dialect/sql/sqlgraph: first work on nodes querying

dialect/sql/graph.go

@@ -10,6 +10,7 @@ import (
 	"database/sql/driver"
 	"encoding/json"
 	"fmt"
+	"math"
 	"sort"
 
 	"github.com/facebookincubator/ent/dialect"
@@ -426,6 +427,64 @@ func DeleteNodes(ctx context.Context, drv dialect.Driver, spec *DeleteSpec) (int
 	return int(affected), tx.Commit()
 }
 
+// QuerySpec holds the information for querying
+// nodes in the graph.
+type QuerySpec struct {
+	Node *NodeSpec // Nodes info.
+	From *Selector // Optional query source (from path).
+
+	Limit     int
+	Offset    int
+	Unique    bool
+	Order     func(*Selector)
+	Predicate func(*Selector)
+
+	ScanValues func() []interface{}
+	Assign     func(...interface{}) error
+}
+
+// QueryNodes query the nodes in the graph and scan them to the given values.
+func QueryNodes(ctx context.Context, drv dialect.Driver, spec *QuerySpec) error {
+	builder := Dialect(drv.Dialect())
+	selector := builder.Select().From(builder.Table(spec.Node.Table))
+	if spec.From != nil {
+		selector = spec.From
+	}
+	selector.Select(spec.Node.Columns...)
+	if pred := spec.Predicate; pred != nil {
+		pred(selector)
+	}
+	if order := spec.Order; order != nil {
+		order(selector)
+	}
+	if spec.Offset != 0 {
+		// Limit is mandatory for the offset clause. We start
+		// with default value, and override it below if needed.
+		selector.Offset(spec.Offset).Limit(math.MaxInt32)
+	}
+	if spec.Limit != 0 {
+		selector.Limit(spec.Limit)
+	}
+	if spec.Unique {
+		selector.Distinct()
+	}
+	rows := &Rows{}
+	query, args := selector.Query()
+	if err := drv.Query(ctx, query, args, rows); err != nil {
+		return err
+	}
+	for rows.Next() {
+		values := spec.ScanValues()
+		if err := rows.Scan(values...); err != nil {
+			return err
+		}
+		if err := spec.Assign(values...); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 type updater struct {
 	graph
 	*UpdateSpec

dialect/sql/graph_test.go

@@ -741,9 +741,13 @@ func TestCreateNode(t *testing.T) {
 }
 
 type user struct {
-	id   int
-	age  int
-	name string
+	id    int
+	age   int
+	name  string
+	edges struct {
+		fk1 int
+		fk2 int
+	}
 }
 
 func (*user) values() []interface{} {
@@ -754,6 +758,11 @@ func (u *user) assign(values ...interface{}) error {
 	u.id = int(values[0].(*NullInt64).Int64)
 	u.age = int(values[1].(*NullInt64).Int64)
 	u.name = values[2].(*NullString).String
+	// loaded with foreign-keys.
+	if len(values) > 3 {
+		u.edges.fk1 = int(values[3].(*NullInt64).Int64)
+		u.edges.fk2 = int(values[4].(*NullInt64).Int64)
+	}
 	return nil
 }
 
@@ -1141,6 +1150,46 @@ func TestDeleteNodes(t *testing.T) {
 	require.Equal(t, 2, affected)
 }
 
+func TestQueryNodes(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	mock.ExpectQuery(escape("SELECT DISTINCT `id`, `age`, `name`, `fk1`, `fk2` FROM `users` WHERE `age` < ? ORDER BY `id` LIMIT ? OFFSET ?")).
+		WithArgs(40, 3, 4).
+		WillReturnRows(sqlmock.NewRows([]string{"id", "age", "name", "fk1", "fk2"}).
+			AddRow(1, 10, nil, nil, nil).
+			AddRow(2, 20, "", 0, 0).
+			AddRow(3, 30, "a8m", 1, 1))
+	var users []*user
+	err = QueryNodes(context.Background(), OpenDB("", db), &QuerySpec{
+		Node: &NodeSpec{
+			Table:   "users",
+			Columns: []string{"id", "age", "name", "fk1", "fk2"},
+			ID:      &FieldSpec{Column: "id", Type: field.TypeInt},
+		},
+		Limit:  3,
+		Offset: 4,
+		Unique: true,
+		Order: func(s *Selector) {
+			s.OrderBy("id")
+		},
+		Predicate: func(s *Selector) {
+			s.Where(LT("age", 40))
+		},
+		ScanValues: func() []interface{} {
+			u := &user{}
+			users = append(users, u)
+			return append(u.values(), &NullInt64{}, &NullInt64{}) // extra values for fks.
+		},
+		Assign: func(values ...interface{}) error {
+			return users[len(users)-1].assign(values...)
+		},
+	})
+	require.NoError(t, err)
+	require.Equal(t, &user{id: 1, age: 10, name: ""}, users[0])
+	require.Equal(t, &user{id: 2, age: 20, name: ""}, users[1])
+	require.Equal(t, &user{id: 3, age: 30, name: "a8m", edges: struct{ fk1, fk2 int }{1, 1}}, users[2])
+}
+
 func escape(query string) string {
 	rows := strings.Split(query, "\n")
 	for i := range rows {