public static HashSet <string> Gather(Expression source)
{
var gatherer = new SqlReferencedAliasGatherer();
gatherer.Visit(source);
return(gatherer.aliases);
}
public static HashSet<string> Gather(Expression source)
{
var gatherer = new SqlReferencedAliasGatherer();
gatherer.Visit(source);
return gatherer.aliases;
}
private static bool CanBeJoinCondition(Expression expression, IEnumerable <string> left, IEnumerable <string> right, IEnumerable <string> all)
{
var referenced = SqlReferencedAliasGatherer.Gather(expression);
var leftOkay = referenced.Intersect(left).Any();
var rightOkay = referenced.Intersect(right).Any();
var subset = referenced.IsSubsetOf(all);
return(leftOkay && rightOkay && subset);
}
protected override Expression VisitJoin(SqlJoinExpression join)
{
join = (SqlJoinExpression)base.VisitJoin(join);
if (join.JoinType == SqlJoinType.CrossApply || join.JoinType == SqlJoinType.OuterApply)
{
if (join.Right is SqlTableExpression)
{
return(new SqlJoinExpression(join.Type, SqlJoinType.Cross, join.Left, join.Right, null));
}
else
{
var select = join.Right as SqlSelectExpression;
if (select != null && select.Take == null && select.Skip == null && !SqlAggregateChecker.HasAggregates(select) && (select.GroupBy == null || select.GroupBy.Count == 0))
{
var selectWithoutWhere = select.ChangeWhere(null);
var referencedAliases = SqlReferencedAliasGatherer.Gather(selectWithoutWhere);
var declaredAliases = SqlDeclaredAliasGatherer.Gather(join.Left);
referencedAliases.IntersectWith(declaredAliases);
if (referencedAliases.Count == 0)
{
var where = select.Where;
select = selectWithoutWhere;
var pc = ColumnProjector.ProjectColumns(new Nominator(Nominator.CanBeColumn), where, select.Columns, select.Alias, SqlDeclaredAliasGatherer.Gather(select.From));
select = select.ChangeColumns(pc.Columns);
where = pc.Projector;
var joinType = (where == null) ? SqlJoinType.Cross : (join.JoinType == SqlJoinType.CrossApply ? SqlJoinType.Inner : SqlJoinType.Left);
return(new SqlJoinExpression(typeof(void), joinType, join.Left, select, where));
}
}
}
}
return(join);
}
