diff --git a/field.go b/field.go
index 16016c34..6015a815 100644
--- a/field.go
+++ b/field.go
@@ -13,6 +13,7 @@ type Field struct {
 	Value             interface{}
 	model             *Model
 	dbName            string
+	isBlank           bool
 	isPrimaryKey      bool
 	autoCreateTime    bool
 	autoUpdateTime    bool
@@ -23,8 +24,8 @@ type Field struct {
 	structField       reflect.StructField
 }
 
-func (f *Field) isBlank() bool {
-	return isBlank(f.reflectValue)
+func (f *Field) parseBlank() {
+	f.isBlank = isBlank(f.reflectValue)
 }
 
 func (f *Field) isScanner() bool {
diff --git a/gorm_test.go b/gorm_test.go
index 54c4c49e..38ec2b54 100644
--- a/gorm_test.go
+++ b/gorm_test.go
@@ -1365,7 +1365,7 @@ func TestQueryChain(t *testing.T) {
 }
 
 func BenchmarkGorm(b *testing.B) {
-	b.N = 5000
+	b.N = 2000
 	for x := 0; x < b.N; x++ {
 		e := strconv.Itoa(x) + "benchmark@example.org"
 		email := BigEmail{Email: e, UserAgent: "pc", RegisteredAt: time.Now()}
@@ -1388,7 +1388,7 @@ func BenchmarkRawSql(b *testing.B) {
 	update_sql := "UPDATE emails SET email = $1, updated_at = $2 WHERE id = $3"
 	delete_sql := "DELETE FROM orders WHERE id = $1"
 
-	b.N = 5000
+	b.N = 2000
 	for x := 0; x < b.N; x++ {
 		var id int64
 		e := strconv.Itoa(x) + "benchmark@example.org"
diff --git a/main.go b/main.go
index 89279783..c3b4027b 100644
--- a/main.go
+++ b/main.go
@@ -2,7 +2,6 @@ package gorm
 
 import (
 	"database/sql"
-
 	"github.com/jinzhu/gorm/dialect"
 )
 
@@ -139,7 +138,7 @@ func (s *DB) Delete(value interface{}) *DB {
 }
 
 func (s *DB) Exec(sql string) *DB {
-	return s.do(nil).exec(sql).db
+	return s.clone().do(nil).exec(sql).db
 }
 
 func (s *DB) Model(value interface{}) *DB {
diff --git a/model.go b/model.go
index a008330b..b5cd3d21 100644
--- a/model.go
+++ b/model.go
@@ -63,47 +63,65 @@ func getStructs(typ reflect.Type) (fs []reflect.StructField) {
 }
 
 func (m *Model) fields(operation string) (fields []*Field) {
+	if len(m._cache_fields[operation]) > 0 {
+		return m._cache_fields[operation]
+	}
+
 	indirect_value := m.reflectData()
 	if !indirect_value.IsValid() {
 		return
 	}
 
-	for _, filed_struct := range getStructs(indirect_value.Type()) {
-		var field Field
-		field.Name = filed_struct.Name
-		field.dbName = toSnake(filed_struct.Name)
-		field.isPrimaryKey = m.primaryKeyDb() == field.dbName
-		value := indirect_value.FieldByName(filed_struct.Name)
-		field.model = m
+	structs := getStructs(indirect_value.Type())
+	c := make(chan *Field, len(structs))
+	for _, field_struct := range structs {
+		go func(field_struct reflect.StructField, c chan *Field) {
+			var field Field
+			field.Name = field_struct.Name
+			field.dbName = toSnake(field_struct.Name)
+			field.isPrimaryKey = m.primaryKeyDb() == field.dbName
+			value := indirect_value.FieldByName(field_struct.Name)
+			field.model = m
 
-		if time_value, is_time := value.Interface().(time.Time); is_time {
-			field.autoCreateTime = "created_at" == field.dbName
-			field.autoUpdateTime = "updated_at" == field.dbName
+			if time_value, is_time := value.Interface().(time.Time); is_time {
+				field.autoCreateTime = "created_at" == field.dbName
+				field.autoUpdateTime = "updated_at" == field.dbName
 
-			switch operation {
-			case "create":
-				if (field.autoCreateTime || field.autoUpdateTime) && time_value.IsZero() {
-					value.Set(reflect.ValueOf(time.Now()))
-				}
-			case "update":
-				if field.autoUpdateTime {
-					value.Set(reflect.ValueOf(time.Now()))
+				switch operation {
+				case "create":
+					if (field.autoCreateTime || field.autoUpdateTime) && time_value.IsZero() {
+						value.Set(reflect.ValueOf(time.Now()))
+					}
+				case "update":
+					if field.autoUpdateTime {
+						value.Set(reflect.ValueOf(time.Now()))
+					}
 				}
 			}
-		}
-
-		field.structField = filed_struct
-		field.reflectValue = value
-		field.Value = value.Interface()
-		field.parseAssociation()
-		fields = append(fields, &field)
+			field.structField = field_struct
+			field.reflectValue = value
+			field.Value = value.Interface()
+			field.parseAssociation()
+			field.parseBlank()
+			c <- &field
+		}(field_struct, c)
 	}
+
+	for i := 0; i < len(structs); i++ {
+		fields = append(fields, <-c)
+	}
+	close(c)
+
+	if len(m._cache_fields) == 0 {
+		m._cache_fields = map[string][]*Field{}
+	}
+	m._cache_fields[operation] = fields
 	return
 }
 
 func (m *Model) columnsHasValue(operation string) (fields []*Field) {
 	for _, field := range m.fields(operation) {
-		if !field.isBlank() {
+		if !field.isBlank {
 			fields = append(fields, field)
 		}
 	}
@@ -236,7 +254,7 @@ func (m *Model) setValueByColumn(name string, value interface{}, out interface{}
 
 func (m *Model) beforeAssociations() (fields []*Field) {
 	for _, field := range m.fields("null") {
-		if field.beforeAssociation && !field.isBlank() {
+		if field.beforeAssociation && !field.isBlank {
 			fields = append(fields, field)
 		}
 	}
@@ -245,7 +263,7 @@ func (m *Model) beforeAssociations() (fields []*Field) {
 
 func (m *Model) afterAssociations() (fields []*Field) {
 	for _, field := range m.fields("null") {
-		if field.afterAssociation && !field.isBlank() {
+		if field.afterAssociation && !field.isBlank {
 			fields = append(fields, field)
 		}
 	}
diff --git a/utils.go b/utils.go
index 0d0b48fd..f72dfe16 100644
--- a/utils.go
+++ b/utils.go
@@ -3,7 +3,6 @@ package gorm
 import (
 	"bytes"
 	"database/sql"
-
 	"reflect"
 	"strconv"
 	"strings"