issue #6098

gorm.go

@@ -144,7 +144,20 @@ func Open(dialector Dialector, opts ...Option) (db *DB, err error) {
 	}
 
 	if config.NamingStrategy == nil {
-		config.NamingStrategy = schema.NamingStrategy{}
+		// Set default value of IdentifierMaxLength according to the database type
+		identifierMaxLength := 64
+		switch dialector.Name() {
+		case "mysql":
+			identifierMaxLength = 64
+		case "postgres":
+			identifierMaxLength = 63
+		case "sqlite":
+			identifierMaxLength = 64
+		case "sqlserver":
+			identifierMaxLength = 128
+		}
+
+		config.NamingStrategy = schema.NamingStrategy{NamingStrategyConfig: schema.NamingStrategyConfig{IdentifierMaxLength: identifierMaxLength}}
 	}
 
 	if config.Logger == nil {

schema/check_test.go

@@ -15,7 +15,7 @@ type UserCheck struct {
 }
 
 func TestParseCheck(t *testing.T) {
-	user, err := schema.Parse(&UserCheck{}, &sync.Map{}, schema.NamingStrategy{})
+	user, err := schema.Parse(&UserCheck{}, &sync.Map{}, schema.NamingStrategy{NamingStrategyConfig: schema.NamingStrategyConfig{IdentifierMaxLength: 64}})
 	if err != nil {
 		t.Fatalf("failed to parse user check, got error %v", err)
 	}

schema/index_test.go

@@ -52,7 +52,7 @@ type CompIdxLevel2B struct {
 }
 
 func TestParseIndex(t *testing.T) {
-	user, err := schema.Parse(&UserIndex{}, &sync.Map{}, schema.NamingStrategy{})
+	user, err := schema.Parse(&UserIndex{}, &sync.Map{}, schema.NamingStrategy{NamingStrategyConfig: schema.NamingStrategyConfig{IdentifierMaxLength: 64}})
 	if err != nil {
 		t.Fatalf("failed to parse user index, got error %v", err)
 	}

schema/naming.go

@@ -32,6 +32,17 @@ type NamingStrategy struct {
 	SingularTable bool
 	NameReplacer  Replacer
 	NoLowerCase   bool
+	NamingStrategyConfig
+}
+
+// This struct is used to configure the behavior NamingStrategy, according to DB.
+// For example, in MySQL, the maximum length of an identifier is 64 characters.
+// In PostgreSQL, the maximum length of an identifier is 63 characters.
+// In SQL Server, the maximum length of an identifier is 128 characters.
+// In SQLite, the maximum length of an identifier is unlimited.
+// In future, we may add more options to NamingStrategyConfig.
+type NamingStrategyConfig struct {
+	IdentifierMaxLength int
 }
 
 // TableName convert string to table name
@@ -89,12 +100,12 @@ func (ns NamingStrategy) formatName(prefix, table, name string) string {
 		prefix, table, name,
 	}, "_"), ".", "_")
 
-	if utf8.RuneCountInString(formattedName) > 64 {
+	if utf8.RuneCountInString(formattedName) > ns.IdentifierMaxLength {
 		h := sha1.New()
 		h.Write([]byte(formattedName))
 		bs := h.Sum(nil)
 
-		formattedName = formattedName[0:56] + hex.EncodeToString(bs)[:8]
+		formattedName = formattedName[0:ns.IdentifierMaxLength-8] + hex.EncodeToString(bs)[:8]
 	}
 	return formattedName
 }

schema/naming_test.go

@@ -57,9 +57,10 @@ func TestToDBName(t *testing.T) {
 
 func TestNamingStrategy(t *testing.T) {
 	ns := NamingStrategy{
-		TablePrefix:   "public.",
+		TablePrefix:          "public.",
-		SingularTable: true,
+		SingularTable:        true,
-		NameReplacer:  strings.NewReplacer("CID", "Cid"),
+		NameReplacer:         strings.NewReplacer("CID", "Cid"),
+		NamingStrategyConfig: NamingStrategyConfig{IdentifierMaxLength: 64},
 	}
 	idxName := ns.IndexName("public.table", "name")
 
@@ -111,7 +112,8 @@ func TestCustomReplacer(t *testing.T) {
 				return strings.NewReplacer("CID", "_Cid").Replace(replaced)
 			},
 		},
-		NoLowerCase: false,
+		NamingStrategyConfig: NamingStrategyConfig{IdentifierMaxLength: 64},
+		NoLowerCase:          false,
 	}
 
 	idxName := ns.IndexName("public.table", "name")
@@ -155,7 +157,8 @@ func TestCustomReplacerWithNoLowerCase(t *testing.T) {
 				return strings.NewReplacer("CID", "_Cid").Replace(replaced)
 			},
 		},
-		NoLowerCase: true,
+		NamingStrategyConfig: NamingStrategyConfig{IdentifierMaxLength: 64},
+		NoLowerCase:          true,
 	}
 
 	idxName := ns.IndexName("public.table", "name")
@@ -189,13 +192,27 @@ func TestCustomReplacerWithNoLowerCase(t *testing.T) {
 	}
 }
 
-func TestFormatNameWithStringLongerThan64Characters(t *testing.T) {
+func TestFormatNameWithStringLongerThanMaxIdentifierLength(t *testing.T) {
-	ns := NamingStrategy{}
+	ns := NamingStrategy{NamingStrategyConfig: NamingStrategyConfig{IdentifierMaxLength: 63}}
 
 	formattedName := ns.formatName("prefix", "table", "thisIsAVeryVeryVeryVeryVeryVeryVeryVeryVeryLongString")
+	if formattedName != "prefix_table_thisIsAVeryVeryVeryVeryVeryVeryVeryVeryVer180f2c67" {
+		t.Errorf("invalid formatted name generated, got %v", formattedName)
+	}
+
+	ns = NamingStrategy{NamingStrategyConfig: NamingStrategyConfig{IdentifierMaxLength: 64}}
+
+	formattedName = ns.formatName("prefix", "table", "thisIsAVeryVeryVeryVeryVeryVeryVeryVeryVeryLongString")
 	if formattedName != "prefix_table_thisIsAVeryVeryVeryVeryVeryVeryVeryVeryVery180f2c67" {
 		t.Errorf("invalid formatted name generated, got %v", formattedName)
 	}
+
+	ns = NamingStrategy{NamingStrategyConfig: NamingStrategyConfig{IdentifierMaxLength: 128}}
+
+	formattedName = ns.formatName("prefix", "table", "thisIsAVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryLongString")
+	if formattedName != "prefix_table_thisIsAVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVery81f06061" {
+		t.Errorf("invalid formatted name generated, got %v", formattedName)
+	}
 }
 
 func TestReplaceEmptyTableName(t *testing.T) {

schema/relationship_test.go

@@ -642,7 +642,7 @@ func TestParseConstraintNameWithSchemaQualifiedLongTableName(t *testing.T) {
 	s, err := schema.Parse(
 		&Book{},
 		&sync.Map{},
-		schema.NamingStrategy{},
+		schema.NamingStrategy{NamingStrategyConfig: schema.NamingStrategyConfig{IdentifierMaxLength: 64}},
 	)
 	if err != nil {
 		t.Fatalf("Failed to parse schema")