[fix] full table scan when with duplicated record (jinzhu#15)

Author: Knight0xffff

callback_create.go

@@ -176,12 +176,19 @@ func createCallback(scope *Scope) {
 // forceReloadAfterCreateCallback will reload columns that having default value, and set it back to current object
 func forceReloadAfterCreateCallback(scope *Scope) {
 	if blankColumnsWithDefaultValue, ok := scope.InstanceGet("gorm:blank_columns_with_default_value"); ok {
+		var shouldScan bool
 		db := scope.DB().New().Table(scope.TableName()).Select(blankColumnsWithDefaultValue.([]string))
 		for _, field := range scope.Fields() {
 			if field.IsPrimaryKey && !field.IsBlank {
 				db = db.Where(fmt.Sprintf("%v = ?", field.DBName), field.Field.Interface())
+				shouldScan = true
 			}
 		}
+
+		if !shouldScan {
+			return
+		}
+
 		db.Scan(scope.Value)
 	}
 }

create_test.go

@@ -3,10 +3,13 @@ package gorm_test
 import (
 	"os"
 	"reflect"
+	"strings"
 	"testing"
 	"time"
 
 	"github.com/jinzhu/now"
+
+	"github.com/jinzhu/gorm"
 )
 
 func TestCreate(t *testing.T) {
@@ -286,3 +289,25 @@ func TestCreateIgnore(t *testing.T) {
 		t.Error("Should ignore duplicate user insert by insert modifier:IGNORE ")
 	}
 }
+
+func TestFixFullTableScanWhenInsertIgnore(t *testing.T) {
+	pandaYuanYuan := Panda{Number: 200408301001}
+
+	if !DB.NewRecord(pandaYuanYuan) || !DB.NewRecord(&pandaYuanYuan) {
+		t.Error("Panda should be new record before create")
+	}
+
+	if count := DB.Create(&pandaYuanYuan).RowsAffected; count != 1 {
+		t.Error("There should be one record be affected when create record")
+	}
+
+	DB.Callback().Query().Register("gorm:fix_full_table_scan", func(scope *gorm.Scope) {
+		if strings.Contains(scope.SQL, "SELECT") && strings.Contains(scope.SQL, "pandas") && len(scope.SQLVars) == 0 {
+		    t.Error("Should skip force reload when ignore duplicate panda insert")
+		}
+	})
+
+	if DB.Dialect().GetName() == "mysql" && DB.Set("gorm:insert_modifier", "IGNORE").Create(&pandaYuanYuan).Error != nil {
+		t.Error("Should ignore duplicate panda insert by insert modifier:IGNORE ")
+	}
+}

migration_test.go

@@ -283,6 +283,11 @@ func getPreparedUser(name string, role string) *User {
 	}
 }
 
+type Panda struct {
+    Number int64 `gorm:"unique_index:number"`
+    Name string `gorm:"column:name;type:varchar(255);default:null"`
+}
+
 func runMigration() {
 	if err := DB.DropTableIfExists(&User{}).Error; err != nil {
 		fmt.Printf("Got error when try to delete table users, %+v\n", err)
@@ -292,7 +297,7 @@ func runMigration() {
 		DB.Exec(fmt.Sprintf("drop table %v;", table))
 	}
 
-	values := []interface{}{&Short{}, &ReallyLongThingThatReferencesShort{}, &ReallyLongTableNameToTestMySQLNameLengthLimit{}, &NotSoLongTableName{}, &Product{}, &Email{}, &Address{}, &CreditCard{}, &Company{}, &Role{}, &Language{}, &HNPost{}, &EngadgetPost{}, &Animal{}, &User{}, &JoinTable{}, &Post{}, &Category{}, &Comment{}, &Cat{}, &Dog{}, &Hamster{}, &Toy{}, &ElementWithIgnoredField{}, &Place{}}
+	values := []interface{}{&Short{}, &ReallyLongThingThatReferencesShort{}, &ReallyLongTableNameToTestMySQLNameLengthLimit{}, &NotSoLongTableName{}, &Product{}, &Email{}, &Address{}, &CreditCard{}, &Company{}, &Role{}, &Language{}, &HNPost{}, &EngadgetPost{}, &Animal{}, &User{}, &JoinTable{}, &Post{}, &Category{}, &Comment{}, &Cat{}, &Dog{}, &Hamster{}, &Toy{}, &ElementWithIgnoredField{}, &Place{}, &Panda{}}
 	for _, value := range values {
 		DB.DropTable(value)
 	}