GORM/GEN

The code generator base on GORM, aims to be developer friendly.

Overview

  • CRUD or DIY query method code generation
  • Auto migration from database to code
  • Transactions, Nested Transactions, Save Point, RollbackTo to Saved Point
  • Competely compatible with GORM
  • Developer Friendly
  • Multiple Generate modes

Installation

To install Gen package, you need to install Go and set your Go workspace first.

1.The first need Go installed(version 1.14+ is required), then you can use the below Go command to install Gen.

go get -u gorm.io/gen

2.Import it in your code:

import "gorm.io/gen"

Quick start

Emphasis: All use cases in this doc are generated under WithContext mode. And if you generate code under WithoutContext mode, please remove WithContext(ctx) before you call any query method, it helps you make code more concise.

# assume the following code in generate.go file
$ cat generate.go
package main

import "gorm.io/gen"

// generate code
func main() {
    // specify the output directory (default: "./query")
    // ### if you want to query without context constrain, set mode gen.WithoutContext ###
    g := gen.NewGenerator(gen.Config{
        OutPath: "../dal/query",
        /* Mode: gen.WithoutContext,*/
    })
  
    // reuse the database connection in Project or create a connection here
    // if you want to use GenerateModel/GenerateModelAs, UseDB is necessray or it will panic
    // db, _ := gorm.Open(mysql.Open("root:@(127.0.0.1:3306)/demo?charset=utf8mb4&parseTime=True&loc=Local"))
    g.UseDB(db)
  
    // apply basic crud api on structs or table models which is specified by table name with function
    // GenerateModel/GenerateModelAs. And generator will generate table models' code when calling Excute.
    g.ApplyBasic(model.User{}, g.GenerateModel("company"), g.GenerateModelAs("people", "Person", gen.FieldIgnore("address")))
    
    // apply diy interfaces on structs or table models
    g.ApplyInterface(func(method model.Method) {}, model.User{}, g.GenerateModel("company"))

    // execute the action of code generation
    g.Execute()
}

Project Directory

Here is a template for best practices:

demo
├── cmd
│   └── generate
│       └── generate.go # execute it will generate codes
├── dal
│   ├── dal.go # create connections with database server here
│   ├── model
│   │   ├── method.go # DIY method interfaces
│   │   └── model.go  # store struct which corresponding to the database table
│   └── query  # generated code's directory
|       ├── user.gen.go # generated code for user
│       └── gen.go # generated code
├── biz
│   └── query.go # call function in dal/gorm_generated.go and query databases
├── config
│   └── config.go # DSN for database server
├── generate.sh # a shell to execute cmd/generate
├── go.mod
├── go.sum
└── main.go

API Examples

Generate

Generate Model

// generate a model struct map to table `people` in database
g.GenerateModel("people")

// generate a struct and specify struct's name
g.GenerateModelAs("people", "People")

// add option to ignore field
g.GenerateModel("people", gen.FieldIgnore("address"), gen.FieldType("id", "int64"))

Field Generate Options

FieldIgnore      // ignore field
FieldIgnoreReg   // ignore field (match with regexp)
FieldRename      // rename field in struct
FieldType        // specify field type
FieldTypeReg     // specify field type (match with regexp)
FieldTag         // specify gorm and json tag
FieldJSONTag     // specify json tag
FieldGORMTag     // specify gorm tag
FieldNewTag      // append new tag
FieldTrimPrefix  // trim column prefix
FieldTrimSuffix  // trim column suffix
FieldAddPrefix   // add prefix to struct member's name
FieldAddSuffix   // add suffix to struct member's name

Field Expression

Create Field

Actually, you're not supposed to create a new field variable, cause it will be accomplished in generated code.

Field Type Detail Type Crerate Function Supported Query Method
generic field NewField IsNull/IsNotNull/Count/Eq/Neq/Gt/Gte/Lt/Lte/Like
int int/int8/.../int64 NewInt/NewInt8/.../NewInt64 Eq/Neq/Gt/Gte/Lt/Lte/In/NotIn/Between/NotBetween/Like/NotLike/Add/Sub/Mul/Div/Mod/FloorDiv/RightShift/LeftShift/BitXor/BitAnd/BitOr/BitFlip
uint uint/uint8/.../uint64 NewUint/NewUint8/.../NewUint64 same with int
float float32/float64 NewFloat32/NewFloat64 Eq/Neq/Gt/Gte/Lt/Lte/In/NotIn/Between/NotBetween/Like/NotLike/Add/Sub/Mul/Div/FloorDiv
string string/[]byte NewString/NewBytes Eq/Neq/Gt/Gte/Lt/Lte/Between/NotBetween/In(val/NotIn(val/Like/NotLike/Regexp/NotRegxp
bool bool NewBool Not/Is/And/Or/Xor/BitXor/BitAnd/BitOr
time time.Time NewTime Eq/Neq/Gt/Gte/Lt/Lte/Between/NotBetween/In/NotIn/Add/Sub

Create field examples:

import "gorm.io/gen/field"

// create a new generic field map to `generic_a`
a := field.NewField("table_name", "generic_a")

// create a field map to `id`
i := field.NewInt("user", "id")

// create a field map to `address`
s := field.NewString("user", "address")

// create a field map to `create_time`
t := field.NewTime("user", "create_time")

CRUD API

Here is a basic struct user and struct DB.

// generated code
// generated code
// generated code
package query

import "gorm.io/gen"

// struct map to table `users` 
type user struct {
    gen.DO
    ID       field.Uint
    Name     field.String
    Age      field.Int
    Address  field.Field
    Birthday field.Time
}

// struct collection
type DB struct {
    db       *gorm.DB
    User     *user
}

Create

Create record
// u refer to query.user
user := model.User{Name: "Modi", Age: 18, Birthday: time.Now()}

u := query.Use(db).User
err := u.WithContext(ctx).Create(&user) // pass pointer of data to Create

err // returns error
Create record with selected fields

Create a record and assgin a value to the fields specified.

u := query.Use(db).User
u.WithContext(ctx).Select(u.Name, u.Age).Create(&user)
// INSERT INTO `users` (`name`,`age`) VALUES ("modi", 18)

Create a record and ignore the values for fields passed to omit

u := query.Use(db).User
u.WithContext(ctx).Omit(u.Name, u.Age).Create(&user)
// INSERT INTO `users` (`Address`, `Birthday`) VALUES ("2021-08-17 20:54:12.000", 18)
Batch Insert

To efficiently insert large number of records, pass a slice to the Create method. GORM will generate a single SQL statement to insert all the data and backfill primary key values.

var users = []model.User{{Name: "modi"}, {Name: "zhangqiang"}, {Name: "songyuan"}}
query.Use(db).User.WithContext(ctx).Create(&users)

for _, user := range users {
    user.ID // 1,2,3
}

You can specify batch size when creating with CreateInBatches, e.g:

var users = []User{{Name: "modi_1"}, ...., {Name: "modi_10000"}}

// batch size 100
query.Use(db).User.WithContext(ctx).CreateInBatches(users, 100)

It will works if you set CreateBatchSize in gorm.Config / gorm.Session

db, err := gorm.Open(sqlite.Open("gorm.db"), &gorm.Config{
    CreateBatchSize: 1000,
})
// OR
db = db.Session(&gorm.Session{CreateBatchSize: 1000})

u := query.NewUser(db)

var users = []User{{Name: "modi_1"}, ...., {Name: "modi_5000"}}

u.WithContext(ctx).Create(&users)
// INSERT INTO users xxx (5 batches)

Query

Retrieving a single object

Generated code provides First, Take, Last methods to retrieve a single object from the database, it adds LIMIT 1 condition when querying the database, and it will return the error ErrRecordNotFound if no record is found.

u := query.Use(db).User

// Get the first record ordered by primary key
user, err := u.WithContext(ctx).First()
// SELECT * FROM users ORDER BY id LIMIT 1;

// Get one record, no specified order
user, err := u.WithContext(ctx).Take()
// SELECT * FROM users LIMIT 1;

// Get last record, ordered by primary key desc
user, err := u.WithContext(ctx).Last()
// SELECT * FROM users ORDER BY id DESC LIMIT 1;

// check error ErrRecordNotFound
errors.Is(err, gorm.ErrRecordNotFound)
Retrieving objects with primary key
u := query.Use(db).User

user, err := u.WithContext(ctx).Where(u.ID.Eq(10)).First()
// SELECT * FROM users WHERE id = 10;

users, err := u.WithContext(ctx).Where(u.ID.In(1,2,3)).Find()
// SELECT * FROM users WHERE id IN (1,2,3);

If the primary key is a string (for example, like a uuid), the query will be written as follows:

user, err := u.WithContext(ctx).Where(u.ID.Eq("1b74413f-f3b8-409f-ac47-e8c062e3472a")).First()
// SELECT * FROM users WHERE id = "1b74413f-f3b8-409f-ac47-e8c062e3472a";
Retrieving all objects
u := query.Use(db).User

// Get all records
users, err := u.WithContext(ctx).Find()
// SELECT * FROM users;
Conditions
String Conditions
u := query.Use(db).User

// Get first matched record
user, err := u.WithContext(ctx).Where(u.Name.Eq("modi")).First()
// SELECT * FROM users WHERE name = 'modi' ORDER BY id LIMIT 1;

// Get all matched records
users, err := u.WithContext(ctx).Where(u.Name.Neq("modi")).Find()
// SELECT * FROM users WHERE name <> 'modi';

// IN
users, err := u.WithContext(ctx).Where(u.Name.In("modi", "zhangqiang")).Find()
// SELECT * FROM users WHERE name IN ('modi','zhangqiang');

// LIKE
users, err := u.WithContext(ctx).Where(u.Name.Like("%modi%")).Find()
// SELECT * FROM users WHERE name LIKE '%modi%';

// AND
users, err := u.WithContext(ctx).Where(u.Name.Eq("modi"), u.Age.Gte(17)).Find()
// SELECT * FROM users WHERE name = 'modi' AND age >= 17;

// Time
users, err := u.WithContext(ctx).Where(u.Birthday.Gt(birthTime).Find()
// SELECT * FROM users WHERE birthday > '2000-01-01 00:00:00';

// BETWEEN
users, err := u.WithContext(ctx).Where(u.Birthday.Between(lastWeek, today)).Find()
// SELECT * FROM users WHERE birthday BETWEEN '2000-01-01 00:00:00' AND '2000-01-08 00:00:00';
Inline Condition
u := query.Use(db).User

// Get by primary key if it were a non-integer type
user, err := u.WithContext(ctx).Where(u.ID.Eq("string_primary_key")).First()
// SELECT * FROM users WHERE id = 'string_primary_key';

// Plain SQL
users, err := u.WithContext(ctx).Where(u.Name.Eq("modi")).Find()
// SELECT * FROM users WHERE name = "modi";

users, err := u.WithContext(ctx).Where(u.Name.Neq("modi"), u.Age.Gt(17)).Find()
// SELECT * FROM users WHERE name <> "modi" AND age > 17;
Not Conditions

Build NOT conditions, works similar to Where

u := query.Use(db).User

user, err := u.WithContext(ctx).Not(u.Name.Eq("modi")).First()
// SELECT * FROM users WHERE NOT name = "modi" ORDER BY id LIMIT 1;

// Not In
users, err := u.WithContext(ctx).Not(u.Name.In("modi", "zhangqiang")).Find()
// SELECT * FROM users WHERE name NOT IN ("modi", "zhangqiang");

// Not In slice of primary keys
user, err := u.WithContext(ctx).Not(u.ID.In(1,2,3)).First()
// SELECT * FROM users WHERE id NOT IN (1,2,3) ORDER BY id LIMIT 1;
Or Conditions
u := query.Use(db).User

users, err := u.WithContext(ctx).Where(u.Role.Eq("admin")).Or(u.Role.Eq("super_admin")).Find()
// SELECT * FROM users WHERE role = 'admin' OR role = 'super_admin';
Group Conditions

Easier to write complicated SQL query with Group Conditions

p := query.Use(db).Pizza

pizzas, err := p.WithContext(ctx).Where(
    p.WithContext(ctx).Where(p.Pizza.Eq("pepperoni")).
        Where(p.Where(p.Size.Eq("small")).Or(p.Size.Eq("medium"))),
).Or(
    p.WithContext(ctx).Where(p.Pizza.Eq("hawaiian")).Where(p.Size.Eq("xlarge")),
).Find()

// SELECT * FROM `pizzas` WHERE (pizza = "pepperoni" AND (size = "small" OR size = "medium")) OR (pizza = "hawaiian" AND size = "xlarge")
Selecting Specific Fields

Select allows you to specify the fields that you want to retrieve from database. Otherwise, GORM will select all fields by default.

u := query.Use(db).User

users, err := u.WithContext(ctx).Select(u.Name, u.Age).Find()
// SELECT name, age FROM users;

u.WithContext(ctx).Select(u.Age.Avg()).Rows()
// SELECT Avg(age) FROM users;
Tuple Query
u := query.Use(db).User

users, err := u.WithContext(ctx).Where(u.Columns(u.ID, u.Name).In(field.Values([][]inferface{}{{1, "modi"}, {2, "zhangqiang"}}))).Find()
// SELECT * FROM `users` WHERE (`id`, `name`) IN ((1,'humodi'),(2,'tom'));
JSON Query
u := query.Use(db).User

users, err := u.WithContext(ctx).Where(gen.Cond(datatypes.JSONQuery("attributes").HasKey("role"))...).Find()
// SELECT * FROM `users` WHERE JSON_EXTRACT(`attributes`,'$.role') IS NOT NULL;
Order

Specify order when retrieving records from the database

u := query.Use(db).User

users, err := u.WithContext(ctx).Order(u.Age.Desc(), u.Name).Find()
// SELECT * FROM users ORDER BY age DESC, name;

// Multiple orders
users, err := u.WithContext(ctx).Order(u.Age.Desc()).Order(u.Name).Find()
// SELECT * FROM users ORDER BY age DESC, name;
Limit & Offset

Limit specify the max number of records to retrieve
Offset specify the number of records to skip before starting to return the records

u := query.Use(db).User

urers, err := u.WithContext(ctx).Limit(3).Find()
// SELECT * FROM users LIMIT 3;

// Cancel limit condition with -1
users, err := u.WithContext(ctx).Limit(10).Limit(-1).Find()
// SELECT * FROM users;

users, err := u.WithContext(ctx).Offset(3).Find()
// SELECT * FROM users OFFSET 3;

users, err := u.WithContext(ctx).Limit(10).Offset(5).Find()
// SELECT * FROM users OFFSET 5 LIMIT 10;

// Cancel offset condition with -1
users, err := u.WithContext(ctx).Offset(10).Offset(-1).Find()
// SELECT * FROM users;
Group By & Having
u := query.Use(db).User

type Result struct {
    Date  time.Time
    Total int
}

var result Result

err := u.WithContext(ctx).Select(u.Name, u.Age.Sum().As("total")).Where(u.Name.Like("%modi%")).Group(u.Name).Scan(&result)
// SELECT name, sum(age) as total FROM `users` WHERE name LIKE "%modi%" GROUP BY `name`

err := u.WithContext(ctx).Select(u.Name, u.Age.Sum().As("total")).Group(u.Name).Having(u.Name.Eq("group")).Scan(&result)
// SELECT name, sum(age) as total FROM `users` GROUP BY `name` HAVING name = "group"

rows, err := u.WithContext(ctx).Select(u.Birthday.As("date"), u.Age.Sum().As("total")).Group(u.Birthday).Rows()
for rows.Next() {
  ...
}

o := query.Use(db).Order

rows, err := o.WithContext(ctx).Select(o.CreateAt.Date().As("date"), o.Amount.Sum().As("total")).Group(o.CreateAt.Date()).Having(u.Amount.Sum().Gt(100)).Rows()
for rows.Next() {
  ...
}

var results []Result

o.WithContext(ctx).Select(o.CreateAt.Date().As("date"), o.WithContext(ctx).Amount.Sum().As("total")).Group(o.CreateAt.Date()).Having(u.Amount.Sum().Gt(100)).Scan(&results)
Distinct

Selecting distinct values from the model

u := query.Use(db).User

users, err := u.WithContext(ctx).Distinct(u.Name, u.Age).Order(u.Name, u.Age.Desc()).Find()

Distinct works with Pluck and Count too

Joins

Specify Joins conditions

u := query.Use(db).User
e := query.Use(db).Email
c := query.Use(db).CreditCard

type Result struct {
    Name  string
    Email string
}

var result Result

err := u.WithContext(ctx).Select(u.Name, e.Email).LeftJoin(e, e.UserID.EqCol(u.ID)).Scan(&result)
// SELECT users.name, emails.email FROM `users` left join emails on emails.user_id = users.id

rows, err := u.WithContext(ctx).Select(u.Name, e.Email).LeftJoin(e, e.UserID.EqCol(u.ID)).Rows()
for rows.Next() {
  ...
}

var results []Result

err := u.WithContext(ctx).Select(u.Name, e.Email).LeftJoin(e, e.UserID.EqCol(u.ID)).Scan(&results)

// multiple joins with parameter
users := u.WithContext(ctx).Join(e, e.UserID.EqCol(u.id), e.Email.Eq("[email protected]")).Join(c, c.UserID.EqCol(u.ID)).Where(c.Number.Eq("411111111111")).Find()
SubQuery

A subquery can be nested within a query, GEN can generate subquery when using a Dao object as param

o := query.Use(db).Order
u := query.Use(db).User

orders, err := o.WithContext(ctx).Where(u.Columns(o.Amount).Gt(o.Select(u.Amount.Avg())).Find()
// SELECT * FROM "orders" WHERE amount > (SELECT AVG(amount) FROM "orders");

subQuery := u.WithContext(ctx).Select(u.Age.Avg()).Where(u.Name.Like("name%"))
users, err := u.WithContext(ctx).Select(u.Age.Avg().As("avgage")).Group(u.Name).Having(u.Columns(u.Age.Avg()).Gt(subQuery).Find()
// SELECT AVG(age) as avgage FROM `users` GROUP BY `name` HAVING AVG(age) > (SELECT AVG(age) FROM `users` WHERE name LIKE "name%")
From SubQuery

GORM allows you using subquery in FROM clause with method Table, for example:

u := query.Use(db).User
p := query.Use(db).Pet

users, err := gen.Table(u.WithContext(ctx).Select(u.Name, u.Age).As("u")).Where(u.Age.Eq(18)).Find()
// SELECT * FROM (SELECT `name`,`age` FROM `users`) as u WHERE `age` = 18

subQuery1 := u.WithContext(ctx).Select(u.Name)
subQuery2 := p.WithContext(ctx).Select(p.Name)
users, err := gen.Table(subQuery1.As("u"), subQuery2.As("p")).Find()
db.Table("(?) as u, (?) as p", subQuery1, subQuery2).Find(&User{})
// SELECT * FROM (SELECT `name` FROM `users`) as u, (SELECT `name` FROM `pets`) as p
Update from SubQuery

Update a table by using SubQuery

u := query.Use(db).User
c := query.Use(db).Company

u.WithContext(ctx).Update(u.CompanyName, c.Select(c.Name).Where(c.ID.EqCol(u.CompanyID)))
// UPDATE "users" SET "company_name" = (SELECT name FROM companies WHERE companies.id = users.company_id);

u.WithContext(ctx).Where(u.Name.Eq("modi")).Update(u.CompanyName, c.Select(c.Name).Where(c.ID.EqCol(u.CompanyID)))
Advanced Query
Iteration

GEN supports iterating through Rows

u := query.Use(db).User
do := u.WithContext(ctx)
rows, err := do.Where(u.Name.Eq("modi")).Rows()
defer rows.Close()

for rows.Next() {
    var user User
    // ScanRows is a method of `gorm.DB`, it can be used to scan a row into a struct
    do.ScanRows(rows, &user)

    // do something
}
FindInBatches

Query and process records in batch

u := query.Use(db).User

// batch size 100
err := u.WithContext(ctx).Where(u.ID.Gt(9)).FindInBatches(&results, 100, func(tx gen.Dao, batch int) error {
    for _, result := range results {
      // batch processing found records
    }
  
    // build a new `u` to use it's api
    // queryUsery := query.NewUser(tx.UnderlyingDB())

    tx.Save(&results)

    batch // Batch 1, 2, 3

    // returns error will stop future batches
    return nil
})
Pluck

Query single column from database and scan into a slice, if you want to query multiple columns, use Select with Scan instead

u := query.Use(db).User

var ages []int64
u.WithContext(ctx).Pluck(u.Age, &ages)

var names []string
u.WithContext(ctx).Pluck(u.Name, &names)

// Distinct Pluck
u.WithContext(ctx).Distinct().Pluck(u.Name, &names)
// SELECT DISTINCT `name` FROM `users`

// Requesting more than one column, use `Scan` or `Find` like this:
db.WithContext(ctx).Select(u.Name, u.Age).Scan(&users)
users, err := db.Select(u.Name, u.Age).Find()
Scopes

Scopes allows you to specify commonly-used queries which can be referenced as method calls

o := query.Use(db).Order

func AmountGreaterThan1000(tx gen.Dao) gen.Dao {
    return tx.Where(o.Amount.Gt(1000))
}

func PaidWithCreditCard(tx gen.Dao) gen.Dao {
    return tx.Where(o.PayModeSign.Eq("C"))
}

func PaidWithCod(tx gen.Dao) gen.Dao {
    return tx.Where(o.PayModeSign.Eq("C"))
}

func OrderStatus(status []string) func (tx gen.Dao) gen.Dao {
    return func (tx gen.Dao) gen.Dao {
      return tx.Where(o.Status.In(status...))
    }
}

orders, err := o.WithContext(ctx).Scopes(AmountGreaterThan1000, PaidWithCreditCard).Find()
// Find all credit card orders and amount greater than 1000

orders, err := o.WithContext(ctx).Scopes(AmountGreaterThan1000, PaidWithCod).Find()
// Find all COD orders and amount greater than 1000

orders, err := o.WithContext(ctx).Scopes(AmountGreaterThan1000, OrderStatus([]string{"paid", "shipped"})).Find()
// Find all paid, shipped orders that amount greater than 1000
Count

Get matched records count

u := query.Use(db).User

count, err := u.WithContext(ctx).Where(u.Name.Eq("modi")).Or(u.Name.Eq("zhangqiang")).Count()
// SELECT count(1) FROM users WHERE name = 'modi' OR name = 'zhangqiang'

count, err := u.WithContext(ctx).Where(u.Name.Eq("modi")).Count()
// SELECT count(1) FROM users WHERE name = 'modi'; (count)

// Count with Distinct
u.WithContext(ctx).Distinct(u.Name).Count()
// SELECT COUNT(DISTINCT(`name`)) FROM `users`

Update

Update single column

When updating a single column with Update, it needs to have any conditions or it will raise error ErrMissingWhereClause, for example:

u := query.Use(db).User

// Update with conditions
u.WithContext(ctx).Where(u.Activate.Is(true)).Update(u.Name, "hello")
// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE active=true;

// Update with conditions
u.WithContext(ctx).Where(u.Activate.Is(true)).Update(u.Age, u.Age.Add(1))
// or
u.WithContext(ctx).Where(u.Activate.Is(true)).UpdateSimple(u.Age.Add(1))
// UPDATE users SET age=age+1, updated_at='2013-11-17 21:34:10' WHERE active=true;
Updates multiple columns

Updates supports update with struct or map[string]interface{}, when updating with struct it will only update non-zero fields by default

u := query.Use(db).User

// Update attributes with `map`
u.WithContext(ctx).Where(u.ID.Eq(111)).Updates(map[string]interface{}{"name": "hello", "age": 18, "active": false})
// UPDATE users SET name='hello', age=18, active=false, updated_at='2013-11-17 21:34:10' WHERE id=111;

// Update attributes with `struct`
u.WithContext(ctx).Where(u.ID.Eq(111)).Updates(model.User{Name: "hello", Age: 18, Active: false})
// UPDATE users SET name='hello', age=18, active=false, updated_at='2013-11-17 21:34:10' WHERE id=111;

// Update with expression
u.WithContext(ctx).Where(u.ID.Eq(111)).UpdateSimple(u.Age.Add(1), u.Number.Add(1))
// UPDATE users SET age=age+1,number=number+1 updated_at='2013-11-17 21:34:10' WHERE id=111;

NOTE When update with struct, GEN will only update non-zero fields, you might want to use map to update attributes or use Select to specify fields to update

Update selected fields

Wait for GORM update to compatible with GEN

If you want to update selected fields or ignore some fields when updating, you can use Select, Omit

u := query.Use(db).User

// Select with Map
// User's ID is `111`:
u.WithContext(ctx).Select(u.Name).Where(u.ID.Eq(111)).Updates(map[string]interface{}{"name": "hello", "age": 18, "active": false})
// UPDATE users SET name='hello' WHERE id=111;

u.WithContext(ctx).Omit(u.Name).Where(u.ID.Eq(111)).Updates(map[string]interface{}{"name": "hello", "age": 18, "active": false})
// UPDATE users SET age=18, active=false, updated_at='2013-11-17 21:34:10' WHERE id=111;

result, err := u.WithContext(ctx).Where(u.ID.Eq(111)).Updates(map[string]interface{}{"name": "hello", "age": 18, "active": false})

result.RowsAffected // affect rows number
err                 // error

Delete

Delete record
e := query.Use(db).Email

// Email's ID is `10`
e.WithContext(ctx).Where(e.ID.Eq(10)).Delete()
// DELETE from emails where id = 10;

// Delete with additional conditions
e.WithContext(ctx).Where(e.ID.Eq(10), e.Name.Eq("modi")).Delete()
// DELETE from emails where id = 10 AND name = "modi";

result, err := e.WithContext(ctx).Where(e.ID.Eq(10), e.Name.Eq("modi")).Delete()

result.RowsAffected // affect rows number
err                 // error
Delete with primary key

GEN allows to delete objects using primary key(s) with inline condition, it works with numbers.

u.WithContext(ctx).Where(u.ID.In(1,2,3)).Delete()
// DELETE FROM users WHERE id IN (1,2,3);
Batch Delete

The specified value has no primary value, GEN will perform a batch delete, it will delete all matched records

e := query.Use(db).Email

e.WithContext(ctx).Where(e.Name.Like("%modi%")).Delete()
// DELETE from emails where email LIKE "%modi%";
Soft Delete

If your model includes a gorm.DeletedAt field (which is included in gorm.Model), it will get soft delete ability automatically!

When calling Delete, the record WON’T be removed from the database, but GORM will set the DeletedAt‘s value to the current time, and the data is not findable with normal Query methods anymore.

// Batch Delete
u.WithContext(ctx).Where(u.Age.Eq(20)).Delete()
// UPDATE users SET deleted_at="2013-10-29 10:23" WHERE age = 20;

// Soft deleted records will be ignored when querying
users, err := u.WithContext(ctx).Where(u.Age.Eq(20)).Find()
// SELECT * FROM users WHERE age = 20 AND deleted_at IS NULL;

If you don’t want to include gorm.Model, you can enable the soft delete feature like:

type User struct {
    ID      int
    Deleted gorm.DeletedAt
    Name    string
}
Find soft deleted records

You can find soft deleted records with Unscoped

users, err := db.WithContext(ctx).Unscoped().Where(u.Age.Eq(20)).Find()
// SELECT * FROM users WHERE age = 20;
Delete permanently

You can delete matched records permanently with Unscoped

o.WithContext(ctx).Unscoped().Where(o.ID.Eq(10)).Delete()
// DELETE FROM orders WHERE id=10;

DIY method

Method interface

Method interface is an abstraction of query methods, all functions it contains are query methods and above comments describe the specific query conditions or logic.
SQL supports simple where query or execute raw SQL. Simple query conditions wrapped by where(), and raw SQL wrapped by sql()(not required)

type Method interface {
    // where("[email protected] and [email protected]")
    SimpleFindByNameAndAge(name string, age int) (gen.T, error)
    
    // sql(select * from users where [email protected])
    FindUserToMap(id int) (gen.M, error)
    
    // insert into users (name,age) values (@name,@age)
    InsertValue(age int, name string) error
}

Return values must contains less than 1 gen.T/gen.M and less than 1 error. You can also use bulitin type (like string/ int) as the return parameter,gen.T represents return a single result struct's pointer, []gen.T represents return an array of result structs' pointer,

Syntax of template
placeholder
  • gen.T represents specified struct or table
  • gen.M represents map[string]interface
  • @@table represents table's name (if method's parameter doesn't contains variable table, GEN will generate table from model struct)
  • @@<columnName> represents column's name or table's name
  • @<name> represents normal query variable
template

Logical operations must be wrapped in {{}},and end must used {{end}}, All templates support nesting

  • if/else if/else the condition accept a bool parameter or operation expression which conforms to Golang syntax.
  • where The where clause will be inserted only if the child elements return something. The key word and or or in front of clause will be removed. And and will be added automatically when there is no junction keyword between query condition clause.
  • Set The set clause will be inserted only if the child elements return something. The , in front of columns array will be removed.And , will be added automatically when there is no junction keyword between query coulmns.
  • ... Coming soon
If clause
{{if cond1}}
    // do something here
{{else if cond2}}
    // do something here
{{else}}
    // do something here
{{end}}

Use case in raw SQL:

// select * from users where {{if name !=""}} [email protected]{{end}}
methond(name string) (gen.T,error) 

Use case in raw SQL template:

select * from @@table where
{{if age>60}}
    status="older"
{{else if age>30}}
    status="middle-ager"
{{else if age>18}}
    status="younger"
{{else}}
    {{if sex=="male"}}
        status="boys"
    {{else}}
        status="girls"
    {{end}}
{{end}}
Where clause
{{where}}
    // do something here
{{end}}

Use case in raw SQL

// select * from {{where}}[email protected]{{end}}
methond(id int) error

Use case in raw SQL template

select * from @@table 
{{where}}
    {{if cond}}[email protected] {{end}}
    {{if name != ""}}@@[email protected]{{end}}
{{end}}
Set clause
{{set}}
    // sepecify update expression here
{{end}}

Use case in raw SQL

// update users {{set}}[email protected]{{end}}
methond() error

Use case in raw SQL template

update @@table 
{{set}}
    {{if name!=""}} [email protected] {{end}}
    {{if age>0}} [email protected] {{end}}
{{end}}
where [email protected]
Method interface example
type Method interface {
    // Where("[email protected] and [email protected]")
    SimpleFindByNameAndAge(name string, age int) (gen.T, error)
    
    // select * from users where [email protected]
    FindUserToMap(id int) (gen.M, error)
    
    // sql(insert into @@table (name,age) values (@name,@age) )
    InsertValue(age int, name string) error
    
    // select name from @@table where [email protected]
    FindNameByID(id int) string
    
    // select * from @@table
    //  {{where}}
    //      id>0
    //      {{if cond}}[email protected] {{end}}
    //      {{if key!="" && value != ""}} or @@[email protected]{{end}}
    //  {{end}}
    FindByIDOrCustom(cond bool, id int, key, value string) ([]gen.T, error)
    
    // update @@table
    //  {{set}}
    //      update_time=now()
    //      {{if name != ""}}
    //          [email protected]
    //      {{end}}
    //  {{end}}
    //  {{where}}
    //      [email protected]
    //  {{end}}
    UpdateName(name string, id int) error
}

Smart select fields

GEN allows select specific fields with Select, if you often use this in your application, maybe you want to define a smaller struct for API usage which can select specific fields automatically, for example:

type User struct {
  ID     uint
  Name   string
  Age    int
  Gender string
  // hundreds of fields
}

type APIUser struct {
  ID   uint
  Name string
}

type Method interface{
    // select * from user
    FindSome() ([]APIUser, error)
}

apiusers, err := u.WithContext(ctx).Limit(10).FindSome()
// SELECT `id`, `name` FROM `users` LIMIT 10

Advanced Topics

Hints

Optimizer hints allow to control the query optimizer to choose a certain query execution plan, GORM supports it with gorm.io/hints, e.g:

import "gorm.io/hints"

u := query.Use(db).User

users, err := u.WithContext(ctx).Clauses(hints.New("MAX_EXECUTION_TIME(10000)")).Find()
// SELECT * /*+ MAX_EXECUTION_TIME(10000) */ FROM `users`

Index hints allow passing index hints to the database in case the query planner gets confused.

import "gorm.io/hints"

u := query.Use(db).User

users, err := u.WithContext(ctx).Clauses(hints.UseIndex("idx_user_name")).Find()
// SELECT * FROM `users` USE INDEX (`idx_user_name`)

users, err := u.WithContext(ctx).Clauses(hints.ForceIndex("idx_user_name", "idx_user_id").ForJoin()).Find()
// SELECT * FROM `users` FORCE INDEX FOR JOIN (`idx_user_name`,`idx_user_id`)"

Maintainers

@riverchu @idersec @qqxhb

@jinzhu

Contributing

You can help to deliver a better GORM/GEN

GitHub

https://github.com/go-gorm/gen