# Migrations ## How do I write a migration file? [See here](https://bun.uptrace.dev/guide/migrations.html#migration-names) As a template, take one of the existing migration files and modify it, or use the below code snippet: ```go /* GoToSocial Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details. You should have received a copy of the GNU Affero General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ package migrations import ( "context" "github.com/uptrace/bun" ) func init() { up := func(ctx context.Context, db *bun.DB) error { return db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error { // your logic here return nil }) } down := func(ctx context.Context, db *bun.DB) error { return db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error { // your logic here return nil }) } if err := Migrations.Register(up, down); err != nil { panic(err) } } ``` ## File format Bun requires a very specific format: 14 digits, then letters or underscores. You can use the following bash command on your branch to generate a suitable migration filename. ```bash echo "$(date --utc +%Y%m%d%H%M%S | head -c 14)_$(git rev-parse --abbrev-ref HEAD).go" ``` ## Rules of thumb 1. **DON'T DROP TABLES**!!!!!!!! 2. Don't make something `NOT NULL` if it's likely to already contain `null` fields.