// TODO: not supported in version 8? see unit test
public static object Evaluate(NullIfExpression nullIf, IArgument arg, Scope scope)
{
var n1 = Evaluate <object>(nullIf.FirstExpression, arg, scope);
var n2 = Evaluate <object>(nullIf.SecondExpression, arg, scope);
return(Equality.Equal(n1, n2) ? null : n1);
}
private static WhenClause MatchingClause(CaseExpression expr, IArgument arg, Scope scope)
{
switch (expr)
{
case SimpleCaseExpression simple:
var input = Evaluate(simple.InputExpression, arg, scope);
return(simple.WhenClauses
.FirstOrDefault(x => Equality.Equal(input, Evaluate(x.WhenExpression, arg, scope))));
case SearchedCaseExpression searched:
return(searched.WhenClauses
.FirstOrDefault(x => Evaluate(x.WhenExpression, arg, scope)));
default:
throw FeatureNotSupportedException.Subtype(expr);
}
}
public static EngineResult Evaluate(BinaryQueryExpressionType type, bool all, Table left, Table right, Env env)
{
// TODO: does offset/fetch/top happen before or after?
if (left.Columns.Count != right.Columns.Count)
{
throw new Exception("tables must have the same number of columns");
}
foreach (var i in Enumerable.Range(0, left.Columns.Count))
{
var a = left.Columns[i];
var b = right.Columns[i];
if (a.Name.Length > 0 && b.Name.Length > 0 && !a.Name.Last().Similar(b.Name.Last()))
{
throw new Exception("columns must have the same names");
}
// TODO: identify lowest common type
if (a.Type != b.Type)
{
throw new Exception("types must match");
}
}
var result = new Table {
Columns = left.Columns
};
bool Contains(Table t, Row r) =>
t.Rows.Any(s =>
Enumerable.Range(0, r.Columns.Count).All(i =>
Equality.Equal(r.Values[i], s.Values[i])));
switch (type)
{
case BinaryQueryExpressionType.Except:
foreach (var x in left.Rows)
{
if (!Contains(right, x) && (all || !Contains(result, x)))
{
result.AddCopy(x, env);
}
}
break;
case BinaryQueryExpressionType.Intersect:
foreach (var x in left.Rows)
{
if (Contains(right, x) && (all || !Contains(result, x)))
{
result.AddCopy(x, env);
}
}
if (all)
{
foreach (var x in right.Rows)
{
if (Contains(left, x))
{
result.AddCopy(x, env);
}
}
}
break;
case BinaryQueryExpressionType.Union:
foreach (var x in left.Rows)
{
if (all || !Contains(result, x))
{
result.AddCopy(x, env);
}
}
foreach (var x in right.Rows)
{
if (all || !Contains(result, x))
{
result.AddCopy(x, env);
}
}
break;
default:
throw FeatureNotSupportedException.Value(type);
}
return(new EngineResult(result));
}