add option to truncate tables with an identity/auto-incr reset

dbmap.go

@@ -372,10 +372,24 @@ func (m *DbMap) TableForType(t reflect.Type) *TableMap {
 
 // Truncate all tables in the DbMap
 func (m *DbMap) TruncateTables() error {
+	return m.truncateTables(false)
+}
+
+// Truncate all tables in the DbMap and reset identity counter
+func (m *DbMap) TruncateTablesIdentityRestart() error {
+	return m.truncateTables(true)
+}
+
+func (m *DbMap) truncateTables(restartIdentity bool) error {
 	var err error
+	var restartClause string
 	for i := range m.tables {
 		table := m.tables[i]
-		_, e := m.Exec(fmt.Sprintf("%s %s;", m.Dialect.TruncateClause(), m.Dialect.QuoteField(table.TableName)))
+		if restartIdentity {
+			restartClause = m.Dialect.RestartIdentityClause(table.TableName)
+		}
+
+		_, e := m.Exec(fmt.Sprintf("%s %s %s;", m.Dialect.TruncateClause(), m.Dialect.QuoteField(table.TableName), restartClause))
 		if e != nil {
 			err = e
 		}

dialect.go

@@ -46,6 +46,9 @@ type Dialect interface {
 	// string used to truncate tables
 	TruncateClause() string
 
+	// string used to reset identity counter when truncating tables
+	RestartIdentityClause(table string) string
+
 	// Get the driver name from a dialect
 	DriverName() string
 }
@@ -139,6 +142,10 @@ func (d SqliteDialect) TruncateClause() string {
 	return "delete from"
 }
 
+func (d SqliteDialect) RestartIdentityClause(table string) string {
+	return ""
+}
+
 ///////////////////////////////////////////////////////
 // PostgreSQL //
 ////////////////
@@ -241,6 +248,10 @@ func (d PostgresDialect) TruncateClause() string {
 	return "truncate"
 }
 
+func (d PostgresDialect) RestartIdentityClause(table string) string {
+	return "restart identity"
+}
+
 ///////////////////////////////////////////////////////
 // MySQL //
 ///////////
@@ -344,3 +355,7 @@ func ReBind(query string, dialect Dialect) string {
 func (m MySQLDialect) TruncateClause() string {
 	return "truncate"
 }
+
+func (d MySQLDialect) RestartIdentityClause(table string) string {
+	return "; alter table " + table + " AUTO_INCREMENT = 1"
+}

modl_test.go

@@ -743,6 +743,44 @@ func TestTruncateTables(t *testing.T) {
 	}
 }
 
+func TestTruncateTablesIdentityRestart(t *testing.T) {
+	dbmap := initDbMap()
+	defer dbmap.DropTables()
+	err := dbmap.CreateTablesIfNotExists()
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Insert some data
+	p1 := &Person{0, 0, 0, "Bob", "Smith", 0}
+	dbmap.Insert(p1)
+	inv := &Invoice{0, 0, 1, "my invoice", 0, true}
+	dbmap.Insert(inv)
+
+	err = dbmap.TruncateTablesIdentityRestart()
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Make sure all rows are deleted
+	people := []Person{}
+	invoices := []Invoice{}
+	dbmap.Select(&people, "SELECT * FROM person_test")
+	if len(people) != 0 {
+		t.Errorf("Expected 0 person rows, got %d", len(people))
+	}
+	dbmap.Select(&invoices, "SELECT * FROM invoice_test")
+	if len(invoices) != 0 {
+		t.Errorf("Expected 0 invoice rows, got %d", len(invoices))
+	}
+
+	p2 := &Person{0, 0, 0, "Other", "Person", 0}
+	dbmap.Insert(p2)
+	if p2.Id != int64(1) {
+		t.Errorf("Expected new person Id to be equal to 1, was %d", p2.Id)
+	}
+}
+
 func TestQuoteTableNames(t *testing.T) {
 	dbmap := initDbMap()
 	defer dbmap.DropTables()