/// <summary>
/// Executes the actual query. Called automatically when the query is evaluated
/// </summary>
public TResult Execute <TResult>(Expression expression)
{
LogLine("\r\n----------------- EXPRESSION --------------------\r\n");
var localExpression = expression;
LogLine(expression.ToString());
// Reduce any parts of the expression that can be evaluated locally
var simplifiedExpression = ExpressionSimplifier.Simplify(this.Queryable, localExpression);
if (simplifiedExpression != localExpression)
{
LogLine("\r\n----------------- SIMPLIFIED EXPRESSION --------------------\r\n");
localExpression = simplifiedExpression;
LogLine(localExpression.ToString());
}
var pipeline = new MongoPipeline <TDocument>(_collection, AllowMongoDiskUse, LoggingDelegate);
try
{
return(pipeline.Execute <TResult>(localExpression));
}
catch (MongoCommandException c)
{
if (c.Message.Contains("$in requires an array as a second argument, found: null"))
{
throw new ArgumentNullException(".Contains on null Enumerable blew up.", c);
}
throw;
}
}
/// <summary>
/// Simplify an expression by evaluating immediately any sub-trees
/// that exist entirely locally. For now, that means anything that's
/// not referenced from a Lambda parameter. If nothing can be evaulated
/// locally, then the original expression is returned. Otherwise, a new
/// expression is returned.
/// </summary>
/// <param name="rootQueryable">Queryable this expression is being executed against</param>
/// <param name="expression">Expression to simplify</param>
public static Expression Simplify(object rootQueryable, Expression expression)
{
// Simplification is accomplished in two passes.
// Pass one, find ALL nodes that can be evaluated locally.
var simplifier = new ExpressionSimplifier();
simplifier.SaveIfSimplifiable(rootQueryable, expression);
// Pass two, do a depth first search of the tree greedily evaluating
// nodes whenever possible.
return(simplifier.Visit(expression));
}
