protected override Expression VisitSelect(SelectExpression select)
{
if (select.From.NodeType != (ExpressionType)MongoExpressionType.Collection)
{
throw new InvalidQueryException("The query is too complex to be processed by MongoDB. Try building a map-reduce query by hand or simplifying the query and using Linq-to-Objects.");
}
bool hasAggregates = new AggregateChecker().HasAggregates(select);
if (select.GroupBy != null)
{
_isMapReduce = true;
}
else if (hasAggregates)
{
if (select.Fields.Count == 1 && select.Fields[0].Expression.NodeType == (ExpressionType)MongoExpressionType.Aggregate)
{
var aggregateExpression = (AggregateExpression)select.Fields[0].Expression;
if (aggregateExpression.AggregateType == AggregateType.Count)
{
_isCount = true;
}
}
if (!_isCount)
{
_isMapReduce = true;
}
}
Visit(select.Where);
return(select);
}
private static bool CanMergeWithFrom(SelectExpression select, bool isTopLevel)
{
var fromSelect = select.From as SelectExpression;
if (fromSelect == null)
return false;
var fromIsSimpleProjection = IsSimpleProjection(fromSelect);
var fromIsNameMapProjection = IsNameMapProjection(fromSelect);
if (!fromIsSimpleProjection && !fromIsNameMapProjection)
return false;
var selectIsNameMapProjection = IsNameMapProjection(select);
var selectHasOrderBy = select.OrderBy != null && select.OrderBy.Count > 0;
var selectHasGroupBy = select.GroupBy != null;
var selectHasAggregates = new AggregateChecker().HasAggregates(select);
var fromHasOrderBy = fromSelect.OrderBy != null && fromSelect.OrderBy.Count > 0;
var fromHasGroupBy = fromSelect.GroupBy != null;
if (selectHasOrderBy && fromHasOrderBy)
return false;
if (selectHasGroupBy && fromHasGroupBy)
return false;
if(fromHasOrderBy && (selectHasGroupBy || selectHasAggregates || select.IsDistinct))
return false;
if(fromHasGroupBy && select.Where != null)
return false;
if(fromSelect.Take != null && (select.Take != null || select.Skip != null || select.IsDistinct || selectHasAggregates || selectHasGroupBy))
return false;
if(fromSelect.Skip != null && (select.Skip != null || select.IsDistinct || selectHasAggregates || selectHasGroupBy))
return false;
if (fromSelect.IsDistinct && (select.Take != null || select.Skip != null || !selectIsNameMapProjection || selectHasGroupBy || selectHasAggregates || (selectHasOrderBy && !isTopLevel)))
return false;
return true;
}
private static bool CanMergeWithFrom(SelectExpression select, bool isTopLevel)
{
var fromSelect = select.From as SelectExpression;
if (fromSelect == null)
{
return(false);
}
var fromIsSimpleProjection = IsSimpleProjection(fromSelect);
var fromIsNameMapProjection = IsNameMapProjection(fromSelect);
if (!fromIsSimpleProjection && !fromIsNameMapProjection)
{
return(false);
}
var selectIsNameMapProjection = IsNameMapProjection(select);
var selectHasOrderBy = select.OrderBy != null && select.OrderBy.Count > 0;
var selectHasGroupBy = select.GroupBy != null;
var selectHasAggregates = new AggregateChecker().HasAggregates(select);
var fromHasOrderBy = fromSelect.OrderBy != null && fromSelect.OrderBy.Count > 0;
var fromHasGroupBy = fromSelect.GroupBy != null;
if (selectHasOrderBy && fromHasOrderBy)
{
return(false);
}
if (selectHasGroupBy && fromHasGroupBy)
{
return(false);
}
if (fromHasOrderBy && (selectHasGroupBy || selectHasAggregates || select.IsDistinct))
{
return(false);
}
if (fromHasGroupBy && select.Where != null)
{
return(false);
}
if (fromSelect.Take != null && (select.Take != null || select.Skip != null || select.IsDistinct || selectHasAggregates || selectHasGroupBy))
{
return(false);
}
if (fromSelect.Skip != null && (select.Skip != null || select.IsDistinct || selectHasAggregates || selectHasGroupBy))
{
return(false);
}
if (fromSelect.IsDistinct && (select.Take != null || select.Skip != null || !selectIsNameMapProjection || selectHasGroupBy || selectHasAggregates || (selectHasOrderBy && !isTopLevel)))
{
return(false);
}
return(true);
}
