/// <summary>
/// The from clause can contain top level concat operators as well.
/// </summary>
/// <param name="fromClause"></param>
/// <param name="queryModel"></param>
public override void VisitMainFromClause(MainFromClause fromClause, QueryModel queryModel)
{
bool processed = false;
if (fromClause.FromExpression is SubQueryExpression)
{
var sq = fromClause.FromExpression as SubQueryExpression;
var qms = Split(sq.QueryModel);
if (qms.Length > 1)
{
processed = true;
// Find which Result operators we should remove for all but the last item.
var lastConcat = queryModel.ResultOperators.Reverse().Where(x => x is ConcatResultOperator).FirstOrDefault();
int? lastConcatIndex = lastConcat == null ? (int?) null : queryModel.ResultOperators.IndexOf(lastConcat);
// Create a new one for each from expression, and substitute in for the current one.
// Recursively process it.
foreach (var qSub in qms)
{
var qm = queryModel.Clone();
qm.MainFromClause.FromExpression = new SubQueryExpression(qSub);
qm.Flatten();
if (lastConcatIndex.HasValue && qSub != qms[qms.Length - 1])
{
for (int i = 0; i < lastConcatIndex + 1; i++)
{
qm.ResultOperators.RemoveAt(0);
}
}
VisitQueryModel(qm);
}
}
}
if (!processed)
{
base.VisitMainFromClause(fromClause, queryModel);
// Models that don't need further processing are "done".
_models.Add(queryModel);
}
}
/// <summary>
/// Given a query model, look at all the result operators for Concat operators, and split everything up
/// into separate query models.
/// </summary>
/// <param name="queryModel"></param>
/// <returns></returns>
private static IEnumerable<QueryModel> SplitQMByConcatResultOperator(QueryModel queryModel)
{
// If there are no concat result operators in the list, then we just bail quickly.
// This is to specifically avoid the Clone operation unless we actually need it.
if (!queryModel.ResultOperators.Where(r => r is ConcatResultOperator).Any())
{
return new QueryModel[] { queryModel };
}
// Now, look for concat operators in the list. Pop them out when we find them.
ConcatResultOperator ro = null;
var qm = queryModel.Clone();
var lst = new List<QueryModel>();
while ((ro = qm.ResultOperators.Reverse().Where(r => r is ConcatResultOperator).Cast<ConcatResultOperator>().FirstOrDefault()) != null)
{
// We are going to make q QueryModel here that uses the second source in the Concat operator.
// This means everything that comes before this query can be ignored - and we want this "source" to
// become the query from clause. Note this also means messing with the "select" clause to make sure it
// isn't doing anything special (select clause comes before result operators, semantically).
QueryModel newQM = NewQMFromOldWithLifting(ro.Source2, qm.MainFromClause.ItemType, qm.MainFromClause.ItemName);
var cc = new CloneContext(new QuerySourceMapping());
var indexToRemoveTo = qm.ResultOperators.IndexOf(ro);
for (int i = indexToRemoveTo + 1; i < qm.ResultOperators.Count; i++)
{
newQM.ResultOperators.Add(qm.ResultOperators[i].Clone(cc));
}
lst.Add(newQM.Flatten());
// Ok - we've taken one branch. We need to remove it from the list of things to look at, and work on the
// next one.
qm.ResultOperators.Remove(ro);
}
// The QueryModel left over needs to be added to the list.
lst.Add(qm.Flatten());
return lst;
}