How to restore a MySQL database “safely”

Question

How should you go about restoring (and backing) up a MySQL database "safely"? By "safely" I mean: the restore should create/overwrite a desired database, but not risk altering anything outside that database .

I have already read https://dev.mysql.com/doc/refman/5.7/en/backup-types.html .

I have external users. They & I may want to exchange backups for restore. We do not have a commercial MySQL Enterprise Backup, and are not looking for a third-party commercial offering.

In Microsoft SQL Server there are BACKUP and RESTORE commands. BACKUP creates a file containing just the database you want; both its rows and all its schema/structure are included. RESTORE accepts such a file, and creates or overwrites its structure. The user can restore to a same-named database, or specify a different database name. This kind of behaviour is just what I am looking for.

In MySQL I have come across 3 possibilities:

1. Most people seem to use mysqldump to create a "dump file", and mysql to read that back in. The dump file contains a list of arbitrary MySQL statements, which are simply executed by mysql . This is quite unacceptable: the file could contain any SQL statements. (Limiting access rights of restoring user to try to ensure it cannot do anything "naughty" is not acceptable.) There is also the issue that the user may have created the dump file with the "Include CREATE Schema" option (MySQL Workbench), which hard-codes the original database name for recreation. This "dump" approach is totally unsuitable to me, and I find it surprising that anyone would use it in a production environment.

2. I have come across MySQL's SELECT ... INTO OUTFILE and LOAD DATA INFILE statements. At least they do not contain SQL code to execute. However, they look like a lot of work, deal with a table at time not the whole database, and don't deal with the structure of the tables, you have to know that yourself for restoring. There is a mysqlimport helper command-line utility, but I don't see anything for the export side, and I don't see it for restoring a complete database.

3. The last is to use what MySQL refers to as "Physical (Raw)" rather than "Logical" Backups. This works on the database directories and files themselves. It is the equivalent of SQL Server's detach / attach method for backing up/restoring. But, as per https://dev.mysql.com/doc/refman/5.7/en/backup-types.html , it has all sorts of caveats, eg "Backups are portable only to other machines that have identical or similar hardware characteristics." (I have no idea, eg some users are Windows versus Windows, I have no idea about their architecture) and "Backups can be performed while the MySQL server is not running. If the server is running, it is necessary to perform appropriate locking so that the server does not change database contents during the backup." (let alone restores).

So can anything satisfy (what I regard as) my modest requirements, as outlined above, for MySQL backup/restore? Am I really the only person who finds the above 3 as the only, yet unacceptable, possible solutions?

Answer 1

If you're not going to use third party tools (like innobackupex for example) then you're limited to use ... mysqldump, which is in the mysql package.
I can't understand why it is not acceptable for you, why you don't like sql commands in those dumps. Best practice,when restoring a single db into the server, which already contains other databases, is to have a separated user, with rights only to write into the restored db. Then even if the user performing restore, would change the sql commands and tried to write to another db, they will not be able to.
When doing raw backup (physical copy of database files) you need to have all the instances down, mysql server not running. Similar hardware means you need to have the same directories as the source server (unless you would change my.cnf before starting the server, and putting all the files to right directories).
When coming into mysql, try to not compare it to sql server - it's totally different approach and philosophy.
But if you would convinced yourself anyhow to use third party tool - I recommend innobackex from Percona, which is free btw.

Answer 2

1 - mysqldump - I use this quite a bit, usually in environments where I am handling all the details myself. I do have one configuration where I use that to send copies of a development database - to be dumped/restored in its entirety - to other developers. It is probably the fastest solution, has some reasonable configuration options (eg, to include/exclude specific tables) and generates very functional SQL code (eg, each INSERT batch is small enough to avoid locking/speed issues). For a "replace entire database" or "replace key tables in a specific database" solution, it works very well. I am not too concerned about the "arbitrary SQL commands" problem - if that is an issue then you likely have other issues with users trying to "do their own thing".

2 - SELECT ... INTO OUTFILE and LOAD DATA INFILE - The problem with these is that if you have any really big tables then the LOAD DATA INFILE statement can cause problems because it is trying to load everything all at once. You also have to add code to create (if needed) or empty the tables before LOAD DATA .

3 - Physical (raw) file transfer. This can work but under limited circumstances. I had one situation with a multi-gigabyte database and decided to compress the raw files, move them to the new machine, uncompress and just tell MySQL "everything is already there". It mostly worked well. But I would not recommend it for any unattended/end-user process due to the MANY possible problems.

What do I recommend?

1 - mysqldump - live with its limitations and risks, set up a script to call mysqldump and compress the file (I am pretty sure there are options in mysqldump to do the compression automatically), include the date in the file name so that there is less confusion as the files are sent around, and make a simple script for users to load the file.

2 - Write your own program. I have done this a few times. This is more work initially but allows you to control every aspect of the process and transfer a file that only contains data without any actual SQL code. You can control the specific database, tables, etc. One catch is that if you make any changes to the table structure, indexes, etc. you will need to make sure that information is somehow transmitted to the receiving problem so that it can change the structures as needed - that is not a problem with mysqldump as it normally replaces the tables, creating the new structures, indexes, etc. This can be written in any language that can connect to MySQL - it does not have to be the same language as your application.

Answer 3

The export tool that complements mysqlimport is mysqldump --tab . This outputs CSV files like SELECT...INTO OUTFILE . It also outputs the table structure in much smaller .sql files. So there are two files for each table.

Once you recreate your tables from the .sql files, you can use mysqlimport to import all the data files. You can even use the mysqlimport --use-threads option to make it load multiple data files in parallel.

This way you have more control over which schema to load the data into, and it should run a lot faster than loading a large SQL dump.