private static bool TryGetExistsSubselect(BoundExpression expression, out BoundExistsSubselect existsSubselect, out bool isNegated)
{
var negation = expression as BoundUnaryExpression;
if (negation != null && negation.Result.Selected.Signature.Kind == UnaryOperatorKind.LogicalNot)
{
if (!TryGetExistsSubselect(negation.Expression, out existsSubselect, out isNegated))
{
return(false);
}
isNegated = !isNegated;
return(true);
}
isNegated = false;
existsSubselect = expression as BoundExistsSubselect;
return(existsSubselect != null);
}
protected override BoundExpression RewriteExistsSubselect(BoundExistsSubselect node)
{
var relation = RewriteRelation(node.Relation);
// TODO: This isn't ideal. In many cases, the relation will not have any output values.
// This means, we've to create a new value slot factory which in turn means that
// we have create multiple slots with the same name. It seems we should think of
// a better way to carry the factories. Maybe we should just expose on specific
// bound nodes?
var facory = node.Relation.GetOutputValues().FirstOrDefault()?.Factory ?? new ValueSlotFactory();
var valueSlot = facory.CreateTemporary(typeof(bool));
var subquery = new Subquery(SubqueryKind.Exists, valueSlot, relation, CurrentPassthru);
var subqueries = _subqueryStack.Peek();
subqueries.Add(subquery);
return(Expression.Value(valueSlot));
}
protected override void VisitExistsSubselect(BoundExistsSubselect node)
{
SubqueryFound = true;
}
