private SqlAggregateSubqueryRewriter(Expression expr)
{
this.aggregateSubqueryInstances = new Dictionary <SqlAggregateSubqueryExpression, Expression>();
this.aggregateSubqueriesBySelectAlias = SqlAggregateSubqueryFinder.Find(expr).OfType <SqlAggregateSubqueryExpression>().ToLookup(a => a.GroupByAlias);
}
