/// <summary>
/// Executes the projection.
/// </summary>
/// <param name="projection">The projection.</param>
/// <param name="okayToDefer">if set to <c>true</c> [okay to defer].</param>
/// <returns></returns>
private Expression ExecuteProjection(ProjectionExpression projection, bool okayToDefer)
{
// parameterize query
projection = (ProjectionExpression)this.Parameterize(projection);
if (this.scope != null)
{
// also convert references to outer alias to named values! these become SQL parameters too
projection = (ProjectionExpression)OuterParameterizer.Parameterize(this.scope.Alias, projection);
}
FixColumnNames(projection);
string commandText = this.linguist.Format(projection.Select);
ReadOnlyCollection <NamedValueExpression> namedValues = NamedValueGatherer.Gather(projection.Select);
QueryCommand command = new QueryCommand(commandText, namedValues.Select(v => new QueryParameter(v.Name, v.Type)));
Expression[] values = namedValues.Select(v => Expression.Convert(this.Visit(v.Value), typeof(object))).ToArray();
return(this.ExecuteProjection(projection, okayToDefer, command, values));
}
/// <summary>
/// Executes the projection.
/// </summary>
/// <param name="projection">The projection.</param>
/// <param name="okayToDefer">if set to <c>true</c> [okay to defer].</param>
/// <param name="command">The command.</param>
/// <param name="values">The values.</param>
/// <returns></returns>
private Expression ExecuteProjection(ProjectionExpression projection, bool okayToDefer, QueryCommand command, Expression[] values)
{
okayToDefer &= (this.receivingMember != null && this.policy.IsDeferLoaded(this.receivingMember));
var saveScope = this.scope;
ParameterExpression reader = Expression.Parameter(typeof(FieldReader), "r" + nReaders++);
this.scope = new Scope(this.scope, reader, projection.Select.Alias, projection.Select.Columns);
LambdaExpression projector = Expression.Lambda(this.Visit(projection.Projector), reader);
this.scope = saveScope;
var entity = EntityFinder.Find(projection.Projector);
string methExecute = okayToDefer ? "ExecuteDeferred" : "Execute";
// call low-level execute directly on supplied DbQueryProvider
Expression result = Expression.Call(this.executor, methExecute, new Type[] { projector.Body.Type }, Expression.Constant(command), projector, Expression.Constant(entity, typeof(MappingEntity)), Expression.NewArrayInit(typeof(object), values));
if (projection.Aggregator != null)
{
// apply aggregator
result = DbExpressionReplacer.Replace(projection.Aggregator.Body, projection.Aggregator.Parameters[0], result);
}
return(result);
}
/// <summary> /// Executes the command. /// </summary> /// <param name="query">The query.</param> /// <param name="paramValues">The param values.</param> /// <returns></returns> public abstract int ExecuteCommand(QueryCommand query, object[] paramValues);
/// <summary> /// Executes the specified command. /// </summary> /// <typeparam name="T"></typeparam> /// <param name="command">The command.</param> /// <param name="fnProjector">The fn projector.</param> /// <param name="entity">The entity.</param> /// <param name="paramValues">The param values.</param> /// <returns></returns> public abstract IEnumerable <T> Execute <T>(QueryCommand command, Func <FieldReader, T> fnProjector, MappingEntity entity, object[] paramValues);