Merge pull request #1029 from nkovacs/mysql-foreign-key-length-fix

Mysql foreign key length fix

association_test.go

@@ -2,6 +2,7 @@ package gorm_test
 
 import (
 	"fmt"
+	"os"
 	"reflect"
 	"sort"
 	"testing"
@@ -840,3 +841,26 @@ func TestForeignKey(t *testing.T) {
 		}
 	}
 }
+
+func TestLongForeignKey(t *testing.T) {
+	if dialect := os.Getenv("GORM_DIALECT"); dialect == "" || dialect == "sqlite" {
+		// sqlite does not support ADD CONSTRAINT in ALTER TABLE
+		return
+	}
+	targetScope := DB.NewScope(&ReallyLongTableNameToTestMySQLNameLengthLimit{})
+	targetTableName := targetScope.TableName()
+	modelScope := DB.NewScope(&NotSoLongTableName{})
+	modelField, ok := modelScope.FieldByName("ReallyLongThingID")
+	if !ok {
+		t.Fatalf("Failed to get field by name: ReallyLongThingID")
+	}
+	targetField, ok := targetScope.FieldByName("ID")
+	if !ok {
+		t.Fatalf("Failed to get field by name: ID")
+	}
+	dest := fmt.Sprintf("%v(%v)", targetTableName, targetField.DBName)
+	err := DB.Model(&NotSoLongTableName{}).AddForeignKey(modelField.DBName, dest, "CASCADE", "CASCADE").Error
+	if err != nil {
+		t.Fatalf(fmt.Sprintf("Failed to create foreign key: %v", err))
+	}
+}

dialect.go

@@ -40,6 +40,9 @@ type Dialect interface {
 	SelectFromDummyTable() string
 	// LastInsertIdReturningSuffix most dbs support LastInsertId, but postgres needs to use `RETURNING`
 	LastInsertIDReturningSuffix(tableName, columnName string) string
+
+	// BuildForeignKeyName returns a foreign key name for the given table, field and reference
+	BuildForeignKeyName(tableName, field, dest string) string
 }
 
 var dialectsMap = map[string]Dialect{}

dialect_common.go

@@ -4,12 +4,18 @@ import (
 	"database/sql"
 	"fmt"
 	"reflect"
+	"regexp"
 	"strings"
 	"time"
 )
 
+// DefaultForeignKeyNamer contains the default foreign key name generator method
+type DefaultForeignKeyNamer struct {
+}
+
 type commonDialect struct {
 	db *sql.DB
+	DefaultForeignKeyNamer
 }
 
 func init() {
@@ -135,3 +141,9 @@ func (commonDialect) SelectFromDummyTable() string {
 func (commonDialect) LastInsertIDReturningSuffix(tableName, columnName string) string {
 	return ""
 }
+
+func (DefaultForeignKeyNamer) BuildForeignKeyName(tableName, field, dest string) string {
+	keyName := fmt.Sprintf("%s_%s_%s_foreign", tableName, field, dest)
+	keyName = regexp.MustCompile("(_*[^a-zA-Z]+_*|_+)").ReplaceAllString(keyName, "_")
+	return keyName
+}

dialect_mysql.go

@@ -1,8 +1,10 @@
 package gorm
 
 import (
+	"crypto/sha1"
 	"fmt"
 	"reflect"
+	"regexp"
 	"strings"
 	"time"
 )
@@ -115,3 +117,18 @@ func (s mysql) currentDatabase() (name string) {
 func (mysql) SelectFromDummyTable() string {
 	return "FROM DUAL"
 }
+
+func (s mysql) BuildForeignKeyName(tableName, field, dest string) string {
+	keyName := s.commonDialect.BuildForeignKeyName(tableName, field, dest)
+	if len(keyName) <= 64 {
+		return keyName
+	}
+	h := sha1.New()
+	h.Write([]byte(keyName))
+	bs := h.Sum(nil)
+
+	// sha1 is 40 digits, keep first 24 characters of destination
+	keyName = regexp.MustCompile("(_*[^a-zA-Z]+_*|_+)").ReplaceAllString(dest, "_")
+
+	return fmt.Sprintf("%s%x", keyName[:24], bs)
+}

dialects/mssql/mssql.go

@@ -24,6 +24,7 @@ func init() {
 
 type mssql struct {
 	db *sql.DB
+	gorm.DefaultForeignKeyNamer
 }
 
 func (mssql) GetName() string {

migration_test.go

@@ -39,6 +39,16 @@ type User struct {
 	IgnoredPointer    *User                 `sql:"-"`
 }
 
+type NotSoLongTableName struct {
+	Id                int64
+	ReallyLongThingID int64
+	ReallyLongThing   ReallyLongTableNameToTestMySQLNameLengthLimit
+}
+
+type ReallyLongTableNameToTestMySQLNameLengthLimit struct {
+	Id int64
+}
+
 type CreditCard struct {
 	ID        int8
 	Number    string
@@ -231,7 +241,7 @@ func runMigration() {
 		DB.Exec(fmt.Sprintf("drop table %v;", table))
 	}
 
-	values := []interface{}{&Product{}, &Email{}, &Address{}, &CreditCard{}, &Company{}, &Role{}, &Language{}, &HNPost{}, &EngadgetPost{}, &Animal{}, &User{}, &JoinTable{}, &Post{}, &Category{}, &Comment{}, &Cat{}, &Dog{}, &Toy{}}
+	values := []interface{}{&ReallyLongTableNameToTestMySQLNameLengthLimit{}, &NotSoLongTableName{}, &Product{}, &Email{}, &Address{}, &CreditCard{}, &Company{}, &Role{}, &Language{}, &HNPost{}, &EngadgetPost{}, &Animal{}, &User{}, &JoinTable{}, &Post{}, &Category{}, &Comment{}, &Cat{}, &Dog{}, &Toy{}}
 	for _, value := range values {
 		DB.DropTable(value)
 	}

scope.go

@@ -1117,8 +1117,7 @@ func (scope *Scope) addIndex(unique bool, indexName string, column ...string) {
 }
 
 func (scope *Scope) addForeignKey(field string, dest string, onDelete string, onUpdate string) {
-	var keyName = fmt.Sprintf("%s_%s_%s_foreign", scope.TableName(), field, dest)
+	keyName := scope.Dialect().BuildForeignKeyName(scope.TableName(), field, dest)
-	keyName = regexp.MustCompile("(_*[^a-zA-Z]+_*|_+)").ReplaceAllString(keyName, "_")
 
 	if scope.Dialect().HasForeignKey(scope.TableName(), keyName) {
 		return