More tests for alter columns migration

Also change the way we handle columns rename migration.
SQLite restrict column addition not to have PRIMARY KEY and/or
UNIQUE attribute, so we have to change from:

add new column -> migrate data from old column to new column ->
rename old table -> create new table with old columns removed ->
migrate data from old table to the new table -> drop old table

to directly:
rename old table -> create new table with renamed columns ->
migrate data from old table to the new table -> drop old table

pkg/database/migrate/migrate.go

@@ -146,7 +146,7 @@ func (m *Migration) up(target, current int64) error {
 
 	// loop through and execute revisions
 	for _, rev := range m.revs {
-		if rev.Revision() > current {
+		if rev.Revision() > current && rev.Revision() <= target {
 			current = rev.Revision()
 			// execute the revision Upgrade.
 			if err := rev.Up(op); err != nil {

pkg/database/migrate/sqlite.go

@@ -85,7 +85,7 @@ func (s *SQLiteDriver) DropColumns(tableName string, columnsToDrop []string) (sq
 	}
 
 	// Clean up proxy table
-	return s.Tx.Exec(fmt.Sprintf("DROP TABLE %s;", proxyName))
+	return s.DropTable(proxyName)
 }
 
 func (s *SQLiteDriver) RenameColumns(tableName string, columnChanges map[string]string) (sql.Result, error) {
@@ -99,30 +99,46 @@ func (s *SQLiteDriver) RenameColumns(tableName string, columnChanges map[string]
 		return nil, err
 	}
 
-	var oldColumns []string
+	// We need a list of columns name to migrate data to the new table
+	var oldColumnsName = selectName(columns)
+
+	// newColumns will be used to create the new table
 	var newColumns []string
-	for k, column := range selectName(columns) {
+
+	for k, column := range oldColumnsName {
+		added := false
 		for Old, New := range columnChanges {
 			if column == Old {
 				columnToAdd := strings.Replace(columns[k], Old, New, 1)
-
-				if results, err := s.AddColumn(tableName, columnToAdd); err != nil {
-					return results, err
-				}
-
-				oldColumns = append(oldColumns, Old)
-				newColumns = append(newColumns, New)
+				newColumns = append(newColumns, columnToAdd)
+				added = true
 				break
 			}
 		}
+		if !added {
+			newColumns = append(newColumns, columns[k])
+		}
 	}
 
-	statement := fmt.Sprintf("UPDATE %s SET %s;", tableName, setForUpdate(oldColumns, newColumns))
-	if results, err := s.Tx.Exec(statement); err != nil {
-		return results, err
+	// Rename current table
+	proxyName := fmt.Sprintf("%s_%s", tableName, uniuri.NewLen(16))
+	if result, err := s.RenameTable(tableName, proxyName); err != nil {
+		return result, err
 	}
 
-	return s.DropColumns(tableName, oldColumns)
+	// Create new table with the new columns
+	if result, err := s.CreateTable(tableName, newColumns); err != nil {
+		return result, err
+	}
+
+	// Migrate data
+	if result, err := s.Tx.Exec(fmt.Sprintf("INSERT INTO %s SELECT %s FROM %s", tableName,
+		strings.Join(oldColumnsName, ", "), proxyName)); err != nil {
+		return result, err
+	}
+
+	// Clean up proxy table
+	return s.DropTable(proxyName)
 }
 
 func (s *SQLiteDriver) getDDLFromTable(tableName string) (string, error) {

pkg/database/migrate/sqlite_test.go

@@ -24,14 +24,10 @@ type AddColumnSample struct {
 	ID   int64  `meddler:"id,pk"`
 	Imel string `meddler:"imel"`
 	Name string `meddler:"name"`
+	Url  string `meddler:"url"`
 	Num  int64  `meddler:"num"`
 }
 
-type RemoveColumnSample struct {
-	ID   int64  `meddler:"id,pk"`
-	Name string `meddler:"name"`
-}
-
 // ---------- revision 1
 
 type revision1 struct{}
@@ -84,12 +80,12 @@ func (r *revision3) Up(op Operation) error {
 	if _, err := op.AddColumn("samples", "url VARCHAR(255)"); err != nil {
 		return err
 	}
-	_, err := op.AddColumn("samples", "likes INTEGER")
+	_, err := op.AddColumn("samples", "num INTEGER")
 	return err
 }
 
 func (r *revision3) Down(op Operation) error {
-	_, err := op.DropColumns("samples", []string{"likes", "url"})
+	_, err := op.DropColumns("samples", []string{"num", "url"})
 	return err
 }
 
@@ -99,6 +95,30 @@ func (r *revision3) Revision() int64 {
 
 // ---------- end of revision 3
 
+// ---------- revision 4
+
+type revision4 struct{}
+
+func (r *revision4) Up(op Operation) error {
+	_, err := op.RenameColumns("samples", map[string]string{
+		"imel": "email",
+	})
+	return err
+}
+
+func (r *revision4) Down(op Operation) error {
+	_, err := op.RenameColumns("samples", map[string]string{
+		"email": "imel",
+	})
+	return err
+}
+
+func (r *revision4) Revision() int64 {
+	return 4
+}
+
+// ----------
+
 var db *sql.DB
 
 var testSchema = `
@@ -163,7 +183,7 @@ func TestMigrateRenameTable(t *testing.T) {
 	}
 
 	if sample.Imel != "foo@bar.com" {
-		t.Errorf("Column doesn't match\n\texpect:\t%s\n\tget:\t%s", "foo@bar.com", sample.Imel)
+		t.Errorf("Column doesn't match. Expect: %s, got: %s", "foo@bar.com", sample.Imel)
 	}
 }
 
@@ -198,6 +218,17 @@ func TestMigrateAddRemoveColumns(t *testing.T) {
 		t.Errorf("Expect length columns: %d\nGot: %d", 5, len(columns))
 	}
 
+	var row = AddColumnSample{
+		ID:   33,
+		Name: "Foo",
+		Imel: "foo@bar.com",
+		Url:  "http://example.com",
+		Num:  42,
+	}
+	if err := meddler.Save(db, "samples", &row); err != nil {
+		t.Errorf("Can not save into database: %q", err)
+	}
+
 	if err := mgr.MigrateTo(1); err != nil {
 		t.Errorf("Can not migrate: %q", err)
 	}
@@ -208,7 +239,36 @@ func TestMigrateAddRemoveColumns(t *testing.T) {
 	}
 
 	if len(another_columns) != 3 {
-		t.Errorf("Expect length columns: %d\nGot: %d", 3, len(columns))
+		t.Errorf("Expect length columns = %d, got: %d", 3, len(columns))
+	}
+}
+
+func TestRenameColumn(t *testing.T) {
+	defer tearDown()
+	if err := setUp(); err != nil {
+		t.Fatalf("Error preparing database: %q", err)
+	}
+
+	Driver = SQLite
+
+	mgr := New(db)
+	if err := mgr.Add(&revision1{}).Add(&revision4{}).MigrateTo(1); err != nil {
+		t.Errorf("Can not migrate: %q", err)
+	}
+
+	loadFixture(t)
+
+	if err := mgr.MigrateTo(4); err != nil {
+		t.Errorf("Can not migrate: %q", err)
+	}
+
+	row := RenameSample{}
+	if err := meddler.QueryRow(db, &row, `SELECT * FROM samples WHERE id = 3;`); err != nil {
+		t.Errorf("Can not query database: %q", err)
+	}
+
+	if row.Email != "crash@bandicoot.io" {
+		t.Errorf("Expect %s, got %s", "crash@bandicoot.io", row.Email)
 	}
 }