diff --git a/callbacks.go b/callbacks.go
index a9a6dd85..4f700081 100644
--- a/callbacks.go
+++ b/callbacks.go
@@ -105,8 +105,11 @@ func (p *processor) Execute(db *DB) {
 			return db.Dialector.Explain(stmt.SQL.String(), stmt.Vars...), db.RowsAffected
 		}, db.Error)
 
-		stmt.reinit()
-		// db.Config.statementPool.Put(stmt)
+		if !stmt.DB.DryRun {
+			stmt.SQL.Reset()
+			stmt.Vars = nil
+			stmt.NamedVars = nil
+		}
 	}
 }
 
diff --git a/callbacks/callmethod.go b/callbacks/callmethod.go
new file mode 100644
index 00000000..a0e9b0e7
--- /dev/null
+++ b/callbacks/callmethod.go
@@ -0,0 +1,21 @@
+package callbacks
+
+import (
+	"reflect"
+
+	"gorm.io/gorm"
+)
+
+func callMethod(db *gorm.DB, fc func(value interface{}, tx *gorm.DB) bool) {
+	tx := db.Session(&gorm.Session{})
+	if called := fc(db.Statement.Dest, tx); !called {
+		switch db.Statement.ReflectValue.Kind() {
+		case reflect.Slice, reflect.Array:
+			for i := 0; i < db.Statement.ReflectValue.Len(); i++ {
+				fc(db.Statement.ReflectValue.Index(i).Addr().Interface(), tx)
+			}
+		case reflect.Struct:
+			fc(db.Statement.ReflectValue.Addr().Interface(), tx)
+		}
+	}
+}
diff --git a/callbacks/create.go b/callbacks/create.go
index 99140612..ec4ee1d1 100644
--- a/callbacks/create.go
+++ b/callbacks/create.go
@@ -10,9 +10,7 @@ import (
 
 func BeforeCreate(db *gorm.DB) {
 	if db.Error == nil && db.Statement.Schema != nil && (db.Statement.Schema.BeforeSave || db.Statement.Schema.BeforeCreate) {
-		tx := db.Session(&gorm.Session{})
-		callMethod := func(value interface{}) bool {
-			var called bool
+		callMethod(db, func(value interface{}, tx *gorm.DB) (called bool) {
 			if db.Statement.Schema.BeforeSave {
 				if i, ok := value.(gorm.BeforeSaveInterface); ok {
 					called = true
@@ -27,18 +25,7 @@ func BeforeCreate(db *gorm.DB) {
 				}
 			}
 			return called
-		}
-
-		if ok := callMethod(db.Statement.Dest); !ok {
-			switch db.Statement.ReflectValue.Kind() {
-			case reflect.Slice, reflect.Array:
-				for i := 0; i < db.Statement.ReflectValue.Len(); i++ {
-					callMethod(db.Statement.ReflectValue.Index(i).Addr().Interface())
-				}
-			case reflect.Struct:
-				callMethod(db.Statement.ReflectValue.Addr().Interface())
-			}
-		}
+		})
 	}
 }
 
@@ -67,28 +54,26 @@ func Create(config *Config) func(db *gorm.DB) {
 					result, err := db.Statement.ConnPool.ExecContext(db.Statement.Context, db.Statement.SQL.String(), db.Statement.Vars...)
 
 					if err == nil {
-						if db.Statement.Schema != nil && db.Statement.Schema.PrioritizedPrimaryField != nil {
-							if _, ok := db.Statement.Schema.FieldsWithDefaultDBValue[db.Statement.Schema.PrioritizedPrimaryField.DBName]; ok {
-								if insertID, err := result.LastInsertId(); err == nil {
-									switch db.Statement.ReflectValue.Kind() {
-									case reflect.Slice, reflect.Array:
-										if config.LastInsertIDReversed {
-											for i := db.Statement.ReflectValue.Len() - 1; i >= 0; i-- {
-												db.Statement.Schema.PrioritizedPrimaryField.Set(db.Statement.ReflectValue.Index(i), insertID)
-												insertID--
-											}
-										} else {
-											for i := 0; i < db.Statement.ReflectValue.Len(); i++ {
-												db.Statement.Schema.PrioritizedPrimaryField.Set(db.Statement.ReflectValue.Index(i), insertID)
-												insertID++
-											}
+						if db.Statement.Schema != nil && db.Statement.Schema.PrioritizedPrimaryField != nil && db.Statement.Schema.PrioritizedPrimaryField.HasDefaultValue {
+							if insertID, err := result.LastInsertId(); err == nil {
+								switch db.Statement.ReflectValue.Kind() {
+								case reflect.Slice, reflect.Array:
+									if config.LastInsertIDReversed {
+										for i := db.Statement.ReflectValue.Len() - 1; i >= 0; i-- {
+											db.Statement.Schema.PrioritizedPrimaryField.Set(db.Statement.ReflectValue.Index(i), insertID)
+											insertID--
+										}
+									} else {
+										for i := 0; i < db.Statement.ReflectValue.Len(); i++ {
+											db.Statement.Schema.PrioritizedPrimaryField.Set(db.Statement.ReflectValue.Index(i), insertID)
+											insertID++
 										}
-									case reflect.Struct:
-										db.Statement.Schema.PrioritizedPrimaryField.Set(db.Statement.ReflectValue, insertID)
 									}
-								} else {
-									db.AddError(err)
+								case reflect.Struct:
+									db.Statement.Schema.PrioritizedPrimaryField.Set(db.Statement.ReflectValue, insertID)
 								}
+							} else {
+								db.AddError(err)
 							}
 						}
 						db.RowsAffected, _ = result.RowsAffected()
@@ -122,19 +107,17 @@ func CreateWithReturning(db *gorm.DB) {
 			db.Statement.WriteString(" RETURNING ")
 
 			var (
-				idx    int
 				fields = make([]*schema.Field, len(sch.FieldsWithDefaultDBValue))
 				values = make([]interface{}, len(sch.FieldsWithDefaultDBValue))
 			)
 
-			for dbName, field := range sch.FieldsWithDefaultDBValue {
-				if idx != 0 {
+			for idx, field := range sch.FieldsWithDefaultDBValue {
+				if idx > 0 {
 					db.Statement.WriteByte(',')
 				}
 
 				fields[idx] = field
-				db.Statement.WriteQuoted(dbName)
-				idx++
+				db.Statement.WriteQuoted(field.DBName)
 			}
 
 			if !db.DryRun {
@@ -149,10 +132,11 @@ func CreateWithReturning(db *gorm.DB) {
 							for idx, field := range fields {
 								values[idx] = field.ReflectValueOf(db.Statement.ReflectValue.Index(int(db.RowsAffected))).Addr().Interface()
 							}
+
+							db.RowsAffected++
 							if err := rows.Scan(values...); err != nil {
 								db.AddError(err)
 							}
-							db.RowsAffected++
 						}
 					case reflect.Struct:
 						for idx, field := range fields {
@@ -161,12 +145,10 @@ func CreateWithReturning(db *gorm.DB) {
 
 						if rows.Next() {
 							db.RowsAffected++
-							err = rows.Scan(values...)
+							db.AddError(rows.Scan(values...))
 						}
 					}
-				}
-
-				if err != nil {
+				} else {
 					db.AddError(err)
 				}
 			}
@@ -182,9 +164,7 @@ func CreateWithReturning(db *gorm.DB) {
 
 func AfterCreate(db *gorm.DB) {
 	if db.Error == nil && db.Statement.Schema != nil && (db.Statement.Schema.AfterSave || db.Statement.Schema.AfterCreate) {
-		tx := db.Session(&gorm.Session{})
-		callMethod := func(value interface{}) bool {
-			var called bool
+		callMethod(db, func(value interface{}, tx *gorm.DB) (called bool) {
 			if db.Statement.Schema.AfterSave {
 				if i, ok := value.(gorm.AfterSaveInterface); ok {
 					called = true
@@ -199,18 +179,7 @@ func AfterCreate(db *gorm.DB) {
 				}
 			}
 			return called
-		}
-
-		if ok := callMethod(db.Statement.Dest); !ok {
-			switch db.Statement.ReflectValue.Kind() {
-			case reflect.Slice, reflect.Array:
-				for i := 0; i < db.Statement.ReflectValue.Len(); i++ {
-					callMethod(db.Statement.ReflectValue.Index(i).Addr().Interface())
-				}
-			case reflect.Struct:
-				callMethod(db.Statement.ReflectValue.Addr().Interface())
-			}
-		}
+		})
 	}
 }
 
@@ -230,7 +199,7 @@ func ConvertToCreateValues(stmt *gorm.Statement) clause.Values {
 		)
 
 		for _, db := range stmt.Schema.DBNames {
-			if stmt.Schema.FieldsWithDefaultDBValue[db] == nil {
+			if field := stmt.Schema.FieldsByDBName[db]; !field.HasDefaultValue || field.DefaultValueInterface != nil {
 				if v, ok := selectColumns[db]; (ok && v) || (!ok && !restricted) {
 					values.Columns = append(values.Columns, clause.Column{Name: db})
 				}
@@ -257,13 +226,13 @@ func ConvertToCreateValues(stmt *gorm.Statement) clause.Values {
 					}
 				}
 
-				for db, field := range stmt.Schema.FieldsWithDefaultDBValue {
-					if v, ok := selectColumns[db]; (ok && v) || (!ok && !restricted) {
+				for _, field := range stmt.Schema.FieldsWithDefaultDBValue {
+					if v, ok := selectColumns[field.DBName]; (ok && v) || (!ok && !restricted) {
 						if v, isZero := field.ValueOf(rv); !isZero {
-							if len(defaultValueFieldsHavingValue[db]) == 0 {
-								defaultValueFieldsHavingValue[db] = make([]interface{}, stmt.ReflectValue.Len())
+							if len(defaultValueFieldsHavingValue[field.DBName]) == 0 {
+								defaultValueFieldsHavingValue[field.DBName] = make([]interface{}, stmt.ReflectValue.Len())
 							}
-							defaultValueFieldsHavingValue[db][i] = v
+							defaultValueFieldsHavingValue[field.DBName][i] = v
 						}
 					}
 				}
@@ -294,10 +263,10 @@ func ConvertToCreateValues(stmt *gorm.Statement) clause.Values {
 				}
 			}
 
-			for db, field := range stmt.Schema.FieldsWithDefaultDBValue {
-				if v, ok := selectColumns[db]; (ok && v) || (!ok && !restricted) {
+			for _, field := range stmt.Schema.FieldsWithDefaultDBValue {
+				if v, ok := selectColumns[field.DBName]; (ok && v) || (!ok && !restricted) {
 					if v, isZero := field.ValueOf(stmt.ReflectValue); !isZero {
-						values.Columns = append(values.Columns, clause.Column{Name: db})
+						values.Columns = append(values.Columns, clause.Column{Name: field.DBName})
 						values.Values[0] = append(values.Values[0], v)
 					}
 				}
diff --git a/callbacks/delete.go b/callbacks/delete.go
index f1a49c11..b246e69f 100644
--- a/callbacks/delete.go
+++ b/callbacks/delete.go
@@ -10,27 +10,14 @@ import (
 
 func BeforeDelete(db *gorm.DB) {
 	if db.Error == nil && db.Statement.Schema != nil && db.Statement.Schema.BeforeDelete {
-		tx := db.Session(&gorm.Session{})
-		callMethod := func(value interface{}) bool {
-			if db.Statement.Schema.BeforeDelete {
-				if i, ok := value.(gorm.BeforeDeleteInterface); ok {
-					db.AddError(i.BeforeDelete(tx))
-					return true
-				}
+		callMethod(db, func(value interface{}, tx *gorm.DB) bool {
+			if i, ok := value.(gorm.BeforeDeleteInterface); ok {
+				db.AddError(i.BeforeDelete(tx))
+				return true
 			}
-			return false
-		}
 
-		if ok := callMethod(db.Statement.Dest); !ok {
-			switch db.Statement.ReflectValue.Kind() {
-			case reflect.Slice, reflect.Array:
-				for i := 0; i < db.Statement.ReflectValue.Len(); i++ {
-					callMethod(db.Statement.ReflectValue.Index(i).Addr().Interface())
-				}
-			case reflect.Struct:
-				callMethod(db.Statement.ReflectValue.Addr().Interface())
-			}
-		}
+			return false
+		})
 	}
 }
 
@@ -86,26 +73,12 @@ func Delete(db *gorm.DB) {
 
 func AfterDelete(db *gorm.DB) {
 	if db.Error == nil && db.Statement.Schema != nil && db.Statement.Schema.AfterDelete {
-		tx := db.Session(&gorm.Session{})
-		callMethod := func(value interface{}) bool {
-			if db.Statement.Schema.AfterDelete {
-				if i, ok := value.(gorm.AfterDeleteInterface); ok {
-					db.AddError(i.AfterDelete(tx))
-					return true
-				}
+		callMethod(db, func(value interface{}, tx *gorm.DB) bool {
+			if i, ok := value.(gorm.AfterDeleteInterface); ok {
+				db.AddError(i.AfterDelete(tx))
+				return true
 			}
 			return false
-		}
-
-		if ok := callMethod(db.Statement.Dest); !ok {
-			switch db.Statement.ReflectValue.Kind() {
-			case reflect.Slice, reflect.Array:
-				for i := 0; i < db.Statement.ReflectValue.Len(); i++ {
-					callMethod(db.Statement.ReflectValue.Index(i).Addr().Interface())
-				}
-			case reflect.Struct:
-				callMethod(db.Statement.ReflectValue.Addr().Interface())
-			}
-		}
+		})
 	}
 }
diff --git a/callbacks/query.go b/callbacks/query.go
index b6667414..41f09375 100644
--- a/callbacks/query.go
+++ b/callbacks/query.go
@@ -188,26 +188,12 @@ func Preload(db *gorm.DB) {
 
 func AfterQuery(db *gorm.DB) {
 	if db.Error == nil && db.Statement.Schema != nil && db.Statement.Schema.AfterFind {
-		tx := db.Session(&gorm.Session{})
-		callMethod := func(value interface{}) bool {
-			if db.Statement.Schema.AfterFind {
-				if i, ok := value.(gorm.AfterFindInterface); ok {
-					db.AddError(i.AfterFind(tx))
-					return true
-				}
+		callMethod(db, func(value interface{}, tx *gorm.DB) bool {
+			if i, ok := value.(gorm.AfterFindInterface); ok {
+				db.AddError(i.AfterFind(tx))
+				return true
 			}
 			return false
-		}
-
-		if ok := callMethod(db.Statement.Dest); !ok {
-			switch db.Statement.ReflectValue.Kind() {
-			case reflect.Slice, reflect.Array:
-				for i := 0; i < db.Statement.ReflectValue.Len(); i++ {
-					callMethod(db.Statement.ReflectValue.Index(i).Addr().Interface())
-				}
-			case reflect.Struct:
-				callMethod(db.Statement.ReflectValue.Addr().Interface())
-			}
-		}
+		})
 	}
 }
diff --git a/callbacks/update.go b/callbacks/update.go
index 9c922956..a41a3c59 100644
--- a/callbacks/update.go
+++ b/callbacks/update.go
@@ -30,9 +30,7 @@ func SetupUpdateReflectValue(db *gorm.DB) {
 
 func BeforeUpdate(db *gorm.DB) {
 	if db.Error == nil && db.Statement.Schema != nil && !db.Statement.UpdatingColumn && (db.Statement.Schema.BeforeSave || db.Statement.Schema.BeforeUpdate) {
-		tx := db.Session(&gorm.Session{})
-		callMethod := func(value interface{}) bool {
-			var called bool
+		callMethod(db, func(value interface{}, tx *gorm.DB) (called bool) {
 			if db.Statement.Schema.BeforeSave {
 				if i, ok := value.(gorm.BeforeSaveInterface); ok {
 					called = true
@@ -46,19 +44,9 @@ func BeforeUpdate(db *gorm.DB) {
 					db.AddError(i.BeforeUpdate(tx))
 				}
 			}
-			return called
-		}
 
-		if ok := callMethod(db.Statement.Dest); !ok {
-			switch db.Statement.ReflectValue.Kind() {
-			case reflect.Slice, reflect.Array:
-				for i := 0; i < db.Statement.ReflectValue.Len(); i++ {
-					callMethod(db.Statement.ReflectValue.Index(i).Addr().Interface())
-				}
-			case reflect.Struct:
-				callMethod(db.Statement.ReflectValue.Addr().Interface())
-			}
-		}
+			return called
+		})
 	}
 }
 
@@ -99,9 +87,7 @@ func Update(db *gorm.DB) {
 
 func AfterUpdate(db *gorm.DB) {
 	if db.Error == nil && db.Statement.Schema != nil && !db.Statement.UpdatingColumn && (db.Statement.Schema.AfterSave || db.Statement.Schema.AfterUpdate) {
-		tx := db.Session(&gorm.Session{})
-		callMethod := func(value interface{}) bool {
-			var called bool
+		callMethod(db, func(value interface{}, tx *gorm.DB) (called bool) {
 			if db.Statement.Schema.AfterSave {
 				if i, ok := value.(gorm.AfterSaveInterface); ok {
 					called = true
@@ -116,18 +102,7 @@ func AfterUpdate(db *gorm.DB) {
 				}
 			}
 			return called
-		}
-
-		if ok := callMethod(db.Statement.Dest); !ok {
-			switch db.Statement.ReflectValue.Kind() {
-			case reflect.Slice, reflect.Array:
-				for i := 0; i < db.Statement.ReflectValue.Len(); i++ {
-					callMethod(db.Statement.ReflectValue.Index(i).Addr().Interface())
-				}
-			case reflect.Struct:
-				callMethod(db.Statement.ReflectValue.Addr().Interface())
-			}
-		}
+		})
 	}
 }
 
diff --git a/gorm.go b/gorm.go
index e6a28635..cea744f7 100644
--- a/gorm.go
+++ b/gorm.go
@@ -25,9 +25,10 @@ type Config struct {
 	NowFunc func() time.Time
 	// DryRun generate sql without execute
 	DryRun bool
-
 	// PrepareStmt executes the given query in cached statement
 	PrepareStmt bool
+	// DisableAutomaticPing
+	DisableAutomaticPing bool
 
 	// ClauseBuilders clause builder
 	ClauseBuilders map[string]clause.ClauseBuilder
@@ -93,8 +94,8 @@ func Open(dialector Dialector, config *Config) (db *DB, err error) {
 		config.ClauseBuilders = map[string]clause.ClauseBuilder{}
 	}
 
-	if dialector != nil {
-		err = dialector.Initialize(db)
+	if config.Dialector != nil {
+		err = config.Dialector.Initialize(db)
 	}
 
 	if config.PrepareStmt {
@@ -104,16 +105,14 @@ func Open(dialector Dialector, config *Config) (db *DB, err error) {
 		}
 	}
 
-	if db.Statement == nil {
-		db.Statement = &Statement{
-			DB:       db,
-			ConnPool: db.ConnPool,
-			Context:  context.Background(),
-			Clauses:  map[string]clause.Clause{},
-		}
+	db.Statement = &Statement{
+		DB:       db,
+		ConnPool: db.ConnPool,
+		Context:  context.Background(),
+		Clauses:  map[string]clause.Clause{},
 	}
 
-	if err == nil {
+	if err == nil && !config.DisableAutomaticPing {
 		if pinger, ok := db.ConnPool.(interface{ Ping() error }); ok {
 			err = pinger.Ping()
 		}
@@ -138,17 +137,8 @@ func (db *DB) Session(config *Session) *DB {
 	)
 
 	if config.Context != nil {
-		if tx.Statement != nil {
-			tx.Statement = tx.Statement.clone()
-			tx.Statement.DB = tx
-		} else {
-			tx.Statement = &Statement{
-				DB:       tx,
-				Clauses:  map[string]clause.Clause{},
-				ConnPool: tx.ConnPool,
-			}
-		}
-
+		tx.Statement = tx.Statement.clone()
+		tx.Statement.DB = tx
 		tx.Statement.Context = config.Context
 	}
 
@@ -160,7 +150,7 @@ func (db *DB) Session(config *Session) *DB {
 	}
 
 	if config.WithConditions {
-		tx.clone = 3
+		tx.clone = 2
 	}
 
 	if config.DryRun {
@@ -200,10 +190,7 @@ func (db *DB) Set(key string, value interface{}) *DB {
 
 // Get get value with key from current db instance's context
 func (db *DB) Get(key string) (interface{}, bool) {
-	if db.Statement != nil {
-		return db.Statement.Settings.Load(key)
-	}
-	return nil, false
+	return db.Statement.Settings.Load(key)
 }
 
 // InstanceSet store value with key into current db instance's context
@@ -215,10 +202,7 @@ func (db *DB) InstanceSet(key string, value interface{}) *DB {
 
 // InstanceGet get value with key from current db instance's context
 func (db *DB) InstanceGet(key string) (interface{}, bool) {
-	if db.Statement != nil {
-		return db.Statement.Settings.Load(fmt.Sprintf("%p", db.Statement) + key)
-	}
-	return nil, false
+	return db.Statement.Settings.Load(fmt.Sprintf("%p", db.Statement) + key)
 }
 
 func (db *DB) SetupJoinTable(model interface{}, field string, joinTable interface{}) error {
@@ -282,22 +266,18 @@ func (db *DB) getInstance() *DB {
 	if db.clone > 0 {
 		tx := &DB{Config: db.Config}
 
-		switch db.clone {
-		case 1: // clone with new statement
+		if db.clone == 1 {
+			// clone with new statement
 			tx.Statement = &Statement{
 				DB:       tx,
 				ConnPool: db.Statement.ConnPool,
 				Context:  db.Statement.Context,
 				Clauses:  map[string]clause.Clause{},
 			}
-		case 2: // with old statement, generate new statement for future call, used to pass to callbacks
-			db.clone = 1
-			tx.Statement = db.Statement
-		case 3: // with clone statement
-			if db.Statement != nil {
-				tx.Statement = db.Statement.clone()
-				tx.Statement.DB = tx
-			}
+		} else {
+			// with clone statement
+			tx.Statement = db.Statement.clone()
+			tx.Statement.DB = tx
 		}
 
 		return tx
diff --git a/migrator/migrator.go b/migrator/migrator.go
index afef65c3..18b2593d 100644
--- a/migrator/migrator.go
+++ b/migrator/migrator.go
@@ -62,7 +62,7 @@ func (m Migrator) FullDataTypeOf(field *schema.Field) (expr clause.Expr) {
 		expr.SQL += " UNIQUE"
 	}
 
-	if field.HasDefaultValue {
+	if field.HasDefaultValue && field.DefaultValue != "" {
 		if field.DataType == schema.String {
 			defaultStmt := &gorm.Statement{Vars: []interface{}{field.DefaultValue}}
 			m.Dialector.BindVarTo(defaultStmt, defaultStmt, field.DefaultValue)
diff --git a/schema/field_test.go b/schema/field_test.go
index cc4b53fc..0936c0d1 100644
--- a/schema/field_test.go
+++ b/schema/field_test.go
@@ -235,7 +235,7 @@ func TestParseFieldWithPermission(t *testing.T) {
 	}
 
 	fields := []schema.Field{
-		{Name: "ID", DBName: "id", BindNames: []string{"ID"}, DataType: schema.Uint, PrimaryKey: true, Size: 64, Creatable: true, Updatable: true, Readable: true},
+		{Name: "ID", DBName: "id", BindNames: []string{"ID"}, DataType: schema.Uint, PrimaryKey: true, Size: 64, Creatable: true, Updatable: true, Readable: true, HasDefaultValue: true},
 		{Name: "Name", DBName: "", BindNames: []string{"Name"}, DataType: "", Tag: `gorm:"-"`, Creatable: false, Updatable: false, Readable: false},
 		{Name: "Name2", DBName: "name2", BindNames: []string{"Name2"}, DataType: schema.String, Tag: `gorm:"->"`, Creatable: false, Updatable: false, Readable: true},
 		{Name: "Name3", DBName: "name3", BindNames: []string{"Name3"}, DataType: schema.String, Tag: `gorm:"<-"`, Creatable: true, Updatable: true, Readable: true},
diff --git a/schema/schema.go b/schema/schema.go
index 9e05303a..d2c4d08b 100644
--- a/schema/schema.go
+++ b/schema/schema.go
@@ -26,7 +26,7 @@ type Schema struct {
 	Fields                    []*Field
 	FieldsByName              map[string]*Field
 	FieldsByDBName            map[string]*Field
-	FieldsWithDefaultDBValue  map[string]*Field // fields with default value assigned by database
+	FieldsWithDefaultDBValue  []*Field // fields with default value assigned by database
 	Relationships             Relationships
 	CreateClauses             []clause.Interface
 	QueryClauses              []clause.Interface
@@ -153,23 +153,14 @@ func Parse(dest interface{}, cacheStore *sync.Map, namer Namer) (*Schema, error)
 				schema.FieldsByName[field.Name] = field
 
 				if v != nil && v.PrimaryKey {
-					if schema.PrioritizedPrimaryField == v {
-						schema.PrioritizedPrimaryField = nil
-					}
-
 					for idx, f := range schema.PrimaryFields {
 						if f == v {
 							schema.PrimaryFields = append(schema.PrimaryFields[0:idx], schema.PrimaryFields[idx+1:]...)
-						} else if schema.PrioritizedPrimaryField == nil {
-							schema.PrioritizedPrimaryField = f
 						}
 					}
 				}
 
 				if field.PrimaryKey {
-					if schema.PrioritizedPrimaryField == nil {
-						schema.PrioritizedPrimaryField = field
-					}
 					schema.PrimaryFields = append(schema.PrimaryFields, field)
 				}
 			}
@@ -192,21 +183,27 @@ func Parse(dest interface{}, cacheStore *sync.Map, namer Namer) (*Schema, error)
 		}
 	}
 
+	if schema.PrioritizedPrimaryField == nil && len(schema.PrimaryFields) == 1 {
+		schema.PrioritizedPrimaryField = schema.PrimaryFields[0]
+	}
+
 	for _, field := range schema.PrimaryFields {
 		schema.PrimaryFieldDBNames = append(schema.PrimaryFieldDBNames, field.DBName)
 	}
 
-	schema.FieldsWithDefaultDBValue = map[string]*Field{}
-	for db, field := range schema.FieldsByDBName {
+	for _, field := range schema.FieldsByDBName {
 		if field.HasDefaultValue && field.DefaultValueInterface == nil {
-			schema.FieldsWithDefaultDBValue[db] = field
+			schema.FieldsWithDefaultDBValue = append(schema.FieldsWithDefaultDBValue, field)
 		}
 	}
 
-	if schema.PrioritizedPrimaryField != nil {
-		switch schema.PrioritizedPrimaryField.DataType {
+	if field := schema.PrioritizedPrimaryField; field != nil {
+		switch field.DataType {
 		case Int, Uint:
-			schema.FieldsWithDefaultDBValue[schema.PrioritizedPrimaryField.DBName] = schema.PrioritizedPrimaryField
+			if !field.HasDefaultValue || field.DefaultValueInterface != nil {
+				schema.FieldsWithDefaultDBValue = append(schema.FieldsWithDefaultDBValue, field)
+			}
+			field.HasDefaultValue = true
 		}
 	}
 
diff --git a/schema/schema_test.go b/schema/schema_test.go
index 82f07fa8..4ec7ff0c 100644
--- a/schema/schema_test.go
+++ b/schema/schema_test.go
@@ -32,7 +32,7 @@ func checkUserSchema(t *testing.T, user *schema.Schema) {
 
 	// check fields
 	fields := []schema.Field{
-		{Name: "ID", DBName: "id", BindNames: []string{"Model", "ID"}, DataType: schema.Uint, PrimaryKey: true, Tag: `gorm:"primarykey"`, TagSettings: map[string]string{"PRIMARYKEY": "PRIMARYKEY"}, Size: 64},
+		{Name: "ID", DBName: "id", BindNames: []string{"Model", "ID"}, DataType: schema.Uint, PrimaryKey: true, Tag: `gorm:"primarykey"`, TagSettings: map[string]string{"PRIMARYKEY": "PRIMARYKEY"}, Size: 64, HasDefaultValue: true},
 		{Name: "CreatedAt", DBName: "created_at", BindNames: []string{"Model", "CreatedAt"}, DataType: schema.Time},
 		{Name: "UpdatedAt", DBName: "updated_at", BindNames: []string{"Model", "UpdatedAt"}, DataType: schema.Time},
 		{Name: "DeletedAt", DBName: "deleted_at", BindNames: []string{"Model", "DeletedAt"}, Tag: `gorm:"index"`, DataType: schema.Time},
@@ -125,7 +125,7 @@ func TestParseSchemaWithAdvancedDataType(t *testing.T) {
 
 	// check fields
 	fields := []schema.Field{
-		{Name: "ID", DBName: "id", BindNames: []string{"ID"}, DataType: schema.Int, PrimaryKey: true, Size: 64},
+		{Name: "ID", DBName: "id", BindNames: []string{"ID"}, DataType: schema.Int, PrimaryKey: true, Size: 64, HasDefaultValue: true},
 		{Name: "Name", DBName: "name", BindNames: []string{"Name"}, DataType: schema.String},
 		{Name: "Birthday", DBName: "birthday", BindNames: []string{"Birthday"}, DataType: schema.Time},
 		{Name: "RegisteredAt", DBName: "registered_at", BindNames: []string{"RegisteredAt"}, DataType: schema.Time},
diff --git a/statement.go b/statement.go
index e3f324b9..2c814547 100644
--- a/statement.go
+++ b/statement.go
@@ -226,6 +226,7 @@ func (stmt Statement) BuildCondtion(query interface{}, args ...interface{}) (con
 			if sql == "" && len(args) == 0 {
 				return
 			} else if len(args) == 0 || (len(args) > 0 && strings.Contains(sql, "?")) || strings.Contains(sql, "@") {
+				// looks like a where condition
 				return []clause.Expression{clause.Expr{SQL: sql, Vars: args}}
 			} else if len(args) == 1 {
 				return []clause.Expression{clause.Eq{Column: sql, Value: args[0]}}
@@ -242,12 +243,6 @@ func (stmt Statement) BuildCondtion(query interface{}, args ...interface{}) (con
 		switch v := arg.(type) {
 		case clause.Expression:
 			conds = append(conds, v)
-		case *DB:
-			if v.Statement != nil {
-				if cs, ok := v.Statement.Clauses["WHERE"]; ok {
-					conds = append(conds, cs.Expression)
-				}
-			}
 		case map[interface{}]interface{}:
 			for i, j := range v {
 				conds = append(conds, clause.Eq{Column: i, Value: j})
@@ -326,7 +321,6 @@ func (stmt *Statement) Parse(value interface{}) (err error) {
 
 func (stmt *Statement) clone() *Statement {
 	newStmt := &Statement{
-		DB:                   stmt.DB,
 		Table:                stmt.Table,
 		Model:                stmt.Model,
 		Dest:                 stmt.Dest,
@@ -357,37 +351,3 @@ func (stmt *Statement) clone() *Statement {
 
 	return newStmt
 }
-
-func (stmt *Statement) reinit() {
-	// stmt.Table = ""
-	// stmt.Model = nil
-	// stmt.Selects = nil
-	// stmt.Omits = nil
-	// stmt.ConnPool = stmt.DB.Config.ConnPool
-	// stmt.Context = context.Background()
-	// stmt.RaiseErrorOnNotFound = false
-
-	// for k := range stmt.Clauses {
-	// 	delete(stmt.Clauses, k)
-	// }
-
-	// for k := range stmt.Joins {
-	// 	delete(stmt.Joins, k)
-	// }
-
-	// for k := range stmt.Preloads {
-	// 	delete(stmt.Preloads, k)
-	// }
-
-	// stmt.Settings.Range(func(k, _ interface{}) bool {
-	// 	stmt.Settings.Delete(k)
-	// 	return true
-	// })
-
-	// stmt.Schema = nil
-	if !stmt.DB.DryRun {
-		stmt.SQL.Reset()
-		stmt.Vars = nil
-		stmt.NamedVars = nil
-	}
-}
diff --git a/tests/benchmark_test.go b/tests/benchmark_test.go
new file mode 100644
index 00000000..c6ce93a2
--- /dev/null
+++ b/tests/benchmark_test.go
@@ -0,0 +1,44 @@
+package tests_test
+
+import (
+	"testing"
+
+	. "gorm.io/gorm/utils/tests"
+)
+
+func BenchmarkCreate(b *testing.B) {
+	var user = *GetUser("bench", Config{})
+
+	for x := 0; x < b.N; x++ {
+		user.ID = 0
+		DB.Create(&user)
+	}
+}
+
+func BenchmarkFind(b *testing.B) {
+	var user = *GetUser("find", Config{})
+	DB.Create(&user)
+
+	for x := 0; x < b.N; x++ {
+		DB.Find(&User{}, "id = ?", user.ID)
+	}
+}
+
+func BenchmarkUpdate(b *testing.B) {
+	var user = *GetUser("find", Config{})
+	DB.Create(&user)
+
+	for x := 0; x < b.N; x++ {
+		DB.Model(&user).Updates(map[string]interface{}{"Age": x})
+	}
+}
+
+func BenchmarkDelete(b *testing.B) {
+	var user = *GetUser("find", Config{})
+
+	for x := 0; x < b.N; x++ {
+		user.ID = 0
+		DB.Create(&user)
+		DB.Delete(&user)
+	}
+}
diff --git a/tests/go.mod b/tests/go.mod
index de58a0de..3c2dfc6c 100644
--- a/tests/go.mod
+++ b/tests/go.mod
@@ -7,7 +7,7 @@ require (
 	gorm.io/driver/mysql v0.0.0-20200602015408-0407d0c21cf0
 	gorm.io/driver/postgres v0.0.0-20200602015520-15fcc29eb286
 	gorm.io/driver/sqlite v1.0.0
-	gorm.io/driver/sqlserver v0.0.0-20200602144728-79c224f6c1a2
+	gorm.io/driver/sqlserver v0.0.0-20200605135528-04ae0f7a15bf
 	gorm.io/gorm v0.0.0-00010101000000-000000000000
 )