Session

GORM provides Session method, which is a New Session Method, it allows to create a new session mode with configuration:


type Session struct {
  DryRun                   bool
  PrepareStmt              bool
  NewDB                    bool
  Initialized              bool
  SkipHooks                bool
  SkipDefaultTransaction   bool
  DisableNestedTransaction bool
  AllowGlobalUpdate        bool
  FullSaveAssociations     bool
  QueryFields              bool
  Context                  context.Context
  Logger                   logger.Interface
  NowFunc                  func() time.Time
  CreateBatchSize          int
}

DryRun

Generates SQL without executing. It can be used to prepare or test generated SQL, for example:


stmt := db.Session(&Session{DryRun: true}).First(&user, 1).Statement
stmt.SQL.String() 
stmt.Vars         


db, err := gorm.Open(sqlite.Open("gorm.db"), &gorm.Config{DryRun: true})


stmt := db.Find(&user, 1).Statement
stmt.SQL.String() 
stmt.SQL.String() 
stmt.Vars

To generate the final SQL, you could use following code:


db.Dialector.Explain(stmt.SQL.String(), stmt.Vars...)

PrepareStmt

PreparedStmt creates prepared statements when executing any SQL and caches them to speed up future calls, for example:


db, err := gorm.Open(sqlite.Open("gorm.db"), &gorm.Config{
  PrepareStmt: true,
})


tx := db.Session(&Session{PrepareStmt: true})
tx.First(&user, 1)
tx.Find(&users)
tx.Model(&user).Update("Age", 18)


stmtManger, ok := tx.ConnPool.(*PreparedStmtDB)


stmtManger.Close()


stmtManger.PreparedSQL 


stmtManger.Stmts 

for sql, stmt := range stmtManger.Stmts {
  sql  
  stmt 
  stmt.Close() 
}

NewDB

Create a new DB without conditions with option NewDB, for example:

tx := db.Where("name = ?", "jinzhu").Session(&gorm.Session{NewDB: true})

tx.First(&user)


tx.First(&user, "id = ?", 10)



tx2 := db.Where("name = ?", "jinzhu").Session(&gorm.Session{})
tx2.First(&user)

Initialized

Create a new initialized DB, which is not Method Chain/Goroutine Safe anymore, refer Method Chaining

tx := db.Session(&gorm.Session{Initialized: true})

Skip Hooks

If you want to skip Hooks methods, you can use the SkipHooks session mode, for example:

DB.Session(&gorm.Session{SkipHooks: true}).Create(&user)

DB.Session(&gorm.Session{SkipHooks: true}).Create(&users)

DB.Session(&gorm.Session{SkipHooks: true}).CreateInBatches(users, 100)

DB.Session(&gorm.Session{SkipHooks: true}).Find(&user)

DB.Session(&gorm.Session{SkipHooks: true}).Delete(&user)

DB.Session(&gorm.Session{SkipHooks: true}).Model(User{}).Where("age > ?", 18).Updates(&user)

DisableNestedTransaction

When using Transaction method inside a DB transaction, GORM will use SavePoint(savedPointName), RollbackTo(savedPointName) to give you the nested transaction support. You can disable it by using the DisableNestedTransaction option, for example:

db.Session(&gorm.Session{
  DisableNestedTransaction: true,
}).CreateInBatches(&users, 100)

AllowGlobalUpdate

GORM doesn’t allow global update/delete by default, will return ErrMissingWhereClause error. You can set this option to true to enable it, for example:

db.Session(&gorm.Session{
  AllowGlobalUpdate: true,
}).Model(&User{}).Update("name", "jinzhu")

FullSaveAssociations

GORM will auto-save associations and its reference using Upsert when creating/updating a record. If you want to update associations’ data, you should use the FullSaveAssociations mode, for example:

db.Session(&gorm.Session{FullSaveAssociations: true}).Updates(&user)

Context

With the Context option, you can set the Context for following SQL operations, for example:

timeoutCtx, _ := context.WithTimeout(context.Background(), time.Second)
tx := db.Session(&Session{Context: timeoutCtx})

tx.First(&user) 
tx.Model(&user).Update("role", "admin")

GORM also provides shortcut method WithContext, here is the definition:

func (db *DB) WithContext(ctx context.Context) *DB {
  return db.Session(&Session{Context: ctx})
}

Logger

Gorm allows customizing built-in logger with the Logger option, for example:

newLogger := logger.New(log.New(os.Stdout, "\r\n", log.LstdFlags),
              logger.Config{
                SlowThreshold: time.Second,
                LogLevel:      logger.Silent,
                Colorful:      false,
              })
db.Session(&Session{Logger: newLogger})

db.Session(&Session{Logger: logger.Default.LogMode(logger.Silent)})

Checkout Logger for more details.

NowFunc

NowFunc allows changing the function to get current time of GORM, for example:

db.Session(&Session{
  NowFunc: func() time.Time {
    return time.Now().Local()
  },
})

Debug

Debug is a shortcut method to change session’s Logger to debug mode, here is the definition:

func (db *DB) Debug() (tx *DB) {
  return db.Session(&Session{
    Logger:         db.Logger.LogMode(logger.Info),
  })
}

QueryFields

Select by fields

db.Session(&gorm.Session{QueryFields: true}).Find(&user)

CreateBatchSize

Default batch size

users = [5000]User{{Name: "jinzhu", Pets: []Pet{pet1, pet2, pet3}}...}

db.Session(&gorm.Session{CreateBatchSize: 1000}).Create(&users)