snapshot of https://github.com/ent/ent.git (master, 2026-09-15; blobs > 131072B omitted)
This commit is contained in:
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doc/md/faq.md
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doc/md/faq.md
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---
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id: faq
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||||
title: Frequently Asked Questions (FAQ)
|
||||
sidebar_label: FAQ
|
||||
---
|
||||
|
||||
## Questions
|
||||
|
||||
[How to create an entity from a struct `T`?](#how-to-create-an-entity-from-a-struct-t)
|
||||
[How to create a struct (or a mutation) level validator?](#how-to-create-a-mutation-level-validator)
|
||||
[How to write an audit-log extension?](#how-to-write-an-audit-log-extension)
|
||||
[How to write custom predicates?](#how-to-write-custom-predicates)
|
||||
[How to add custom predicates to the codegen assets?](#how-to-add-custom-predicates-to-the-codegen-assets)
|
||||
[How to define a network address field in PostgreSQL?](#how-to-define-a-network-address-field-in-postgresql)
|
||||
[How to customize time fields to type `DATETIME` in MySQL?](#how-to-customize-time-fields-to-type-datetime-in-mysql)
|
||||
[How to use a custom generator of IDs?](#how-to-use-a-custom-generator-of-ids)
|
||||
[How to use a custom XID globally unique ID?](#how-to-use-a-custom-xid-globally-unique-id)
|
||||
[How to define a spatial data type field in MySQL?](#how-to-define-a-spatial-data-type-field-in-mysql)
|
||||
[How to extend the generated models?](#how-to-extend-the-generated-models)
|
||||
[How to extend the generated builders?](#how-to-extend-the-generated-builders)
|
||||
[How to store Protobuf objects in a BLOB column?](#how-to-store-protobuf-objects-in-a-blob-column)
|
||||
[How to add `CHECK` constraints to table?](#how-to-add-check-constraints-to-table)
|
||||
[How to define a custom precision numeric field?](#how-to-define-a-custom-precision-numeric-field)
|
||||
[How to configure two or more `DB` to separate read and write?](#how-to-configure-two-or-more-db-to-separate-read-and-write)
|
||||
[How to configure `json.Marshal` to inline the `edges` keys in the top level object?](#how-to-configure-jsonmarshal-to-inline-the-edges-keys-in-the-top-level-object)
|
||||
|
||||
## Answers
|
||||
|
||||
#### How to create an entity from a struct `T`?
|
||||
|
||||
The different builders don't support the option of setting the entity fields (or edges) from a given struct `T`.
|
||||
The reason is that there's no way to distinguish between zero/real values when updating the database (for example, `&ent.T{Age: 0, Name: ""}`).
|
||||
Setting these values, may set incorrect values in the database or update unnecessary columns.
|
||||
|
||||
However, the [external template](templates.md) option lets you extend the default code-generation assets by adding custom logic.
|
||||
For example, in order to generate a method for each of the create-builders, that accepts a struct as an input and configure the builder,
|
||||
use the following template:
|
||||
|
||||
```gotemplate
|
||||
{{ range $n := $.Nodes }}
|
||||
{{ $builder := $n.CreateName }}
|
||||
{{ $receiver := $n.CreateReceiver }}
|
||||
|
||||
func ({{ $receiver }} *{{ $builder }}) Set{{ $n.Name }}(input *{{ $n.Name }}) *{{ $builder }} {
|
||||
{{- range $f := $n.Fields }}
|
||||
{{- $setter := print "Set" $f.StructField }}
|
||||
{{ $receiver }}.{{ $setter }}(input.{{ $f.StructField }})
|
||||
{{- end }}
|
||||
return {{ $receiver }}
|
||||
}
|
||||
{{ end }}
|
||||
```
|
||||
|
||||
#### How to create a mutation level validator?
|
||||
|
||||
In order to implement a mutation-level validator, you can either use [schema hooks](hooks.md#schema-hooks) for validating
|
||||
changes applied on one entity type, or use [transaction hooks](transactions.md#hooks) for validating mutations that being
|
||||
applied on multiple entity types (e.g. a GraphQL mutation). For example:
|
||||
|
||||
```go
|
||||
// A VersionHook is a dummy example for a hook that validates the "version" field
|
||||
// is incremented by 1 on each update. Note that this is just a dummy example, and
|
||||
// it doesn't promise consistency in the database.
|
||||
func VersionHook() ent.Hook {
|
||||
type OldSetVersion interface {
|
||||
SetVersion(int)
|
||||
Version() (int, bool)
|
||||
OldVersion(context.Context) (int, error)
|
||||
}
|
||||
return func(next ent.Mutator) ent.Mutator {
|
||||
return ent.MutateFunc(func(ctx context.Context, m ent.Mutation) (ent.Value, error) {
|
||||
ver, ok := m.(OldSetVersion)
|
||||
if !ok {
|
||||
return next.Mutate(ctx, m)
|
||||
}
|
||||
oldV, err := ver.OldVersion(ctx)
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
curV, exists := ver.Version()
|
||||
if !exists {
|
||||
return nil, fmt.Errorf("version field is required in update mutation")
|
||||
}
|
||||
if curV != oldV+1 {
|
||||
return nil, fmt.Errorf("version field must be incremented by 1")
|
||||
}
|
||||
// Add an SQL predicate that validates the "version" column is equal
|
||||
// to "oldV" (ensure it wasn't changed during the mutation by others).
|
||||
return next.Mutate(ctx, m)
|
||||
})
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
#### How to write an audit-log extension?
|
||||
|
||||
The preferred way for writing such an extension is to use [ent.Mixin](schema-mixin.md). Use the `Fields` option for
|
||||
setting the fields that are shared between all schemas that import the mixed-schema, and use the `Hooks` option for
|
||||
attaching a mutation-hook for all mutations that are being applied on these schemas. Here's an example, based on a
|
||||
discussion in the [repository issue-tracker](https://github.com/ent/ent/issues/830):
|
||||
|
||||
```go
|
||||
// AuditMixin implements the ent.Mixin for sharing
|
||||
// audit-log capabilities with package schemas.
|
||||
type AuditMixin struct{
|
||||
mixin.Schema
|
||||
}
|
||||
|
||||
// Fields of the AuditMixin.
|
||||
func (AuditMixin) Fields() []ent.Field {
|
||||
return []ent.Field{
|
||||
field.Time("created_at").
|
||||
Immutable().
|
||||
Default(time.Now),
|
||||
field.Int("created_by").
|
||||
Optional(),
|
||||
field.Time("updated_at").
|
||||
Default(time.Now).
|
||||
UpdateDefault(time.Now),
|
||||
field.Int("updated_by").
|
||||
Optional(),
|
||||
}
|
||||
}
|
||||
|
||||
// Hooks of the AuditMixin.
|
||||
func (AuditMixin) Hooks() []ent.Hook {
|
||||
return []ent.Hook{
|
||||
hooks.AuditHook,
|
||||
}
|
||||
}
|
||||
|
||||
// A AuditHook is an example for audit-log hook.
|
||||
func AuditHook(next ent.Mutator) ent.Mutator {
|
||||
// AuditLogger wraps the methods that are shared between all mutations of
|
||||
// schemas that embed the AuditLog mixin. The variable "exists" is true, if
|
||||
// the field already exists in the mutation (e.g. was set by a different hook).
|
||||
type AuditLogger interface {
|
||||
SetCreatedAt(time.Time)
|
||||
CreatedAt() (value time.Time, exists bool)
|
||||
SetCreatedBy(int)
|
||||
CreatedBy() (id int, exists bool)
|
||||
SetUpdatedAt(time.Time)
|
||||
UpdatedAt() (value time.Time, exists bool)
|
||||
SetUpdatedBy(int)
|
||||
UpdatedBy() (id int, exists bool)
|
||||
}
|
||||
return ent.MutateFunc(func(ctx context.Context, m ent.Mutation) (ent.Value, error) {
|
||||
ml, ok := m.(AuditLogger)
|
||||
if !ok {
|
||||
return nil, fmt.Errorf("unexpected audit-log call from mutation type %T", m)
|
||||
}
|
||||
usr, err := viewer.UserFromContext(ctx)
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
switch op := m.Op(); {
|
||||
case op.Is(ent.OpCreate):
|
||||
ml.SetCreatedAt(time.Now())
|
||||
if _, exists := ml.CreatedBy(); !exists {
|
||||
ml.SetCreatedBy(usr.ID)
|
||||
}
|
||||
case op.Is(ent.OpUpdateOne | ent.OpUpdate):
|
||||
ml.SetUpdatedAt(time.Now())
|
||||
if _, exists := ml.UpdatedBy(); !exists {
|
||||
ml.SetUpdatedBy(usr.ID)
|
||||
}
|
||||
}
|
||||
return next.Mutate(ctx, m)
|
||||
})
|
||||
}
|
||||
```
|
||||
|
||||
#### How to write custom predicates?
|
||||
|
||||
Users can provide custom predicates to apply on the query before it's executed. For example:
|
||||
|
||||
```go
|
||||
pets := client.Pet.
|
||||
Query().
|
||||
Where(predicate.Pet(func(s *sql.Selector) {
|
||||
s.Where(sql.InInts(pet.OwnerColumn, 1, 2, 3))
|
||||
})).
|
||||
AllX(ctx)
|
||||
|
||||
users := client.User.
|
||||
Query().
|
||||
Where(predicate.User(func(s *sql.Selector) {
|
||||
s.Where(sqljson.ValueContains(user.FieldTags, "tag"))
|
||||
})).
|
||||
AllX(ctx)
|
||||
```
|
||||
|
||||
For more examples, go to the [predicates](predicates.md#custom-predicates) page, or search in the repository
|
||||
issue-tracker for more advance examples like [issue-842](https://github.com/ent/ent/issues/842#issuecomment-707896368).
|
||||
|
||||
#### How to add custom predicates to the codegen assets?
|
||||
|
||||
The [template](templates.md) option enables the capability for extending or overriding the default codegen assets.
|
||||
In order to generate a type-safe predicate for the [example above](#how-to-write-custom-predicates), use the template
|
||||
option for doing it as follows:
|
||||
|
||||
```gotemplate
|
||||
{{/* A template that adds the "<F>Glob" predicate for all string fields. */}}
|
||||
{{ define "where/additional/strings" }}
|
||||
{{ range $f := $.Fields }}
|
||||
{{ if $f.IsString }}
|
||||
{{ $func := print $f.StructField "Glob" }}
|
||||
// {{ $func }} applies the Glob predicate on the {{ quote $f.Name }} field.
|
||||
func {{ $func }}(pattern string) predicate.{{ $.Name }} {
|
||||
return predicate.{{ $.Name }}(func(s *sql.Selector) {
|
||||
s.Where(sql.P(func(b *sql.Builder) {
|
||||
b.Ident(s.C({{ $f.Constant }})).WriteString(" glob" ).Arg(pattern)
|
||||
}))
|
||||
})
|
||||
}
|
||||
{{ end }}
|
||||
{{ end }}
|
||||
{{ end }}
|
||||
```
|
||||
|
||||
#### How to define a network address field in PostgreSQL?
|
||||
|
||||
The [GoType](schema-fields.mdx#go-type) and the [SchemaType](schema-fields.mdx#database-type)
|
||||
options allow users to define database-specific fields. For example, in order to define a
|
||||
[`macaddr`](https://www.postgresql.org/docs/13/datatype-net-types.html#DATATYPE-MACADDR) field, use the following configuration:
|
||||
|
||||
```go
|
||||
func (T) Fields() []ent.Field {
|
||||
return []ent.Field{
|
||||
field.String("mac").
|
||||
GoType(&MAC{}).
|
||||
SchemaType(map[string]string{
|
||||
dialect.Postgres: "macaddr",
|
||||
}).
|
||||
Validate(func(s string) error {
|
||||
_, err := net.ParseMAC(s)
|
||||
return err
|
||||
}),
|
||||
}
|
||||
}
|
||||
|
||||
// MAC represents a physical hardware address.
|
||||
type MAC struct {
|
||||
net.HardwareAddr
|
||||
}
|
||||
|
||||
// Scan implements the Scanner interface.
|
||||
func (m *MAC) Scan(value any) (err error) {
|
||||
switch v := value.(type) {
|
||||
case nil:
|
||||
case []byte:
|
||||
m.HardwareAddr, err = net.ParseMAC(string(v))
|
||||
case string:
|
||||
m.HardwareAddr, err = net.ParseMAC(v)
|
||||
default:
|
||||
err = fmt.Errorf("unexpected type %T", v)
|
||||
}
|
||||
return
|
||||
}
|
||||
|
||||
// Value implements the driver Valuer interface.
|
||||
func (m MAC) Value() (driver.Value, error) {
|
||||
return m.HardwareAddr.String(), nil
|
||||
}
|
||||
```
|
||||
Note that, if the database doesn't support the `macaddr` type (e.g. SQLite on testing), the field fallback to its
|
||||
native type (i.e. `string`).
|
||||
|
||||
`inet` example:
|
||||
|
||||
```go
|
||||
func (T) Fields() []ent.Field {
|
||||
return []ent.Field{
|
||||
field.String("ip").
|
||||
GoType(&Inet{}).
|
||||
SchemaType(map[string]string{
|
||||
dialect.Postgres: "inet",
|
||||
}).
|
||||
Validate(func(s string) error {
|
||||
if net.ParseIP(s) == nil {
|
||||
return fmt.Errorf("invalid value for ip %q", s)
|
||||
}
|
||||
return nil
|
||||
}),
|
||||
}
|
||||
}
|
||||
|
||||
// Inet represents a single IP address
|
||||
type Inet struct {
|
||||
net.IP
|
||||
}
|
||||
|
||||
// Scan implements the Scanner interface
|
||||
func (i *Inet) Scan(value any) (err error) {
|
||||
switch v := value.(type) {
|
||||
case nil:
|
||||
case []byte:
|
||||
if i.IP = net.ParseIP(string(v)); i.IP == nil {
|
||||
err = fmt.Errorf("invalid value for ip %q", v)
|
||||
}
|
||||
case string:
|
||||
if i.IP = net.ParseIP(v); i.IP == nil {
|
||||
err = fmt.Errorf("invalid value for ip %q", v)
|
||||
}
|
||||
default:
|
||||
err = fmt.Errorf("unexpected type %T", v)
|
||||
}
|
||||
return
|
||||
}
|
||||
|
||||
// Value implements the driver Valuer interface
|
||||
func (i Inet) Value() (driver.Value, error) {
|
||||
return i.IP.String(), nil
|
||||
}
|
||||
```
|
||||
|
||||
#### How to customize time fields to type `DATETIME` in MySQL?
|
||||
|
||||
`Time` fields use the MySQL `TIMESTAMP` type in the schema creation by default, and this type
|
||||
has a range of '1970-01-01 00:00:01' UTC to '2038-01-19 03:14:07' UTC (see, [MySQL docs](https://dev.mysql.com/doc/refman/5.6/en/datetime.html)).
|
||||
|
||||
In order to customize time fields for a wider range, use the MySQL `DATETIME` as follows:
|
||||
```go
|
||||
field.Time("birth_date").
|
||||
Optional().
|
||||
SchemaType(map[string]string{
|
||||
dialect.MySQL: "datetime",
|
||||
}),
|
||||
```
|
||||
|
||||
#### How to use a custom generator of IDs?
|
||||
|
||||
If you're using a custom ID generator instead of using auto-incrementing IDs in
|
||||
your database (e.g. Twitter's [Snowflake](https://github.com/twitter-archive/snowflake/tree/snowflake-2010)),
|
||||
you will need to write a custom ID field which automatically calls the generator
|
||||
on resource creation.
|
||||
|
||||
To achieve this, you can either make use of `DefaultFunc` or of schema hooks -
|
||||
depending on your use case. If the generator does not return an error,
|
||||
`DefaultFunc` is more concise, whereas setting a hook on resource creation
|
||||
will allow you to capture errors as well. An example of how to use
|
||||
`DefaultFunc` can be seen in the section regarding [the ID field](schema-fields.mdx#id-field).
|
||||
|
||||
Here is an example of how to use a custom generator with hooks, taking as an
|
||||
example [sonyflake](https://github.com/sony/sonyflake).
|
||||
|
||||
```go
|
||||
// BaseMixin to be shared will all different schemas.
|
||||
type BaseMixin struct {
|
||||
mixin.Schema
|
||||
}
|
||||
|
||||
// Fields of the Mixin.
|
||||
func (BaseMixin) Fields() []ent.Field {
|
||||
return []ent.Field{
|
||||
field.Uint64("id"),
|
||||
}
|
||||
}
|
||||
|
||||
// Hooks of the Mixin.
|
||||
func (BaseMixin) Hooks() []ent.Hook {
|
||||
return []ent.Hook{
|
||||
hook.On(IDHook(), ent.OpCreate),
|
||||
}
|
||||
}
|
||||
|
||||
func IDHook() ent.Hook {
|
||||
sf := sonyflake.NewSonyflake(sonyflake.Settings{})
|
||||
type IDSetter interface {
|
||||
SetID(uint64)
|
||||
}
|
||||
return func(next ent.Mutator) ent.Mutator {
|
||||
return ent.MutateFunc(func(ctx context.Context, m ent.Mutation) (ent.Value, error) {
|
||||
is, ok := m.(IDSetter)
|
||||
if !ok {
|
||||
return nil, fmt.Errorf("unexpected mutation %T", m)
|
||||
}
|
||||
id, err := sf.NextID()
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
is.SetID(id)
|
||||
return next.Mutate(ctx, m)
|
||||
})
|
||||
}
|
||||
}
|
||||
|
||||
// User holds the schema definition for the User entity.
|
||||
type User struct {
|
||||
ent.Schema
|
||||
}
|
||||
|
||||
// Mixin of the User.
|
||||
func (User) Mixin() []ent.Mixin {
|
||||
return []ent.Mixin{
|
||||
// Embed the BaseMixin in the user schema.
|
||||
BaseMixin{},
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
#### How to use a custom XID globally unique ID?
|
||||
|
||||
Package [xid](https://github.com/rs/xid) is a globally unique ID generator library that uses the [Mongo Object ID](https://docs.mongodb.org/manual/reference/object-id/)
|
||||
algorithm to generate a 12 byte, 20 character ID with no configuration. The xid package comes with [database/sql](https://pkg.go.dev/database/sql) `sql.Scanner` and `driver.Valuer` interfaces required by Ent for serialization.
|
||||
|
||||
To store an XID in any string field use the [GoType](schema-fields.mdx#go-type) schema configuration:
|
||||
|
||||
```go
|
||||
// Fields of type T.
|
||||
func (T) Fields() []ent.Field {
|
||||
return []ent.Field{
|
||||
field.String("id").
|
||||
GoType(xid.ID{}).
|
||||
DefaultFunc(xid.New),
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Or as a reusable [Mixin](schema-mixin.md) across multiple schemas:
|
||||
|
||||
```go
|
||||
package schema
|
||||
|
||||
import (
|
||||
"entgo.io/ent"
|
||||
"entgo.io/ent/schema/field"
|
||||
"entgo.io/ent/schema/mixin"
|
||||
"github.com/rs/xid"
|
||||
)
|
||||
|
||||
// BaseMixin to be shared will all different schemas.
|
||||
type BaseMixin struct {
|
||||
mixin.Schema
|
||||
}
|
||||
|
||||
// Fields of the User.
|
||||
func (BaseMixin) Fields() []ent.Field {
|
||||
return []ent.Field{
|
||||
field.String("id").
|
||||
GoType(xid.ID{}).
|
||||
DefaultFunc(xid.New),
|
||||
}
|
||||
}
|
||||
|
||||
// User holds the schema definition for the User entity.
|
||||
type User struct {
|
||||
ent.Schema
|
||||
}
|
||||
|
||||
// Mixin of the User.
|
||||
func (User) Mixin() []ent.Mixin {
|
||||
return []ent.Mixin{
|
||||
// Embed the BaseMixin in the user schema.
|
||||
BaseMixin{},
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
In order to use extended identifiers (XIDs) with gqlgen, follow the configuration mentioned in the [issue tracker](https://github.com/ent/ent/issues/1526#issuecomment-831034884).
|
||||
|
||||
#### How to define a spatial data type field in MySQL?
|
||||
|
||||
The [GoType](schema-fields.mdx#go-type) and the [SchemaType](schema-fields.mdx#database-type)
|
||||
options allow users to define database-specific fields. For example, in order to define a
|
||||
[`POINT`](https://dev.mysql.com/doc/refman/8.0/en/spatial-type-overview.html) field, use the following configuration:
|
||||
|
||||
```go
|
||||
// Fields of the Location.
|
||||
func (Location) Fields() []ent.Field {
|
||||
return []ent.Field{
|
||||
field.String("name"),
|
||||
field.Other("coords", &Point{}).
|
||||
SchemaType(Point{}.SchemaType()),
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
```go
|
||||
package schema
|
||||
|
||||
import (
|
||||
"database/sql/driver"
|
||||
"fmt"
|
||||
|
||||
"entgo.io/ent/dialect"
|
||||
"entgo.io/ent/dialect/sql"
|
||||
"github.com/paulmach/orb"
|
||||
"github.com/paulmach/orb/encoding/wkb"
|
||||
)
|
||||
|
||||
// A Point consists of (X,Y) or (Lat, Lon) coordinates
|
||||
// and it is stored in MySQL the POINT spatial data type.
|
||||
type Point [2]float64
|
||||
|
||||
// Scan implements the Scanner interface.
|
||||
func (p *Point) Scan(value any) error {
|
||||
bin, ok := value.([]byte)
|
||||
if !ok {
|
||||
return fmt.Errorf("invalid binary value for point")
|
||||
}
|
||||
var op orb.Point
|
||||
if err := wkb.Scanner(&op).Scan(bin[4:]); err != nil {
|
||||
return err
|
||||
}
|
||||
p[0], p[1] = op.X(), op.Y()
|
||||
return nil
|
||||
}
|
||||
|
||||
// Value implements the driver Valuer interface.
|
||||
func (p Point) Value() (driver.Value, error) {
|
||||
op := orb.Point{p[0], p[1]}
|
||||
return wkb.Value(op).Value()
|
||||
}
|
||||
|
||||
// FormatParam implements the sql.ParamFormatter interface to tell the SQL
|
||||
// builder that the placeholder for a Point parameter needs to be formatted.
|
||||
func (p Point) FormatParam(placeholder string, info *sql.StmtInfo) string {
|
||||
if info.Dialect == dialect.MySQL {
|
||||
return "ST_GeomFromWKB(" + placeholder + ")"
|
||||
}
|
||||
return placeholder
|
||||
}
|
||||
|
||||
// SchemaType defines the schema-type of the Point object.
|
||||
func (Point) SchemaType() map[string]string {
|
||||
return map[string]string{
|
||||
dialect.MySQL: "POINT",
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
A full example exists in the [example repository](https://github.com/a8m/entspatial).
|
||||
|
||||
|
||||
#### How to extend the generated models?
|
||||
|
||||
Ent supports extending generated types (both global types and models) using custom templates. For example, in order to
|
||||
add additional struct fields or methods to the generated model, we can override the `model/fields/additional` template like in this
|
||||
[example](https://github.com/ent/ent/blob/dd4792f5b30bdd2db0d9a593a977a54cb3f0c1ce/examples/entcpkg/ent/template/static.tmpl).
|
||||
|
||||
|
||||
If your custom fields/methods require additional imports, you can add those imports using custom templates as well:
|
||||
|
||||
```gotemplate
|
||||
{{- define "import/additional/field_types" -}}
|
||||
"github.com/path/to/your/custom/type"
|
||||
{{- end -}}
|
||||
|
||||
{{- define "import/additional/client_dependencies" -}}
|
||||
"github.com/path/to/your/custom/type"
|
||||
{{- end -}}
|
||||
```
|
||||
|
||||
#### How to extend the generated builders?
|
||||
|
||||
See the *[Injecting External Dependencies](code-gen.md#external-dependencies)* section, or follow the
|
||||
example on [GitHub](https://github.com/ent/ent/tree/master/examples/entcpkg).
|
||||
|
||||
#### How to store Protobuf objects in a BLOB column?
|
||||
|
||||
Assuming we have a Protobuf message defined:
|
||||
```protobuf
|
||||
syntax = "proto3";
|
||||
|
||||
package pb;
|
||||
|
||||
option go_package = "project/pb";
|
||||
|
||||
message Hi {
|
||||
string Greeting = 1;
|
||||
}
|
||||
```
|
||||
|
||||
We add receiver methods to the generated protobuf struct such that it implements [ValueScanner](https://pkg.go.dev/entgo.io/ent/schema/field#ValueScanner)
|
||||
|
||||
```go
|
||||
func (x *Hi) Value() (driver.Value, error) {
|
||||
return proto.Marshal(x)
|
||||
}
|
||||
|
||||
func (x *Hi) Scan(src any) error {
|
||||
if src == nil {
|
||||
return nil
|
||||
}
|
||||
if b, ok := src.([]byte); ok {
|
||||
if err := proto.Unmarshal(b, x); err != nil {
|
||||
return err
|
||||
}
|
||||
return nil
|
||||
}
|
||||
return fmt.Errorf("unexpected type %T", src)
|
||||
}
|
||||
```
|
||||
|
||||
We add a new `field.Bytes` to our schema, setting the generated protobuf struct as its underlying `GoType`:
|
||||
|
||||
```go
|
||||
// Fields of the Message.
|
||||
func (Message) Fields() []ent.Field {
|
||||
return []ent.Field{
|
||||
field.Bytes("hi").
|
||||
GoType(&pb.Hi{}),
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Test that it works:
|
||||
|
||||
```go
|
||||
package main
|
||||
|
||||
import (
|
||||
"context"
|
||||
"testing"
|
||||
|
||||
"project/ent/enttest"
|
||||
"project/pb"
|
||||
|
||||
_ "github.com/mattn/go-sqlite3"
|
||||
"github.com/stretchr/testify/require"
|
||||
)
|
||||
|
||||
func TestMain(t *testing.T) {
|
||||
client := enttest.Open(t, "sqlite3", "file:ent?mode=memory&cache=shared&_fk=1")
|
||||
defer client.Close()
|
||||
|
||||
msg := client.Message.Create().
|
||||
SetHi(&pb.Hi{
|
||||
Greeting: "hello",
|
||||
}).
|
||||
SaveX(context.TODO())
|
||||
|
||||
ret := client.Message.GetX(context.TODO(), msg.ID)
|
||||
require.Equal(t, "hello", ret.Hi.Greeting)
|
||||
}
|
||||
```
|
||||
|
||||
#### How to add `CHECK` constraints to table?
|
||||
|
||||
The [`entsql.Annotation`](schema-annotations.md) option allows adding custom `CHECK` constraints to the `CREATE TABLE`
|
||||
statement. In order to add `CHECK` constraints to your schema, use the following example:
|
||||
|
||||
```go
|
||||
func (User) Annotations() []schema.Annotation {
|
||||
return []schema.Annotation{
|
||||
&entsql.Annotation{
|
||||
// The `Check` option allows adding an
|
||||
// unnamed CHECK constraint to table DDL.
|
||||
Check: "website <> 'entgo.io'",
|
||||
|
||||
// The `Checks` option allows adding multiple CHECK constraints
|
||||
// to table creation. The keys are used as the constraint names.
|
||||
Checks: map[string]string{
|
||||
"valid_nickname": "nickname <> firstname",
|
||||
"valid_firstname": "length(first_name) > 1",
|
||||
},
|
||||
},
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
#### How to define a custom precision numeric field?
|
||||
|
||||
Using [GoType](schema-fields.mdx#go-type) and [SchemaType](schema-fields.mdx#database-type) it is possible to define
|
||||
custom precision numeric fields. For example, defining a field that uses [big.Int](https://pkg.go.dev/math/big).
|
||||
|
||||
```go
|
||||
func (T) Fields() []ent.Field {
|
||||
return []ent.Field{
|
||||
field.Int("precise").
|
||||
GoType(new(BigInt)).
|
||||
SchemaType(map[string]string{
|
||||
dialect.SQLite: "numeric(78, 0)",
|
||||
dialect.Postgres: "numeric(78, 0)",
|
||||
}),
|
||||
}
|
||||
}
|
||||
|
||||
type BigInt struct {
|
||||
big.Int
|
||||
}
|
||||
|
||||
func (b *BigInt) Scan(src any) error {
|
||||
var i sql.NullString
|
||||
if err := i.Scan(src); err != nil {
|
||||
return err
|
||||
}
|
||||
if !i.Valid {
|
||||
return nil
|
||||
}
|
||||
if _, ok := b.Int.SetString(i.String, 10); ok {
|
||||
return nil
|
||||
}
|
||||
return fmt.Errorf("could not scan type %T with value %v into BigInt", src, src)
|
||||
}
|
||||
|
||||
func (b *BigInt) Value() (driver.Value, error) {
|
||||
return b.String(), nil
|
||||
}
|
||||
```
|
||||
|
||||
#### How to configure two or more `DB` to separate read and write?
|
||||
|
||||
You can wrap the `dialect.Driver` with your own driver and implement this logic. For example.
|
||||
|
||||
You can extend it, add support for multiple read replicas and add some load-balancing magic.
|
||||
|
||||
```go
|
||||
func main() {
|
||||
// ...
|
||||
wd, err := sql.Open(dialect.MySQL, "root:pass@tcp(<addr>)/<database>?parseTime=True")
|
||||
if err != nil {
|
||||
log.Fatal(err)
|
||||
}
|
||||
rd, err := sql.Open(dialect.MySQL, "readonly:pass@tcp(<addr>)/<database>?parseTime=True")
|
||||
if err != nil {
|
||||
log.Fatal(err)
|
||||
}
|
||||
client := ent.NewClient(ent.Driver(&multiDriver{w: wd, r: rd}))
|
||||
defer client.Close()
|
||||
// Use the client here.
|
||||
}
|
||||
|
||||
type multiDriver struct {
|
||||
r, w dialect.Driver
|
||||
}
|
||||
|
||||
var _ dialect.Driver = (*multiDriver)(nil)
|
||||
|
||||
func (d *multiDriver) Query(ctx context.Context, query string, args, v any) error {
|
||||
e := d.r
|
||||
// Mutation statements that use the RETURNING clause.
|
||||
if ent.QueryFromContext(ctx) == nil {
|
||||
e = d.w
|
||||
}
|
||||
return e.Query(ctx, query, args, v)
|
||||
}
|
||||
|
||||
func (d *multiDriver) Exec(ctx context.Context, query string, args, v any) error {
|
||||
return d.w.Exec(ctx, query, args, v)
|
||||
}
|
||||
|
||||
func (d *multiDriver) Tx(ctx context.Context) (dialect.Tx, error) {
|
||||
return d.w.Tx(ctx)
|
||||
}
|
||||
|
||||
func (d *multiDriver) BeginTx(ctx context.Context, opts *sql.TxOptions) (dialect.Tx, error) {
|
||||
return d.w.(interface {
|
||||
BeginTx(context.Context, *sql.TxOptions) (dialect.Tx, error)
|
||||
}).BeginTx(ctx, opts)
|
||||
}
|
||||
|
||||
func (d *multiDriver) Close() error {
|
||||
rerr := d.r.Close()
|
||||
werr := d.w.Close()
|
||||
if rerr != nil {
|
||||
return rerr
|
||||
}
|
||||
if werr != nil {
|
||||
return werr
|
||||
}
|
||||
return nil
|
||||
}
|
||||
|
||||
func (d *multiDriver) Dialect() string {
|
||||
return d.r.Dialect()
|
||||
}
|
||||
```
|
||||
|
||||
#### How to configure `json.Marshal` to inline the `edges` keys in the top level object?
|
||||
|
||||
To encode entities without the `edges` attribute, users can follow these two steps:
|
||||
|
||||
1. Omit the default `edges` tag generated by Ent.
|
||||
2. Extend the generated models with a custom MarshalJSON method.
|
||||
|
||||
These two steps can be automated using [codegen extensions](extension.md), and a full working example is available under
|
||||
the [examples/jsonencode](https://github.com/ent/ent/tree/master/examples/jsonencode) directory.
|
||||
|
||||
```go title="ent/entc.go" {17,28}
|
||||
//go:build ignore
|
||||
// +build ignore
|
||||
|
||||
package main
|
||||
|
||||
import (
|
||||
"log"
|
||||
|
||||
"entgo.io/ent/entc"
|
||||
"entgo.io/ent/entc/gen"
|
||||
"entgo.io/ent/schema/edge"
|
||||
)
|
||||
|
||||
func main() {
|
||||
opts := []entc.Option{
|
||||
entc.Extensions{
|
||||
&EncodeExtension{},
|
||||
),
|
||||
}
|
||||
err := entc.Generate("./schema", &gen.Config{}, opts...)
|
||||
if err != nil {
|
||||
log.Fatalf("running ent codegen: %v", err)
|
||||
}
|
||||
}
|
||||
|
||||
// EncodeExtension is an implementation of entc.Extension that adds a MarshalJSON
|
||||
// method to each generated type <T> and inlines the Edges field to the top level JSON.
|
||||
type EncodeExtension struct {
|
||||
entc.DefaultExtension
|
||||
}
|
||||
|
||||
// Templates of the extension.
|
||||
func (e *EncodeExtension) Templates() []*gen.Template {
|
||||
return []*gen.Template{
|
||||
gen.MustParse(gen.NewTemplate("model/additional/jsonencode").
|
||||
Parse(`
|
||||
{{ if $.Edges }}
|
||||
// MarshalJSON implements the json.Marshaler interface.
|
||||
func ({{ $.Receiver }} *{{ $.Name }}) MarshalJSON() ([]byte, error) {
|
||||
type Alias {{ $.Name }}
|
||||
return json.Marshal(&struct {
|
||||
*Alias
|
||||
{{ $.Name }}Edges
|
||||
}{
|
||||
Alias: (*Alias)({{ $.Receiver }}),
|
||||
{{ $.Name }}Edges: {{ $.Receiver }}.Edges,
|
||||
})
|
||||
}
|
||||
{{ end }}
|
||||
`)),
|
||||
}
|
||||
}
|
||||
|
||||
// Hooks of the extension.
|
||||
func (e *EncodeExtension) Hooks() []gen.Hook {
|
||||
return []gen.Hook{
|
||||
func(next gen.Generator) gen.Generator {
|
||||
return gen.GenerateFunc(func(g *gen.Graph) error {
|
||||
tag := edge.Annotation{StructTag: `json:"-"`}
|
||||
for _, n := range g.Nodes {
|
||||
n.Annotations.Set(tag.Name(), tag)
|
||||
}
|
||||
return next.Generate(g)
|
||||
})
|
||||
},
|
||||
}
|
||||
}
|
||||
```
|
||||
Reference in New Issue
Block a user