internal Expression Rewrite()
{
var keys = Grouping.KeyProjection;
var keyColumns = new ColumnProjector(TabularExpressionHelper.CanBeColumn).ProjectColumns(keys);
var keyFilters = keyColumns.Columns.Select(c => Expression.Equal(c.Expression, c.Expression)).Aggregate((x, y) => Expression.And(x, y));
var subQueryBase =
new CalculateTableExpression(Grouping.SubQueryProjectionExpression.Type,
Grouping.SubQueryProjectionExpression.Source, keyFilters);
var subQuery = new SubQueryProjection(Grouping.SubQueryProjectionExpression.Type, new ProjectionExpression(subQueryBase, Grouping.SubQueryProjectionExpression.Projector));
Type groupType =
typeof(TabularGrouping <,>).MakeGenericType(new Type[]
{ Grouping.KeyProjection.Type, Grouping.SubQueryProjectionExpression.Type });
return(new ProjectionExpression(new SummarizeExpression(groupType, new List <ColumnDeclaration>().AsReadOnly(), Grouping.SubQueryProjectionExpression.Source), subQuery));
}
/// <summary>
/// Transform subordinate queries
/// </summary>
/// <param name="projectionExpression">subordinate query</param>
/// <returns>converted projection</returns>
protected override Expression VisitSubQuery(SubQueryProjection projectionExpression)
{
var exp = (DaxExpression) new SubQueryProjectionBuilder().Visit(projectionExpression.Projection.Source);
var projection = new ProjectionExpression(exp, projectionExpression.Projection.Projector);
var q = new SubQueryProjection(projectionExpression.Type, projection);
LambdaExpression subQuery = Expression.Lambda(q, _row);
MethodInfo mi;
if (projectionExpression.Type.IsGenericType)
{
Type elementType = TypeSystem.GetElementType(projectionExpression.Type);
mi = _executeSubQuery.MakeGenericMethod(elementType);
}
else
{
mi = _executeSubQuery.MakeGenericMethod(subQuery.Body.Type);
}
return(Expression.Convert(Expression.Call(_row, mi, Expression.Constant(subQuery)), projectionExpression.Type));
//MethodInfo mireturn base.Visit(projectionExpression);
}
/// <summary>
/// Skip subordinate queries
/// </summary>
/// <param name="projectionExpression">sub query</param>
/// <returns>the expression</returns>
protected override Expression VisitSubQuery(SubQueryProjection projectionExpression)
{
Visit(projectionExpression.Projection);
return(projectionExpression);
}
