protected AggregateExpression UpdateAggregate(AggregateExpression aggregate, Type type, string aggType, Expression arg, bool isDistinct)
{
if (type != aggregate.Type || aggType != aggregate.AggregateName || arg != aggregate.Argument || isDistinct != aggregate.IsDistinct)
{
return new AggregateExpression(type, aggType, arg, isDistinct);
}
return aggregate;
}
protected override Expression VisitAggregate(AggregateExpression aggregate)
{
// COUNT(*) forces all fields to be retained in subquery
if (aggregate.AggregateName == "Count" && aggregate.Argument == null)
{
this.retainAllFields = true;
}
return base.VisitAggregate(aggregate);
}
protected virtual Expression VisitAggregate(AggregateExpression aggregate)
{
var arg = this.Visit(aggregate.Argument);
return this.UpdateAggregate(aggregate, aggregate.Type, aggregate.AggregateName, arg, aggregate.IsDistinct);
}
protected override Expression VisitAggregate(AggregateExpression aggregate)
{
this.hasAggregate = true;
return aggregate;
}
protected override Expression VisitAggregate(AggregateExpression aggregate)
{
this.WriteAggregateName(aggregate.AggregateName);
this.Write("(");
if (aggregate.IsDistinct)
{
this.Write("DISTINCT ");
}
if (aggregate.Argument != null)
{
this.VisitValue(aggregate.Argument);
}
else if (RequiresAsteriskWhenNoArgument(aggregate.AggregateName))
{
this.Write("*");
}
this.Write(")");
return aggregate;
}
protected virtual bool CompareAggregate(AggregateExpression a, AggregateExpression b)
{
return a.AggregateName == b.AggregateName && this.Compare(a.Argument, b.Argument);
}
protected virtual Expression BindAggregate(Expression source, string aggName, Type returnType, LambdaExpression argument, bool isRoot)
{
bool hasPredicateArg = this.language.AggregateArgumentIsPredicate(aggName);
bool isDistinct = false;
bool argumentWasPredicate = false;
bool useAlternateArg = false;
// check for distinct
MethodCallExpression mcs = source as MethodCallExpression;
if (mcs != null && !hasPredicateArg && argument == null)
{
if (mcs.Method.Name == "Distinct" && mcs.Arguments.Count == 1 &&
(mcs.Method.DeclaringType == typeof(Queryable) || mcs.Method.DeclaringType == typeof(Enumerable))
&& this.language.AllowDistinctInAggregates)
{
source = mcs.Arguments[0];
isDistinct = true;
}
}
if (argument != null && hasPredicateArg)
{
// convert query.Count(predicate) into query.Where(predicate).Count()
source = Expression.Call(typeof(Queryable), "Where", new[] { TypeHelper.GetElementType(source.Type) }, source, argument);
argument = null;
argumentWasPredicate = true;
}
ProjectionExpression projection = this.VisitSequence(source);
Expression argExpr = null;
if (argument != null)
{
this.map[argument.Parameters[0]] = projection.Projector;
argExpr = this.Visit(argument.Body);
}
else if (!hasPredicateArg || useAlternateArg)
{
argExpr = projection.Projector;
}
var alias = this.GetNextAlias();
Expression aggExpr = new AggregateExpression(returnType, aggName, argExpr, isDistinct);
var colType = this.language.TypeSystem.GetStorageType(returnType);
SelectExpression select = new SelectExpression(alias, new FieldDeclaration[] { new FieldDeclaration("", aggExpr, colType) }, projection.Select, null);
if (isRoot)
{
ParameterExpression p = Expression.Parameter(typeof(IEnumerable<>).MakeGenericType(aggExpr.Type), "p");
LambdaExpression gator = Expression.Lambda(Expression.Call(typeof(Enumerable), "Single", new Type[] { returnType }, p), p);
return new ProjectionExpression(select, new FieldExpression(
returnType,
this.language.TypeSystem.GetStorageType(returnType),
alias,
""),
gator);
}
ScalarExpression subquery = new ScalarExpression(returnType, select);
// if we can find the corresponding group-info we can build a special AggregateSubquery node that will enable us to
// optimize the aggregate expression later using AggregateRewriter
GroupByInfo info;
if (!argumentWasPredicate && this.GroupByMap.TryGetValue(projection, out info))
{
// use the element expression from the group-by info to rebind the argument so the resulting expression is one that
// would be legal to add to the fields in the select expression that has the corresponding group-by clause.
if (argument != null)
{
this.map[argument.Parameters[0]] = info.Element;
argExpr = this.Visit(argument.Body);
}
else if (!hasPredicateArg || useAlternateArg)
{
argExpr = info.Element;
}
aggExpr = new AggregateExpression(returnType, aggName, argExpr, isDistinct);
// check for easy to optimize case. If the projection that our aggregate is based on is really the 'group' argument from
// the query.GroupBy(xxx, (key, group) => yyy) method then whatever expression we return here will automatically
// become part of the select expression that has the group-by clause, so just return the simple aggregate expression.
if (projection == this.currentGroupElement)
return aggExpr;
return new AggregateSubqueryExpression(info.Alias, aggExpr, subquery);
}
return subquery;
}
