docker-composeでmysqlのバージョン変えたら起動しなくなった

# mysqlのバージョンダウン

何の指定もしていなかったのでMySQL8．0になってた。
使わなければならないversionが5.7だったので以下のように変更。

```docker-compose.yml
    mysql:
      image: mysql
```
↓

```docker-compose.yml
    mysql:
      image: mysql:5.7
```

上記変更後にコンテナとイメージを削除したが、以下のようなエラーが出てmysqlが起動しない。

```
╰─➤  docker-compose logs
Attaching to db, app, datastore
db           | 2019-11-06 08:52:29+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 5.7.28-1debian9 started.
db           | 2019-11-06 08:52:29+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'
db           | 2019-11-06 08:52:29+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 5.7.28-1debian9 started.
db           | 2019-11-06T08:52:30.311329Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
db           | 2019-11-06T08:52:30.312624Z 0 [Note] mysqld (mysqld 5.7.28) starting as process 1 ...
db           | 2019-11-06T08:52:30.315158Z 0 [Note] InnoDB: PUNCH HOLE support available
db           | 2019-11-06T08:52:30.315237Z 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
db           | 2019-11-06T08:52:30.315242Z 0 [Note] InnoDB: Uses event mutexes
db           | 2019-11-06T08:52:30.315245Z 0 [Note] InnoDB: GCC builtin __atomic_thread_fence() is used for memory barrier
db           | 2019-11-06T08:52:30.315247Z 0 [Note] InnoDB: Compressed tables use zlib 1.2.11
db           | 2019-11-06T08:52:30.315249Z 0 [Note] InnoDB: Using Linux native AIO
db           | 2019-11-06T08:52:30.315430Z 0 [Note] InnoDB: Number of pools: 1
db           | 2019-11-06T08:52:30.315535Z 0 [Note] InnoDB: Using CPU crc32 instructions
db           | 2019-11-06T08:52:30.326656Z 0 [Note] InnoDB: Initializing buffer pool, total size = 128M, instances = 1, chunk size = 128M
db           | 2019-11-06T08:52:30.332340Z 0 [Note] InnoDB: Completed initialization of buffer pool
db           | 2019-11-06T08:52:30.334084Z 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the man page of setpriority().
db           | 2019-11-06T08:52:30.349831Z 0 [ERROR] [FATAL] InnoDB: Table flags are 0 in the data dictionary but the flags in file ./ibdata1 are 0x4800!
db           | 2019-11-06 08:52:30 0x7fc5052d8740  InnoDB: Assertion failure in thread 140484172154688 in file ut0ut.cc line 918
db           | InnoDB: We intentionally generate a memory trap.
db           | InnoDB: Submit a detailed bug report to http://bugs.mysql.com.
db           | InnoDB: If you get repeated assertion failures or crashes, even
db           | InnoDB: immediately after the mysqld startup, there may be
db           | InnoDB: corruption in the InnoDB tablespace. Please refer to
db           | InnoDB: http://dev.mysql.com/doc/refman/5.7/en/forcing-innodb-recovery.html
db           | InnoDB: about forcing recovery.
db           | 08:52:30 UTC - mysqld got signal 6 ;
db           | This could be because you hit a bug. It is also possible that this binary
db           | or one of the libraries it was linked against is corrupt, improperly built,
db           | or misconfigured. This error can also be caused by malfunctioning hardware.
db           | Attempting to collect some information that could help diagnose the problem.
db           | As this is a crash and something is definitely wrong, the information
db           | collection process might fail.
```

ぐぐってみると以下のサイトに同様の現象が出てた。
http://unot13.hatenablog.com/entry/2018/09/01/103148

とりあえず以下のコマンドで起動できた。

### コンテナ削除
```
docker ps -a
```

上記で出てきたコンテナの削除

```
docker rm コンテナID
```

### イメージの削除

```
docker images
```
上記で出てきたイメージの削除

```
docker rmi イメージ名
```

### volumeの削除

```
docker volume ls
```

上記で出てきたvolumeの削除

```
docker volume rm VOLUMEのID
```

### buildのやり直し

```
docker-compose build --no-cache
```

### 起動
```
docker-compose up -d
```

無事に起動できました。