Support non-integer autoincrement fields in postgres

dialect.go

@@ -32,8 +32,6 @@ type Dialect interface {
 	// string to truncate tables
 	TruncateClause() string
 
-	InsertAutoIncr(exec SqlExecutor, insertSql string, params ...interface{}) (int64, error)
-
 	// bind variable string to use when forming SQL statements
 	// in many dbs it is "?", but Postgres appears to use $1
 	//
@@ -53,6 +51,25 @@ type Dialect interface {
 	QuotedTableForQuery(schema string, table string) string
 }
 
+// IntegerAutoIncrInserter is implemented by dialects that can perform
+// inserts with automatically incremented integer primary keys.  If
+// the dialect can handle automatic assignment of more than just
+// integers, see TargetedAutoIncrInserter.
+type IntegerAutoIncrInserter interface {
+	InsertAutoIncr(exec SqlExecutor, insertSql string, params ...interface{}) (int64, error)
+}
+
+// TargetedAutoIncrInserter is implemented by dialects that can
+// perform automatic assignment of any primary key type (i.e. strings
+// for uuids, integers for serials, etc).
+type TargetedAutoIncrInserter interface {
+	// InsertAutoIncrToTarget runs an insert operation and assigns the
+	// resulting automatically generated primary key directly to the
+	// passed in target, which should be a pointer to the primary key
+	// element.
+	InsertAutoIncrToTarget(exec SqlExecutor, insertSql string, target interface{}, params ...interface{}) error
+}
+
 func standardInsertAutoIncr(exec SqlExecutor, insertSql string, params ...interface{}) (int64, error) {
 	res, err := exec.Exec(insertSql, params...)
 	if err != nil {
@@ -225,20 +242,19 @@ func (d PostgresDialect) BindVar(i int) string {
 	return fmt.Sprintf("$%d", i+1)
 }
 
-func (d PostgresDialect) InsertAutoIncr(exec SqlExecutor, insertSql string, params ...interface{}) (int64, error) {
+func (d PostgresDialect) InsertAutoIncrToTarget(exec SqlExecutor, insertSql string, target interface{}, params ...interface{}) error {
 	rows, err := exec.query(insertSql, params...)
 	if err != nil {
-		return 0, err
+		return err
 	}
 	defer rows.Close()
 
 	if rows.Next() {
-		var id int64
-		err := rows.Scan(&id)
-		return id, err
+		err := rows.Scan(target)
+		return err
 	}
 
-	return 0, errors.New("No serial value returned for insert: " + insertSql + " Encountered error: " + rows.Err().Error())
+	return errors.New("No serial value returned for insert: " + insertSql + " Encountered error: " + rows.Err().Error())
 }
 
 func (d PostgresDialect) QuoteField(f string) string {

gorp.go

@@ -1843,18 +1843,28 @@ func insert(m *DbMap, exec SqlExecutor, list ...interface{}) error {
 		}
 
 		if bi.autoIncrIdx > -1 {
-			id, err := m.Dialect.InsertAutoIncr(exec, bi.query, bi.args...)
-			if err != nil {
-				return err
-			}
 			f := elem.FieldByName(bi.autoIncrFieldName)
-			k := f.Kind()
-			if (k == reflect.Int) || (k == reflect.Int16) || (k == reflect.Int32) || (k == reflect.Int64) {
-				f.SetInt(id)
-			} else if (k == reflect.Uint16) || (k == reflect.Uint32) || (k == reflect.Uint64) {
-				f.SetUint(uint64(id))
-			} else {
-				return fmt.Errorf("gorp: Cannot set autoincrement value on non-Int field. SQL=%s  autoIncrIdx=%d autoIncrFieldName=%s", bi.query, bi.autoIncrIdx, bi.autoIncrFieldName)
+			switch inserter := m.Dialect.(type) {
+			case IntegerAutoIncrInserter:
+				id, err := inserter.InsertAutoIncr(exec, bi.query, bi.args...)
+				if err != nil {
+					return err
+				}
+				k := f.Kind()
+				if (k == reflect.Int) || (k == reflect.Int16) || (k == reflect.Int32) || (k == reflect.Int64) {
+					f.SetInt(id)
+				} else if (k == reflect.Uint16) || (k == reflect.Uint32) || (k == reflect.Uint64) {
+					f.SetUint(uint64(id))
+				} else {
+					return fmt.Errorf("gorp: Cannot set autoincrement value on non-Int field. SQL=%s  autoIncrIdx=%d autoIncrFieldName=%s", bi.query, bi.autoIncrIdx, bi.autoIncrFieldName)
+				}
+			case TargetedAutoIncrInserter:
+				err := inserter.InsertAutoIncrToTarget(exec, bi.query, f.Addr().Interface(), bi.args...)
+				if err != nil {
+					return err
+				}
+			default:
+				return fmt.Errorf("gorp: Cannot use autoincrement fields on dialects that do not implement an autoincrementing interface")
 			}
 		} else {
 			_, err := exec.Exec(bi.query, bi.args...)