public AggregateSubqueryExpression(IdentifiableAlias groupByAlias, Expression aggregateInGroupSelect, ScalarExpression aggregateAsSubquery)
: base(DbExpressionType.AggregateSubquery, aggregateAsSubquery.Type)
{
this.aggregateInGroupSelect = aggregateInGroupSelect;
this.groupByAlias = groupByAlias;
this.aggregateAsSubquery = aggregateAsSubquery;
}
protected AggregateSubqueryExpression UpdateAggregateSubquery(AggregateSubqueryExpression aggregate, ScalarExpression subquery)
{
if (subquery != aggregate.AggregateAsSubquery)
{
return new AggregateSubqueryExpression(aggregate.GroupByAlias, aggregate.AggregateInGroupSelect, subquery);
}
return aggregate;
}
protected virtual Expression VisitScalar(ScalarExpression scalar)
{
var select = (SelectExpression)this.Visit(scalar.Select);
return this.UpdateScalar(scalar, select);
}
protected ScalarExpression UpdateScalar(ScalarExpression scalar, SelectExpression select)
{
if (select != scalar.Select)
{
return new ScalarExpression(scalar.Type, select);
}
return scalar;
}
protected override Expression VisitScalar(ScalarExpression subquery)
{
this.Write("(");
this.WriteLine(Indentation.Inner);
this.Visit(subquery.Select);
this.WriteLine(Indentation.Same);
this.Write(")");
this.Indent(Indentation.Outer);
return subquery;
}
protected virtual bool CompareScalar(ScalarExpression a, ScalarExpression b)
{
return this.Compare(a.Select, b.Select);
}
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;
}
