protected virtual Expression VisitExists(ExistsExpression exists)
{
var select = (SelectExpression)this.Visit(exists.Select);
return this.UpdateExists(exists, select);
}
protected ExistsExpression UpdateExists(ExistsExpression exists, SelectExpression select)
{
if (select != exists.Select)
{
return new ExistsExpression(select);
}
return exists;
}
protected override Expression VisitExists(ExistsExpression exists)
{
this.Write("EXISTS(");
this.WriteLine(Indentation.Inner);
this.Visit(exists.Select);
this.WriteLine(Indentation.Same);
this.Write(")");
this.Indent(Indentation.Outer);
return exists;
}
protected virtual bool CompareExists(ExistsExpression a, ExistsExpression b)
{
return this.Compare(a.Select, b.Select);
}
private Expression BindAnyAll(Expression source, MethodInfo method, LambdaExpression predicate, bool isRoot)
{
bool isAll = method.Name == "All";
ConstantExpression constSource = source as ConstantExpression;
if (constSource != null && !IsQuery(constSource))
{
System.Diagnostics.Debug.Assert(!isRoot);
Expression where = null;
foreach (object value in (IEnumerable)constSource.Value)
{
Expression expr = Expression.Invoke(predicate, Expression.Constant(value, predicate.Parameters[0].Type));
if (where == null)
{
where = expr;
}
else if (isAll)
{
where = where.And(expr);
}
else
{
where = where.Or(expr);
}
}
return this.Visit(where);
}
else
{
if (isAll)
{
predicate = Expression.Lambda(Expression.Not(predicate.Body), predicate.Parameters.ToArray());
}
if (predicate != null)
{
source = Expression.Call(typeof(Enumerable), "Where", method.GetGenericArguments(), source, predicate);
}
ProjectionExpression projection = this.VisitSequence(source);
Expression result = new ExistsExpression(projection.Select);
if (isAll)
{
result = Expression.Not(result);
}
if (isRoot)
{
if (this.language.AllowSubqueryInSelectWithoutFrom)
{
return GetSingletonSequence(result, "SingleOrDefault");
}
else
{
// use count aggregate instead of exists
var colType = this.language.TypeSystem.GetStorageType(typeof(int));
var newSelect = projection.Select.SetFields(
new[] { new FieldDeclaration("value", new AggregateExpression(typeof(int), "Count", null, false), colType) }
);
var colx = new FieldExpression(typeof(int), colType, newSelect.Alias, "value");
var exp = isAll
? colx.Equal(Expression.Constant(0))
: colx.GreaterThan(Expression.Constant(0));
return new ProjectionExpression(
newSelect, exp, Aggregator.GetAggregator(typeof(bool), typeof(IEnumerable<bool>))
);
}
}
return result;
}
}
protected virtual Expression BindIntersect(Expression outerSource, Expression innerSource, bool negate)
{
// SELECT * FROM outer WHERE EXISTS(SELECT * FROM inner WHERE inner = outer))
ProjectionExpression outerProjection = this.VisitSequence(outerSource);
ProjectionExpression innerProjection = this.VisitSequence(innerSource);
Expression exists = new ExistsExpression(
new SelectExpression(new IdentifiableAlias(), null, innerProjection.Select, innerProjection.Projector.Equal(outerProjection.Projector))
);
if (negate)
exists = Expression.Not(exists);
var alias = this.GetNextAlias();
ProjectedFields pc = this.ProjectFields(outerProjection.Projector, alias, outerProjection.Select.Alias);
return new ProjectionExpression(
new SelectExpression(alias, pc.Fields, outerProjection.Select, exists),
pc.Projector, outerProjection.Aggregator
);
}