protected HqlTreeNode VisitNhDistinct(NhDistinctExpression expression)
{
var visitor = new HqlGeneratorExpressionTreeVisitor(_parameters);
return(_hqlTreeBuilder.DistinctHolder(
_hqlTreeBuilder.Distinct(),
visitor.VisitExpression(expression.Expression)));
}
public void Visit(Expression expression)
{
var distinct = expression as NhDistinctExpression;
if (distinct != null)
{
expression = distinct.Expression;
}
// Find the sub trees that can be expressed purely in HQL
var nominator = new SelectClauseHqlNominator(_parameters);
expression = nominator.Visit(expression);
_hqlNodes = nominator.HqlCandidates;
// Linq2SQL ignores calls to local methods. Linq2EF seems to not support
// calls to local methods at all. For NHibernate we support local methods,
// but prevent their use together with server-side distinct, since it may
// end up being wrong.
if (distinct != null && nominator.ContainsUntranslatedMethodCalls)
{
throw new NotSupportedException("Cannot use distinct on result that depends on methods for which no SQL equivalent exist.");
}
// Now visit the tree
var projection = VisitExpression(expression);
if ((projection != expression) && !_hqlNodes.Contains(expression))
{
ProjectionExpression = Expression.Lambda(projection, _inputParameter);
}
// Handle any boolean results in the output nodes
_hqlTreeNodes = _hqlTreeNodes.ConvertAll(node => node.ToArithmeticExpression());
if (distinct != null)
{
var treeNodes = new List <HqlTreeNode>(_hqlTreeNodes.Count + 1)
{
_hqlTreeBuilder.Distinct()
};
treeNodes.AddRange(_hqlTreeNodes);
_hqlTreeNodes = new List <HqlExpression>(1)
{
_hqlTreeBuilder.ExpressionSubTreeHolder(treeNodes)
};
}
}
