protected override Expression VisitExists(ExistsExpression exists)
{
// how did we get here? Translate exists into count query
var colType = this.linguist.Language.TypeSystem.GetColumnType(typeof(int));
var newSelect = exists.Select.SetColumns(
new[] { new ColumnDeclaration("value", new AggregateExpression(typeof(int), "Count", null, false), colType) }
);
var projection =
new ProjectionExpression(
newSelect,
new ColumnExpression(typeof(int), colType, newSelect.Alias, "value"),
Aggregator.GetAggregator(typeof(int), typeof(IEnumerable <int>))
);
var expression = projection.GreaterThan(Expression.Constant(0));
return(this.Visit(expression));
}
protected virtual Expression VisitExists(ExistsExpression exists)
{
var select = (SelectExpression)this.Visit(exists.Select);
return(this.UpdateExists(exists, select));
}
protected virtual bool CompareExists(ExistsExpression a, ExistsExpression b)
{
return(this.Compare(a.Select, b.Select));
}