecutionPlan(projection, provider));
}