Function OrderByNeighborTerms

dialect/sql/sqlgraph/graph.go:522–560

OrderByNeighborTerms appends ordering based on the number of neighbors. For example, order users by their number of posts.

(q *sql.Selector, s *Step, opts ...sql.OrderTerm)

// OrderByNeighborTerms appends ordering based on the number of neighbors.
// For example, order users by their number of posts.
func OrderByNeighborTerms(q *sql.Selector, s *Step, opts ...sql.OrderTerm) {
	var (
		join  *sql.Selector
		build = sql.Dialect(q.Dialect())
	)
	switch {
	case s.FromEdgeOwner():
		toT := build.Table(s.To.Table).Schema(s.To.Schema)
		join = build.Select(toT.C(s.To.Column)).
			From(toT)
		selectTerms(join, opts)
		q.LeftJoin(join).
			On(q.C(s.Edge.Columns[0]), join.C(s.To.Column))
	case s.ThroughEdgeTable():
		pk1, pk2 := s.Edge.Columns[1], s.Edge.Columns[0]
		if s.Edge.Inverse {
			pk1, pk2 = pk2, pk1
		}
		toT := build.Table(s.To.Table).Schema(s.To.Schema)
		joinT := build.Table(s.Edge.Table).Schema(s.Edge.Schema)
		join = build.Select(pk2).
			From(toT).
			Join(joinT).
			On(toT.C(s.To.Column), joinT.C(pk1)).
			GroupBy(pk2)
		selectTerms(join, opts)
		q.LeftJoin(join).
			On(q.C(s.From.Column), join.C(pk2))
	case s.ToEdgeOwner():
		toT := build.Table(s.Edge.Table).Schema(s.Edge.Schema)
		join = build.Select(toT.C(s.Edge.Columns[0])).
			From(toT).
			GroupBy(toT.C(s.Edge.Columns[0]))
		selectTerms(join, opts)
		q.LeftJoin(join).
			On(q.C(s.From.Column), join.C(s.Edge.Columns[0]))
	}
	orderTerms(q, join, opts)
}

// NeighborsLimit provides a modifier function that limits the
// number of neighbors (rows) loaded per parent row (node).