protected override Expression VisitSelect(SqlSelectExpression select)
{
var savedIsTopLevel = this.isTopLevel;
this.isTopLevel = false;
select = (SqlSelectExpression)base.VisitSelect(select);
// Attempt to merge subqueries that would have been removed by the above
// logic except for the existence of a where clause
while (this.CanMergeWithFrom(select))
{
var fromSelect = select.From.GetLeftMostSelect();
this.CanMergeWithFrom(select);
// remove the redundant subquery
select = SubqueryRemover.Remove(select, fromSelect);
// merge where expressions
var where = select.Where;
if (fromSelect.Where != null)
{
if (where != null)
{
where = Expression.And(fromSelect.Where, where);
}
else
{
where = fromSelect.Where;
}
}
var orderBy = select.OrderBy != null && select.OrderBy.Count > 0 ? select.OrderBy : fromSelect.OrderBy;
var groupBy = select.GroupBy != null && select.GroupBy.Count > 0 ? select.GroupBy : fromSelect.GroupBy;
var skip = select.Skip ?? fromSelect.Skip;
var take = select.Take ?? fromSelect.Take;
var isDistinct = select.Distinct || fromSelect.Distinct;
if (where != select.Where || orderBy != select.OrderBy || groupBy != select.GroupBy || isDistinct != select.Distinct || skip != select.Skip || take != select.Take)
{
select = new SqlSelectExpression(select.Type, select.Alias, select.Columns, select.From, where, orderBy, groupBy, isDistinct, skip, take, select.ForUpdate);
}
}
this.isTopLevel = savedIsTopLevel;
return(select);
}
protected override Expression VisitSelect(SqlSelectExpression select)
{
select = (SqlSelectExpression)base.VisitSelect(select);
// Expand all purely redundant subqueries
var redundantQueries = SqlRedundantSubqueryFinder.Find(select.From);
if (redundantQueries != null)
{
select = SubqueryRemover.Remove(select, redundantQueries);
}
return(select);
}
protected override Expression VisitProjection(SqlProjectionExpression projection)
{
projection = (SqlProjectionExpression)base.VisitProjection(projection);
if (projection.Select.From is SqlSelectExpression)
{
var redundantQueries = SqlRedundantSubqueryFinder.Find(projection.Select);
if (redundantQueries != null)
{
projection = SubqueryRemover.Remove(projection, redundantQueries);
}
}
return(projection);
}