Function createDatabaseFromTemplate

coderd/database/dbtestutil/postgres.go:188–227

createDatabaseFromTemplate creates a new database from a template database. If templateDBName is empty, it will create a new template database based on the current migrations, and name it "tpl_ ". Or if it's already been created, it will use that.

(t TBSubset, connParams ConnectionParams, db *sql.DB, newDBName string, templateDBName string)

// the current migrations, and name it "tpl_<migrations_hash>". Or if it's
// already been created, it will use that.
func createDatabaseFromTemplate(t TBSubset, connParams ConnectionParams, db *sql.DB, newDBName string, templateDBName string) error {
	t.Helper()

	emptyTemplateDBName := templateDBName == ""
	if emptyTemplateDBName {
		templateDBName = fmt.Sprintf("tpl_%s", migrations.GetMigrationsHash()[:32])
	}
	_, err := db.Exec("CREATE DATABASE " + newDBName + " WITH TEMPLATE " + templateDBName)
	if err == nil {
		// Template database already exists and we successfully created the new database.
		return nil
	}
	tplDbDoesNotExistOccurred := strings.Contains(err.Error(), "template database") && strings.Contains(err.Error(), "does not exist")
	if (tplDbDoesNotExistOccurred && !emptyTemplateDBName) || !tplDbDoesNotExistOccurred {
		// First and case: user passed a templateDBName that doesn't exist.
		// Second and case: some other error.
		return xerrors.Errorf("create db with template: %w", err)
	}
	if !emptyTemplateDBName {
		// sanity check
		panic("templateDBName is not empty. there's a bug in the code above")
	}

	// The templateDBName is empty, so we need to create the template database.
	err = createAndInitDatabase(t, connParams, db, templateDBName, func(tplDb *sql.DB) error {
		if err := migrations.Up(tplDb); err != nil {
			return xerrors.Errorf("migrate template db: %w", err)
		}
		return nil
	})
	if err != nil {
		return xerrors.Errorf("create template database: %w", err)
	}

	// Try to create the database again now that a template exists.
	if _, err = db.Exec("CREATE DATABASE " + newDBName + " WITH TEMPLATE " + templateDBName); err != nil {
		return xerrors.Errorf("create db with template after migrations: %w", err)
	}
	return nil
}

func createAndInitDatabase(t TBSubset, connParams ConnectionParams, db *sql.DB, name string, initialize func(*sql.DB) error) error {
	// We will use a tx to obtain a lock, so another test or process doesn't race with us.