ent/doc: O2M same type example

Reviewed By: alexsn

Differential Revision: D17050185

fbshipit-source-id: ef12cc82ab9bf155713faf94129fd5fe503664e4

examples/o2mrecur/README.md

@@ -0,0 +1,11 @@
+# Tree O2M Relation
+
+In this example, we have a recursive O2M relation between tree's nodes and their children (or their parent).  
+Each node in the tree **has many** children, and **has one** parent. If node A adds B to its children,
+B can get its owner using the `owner` edge.
+
+### Generate Assets
+
+```console
+go generate ./...
+```

examples/o2mrecur/ent/client.go

@@ -0,0 +1,124 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package ent
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/migrate"
+
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/node"
+
+	"github.com/facebookincubator/ent/dialect/sql"
+)
+
+// Client is the client that holds all ent builders.
+type Client struct {
+	config
+	// Schema is the client for creating, migrating and dropping schema.
+	Schema *migrate.Schema
+	// Node is the client for interacting with the Node builders.
+	Node *NodeClient
+}
+
+// NewClient creates a new client configured with the given options.
+func NewClient(opts ...Option) *Client {
+	c := config{log: log.Println}
+	c.options(opts...)
+	return &Client{
+		config: c,
+		Schema: migrate.NewSchema(c.driver),
+		Node:   NewNodeClient(c),
+	}
+}
+
+// Tx returns a new transactional client.
+func (c *Client) Tx(ctx context.Context) (*Tx, error) {
+	if _, ok := c.driver.(*txDriver); ok {
+		return nil, fmt.Errorf("ent: cannot start a transaction within a transaction")
+	}
+	tx, err := newTx(ctx, c.driver)
+	if err != nil {
+		return nil, fmt.Errorf("ent: starting a transaction: %v", err)
+	}
+	cfg := config{driver: tx, log: c.log, verbose: c.verbose}
+	return &Tx{
+		config: cfg,
+		Node:   NewNodeClient(cfg),
+	}, nil
+}
+
+// NodeClient is a client for the Node schema.
+type NodeClient struct {
+	config
+}
+
+// NewNodeClient returns a client for the Node from the given config.
+func NewNodeClient(c config) *NodeClient {
+	return &NodeClient{config: c}
+}
+
+// Create returns a create builder for Node.
+func (c *NodeClient) Create() *NodeCreate {
+	return &NodeCreate{config: c.config}
+}
+
+// Update returns an update builder for Node.
+func (c *NodeClient) Update() *NodeUpdate {
+	return &NodeUpdate{config: c.config}
+}
+
+// UpdateOne returns an update builder for the given entity.
+func (c *NodeClient) UpdateOne(n *Node) *NodeUpdateOne {
+	return c.UpdateOneID(n.ID)
+}
+
+// UpdateOneID returns an update builder for the given id.
+func (c *NodeClient) UpdateOneID(id int) *NodeUpdateOne {
+	return &NodeUpdateOne{config: c.config, id: id}
+}
+
+// Delete returns a delete builder for Node.
+func (c *NodeClient) Delete() *NodeDelete {
+	return &NodeDelete{config: c.config}
+}
+
+// DeleteOne returns a delete builder for the given entity.
+func (c *NodeClient) DeleteOne(n *Node) *NodeDeleteOne {
+	return c.DeleteOneID(n.ID)
+}
+
+// DeleteOneID returns a delete builder for the given id.
+func (c *NodeClient) DeleteOneID(id int) *NodeDeleteOne {
+	return &NodeDeleteOne{c.Delete().Where(node.ID(id))}
+}
+
+// Create returns a query builder for Node.
+func (c *NodeClient) Query() *NodeQuery {
+	return &NodeQuery{config: c.config}
+}
+
+// QueryParent queries the parent edge of a Node.
+func (c *NodeClient) QueryParent(n *Node) *NodeQuery {
+	query := &NodeQuery{config: c.config}
+	id := n.ID
+	t1 := sql.Table(node.Table)
+	t2 := sql.Select(node.ParentColumn).
+		From(sql.Table(node.ParentTable)).
+		Where(sql.EQ(node.FieldID, id))
+	query.sql = sql.Select().From(t1).Join(t2).On(t1.C(node.FieldID), t2.C(node.ParentColumn))
+
+	return query
+}
+
+// QueryChildren queries the children edge of a Node.
+func (c *NodeClient) QueryChildren(n *Node) *NodeQuery {
+	query := &NodeQuery{config: c.config}
+	id := n.ID
+	query.sql = sql.Select().From(sql.Table(node.Table)).
+		Where(sql.EQ(node.ChildrenColumn, id))
+
+	return query
+}

examples/o2mrecur/ent/config.go

@@ -0,0 +1,51 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package ent
+
+import (
+	"github.com/facebookincubator/ent/dialect"
+)
+
+// Option function to configure the client.
+type Option func(*config)
+
+// Config is the configuration for the client and its builder.
+type config struct {
+	// driver is the driver used for execute database requests.
+	driver dialect.Driver
+	// verbose enable a verbosity logging.
+	verbose bool
+	// log used for logging on verbose mode.
+	log func(...interface{})
+}
+
+// Options applies the options on the config object.
+func (c *config) options(opts ...Option) {
+	for _, opt := range opts {
+		opt(c)
+	}
+	if c.verbose {
+		c.driver = dialect.Debug(c.driver, c.log)
+	}
+}
+
+// Verbose sets the client logging to verbose.
+func Verbose() Option {
+	return func(c *config) {
+		c.verbose = true
+	}
+}
+
+// Log sets the client logging to verbose.
+func Log(fn func(...interface{})) Option {
+	return func(c *config) {
+		c.log = fn
+	}
+}
+
+// Driver configures the client driver.
+func Driver(driver dialect.Driver) Option {
+	return func(c *config) {
+		c.driver = driver
+	}
+}

examples/o2mrecur/ent/context.go

@@ -0,0 +1,20 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package ent
+
+import (
+	"context"
+)
+
+type contextKey struct{}
+
+// FromContext returns the Client stored in a context, or nil if there isn't one.
+func FromContext(ctx context.Context) *Client {
+	c, _ := ctx.Value(contextKey{}).(*Client)
+	return c
+}
+
+// NewContext returns a new context with the given Client attached.
+func NewContext(parent context.Context, c *Client) context.Context {
+	return context.WithValue(parent, contextKey{}, c)
+}

examples/o2mrecur/ent/ent.go

@@ -0,0 +1,192 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package ent
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/facebookincubator/ent/dialect"
+	"github.com/facebookincubator/ent/dialect/sql"
+)
+
+// Order applies an ordering on either graph traversal or sql selector.
+type Order func(*sql.Selector)
+
+// Asc applies the given fields in ASC order.
+func Asc(fields ...string) Order {
+	return Order(
+		func(s *sql.Selector) {
+			for _, f := range fields {
+				s.OrderBy(sql.Asc(f))
+			}
+		},
+	)
+}
+
+// Desc applies the given fields in DESC order.
+func Desc(fields ...string) Order {
+	return Order(
+		func(s *sql.Selector) {
+			for _, f := range fields {
+				s.OrderBy(sql.Desc(f))
+			}
+		},
+	)
+}
+
+// Aggregate applies an aggregation step on the group-by traversal/selector.
+type Aggregate struct {
+	// SQL the column wrapped with the aggregation function.
+	SQL func(*sql.Selector) string
+}
+
+// As is a pseudo aggregation function for renaming another other functions with custom names. For example:
+//
+//	GroupBy(field1, field2).
+//	Aggregate(ent.As(ent.Sum(field1), "sum_field1"), (ent.As(ent.Sum(field2), "sum_field2")).
+//	Scan(ctx, &v)
+//
+func As(fn Aggregate, end string) Aggregate {
+	return Aggregate{
+		SQL: func(s *sql.Selector) string {
+			return sql.As(fn.SQL(s), end)
+		},
+	}
+}
+
+// Count applies the "count" aggregation function on each group.
+func Count() Aggregate {
+	return Aggregate{
+		SQL: func(s *sql.Selector) string {
+			return sql.Count("*")
+		},
+	}
+}
+
+// Max applies the "max" aggregation function on the given field of each group.
+func Max(field string) Aggregate {
+	return Aggregate{
+		SQL: func(s *sql.Selector) string {
+			return sql.Max(s.C(field))
+		},
+	}
+}
+
+// Mean applies the "mean" aggregation function on the given field of each group.
+func Mean(field string) Aggregate {
+	return Aggregate{
+		SQL: func(s *sql.Selector) string {
+			return sql.Avg(s.C(field))
+		},
+	}
+}
+
+// Min applies the "min" aggregation function on the given field of each group.
+func Min(field string) Aggregate {
+	return Aggregate{
+		SQL: func(s *sql.Selector) string {
+			return sql.Min(s.C(field))
+		},
+	}
+}
+
+// Sum applies the "sum" aggregation function on the given field of each group.
+func Sum(field string) Aggregate {
+	return Aggregate{
+		SQL: func(s *sql.Selector) string {
+			return sql.Sum(s.C(field))
+		},
+	}
+}
+
+// ErrNotFound returns when trying to fetch a specific entity and it was not found in the database.
+type ErrNotFound struct {
+	label string
+}
+
+// Error implements the error interface.
+func (e *ErrNotFound) Error() string {
+	return fmt.Sprintf("ent: %s not found", e.label)
+}
+
+// IsNotFound returns a boolean indicating whether the error is a not found error.
+func IsNotFound(err error) bool {
+	_, ok := err.(*ErrNotFound)
+	return ok
+}
+
+// MaskNotFound masks nor found error.
+func MaskNotFound(err error) error {
+	if IsNotFound(err) {
+		return nil
+	}
+	return err
+}
+
+// ErrNotSingular returns when trying to fetch a singular entity and more then one was found in the database.
+type ErrNotSingular struct {
+	label string
+}
+
+// Error implements the error interface.
+func (e *ErrNotSingular) Error() string {
+	return fmt.Sprintf("ent: %s not singular", e.label)
+}
+
+// IsNotSingular returns a boolean indicating whether the error is a not singular error.
+func IsNotSingular(err error) bool {
+	_, ok := err.(*ErrNotSingular)
+	return ok
+}
+
+// ErrConstraintFailed returns when trying to create/update one or more entities and
+// one or more of their constraints failed. For example, violation of edge or field uniqueness.
+type ErrConstraintFailed struct {
+	msg  string
+	wrap error
+}
+
+// Error implements the error interface.
+func (e ErrConstraintFailed) Error() string {
+	return fmt.Sprintf("ent: unique constraint failed: %s", e.msg)
+}
+
+// Unwrap implements the errors.Wrapper interface.
+func (e *ErrConstraintFailed) Unwrap() error {
+	return e.wrap
+}
+
+// IsConstraintFailure returns a boolean indicating whether the error is a constraint failure.
+func IsConstraintFailure(err error) bool {
+	_, ok := err.(*ErrConstraintFailed)
+	return ok
+}
+
+func isSQLConstraintError(err error) (*ErrConstraintFailed, bool) {
+	// Error number 1062 is ER_DUP_ENTRY in mysql, and "UNIQUE constraint failed" is SQLite prefix.
+	if msg := err.Error(); strings.HasPrefix(msg, "Error 1062") || strings.HasPrefix(msg, "UNIQUE constraint failed") {
+		return &ErrConstraintFailed{msg, err}, true
+	}
+	return nil, false
+}
+
+// rollback calls to tx.Rollback and wraps the given error with the rollback error if occurred.
+func rollback(tx dialect.Tx, err error) error {
+	if rerr := tx.Rollback(); rerr != nil {
+		err = fmt.Errorf("%s: %v", err.Error(), rerr)
+	}
+	if err, ok := isSQLConstraintError(err); ok {
+		return err
+	}
+	return err
+}
+
+// keys returns the keys/ids from the edge map.
+func keys(m map[int]struct{}) []int {
+	s := make([]int, 0, len(m))
+	for id, _ := range m {
+		s = append(s, id)
+	}
+	return s
+}

examples/o2mrecur/ent/example_test.go

@@ -0,0 +1,53 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package ent
+
+import (
+	"context"
+	"log"
+
+	"github.com/facebookincubator/ent/dialect/sql"
+)
+
+// dsn for the database. In order to run the tests locally, run the following command:
+//
+//	 ENT_INTEGRATION_ENDPOINT="root:pass@tcp(localhost:3306)/test?parseTime=True" go test -v
+//
+var dsn string
+
+func ExampleNode() {
+	if dsn == "" {
+		return
+	}
+	ctx := context.Background()
+	drv, err := sql.Open("mysql", dsn)
+	if err != nil {
+		log.Fatalf("failed creating database client: %v", err)
+	}
+	defer drv.Close()
+	client := NewClient(Driver(drv))
+	// creating vertices for the node's edges.
+	n1 := client.Node.
+		Create().
+		SetValue(1).
+		SaveX(ctx)
+	log.Println("node created:", n1)
+
+	// create node vertex with its edges.
+	n := client.Node.
+		Create().
+		SetValue(1).
+		AddChildren(n1).
+		SaveX(ctx)
+	log.Println("node created:", n)
+
+	// query edges.
+
+	n1, err = n.QueryChildren().First(ctx)
+	if err != nil {
+		log.Fatalf("failed querying children: %v", err)
+	}
+	log.Println("children found:", n1)
+
+	// Output:
+}

examples/o2mrecur/ent/generate.go

@@ -0,0 +1,3 @@
+package ent
+
+//go:generate go run ../../../entc/cmd/entc/entc.go generate --header "Code generated (@generated) by entc, DO NOT EDIT." ./schema

examples/o2mrecur/ent/migrate/migrate.go

@@ -0,0 +1,48 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package migrate
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/facebookincubator/ent/dialect"
+	"github.com/facebookincubator/ent/dialect/sql/schema"
+)
+
+var (
+	// WithGlobalUniqueID sets the universal ids options to the migration.
+	// If this option is enabled, ent migration will allocate a 1<<32 range
+	// for the ids of each entity (table).
+	// Note that this option cannot be applied on tables that already exist.
+	WithGlobalUniqueID = schema.WithGlobalUniqueID
+	// WithDropColumn sets the drop column option to the migration.
+	// If this option is enabled, ent migration will drop old columns
+	// that were used for both fields and edges. This defaults to false.
+	WithDropColumn = schema.WithDropColumn
+	// WithDropIndex sets the drop index option to the migration.
+	// If this option is enabled, ent migration will drop old indexes
+	// that were defined in the schema. This defaults to false.
+	// Note that unique constraints are defined using `UNIQUE INDEX`,
+	// and therefore, it's recommended to enable this option to get more
+	// flexibility in the schema changes.
+	WithDropIndex = schema.WithDropIndex
+)
+
+// Schema is the API for creating, migrating and dropping a schema.
+type Schema struct {
+	drv         dialect.Driver
+	universalID bool
+}
+
+// NewSchema creates a new schema client.
+func NewSchema(drv dialect.Driver) *Schema { return &Schema{drv: drv} }
+
+// Create creates all schema resources.
+func (s *Schema) Create(ctx context.Context, opts ...schema.MigrateOption) error {
+	migrate, err := schema.NewMigrate(s.drv, opts...)
+	if err != nil {
+		return fmt.Errorf("ent/migrate: %v", err)
+	}
+	return migrate.Create(ctx, Tables...)
+}

examples/o2mrecur/ent/migrate/schema.go

@@ -0,0 +1,40 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package migrate
+
+import (
+	"github.com/facebookincubator/ent/dialect/sql/schema"
+	"github.com/facebookincubator/ent/schema/field"
+)
+
+var (
+	// NodesColumns holds the columns for the "nodes" table.
+	NodesColumns = []*schema.Column{
+		{Name: "id", Type: field.TypeInt, Increment: true},
+		{Name: "value", Type: field.TypeInt},
+		{Name: "parent_id", Type: field.TypeInt, Nullable: true},
+	}
+	// NodesTable holds the schema information for the "nodes" table.
+	NodesTable = &schema.Table{
+		Name:       "nodes",
+		Columns:    NodesColumns,
+		PrimaryKey: []*schema.Column{NodesColumns[0]},
+		ForeignKeys: []*schema.ForeignKey{
+			{
+				Symbol:  "nodes_nodes_children",
+				Columns: []*schema.Column{NodesColumns[2]},
+
+				RefColumns: []*schema.Column{NodesColumns[0]},
+				OnDelete:   schema.SetNull,
+			},
+		},
+	}
+	// Tables holds all the tables in the schema.
+	Tables = []*schema.Table{
+		NodesTable,
+	}
+)
+
+func init() {
+	NodesTable.ForeignKeys[0].RefTable = NodesTable
+}

examples/o2mrecur/ent/node.go

@@ -0,0 +1,96 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package ent
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/facebookincubator/ent/dialect/sql"
+)
+
+// Node is the model entity for the Node schema.
+type Node struct {
+	config
+	// ID of the ent.
+	ID int `json:"id,omitempty"`
+	// Value holds the value of the "value" field.
+	Value int `json:"value,omitempty"`
+}
+
+// FromRows scans the sql response data into Node.
+func (n *Node) FromRows(rows *sql.Rows) error {
+	var vn struct {
+		ID    int
+		Value sql.NullInt64
+	}
+	// the order here should be the same as in the `node.Columns`.
+	if err := rows.Scan(
+		&vn.ID,
+		&vn.Value,
+	); err != nil {
+		return err
+	}
+	n.ID = vn.ID
+	n.Value = int(vn.Value.Int64)
+	return nil
+}
+
+// QueryParent queries the parent edge of the Node.
+func (n *Node) QueryParent() *NodeQuery {
+	return (&NodeClient{n.config}).QueryParent(n)
+}
+
+// QueryChildren queries the children edge of the Node.
+func (n *Node) QueryChildren() *NodeQuery {
+	return (&NodeClient{n.config}).QueryChildren(n)
+}
+
+// Update returns a builder for updating this Node.
+// Note that, you need to call Node.Unwrap() before calling this method, if this Node
+// was returned from a transaction, and the transaction was committed or rolled back.
+func (n *Node) Update() *NodeUpdateOne {
+	return (&NodeClient{n.config}).UpdateOne(n)
+}
+
+// Unwrap unwraps the entity that was returned from a transaction after it was closed,
+// so that all next queries will be executed through the driver which created the transaction.
+func (n *Node) Unwrap() *Node {
+	tx, ok := n.config.driver.(*txDriver)
+	if !ok {
+		panic("ent: Node is not a transactional entity")
+	}
+	n.config.driver = tx.drv
+	return n
+}
+
+// String implements the fmt.Stringer.
+func (n *Node) String() string {
+	buf := bytes.NewBuffer(nil)
+	buf.WriteString("Node(")
+	buf.WriteString(fmt.Sprintf("id=%v", n.ID))
+	buf.WriteString(fmt.Sprintf(", value=%v", n.Value))
+	buf.WriteString(")")
+	return buf.String()
+}
+
+// Nodes is a parsable slice of Node.
+type Nodes []*Node
+
+// FromRows scans the sql response data into Nodes.
+func (n *Nodes) FromRows(rows *sql.Rows) error {
+	for rows.Next() {
+		vn := &Node{}
+		if err := vn.FromRows(rows); err != nil {
+			return err
+		}
+		*n = append(*n, vn)
+	}
+	return nil
+}
+
+func (n Nodes) config(cfg config) {
+	for i := range n {
+		n[i].config = cfg
+	}
+}

examples/o2mrecur/ent/node/node.go

@@ -0,0 +1,29 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package node
+
+const (
+	// Label holds the string label denoting the node type in the database.
+	Label = "node"
+	// FieldID holds the string denoting the id field in the database.
+	FieldID = "id"
+	// FieldValue holds the string denoting the value vertex property in the database.
+	FieldValue = "value"
+
+	// Table holds the table name of the node in the database.
+	Table = "nodes"
+	// ParentTable is the table the holds the parent relation/edge.
+	ParentTable = "nodes"
+	// ParentColumn is the table column denoting the parent relation/edge.
+	ParentColumn = "parent_id"
+	// ChildrenTable is the table the holds the children relation/edge.
+	ChildrenTable = "nodes"
+	// ChildrenColumn is the table column denoting the children relation/edge.
+	ChildrenColumn = "parent_id"
+)
+
+// Columns holds all SQL columns are node fields.
+var Columns = []string{
+	FieldID,
+	FieldValue,
+}

examples/o2mrecur/ent/node/where.go

@@ -0,0 +1,300 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package node
+
+import (
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/predicate"
+
+	"github.com/facebookincubator/ent/dialect/sql"
+)
+
+// ID filters vertices based on their identifier.
+func ID(id int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.EQ(s.C(FieldID), id))
+		},
+	)
+}
+
+// IDEQ applies the EQ predicate on the ID field.
+func IDEQ(id int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.EQ(s.C(FieldID), id))
+		},
+	)
+}
+
+// IDNEQ applies the NEQ predicate on the ID field.
+func IDNEQ(id int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.NEQ(s.C(FieldID), id))
+		},
+	)
+}
+
+// IDGT applies the GT predicate on the ID field.
+func IDGT(id int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.GT(s.C(FieldID), id))
+		},
+	)
+}
+
+// IDGTE applies the GTE predicate on the ID field.
+func IDGTE(id int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.GTE(s.C(FieldID), id))
+		},
+	)
+}
+
+// IDLT applies the LT predicate on the ID field.
+func IDLT(id int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.LT(s.C(FieldID), id))
+		},
+	)
+}
+
+// IDLTE applies the LTE predicate on the ID field.
+func IDLTE(id int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.LTE(s.C(FieldID), id))
+		},
+	)
+}
+
+// IDIn applies the In predicate on the ID field.
+func IDIn(ids ...int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			// if not arguments were provided, append the FALSE constants,
+			// since we can't apply "IN ()". This will make this predicate falsy.
+			if len(ids) == 0 {
+				s.Where(sql.False())
+				return
+			}
+			v := make([]interface{}, len(ids))
+			for i := range v {
+				v[i] = ids[i]
+			}
+			s.Where(sql.In(s.C(FieldID), v...))
+		},
+	)
+}
+
+// IDNotIn applies the NotIn predicate on the ID field.
+func IDNotIn(ids ...int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			// if not arguments were provided, append the FALSE constants,
+			// since we can't apply "IN ()". This will make this predicate falsy.
+			if len(ids) == 0 {
+				s.Where(sql.False())
+				return
+			}
+			v := make([]interface{}, len(ids))
+			for i := range v {
+				v[i] = ids[i]
+			}
+			s.Where(sql.NotIn(s.C(FieldID), v...))
+		},
+	)
+}
+
+// Value applies equality check predicate on the "value" field. It's identical to ValueEQ.
+func Value(v int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.EQ(s.C(FieldValue), v))
+		},
+	)
+}
+
+// ValueEQ applies the EQ predicate on the "value" field.
+func ValueEQ(v int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.EQ(s.C(FieldValue), v))
+		},
+	)
+}
+
+// ValueNEQ applies the NEQ predicate on the "value" field.
+func ValueNEQ(v int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.NEQ(s.C(FieldValue), v))
+		},
+	)
+}
+
+// ValueGT applies the GT predicate on the "value" field.
+func ValueGT(v int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.GT(s.C(FieldValue), v))
+		},
+	)
+}
+
+// ValueGTE applies the GTE predicate on the "value" field.
+func ValueGTE(v int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.GTE(s.C(FieldValue), v))
+		},
+	)
+}
+
+// ValueLT applies the LT predicate on the "value" field.
+func ValueLT(v int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.LT(s.C(FieldValue), v))
+		},
+	)
+}
+
+// ValueLTE applies the LTE predicate on the "value" field.
+func ValueLTE(v int) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			s.Where(sql.LTE(s.C(FieldValue), v))
+		},
+	)
+}
+
+// ValueIn applies the In predicate on the "value" field.
+func ValueIn(vs ...int) predicate.Node {
+	v := make([]interface{}, len(vs))
+	for i := range v {
+		v[i] = vs[i]
+	}
+	return predicate.Node(
+		func(s *sql.Selector) {
+			// if not arguments were provided, append the FALSE constants,
+			// since we can't apply "IN ()". This will make this predicate falsy.
+			if len(vs) == 0 {
+				s.Where(sql.False())
+				return
+			}
+			s.Where(sql.In(s.C(FieldValue), v...))
+		},
+	)
+}
+
+// ValueNotIn applies the NotIn predicate on the "value" field.
+func ValueNotIn(vs ...int) predicate.Node {
+	v := make([]interface{}, len(vs))
+	for i := range v {
+		v[i] = vs[i]
+	}
+	return predicate.Node(
+		func(s *sql.Selector) {
+			// if not arguments were provided, append the FALSE constants,
+			// since we can't apply "IN ()". This will make this predicate falsy.
+			if len(vs) == 0 {
+				s.Where(sql.False())
+				return
+			}
+			s.Where(sql.NotIn(s.C(FieldValue), v...))
+		},
+	)
+}
+
+// HasParent applies the HasEdge predicate on the "parent" edge.
+func HasParent() predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			t1 := s.Table()
+			s.Where(sql.NotNull(t1.C(ParentColumn)))
+		},
+	)
+}
+
+// HasParentWith applies the HasEdge predicate on the "parent" edge with a given conditions (other predicates).
+func HasParentWith(preds ...predicate.Node) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			t1 := s.Table()
+			t2 := sql.Select(FieldID).From(sql.Table(ParentTable))
+			for _, p := range preds {
+				p(t2)
+			}
+			s.Where(sql.In(t1.C(ParentColumn), t2))
+		},
+	)
+}
+
+// HasChildren applies the HasEdge predicate on the "children" edge.
+func HasChildren() predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			t1 := s.Table()
+			s.Where(
+				sql.In(
+					t1.C(FieldID),
+					sql.Select(ChildrenColumn).
+						From(sql.Table(ChildrenTable)).
+						Where(sql.NotNull(ChildrenColumn)),
+				),
+			)
+		},
+	)
+}
+
+// HasChildrenWith applies the HasEdge predicate on the "children" edge with a given conditions (other predicates).
+func HasChildrenWith(preds ...predicate.Node) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			t1 := s.Table()
+			t2 := sql.Select(ChildrenColumn).From(sql.Table(ChildrenTable))
+			for _, p := range preds {
+				p(t2)
+			}
+			s.Where(sql.In(t1.C(FieldID), t2))
+		},
+	)
+}
+
+// And groups list of predicates with the AND operator between them.
+func And(predicates ...predicate.Node) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			for _, p := range predicates {
+				p(s)
+			}
+		},
+	)
+}
+
+// Or groups list of predicates with the OR operator between them.
+func Or(predicates ...predicate.Node) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			for i, p := range predicates {
+				if i > 0 {
+					s.Or()
+				}
+				p(s)
+			}
+		},
+	)
+}
+
+// Not applies the not operator on the given predicate.
+func Not(p predicate.Node) predicate.Node {
+	return predicate.Node(
+		func(s *sql.Selector) {
+			p(s.Not())
+		},
+	)
+}

examples/o2mrecur/ent/node_create.go

@@ -0,0 +1,149 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package ent
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/node"
+
+	"github.com/facebookincubator/ent/dialect/sql"
+)
+
+// NodeCreate is the builder for creating a Node entity.
+type NodeCreate struct {
+	config
+	value    *int
+	parent   map[int]struct{}
+	children map[int]struct{}
+}
+
+// SetValue sets the value field.
+func (nc *NodeCreate) SetValue(i int) *NodeCreate {
+	nc.value = &i
+	return nc
+}
+
+// SetParentID sets the parent edge to Node by id.
+func (nc *NodeCreate) SetParentID(id int) *NodeCreate {
+	if nc.parent == nil {
+		nc.parent = make(map[int]struct{})
+	}
+	nc.parent[id] = struct{}{}
+	return nc
+}
+
+// SetNillableParentID sets the parent edge to Node by id if the given value is not nil.
+func (nc *NodeCreate) SetNillableParentID(id *int) *NodeCreate {
+	if id != nil {
+		nc = nc.SetParentID(*id)
+	}
+	return nc
+}
+
+// SetParent sets the parent edge to Node.
+func (nc *NodeCreate) SetParent(n *Node) *NodeCreate {
+	return nc.SetParentID(n.ID)
+}
+
+// AddChildIDs adds the children edge to Node by ids.
+func (nc *NodeCreate) AddChildIDs(ids ...int) *NodeCreate {
+	if nc.children == nil {
+		nc.children = make(map[int]struct{})
+	}
+	for i := range ids {
+		nc.children[ids[i]] = struct{}{}
+	}
+	return nc
+}
+
+// AddChildren adds the children edges to Node.
+func (nc *NodeCreate) AddChildren(n ...*Node) *NodeCreate {
+	ids := make([]int, len(n))
+	for i := range n {
+		ids[i] = n[i].ID
+	}
+	return nc.AddChildIDs(ids...)
+}
+
+// Save creates the Node in the database.
+func (nc *NodeCreate) Save(ctx context.Context) (*Node, error) {
+	if nc.value == nil {
+		return nil, errors.New("ent: missing required field \"value\"")
+	}
+	if len(nc.parent) > 1 {
+		return nil, errors.New("ent: multiple assignments on a unique edge \"parent\"")
+	}
+	return nc.sqlSave(ctx)
+}
+
+// SaveX calls Save and panics if Save returns an error.
+func (nc *NodeCreate) SaveX(ctx context.Context) *Node {
+	v, err := nc.Save(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
+func (nc *NodeCreate) sqlSave(ctx context.Context) (*Node, error) {
+	var (
+		res sql.Result
+		n   = &Node{config: nc.config}
+	)
+	tx, err := nc.driver.Tx(ctx)
+	if err != nil {
+		return nil, err
+	}
+	builder := sql.Insert(node.Table).Default(nc.driver.Dialect())
+	if nc.value != nil {
+		builder.Set(node.FieldValue, *nc.value)
+		n.Value = *nc.value
+	}
+	query, args := builder.Query()
+	if err := tx.Exec(ctx, query, args, &res); err != nil {
+		return nil, rollback(tx, err)
+	}
+	id, err := res.LastInsertId()
+	if err != nil {
+		return nil, rollback(tx, err)
+	}
+	n.ID = int(id)
+	if len(nc.parent) > 0 {
+		for eid := range nc.parent {
+			query, args := sql.Update(node.ParentTable).
+				Set(node.ParentColumn, eid).
+				Where(sql.EQ(node.FieldID, id)).
+				Query()
+			if err := tx.Exec(ctx, query, args, &res); err != nil {
+				return nil, rollback(tx, err)
+			}
+		}
+	}
+	if len(nc.children) > 0 {
+		p := sql.P()
+		for eid := range nc.children {
+			p.Or().EQ(node.FieldID, eid)
+		}
+		query, args := sql.Update(node.ChildrenTable).
+			Set(node.ChildrenColumn, id).
+			Where(sql.And(p, sql.IsNull(node.ChildrenColumn))).
+			Query()
+		if err := tx.Exec(ctx, query, args, &res); err != nil {
+			return nil, rollback(tx, err)
+		}
+		affected, err := res.RowsAffected()
+		if err != nil {
+			return nil, rollback(tx, err)
+		}
+		if int(affected) < len(nc.children) {
+			return nil, rollback(tx, &ErrConstraintFailed{msg: fmt.Sprintf("one of \"children\" %v already connected to a different \"Node\"", keys(nc.children))})
+		}
+	}
+	if err := tx.Commit(); err != nil {
+		return nil, err
+	}
+	return n, nil
+}

examples/o2mrecur/ent/node_delete.go

@@ -0,0 +1,61 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package ent
+
+import (
+	"context"
+
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/node"
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/predicate"
+
+	"github.com/facebookincubator/ent/dialect/sql"
+)
+
+// NodeDelete is the builder for deleting a Node entity.
+type NodeDelete struct {
+	config
+	predicates []predicate.Node
+}
+
+// Where adds a new predicate for the builder.
+func (nd *NodeDelete) Where(ps ...predicate.Node) *NodeDelete {
+	nd.predicates = append(nd.predicates, ps...)
+	return nd
+}
+
+// Exec executes the deletion query.
+func (nd *NodeDelete) Exec(ctx context.Context) error {
+	return nd.sqlExec(ctx)
+}
+
+// ExecX is like Exec, but panics if an error occurs.
+func (nd *NodeDelete) ExecX(ctx context.Context) {
+	if err := nd.Exec(ctx); err != nil {
+		panic(err)
+	}
+}
+
+func (nd *NodeDelete) sqlExec(ctx context.Context) error {
+	var res sql.Result
+	selector := sql.Select().From(sql.Table(node.Table))
+	for _, p := range nd.predicates {
+		p(selector)
+	}
+	query, args := sql.Delete(node.Table).FromSelect(selector).Query()
+	return nd.driver.Exec(ctx, query, args, &res)
+}
+
+// NodeDeleteOne is the builder for deleting a single Node entity.
+type NodeDeleteOne struct {
+	nd *NodeDelete
+}
+
+// Exec executes the deletion query.
+func (ndo *NodeDeleteOne) Exec(ctx context.Context) error {
+	return ndo.nd.Exec(ctx)
+}
+
+// ExecX is like Exec, but panics if an error occurs.
+func (ndo *NodeDeleteOne) ExecX(ctx context.Context) {
+	ndo.nd.ExecX(ctx)
+}

examples/o2mrecur/ent/node_query.go

@@ -0,0 +1,495 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package ent
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"math"
+
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/node"
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/predicate"
+
+	"github.com/facebookincubator/ent/dialect/sql"
+)
+
+// NodeQuery is the builder for querying Node entities.
+type NodeQuery struct {
+	config
+	limit      *int
+	offset     *int
+	order      []Order
+	unique     []string
+	predicates []predicate.Node
+	// intermediate queries.
+	sql *sql.Selector
+}
+
+// Where adds a new predicate for the builder.
+func (nq *NodeQuery) Where(ps ...predicate.Node) *NodeQuery {
+	nq.predicates = append(nq.predicates, ps...)
+	return nq
+}
+
+// Limit adds a limit step to the query.
+func (nq *NodeQuery) Limit(limit int) *NodeQuery {
+	nq.limit = &limit
+	return nq
+}
+
+// Offset adds an offset step to the query.
+func (nq *NodeQuery) Offset(offset int) *NodeQuery {
+	nq.offset = &offset
+	return nq
+}
+
+// Order adds an order step to the query.
+func (nq *NodeQuery) Order(o ...Order) *NodeQuery {
+	nq.order = append(nq.order, o...)
+	return nq
+}
+
+// QueryParent chains the current query on the parent edge.
+func (nq *NodeQuery) QueryParent() *NodeQuery {
+	query := &NodeQuery{config: nq.config}
+	t1 := sql.Table(node.Table)
+	t2 := nq.sqlQuery()
+	t2.Select(t2.C(node.ParentColumn))
+	query.sql = sql.Select(t1.Columns(node.Columns...)...).
+		From(t1).
+		Join(t2).
+		On(t1.C(node.FieldID), t2.C(node.ParentColumn))
+	return query
+}
+
+// QueryChildren chains the current query on the children edge.
+func (nq *NodeQuery) QueryChildren() *NodeQuery {
+	query := &NodeQuery{config: nq.config}
+	t1 := sql.Table(node.Table)
+	t2 := nq.sqlQuery()
+	t2.Select(t2.C(node.FieldID))
+	query.sql = sql.Select().
+		From(t1).
+		Join(t2).
+		On(t1.C(node.ChildrenColumn), t2.C(node.FieldID))
+	return query
+}
+
+// Get returns a Node entity by its id.
+func (nq *NodeQuery) Get(ctx context.Context, id int) (*Node, error) {
+	return nq.Where(node.ID(id)).Only(ctx)
+}
+
+// GetX is like Get, but panics if an error occurs.
+func (nq *NodeQuery) GetX(ctx context.Context, id int) *Node {
+	n, err := nq.Get(ctx, id)
+	if err != nil {
+		panic(err)
+	}
+	return n
+}
+
+// First returns the first Node entity in the query. Returns *ErrNotFound when no node was found.
+func (nq *NodeQuery) First(ctx context.Context) (*Node, error) {
+	ns, err := nq.Limit(1).All(ctx)
+	if err != nil {
+		return nil, err
+	}
+	if len(ns) == 0 {
+		return nil, &ErrNotFound{node.Label}
+	}
+	return ns[0], nil
+}
+
+// FirstX is like First, but panics if an error occurs.
+func (nq *NodeQuery) FirstX(ctx context.Context) *Node {
+	n, err := nq.First(ctx)
+	if err != nil && !IsNotFound(err) {
+		panic(err)
+	}
+	return n
+}
+
+// FirstID returns the first Node id in the query. Returns *ErrNotFound when no id was found.
+func (nq *NodeQuery) FirstID(ctx context.Context) (id int, err error) {
+	var ids []int
+	if ids, err = nq.Limit(1).IDs(ctx); err != nil {
+		return
+	}
+	if len(ids) == 0 {
+		err = &ErrNotFound{node.Label}
+		return
+	}
+	return ids[0], nil
+}
+
+// FirstXID is like FirstID, but panics if an error occurs.
+func (nq *NodeQuery) FirstXID(ctx context.Context) int {
+	id, err := nq.FirstID(ctx)
+	if err != nil && !IsNotFound(err) {
+		panic(err)
+	}
+	return id
+}
+
+// Only returns the only Node entity in the query, returns an error if not exactly one entity was returned.
+func (nq *NodeQuery) Only(ctx context.Context) (*Node, error) {
+	ns, err := nq.Limit(2).All(ctx)
+	if err != nil {
+		return nil, err
+	}
+	switch len(ns) {
+	case 1:
+		return ns[0], nil
+	case 0:
+		return nil, &ErrNotFound{node.Label}
+	default:
+		return nil, &ErrNotSingular{node.Label}
+	}
+}
+
+// OnlyX is like Only, but panics if an error occurs.
+func (nq *NodeQuery) OnlyX(ctx context.Context) *Node {
+	n, err := nq.Only(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return n
+}
+
+// OnlyID returns the only Node id in the query, returns an error if not exactly one id was returned.
+func (nq *NodeQuery) OnlyID(ctx context.Context) (id int, err error) {
+	var ids []int
+	if ids, err = nq.Limit(2).IDs(ctx); err != nil {
+		return
+	}
+	switch len(ids) {
+	case 1:
+		id = ids[0]
+	case 0:
+		err = &ErrNotFound{node.Label}
+	default:
+		err = &ErrNotSingular{node.Label}
+	}
+	return
+}
+
+// OnlyXID is like OnlyID, but panics if an error occurs.
+func (nq *NodeQuery) OnlyXID(ctx context.Context) int {
+	id, err := nq.OnlyID(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return id
+}
+
+// All executes the query and returns a list of Nodes.
+func (nq *NodeQuery) All(ctx context.Context) ([]*Node, error) {
+	return nq.sqlAll(ctx)
+}
+
+// AllX is like All, but panics if an error occurs.
+func (nq *NodeQuery) AllX(ctx context.Context) []*Node {
+	ns, err := nq.All(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return ns
+}
+
+// IDs executes the query and returns a list of Node ids.
+func (nq *NodeQuery) IDs(ctx context.Context) ([]int, error) {
+	return nq.sqlIDs(ctx)
+}
+
+// IDsX is like IDs, but panics if an error occurs.
+func (nq *NodeQuery) IDsX(ctx context.Context) []int {
+	ids, err := nq.IDs(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return ids
+}
+
+// Count returns the count of the given query.
+func (nq *NodeQuery) Count(ctx context.Context) (int, error) {
+	return nq.sqlCount(ctx)
+}
+
+// CountX is like Count, but panics if an error occurs.
+func (nq *NodeQuery) CountX(ctx context.Context) int {
+	count, err := nq.Count(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return count
+}
+
+// Exist returns true if the query has elements in the graph.
+func (nq *NodeQuery) Exist(ctx context.Context) (bool, error) {
+	return nq.sqlExist(ctx)
+}
+
+// ExistX is like Exist, but panics if an error occurs.
+func (nq *NodeQuery) ExistX(ctx context.Context) bool {
+	exist, err := nq.Exist(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return exist
+}
+
+// Clone returns a duplicate of the query builder, including all associated steps. It can be
+// used to prepare common query builders and use them differently after the clone is made.
+func (nq *NodeQuery) Clone() *NodeQuery {
+	return &NodeQuery{
+		config:     nq.config,
+		limit:      nq.limit,
+		offset:     nq.offset,
+		order:      append([]Order{}, nq.order...),
+		unique:     append([]string{}, nq.unique...),
+		predicates: append([]predicate.Node{}, nq.predicates...),
+		// clone intermediate queries.
+		sql: nq.sql.Clone(),
+	}
+}
+
+// GroupBy used to group vertices by one or more fields/columns.
+// It is often used with aggregate functions, like: count, max, mean, min, sum.
+//
+// Example:
+//
+//	var v []struct {
+//		Value int `json:"value,omitempty"`
+//		Count int `json:"count,omitempty"`
+//	}
+//
+//	client.Node.Query().
+//		GroupBy(node.FieldValue).
+//		Aggregate(ent.Count()).
+//		Scan(ctx, &v)
+//
+func (nq *NodeQuery) GroupBy(field string, fields ...string) *NodeGroupBy {
+	group := &NodeGroupBy{config: nq.config}
+	group.fields = append([]string{field}, fields...)
+	group.sql = nq.sqlQuery()
+	return group
+}
+
+func (nq *NodeQuery) sqlAll(ctx context.Context) ([]*Node, error) {
+	rows := &sql.Rows{}
+	selector := nq.sqlQuery()
+	if unique := nq.unique; len(unique) == 0 {
+		selector.Distinct()
+	}
+	query, args := selector.Query()
+	if err := nq.driver.Query(ctx, query, args, rows); err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var ns Nodes
+	if err := ns.FromRows(rows); err != nil {
+		return nil, err
+	}
+	ns.config(nq.config)
+	return ns, nil
+}
+
+func (nq *NodeQuery) sqlCount(ctx context.Context) (int, error) {
+	rows := &sql.Rows{}
+	selector := nq.sqlQuery()
+	unique := []string{node.FieldID}
+	if len(nq.unique) > 0 {
+		unique = nq.unique
+	}
+	selector.Count(sql.Distinct(selector.Columns(unique...)...))
+	query, args := selector.Query()
+	if err := nq.driver.Query(ctx, query, args, rows); err != nil {
+		return 0, err
+	}
+	defer rows.Close()
+	if !rows.Next() {
+		return 0, errors.New("ent: no rows found")
+	}
+	var n int
+	if err := rows.Scan(&n); err != nil {
+		return 0, fmt.Errorf("ent: failed reading count: %v", err)
+	}
+	return n, nil
+}
+
+func (nq *NodeQuery) sqlExist(ctx context.Context) (bool, error) {
+	n, err := nq.sqlCount(ctx)
+	if err != nil {
+		return false, fmt.Errorf("ent: check existence: %v", err)
+	}
+	return n > 0, nil
+}
+
+func (nq *NodeQuery) sqlIDs(ctx context.Context) ([]int, error) {
+	vs, err := nq.sqlAll(ctx)
+	if err != nil {
+		return nil, err
+	}
+	var ids []int
+	for _, v := range vs {
+		ids = append(ids, v.ID)
+	}
+	return ids, nil
+}
+
+func (nq *NodeQuery) sqlQuery() *sql.Selector {
+	t1 := sql.Table(node.Table)
+	selector := sql.Select(t1.Columns(node.Columns...)...).From(t1)
+	if nq.sql != nil {
+		selector = nq.sql
+		selector.Select(selector.Columns(node.Columns...)...)
+	}
+	for _, p := range nq.predicates {
+		p(selector)
+	}
+	for _, p := range nq.order {
+		p(selector)
+	}
+	if offset := nq.offset; offset != nil {
+		// limit is mandatory for offset clause. We start
+		// with default value, and override it below if needed.
+		selector.Offset(*offset).Limit(math.MaxInt64)
+	}
+	if limit := nq.limit; limit != nil {
+		selector.Limit(*limit)
+	}
+	return selector
+}
+
+// NodeQuery is the builder for group-by Node entities.
+type NodeGroupBy struct {
+	config
+	fields []string
+	fns    []Aggregate
+	// intermediate queries.
+	sql *sql.Selector
+}
+
+// Aggregate adds the given aggregation functions to the group-by query.
+func (ngb *NodeGroupBy) Aggregate(fns ...Aggregate) *NodeGroupBy {
+	ngb.fns = append(ngb.fns, fns...)
+	return ngb
+}
+
+// Scan applies the group-by query and scan the result into the given value.
+func (ngb *NodeGroupBy) Scan(ctx context.Context, v interface{}) error {
+	return ngb.sqlScan(ctx, v)
+}
+
+// ScanX is like Scan, but panics if an error occurs.
+func (ngb *NodeGroupBy) ScanX(ctx context.Context, v interface{}) {
+	if err := ngb.Scan(ctx, v); err != nil {
+		panic(err)
+	}
+}
+
+// Strings returns list of strings from group-by. It is only allowed when querying group-by with one field.
+func (ngb *NodeGroupBy) Strings(ctx context.Context) ([]string, error) {
+	if len(ngb.fields) > 1 {
+		return nil, errors.New("ent: NodeGroupBy.Strings is not achievable when grouping more than 1 field")
+	}
+	var v []string
+	if err := ngb.Scan(ctx, &v); err != nil {
+		return nil, err
+	}
+	return v, nil
+}
+
+// StringsX is like Strings, but panics if an error occurs.
+func (ngb *NodeGroupBy) StringsX(ctx context.Context) []string {
+	v, err := ngb.Strings(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
+// Ints returns list of ints from group-by. It is only allowed when querying group-by with one field.
+func (ngb *NodeGroupBy) Ints(ctx context.Context) ([]int, error) {
+	if len(ngb.fields) > 1 {
+		return nil, errors.New("ent: NodeGroupBy.Ints is not achievable when grouping more than 1 field")
+	}
+	var v []int
+	if err := ngb.Scan(ctx, &v); err != nil {
+		return nil, err
+	}
+	return v, nil
+}
+
+// IntsX is like Ints, but panics if an error occurs.
+func (ngb *NodeGroupBy) IntsX(ctx context.Context) []int {
+	v, err := ngb.Ints(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
+// Float64s returns list of float64s from group-by. It is only allowed when querying group-by with one field.
+func (ngb *NodeGroupBy) Float64s(ctx context.Context) ([]float64, error) {
+	if len(ngb.fields) > 1 {
+		return nil, errors.New("ent: NodeGroupBy.Float64s is not achievable when grouping more than 1 field")
+	}
+	var v []float64
+	if err := ngb.Scan(ctx, &v); err != nil {
+		return nil, err
+	}
+	return v, nil
+}
+
+// Float64sX is like Float64s, but panics if an error occurs.
+func (ngb *NodeGroupBy) Float64sX(ctx context.Context) []float64 {
+	v, err := ngb.Float64s(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
+// Bools returns list of bools from group-by. It is only allowed when querying group-by with one field.
+func (ngb *NodeGroupBy) Bools(ctx context.Context) ([]bool, error) {
+	if len(ngb.fields) > 1 {
+		return nil, errors.New("ent: NodeGroupBy.Bools is not achievable when grouping more than 1 field")
+	}
+	var v []bool
+	if err := ngb.Scan(ctx, &v); err != nil {
+		return nil, err
+	}
+	return v, nil
+}
+
+// BoolsX is like Bools, but panics if an error occurs.
+func (ngb *NodeGroupBy) BoolsX(ctx context.Context) []bool {
+	v, err := ngb.Bools(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
+func (ngb *NodeGroupBy) sqlScan(ctx context.Context, v interface{}) error {
+	rows := &sql.Rows{}
+	query, args := ngb.sqlQuery().Query()
+	if err := ngb.driver.Query(ctx, query, args, rows); err != nil {
+		return err
+	}
+	defer rows.Close()
+	return sql.ScanSlice(rows, v)
+}
+
+func (ngb *NodeGroupBy) sqlQuery() *sql.Selector {
+	selector := ngb.sql
+	columns := make([]string, 0, len(ngb.fields)+len(ngb.fns))
+	columns = append(columns, ngb.fields...)
+	for _, fn := range ngb.fns {
+		columns = append(columns, fn.SQL(selector))
+	}
+	return selector.Select(columns...).GroupBy(ngb.fields...)
+}

examples/o2mrecur/ent/node_update.go

@@ -0,0 +1,462 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package ent
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/node"
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/predicate"
+
+	"github.com/facebookincubator/ent/dialect/sql"
+)
+
+// NodeUpdate is the builder for updating Node entities.
+type NodeUpdate struct {
+	config
+	value           *int
+	parent          map[int]struct{}
+	children        map[int]struct{}
+	clearedParent   bool
+	removedChildren map[int]struct{}
+	predicates      []predicate.Node
+}
+
+// Where adds a new predicate for the builder.
+func (nu *NodeUpdate) Where(ps ...predicate.Node) *NodeUpdate {
+	nu.predicates = append(nu.predicates, ps...)
+	return nu
+}
+
+// SetValue sets the value field.
+func (nu *NodeUpdate) SetValue(i int) *NodeUpdate {
+	nu.value = &i
+	return nu
+}
+
+// SetParentID sets the parent edge to Node by id.
+func (nu *NodeUpdate) SetParentID(id int) *NodeUpdate {
+	if nu.parent == nil {
+		nu.parent = make(map[int]struct{})
+	}
+	nu.parent[id] = struct{}{}
+	return nu
+}
+
+// SetNillableParentID sets the parent edge to Node by id if the given value is not nil.
+func (nu *NodeUpdate) SetNillableParentID(id *int) *NodeUpdate {
+	if id != nil {
+		nu = nu.SetParentID(*id)
+	}
+	return nu
+}
+
+// SetParent sets the parent edge to Node.
+func (nu *NodeUpdate) SetParent(n *Node) *NodeUpdate {
+	return nu.SetParentID(n.ID)
+}
+
+// AddChildIDs adds the children edge to Node by ids.
+func (nu *NodeUpdate) AddChildIDs(ids ...int) *NodeUpdate {
+	if nu.children == nil {
+		nu.children = make(map[int]struct{})
+	}
+	for i := range ids {
+		nu.children[ids[i]] = struct{}{}
+	}
+	return nu
+}
+
+// AddChildren adds the children edges to Node.
+func (nu *NodeUpdate) AddChildren(n ...*Node) *NodeUpdate {
+	ids := make([]int, len(n))
+	for i := range n {
+		ids[i] = n[i].ID
+	}
+	return nu.AddChildIDs(ids...)
+}
+
+// ClearParent clears the parent edge to Node.
+func (nu *NodeUpdate) ClearParent() *NodeUpdate {
+	nu.clearedParent = true
+	return nu
+}
+
+// RemoveChildIDs removes the children edge to Node by ids.
+func (nu *NodeUpdate) RemoveChildIDs(ids ...int) *NodeUpdate {
+	if nu.removedChildren == nil {
+		nu.removedChildren = make(map[int]struct{})
+	}
+	for i := range ids {
+		nu.removedChildren[ids[i]] = struct{}{}
+	}
+	return nu
+}
+
+// RemoveChildren removes children edges to Node.
+func (nu *NodeUpdate) RemoveChildren(n ...*Node) *NodeUpdate {
+	ids := make([]int, len(n))
+	for i := range n {
+		ids[i] = n[i].ID
+	}
+	return nu.RemoveChildIDs(ids...)
+}
+
+// Save executes the query and returns the number of rows/vertices matched by this operation.
+func (nu *NodeUpdate) Save(ctx context.Context) (int, error) {
+	if len(nu.parent) > 1 {
+		return 0, errors.New("ent: multiple assignments on a unique edge \"parent\"")
+	}
+	return nu.sqlSave(ctx)
+}
+
+// SaveX is like Save, but panics if an error occurs.
+func (nu *NodeUpdate) SaveX(ctx context.Context) int {
+	affected, err := nu.Save(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return affected
+}
+
+// Exec executes the query.
+func (nu *NodeUpdate) Exec(ctx context.Context) error {
+	_, err := nu.Save(ctx)
+	return err
+}
+
+// ExecX is like Exec, but panics if an error occurs.
+func (nu *NodeUpdate) ExecX(ctx context.Context) {
+	if err := nu.Exec(ctx); err != nil {
+		panic(err)
+	}
+}
+
+func (nu *NodeUpdate) sqlSave(ctx context.Context) (n int, err error) {
+	selector := sql.Select(node.FieldID).From(sql.Table(node.Table))
+	for _, p := range nu.predicates {
+		p(selector)
+	}
+	rows := &sql.Rows{}
+	query, args := selector.Query()
+	if err = nu.driver.Query(ctx, query, args, rows); err != nil {
+		return 0, err
+	}
+	defer rows.Close()
+	var ids []int
+	for rows.Next() {
+		var id int
+		if err := rows.Scan(&id); err != nil {
+			return 0, fmt.Errorf("ent: failed reading id: %v", err)
+		}
+		ids = append(ids, id)
+	}
+	if len(ids) == 0 {
+		return 0, nil
+	}
+
+	tx, err := nu.driver.Tx(ctx)
+	if err != nil {
+		return 0, err
+	}
+	var (
+		update  bool
+		res     sql.Result
+		builder = sql.Update(node.Table).Where(sql.InInts(node.FieldID, ids...))
+	)
+	if nu.value != nil {
+		update = true
+		builder.Set(node.FieldValue, *nu.value)
+	}
+	if update {
+		query, args := builder.Query()
+		if err := tx.Exec(ctx, query, args, &res); err != nil {
+			return 0, rollback(tx, err)
+		}
+	}
+	if nu.clearedParent {
+		query, args := sql.Update(node.ParentTable).
+			SetNull(node.ParentColumn).
+			Where(sql.InInts(node.FieldID, ids...)).
+			Query()
+		if err := tx.Exec(ctx, query, args, &res); err != nil {
+			return 0, rollback(tx, err)
+		}
+	}
+	if len(nu.parent) > 0 {
+		for eid := range nu.parent {
+			query, args := sql.Update(node.ParentTable).
+				Set(node.ParentColumn, eid).
+				Where(sql.InInts(node.FieldID, ids...)).
+				Query()
+			if err := tx.Exec(ctx, query, args, &res); err != nil {
+				return 0, rollback(tx, err)
+			}
+		}
+	}
+	if len(nu.removedChildren) > 0 {
+		eids := make([]int, len(nu.removedChildren))
+		for eid := range nu.removedChildren {
+			eids = append(eids, eid)
+		}
+		query, args := sql.Update(node.ChildrenTable).
+			SetNull(node.ChildrenColumn).
+			Where(sql.InInts(node.ChildrenColumn, ids...)).
+			Where(sql.InInts(node.FieldID, eids...)).
+			Query()
+		if err := tx.Exec(ctx, query, args, &res); err != nil {
+			return 0, rollback(tx, err)
+		}
+	}
+	if len(nu.children) > 0 {
+		for _, id := range ids {
+			p := sql.P()
+			for eid := range nu.children {
+				p.Or().EQ(node.FieldID, eid)
+			}
+			query, args := sql.Update(node.ChildrenTable).
+				Set(node.ChildrenColumn, id).
+				Where(sql.And(p, sql.IsNull(node.ChildrenColumn))).
+				Query()
+			if err := tx.Exec(ctx, query, args, &res); err != nil {
+				return 0, rollback(tx, err)
+			}
+			affected, err := res.RowsAffected()
+			if err != nil {
+				return 0, rollback(tx, err)
+			}
+			if int(affected) < len(nu.children) {
+				return 0, rollback(tx, &ErrConstraintFailed{msg: fmt.Sprintf("one of \"children\" %v already connected to a different \"Node\"", keys(nu.children))})
+			}
+		}
+	}
+	if err = tx.Commit(); err != nil {
+		return 0, err
+	}
+	return len(ids), nil
+}
+
+// NodeUpdateOne is the builder for updating a single Node entity.
+type NodeUpdateOne struct {
+	config
+	id              int
+	value           *int
+	parent          map[int]struct{}
+	children        map[int]struct{}
+	clearedParent   bool
+	removedChildren map[int]struct{}
+}
+
+// SetValue sets the value field.
+func (nuo *NodeUpdateOne) SetValue(i int) *NodeUpdateOne {
+	nuo.value = &i
+	return nuo
+}
+
+// SetParentID sets the parent edge to Node by id.
+func (nuo *NodeUpdateOne) SetParentID(id int) *NodeUpdateOne {
+	if nuo.parent == nil {
+		nuo.parent = make(map[int]struct{})
+	}
+	nuo.parent[id] = struct{}{}
+	return nuo
+}
+
+// SetNillableParentID sets the parent edge to Node by id if the given value is not nil.
+func (nuo *NodeUpdateOne) SetNillableParentID(id *int) *NodeUpdateOne {
+	if id != nil {
+		nuo = nuo.SetParentID(*id)
+	}
+	return nuo
+}
+
+// SetParent sets the parent edge to Node.
+func (nuo *NodeUpdateOne) SetParent(n *Node) *NodeUpdateOne {
+	return nuo.SetParentID(n.ID)
+}
+
+// AddChildIDs adds the children edge to Node by ids.
+func (nuo *NodeUpdateOne) AddChildIDs(ids ...int) *NodeUpdateOne {
+	if nuo.children == nil {
+		nuo.children = make(map[int]struct{})
+	}
+	for i := range ids {
+		nuo.children[ids[i]] = struct{}{}
+	}
+	return nuo
+}
+
+// AddChildren adds the children edges to Node.
+func (nuo *NodeUpdateOne) AddChildren(n ...*Node) *NodeUpdateOne {
+	ids := make([]int, len(n))
+	for i := range n {
+		ids[i] = n[i].ID
+	}
+	return nuo.AddChildIDs(ids...)
+}
+
+// ClearParent clears the parent edge to Node.
+func (nuo *NodeUpdateOne) ClearParent() *NodeUpdateOne {
+	nuo.clearedParent = true
+	return nuo
+}
+
+// RemoveChildIDs removes the children edge to Node by ids.
+func (nuo *NodeUpdateOne) RemoveChildIDs(ids ...int) *NodeUpdateOne {
+	if nuo.removedChildren == nil {
+		nuo.removedChildren = make(map[int]struct{})
+	}
+	for i := range ids {
+		nuo.removedChildren[ids[i]] = struct{}{}
+	}
+	return nuo
+}
+
+// RemoveChildren removes children edges to Node.
+func (nuo *NodeUpdateOne) RemoveChildren(n ...*Node) *NodeUpdateOne {
+	ids := make([]int, len(n))
+	for i := range n {
+		ids[i] = n[i].ID
+	}
+	return nuo.RemoveChildIDs(ids...)
+}
+
+// Save executes the query and returns the updated entity.
+func (nuo *NodeUpdateOne) Save(ctx context.Context) (*Node, error) {
+	if len(nuo.parent) > 1 {
+		return nil, errors.New("ent: multiple assignments on a unique edge \"parent\"")
+	}
+	return nuo.sqlSave(ctx)
+}
+
+// SaveX is like Save, but panics if an error occurs.
+func (nuo *NodeUpdateOne) SaveX(ctx context.Context) *Node {
+	n, err := nuo.Save(ctx)
+	if err != nil {
+		panic(err)
+	}
+	return n
+}
+
+// Exec executes the query on the entity.
+func (nuo *NodeUpdateOne) Exec(ctx context.Context) error {
+	_, err := nuo.Save(ctx)
+	return err
+}
+
+// ExecX is like Exec, but panics if an error occurs.
+func (nuo *NodeUpdateOne) ExecX(ctx context.Context) {
+	if err := nuo.Exec(ctx); err != nil {
+		panic(err)
+	}
+}
+
+func (nuo *NodeUpdateOne) sqlSave(ctx context.Context) (n *Node, err error) {
+	selector := sql.Select(node.Columns...).From(sql.Table(node.Table))
+	node.ID(nuo.id)(selector)
+	rows := &sql.Rows{}
+	query, args := selector.Query()
+	if err = nuo.driver.Query(ctx, query, args, rows); err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var ids []int
+	for rows.Next() {
+		var id int
+		n = &Node{config: nuo.config}
+		if err := n.FromRows(rows); err != nil {
+			return nil, fmt.Errorf("ent: failed scanning row into Node: %v", err)
+		}
+		id = n.ID
+		ids = append(ids, id)
+	}
+	switch n := len(ids); {
+	case n == 0:
+		return nil, fmt.Errorf("ent: Node not found with id: %v", nuo.id)
+	case n > 1:
+		return nil, fmt.Errorf("ent: more than one Node with the same id: %v", nuo.id)
+	}
+
+	tx, err := nuo.driver.Tx(ctx)
+	if err != nil {
+		return nil, err
+	}
+	var (
+		update  bool
+		res     sql.Result
+		builder = sql.Update(node.Table).Where(sql.InInts(node.FieldID, ids...))
+	)
+	if nuo.value != nil {
+		update = true
+		builder.Set(node.FieldValue, *nuo.value)
+		n.Value = *nuo.value
+	}
+	if update {
+		query, args := builder.Query()
+		if err := tx.Exec(ctx, query, args, &res); err != nil {
+			return nil, rollback(tx, err)
+		}
+	}
+	if nuo.clearedParent {
+		query, args := sql.Update(node.ParentTable).
+			SetNull(node.ParentColumn).
+			Where(sql.InInts(node.FieldID, ids...)).
+			Query()
+		if err := tx.Exec(ctx, query, args, &res); err != nil {
+			return nil, rollback(tx, err)
+		}
+	}
+	if len(nuo.parent) > 0 {
+		for eid := range nuo.parent {
+			query, args := sql.Update(node.ParentTable).
+				Set(node.ParentColumn, eid).
+				Where(sql.InInts(node.FieldID, ids...)).
+				Query()
+			if err := tx.Exec(ctx, query, args, &res); err != nil {
+				return nil, rollback(tx, err)
+			}
+		}
+	}
+	if len(nuo.removedChildren) > 0 {
+		eids := make([]int, len(nuo.removedChildren))
+		for eid := range nuo.removedChildren {
+			eids = append(eids, eid)
+		}
+		query, args := sql.Update(node.ChildrenTable).
+			SetNull(node.ChildrenColumn).
+			Where(sql.InInts(node.ChildrenColumn, ids...)).
+			Where(sql.InInts(node.FieldID, eids...)).
+			Query()
+		if err := tx.Exec(ctx, query, args, &res); err != nil {
+			return nil, rollback(tx, err)
+		}
+	}
+	if len(nuo.children) > 0 {
+		for _, id := range ids {
+			p := sql.P()
+			for eid := range nuo.children {
+				p.Or().EQ(node.FieldID, eid)
+			}
+			query, args := sql.Update(node.ChildrenTable).
+				Set(node.ChildrenColumn, id).
+				Where(sql.And(p, sql.IsNull(node.ChildrenColumn))).
+				Query()
+			if err := tx.Exec(ctx, query, args, &res); err != nil {
+				return nil, rollback(tx, err)
+			}
+			affected, err := res.RowsAffected()
+			if err != nil {
+				return nil, rollback(tx, err)
+			}
+			if int(affected) < len(nuo.children) {
+				return nil, rollback(tx, &ErrConstraintFailed{msg: fmt.Sprintf("one of \"children\" %v already connected to a different \"Node\"", keys(nuo.children))})
+			}
+		}
+	}
+	if err = tx.Commit(); err != nil {
+		return nil, err
+	}
+	return n, nil
+}

examples/o2mrecur/ent/predicate/predicate.go

@@ -0,0 +1,10 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package predicate
+
+import (
+	"github.com/facebookincubator/ent/dialect/sql"
+)
+
+// Node is the predicate function for node builders.
+type Node func(*sql.Selector)

examples/o2mrecur/ent/schema/node.go

@@ -0,0 +1,28 @@
+package schema
+
+import (
+	"github.com/facebookincubator/ent"
+	"github.com/facebookincubator/ent/schema/edge"
+	"github.com/facebookincubator/ent/schema/field"
+)
+
+// Node holds the schema definition for the Node entity.
+type Node struct {
+	ent.Schema
+}
+
+// Fields of the Node.
+func (Node) Fields() []ent.Field {
+	return []ent.Field{
+		field.Int("value"),
+	}
+}
+
+// Edges of the Node.
+func (Node) Edges() []ent.Edge {
+	return []ent.Edge{
+		edge.To("children", Node.Type).
+			From("parent").
+			Unique(),
+	}
+}

examples/o2mrecur/ent/tx.go

@@ -0,0 +1,93 @@
+// Code generated (@generated) by entc, DO NOT EDIT.
+
+package ent
+
+import (
+	"context"
+
+	"github.com/facebookincubator/ent/dialect"
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/migrate"
+)
+
+// Tx is a transactional client that is created by calling Client.Tx().
+type Tx struct {
+	config
+	// Node is the client for interacting with the Node builders.
+	Node *NodeClient
+}
+
+// Commit commits the transaction.
+func (tx *Tx) Commit() error {
+	return tx.config.driver.(*txDriver).tx.Commit()
+}
+
+// Rollback rollbacks the transaction.
+func (tx *Tx) Rollback() error {
+	return tx.config.driver.(*txDriver).tx.Rollback()
+}
+
+// Client returns a Client that binds to current transaction.
+func (tx *Tx) Client() *Client {
+	return &Client{
+		config: tx.config,
+		Schema: migrate.NewSchema(tx.driver),
+		Node:   NewNodeClient(tx.config),
+	}
+}
+
+// txDriver wraps the given dialect.Tx with a nop dialect.Driver implementation.
+// The idea is to support transactions without adding any extra code to the builders.
+// When a builder calls to driver.Tx(), it gets the same dialect.Tx instance.
+// Commit and Rollback are nop for the internal builders and the user must call one
+// of them in order to commit or rollback the transaction.
+//
+// If a closed transaction is embedded in one of the generated entities, and the entity
+// applies a query, for example: Node.QueryXXX(), the query will be executed
+// through the driver which created this transaction.
+//
+// Note that txDriver is not goroutine safe.
+type txDriver struct {
+	// the driver we started the transaction from.
+	drv dialect.Driver
+	// tx is the underlying transaction.
+	tx dialect.Tx
+}
+
+// newTx creates a new transactional driver.
+func newTx(ctx context.Context, drv dialect.Driver) (*txDriver, error) {
+	tx, err := drv.Tx(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return &txDriver{tx: tx, drv: drv}, nil
+}
+
+// Tx returns the transaction wrapper (txDriver) to avoid Commit or Rollback calls
+// from the internal builders. Should be called only by the internal builders.
+func (tx *txDriver) Tx(context.Context) (dialect.Tx, error) { return tx, nil }
+
+// Dialect returns the dialect of the driver we started the transaction from.
+func (tx *txDriver) Dialect() string { return tx.drv.Dialect() }
+
+// Close is a nop close.
+func (*txDriver) Close() error { return nil }
+
+// Commit is a nop commit for the internal builders.
+// User must call `Tx.Commit` in order to commit the transaction.
+func (*txDriver) Commit() error { return nil }
+
+// Rollback is a nop rollback for the internal builders.
+// User must call `Tx.Rollback` in order to rollback the transaction.
+func (*txDriver) Rollback() error { return nil }
+
+// Exec calls tx.Exec.
+func (tx *txDriver) Exec(ctx context.Context, query string, args, v interface{}) error {
+	return tx.tx.Exec(ctx, query, args, v)
+}
+
+// Query calls tx.Query.
+func (tx *txDriver) Query(ctx context.Context, query string, args, v interface{}) error {
+	return tx.tx.Query(ctx, query, args, v)
+}
+
+var _ dialect.Driver = (*txDriver)(nil)

examples/o2mrecur/o2mrecur.go

@@ -0,0 +1,96 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent"
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/node"
+
+	"github.com/facebookincubator/ent/dialect/sql"
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func main() {
+	db, err := sql.Open("sqlite3", "file:o2o2types?mode=memory&cache=shared&_fk=1")
+	if err != nil {
+		log.Fatalf("failed opening connection to sqlite: %v", err)
+	}
+	defer db.Close()
+	client := ent.NewClient(ent.Driver(db))
+	ctx := context.Background()
+	// run the auto migration tool.
+	if err := client.Schema.Create(ctx); err != nil {
+		log.Fatalf("failed creating schema resources: %v", err)
+	}
+	if err := Do(ctx, client); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func Do(ctx context.Context, client *ent.Client) error {
+	root, err := client.Node.
+		Create().
+		SetValue(2).
+		Save(ctx)
+	if err != nil {
+		return fmt.Errorf("creating the root: %v", err)
+	}
+
+	// Add additional nodes to the tree:
+	//
+	//       2
+	//     /   \
+	//    1     4
+	//        /   \
+	//       3     5
+	//
+
+	// Unlike `Create`, `CreateX` panics if an error occurs.
+	n1 := client.Node.
+		Create().
+		SetValue(1).
+		SetParent(root).
+		SaveX(ctx)
+	n4 := client.Node.
+		Create().
+		SetValue(4).
+		SetParent(root).
+		SaveX(ctx)
+	n3 := client.Node.
+		Create().
+		SetValue(3).
+		SetParent(n4).
+		SaveX(ctx)
+	n5 := client.Node.
+		Create().
+		SetValue(5).
+		SetParent(n4).
+		SaveX(ctx)
+
+	fmt.Println("Tree leafs", []int{n1.Value, n3.Value, n5.Value})
+	// Output: Tree leafs [1 3 5]
+
+	// Get all leafs (nodes without children).
+	// Unlike `Int`, `IntX` panics if an error occurs.
+	ints := client.Node.
+		Query().                             // All nodes.
+		Where(node.Not(node.HasChildren())). // Only leafs.
+		Order(ent.Asc(node.FieldValue)).     // Order by their `value` field.
+		GroupBy(node.FieldValue).            // Extract only the `value` field.
+		IntsX(ctx)
+	fmt.Println(ints)
+	// Output: [1 3 5]
+
+	// Get orphan nodes (nodes without parent).
+	// Unlike `Only`, `OnlyX` panics if an error occurs.
+	orphan := client.Node.
+		Query().
+		Where(node.Not(node.HasParent())).
+		OnlyX(ctx)
+	fmt.Println(orphan)
+	// Output: Node(id=1, value=2)
+
+	return nil
+}

examples/o2orecur/o2orecur.go

@@ -28,6 +28,7 @@ func main() {
 		log.Fatal(err)
 	}
 }
+
 func Do(ctx context.Context, client *ent.Client) error {
 	head, err := client.Node.
 		Create().