Mysql – Installed thesql 8 on Mac then thesql 5.7 now now they wont work

The problem is that MySQL 5.5 does not support GTIDs, but MySQL 5.7 does and have it activated by default.

As the MySQL manual suggests, you can disable GTIDs on the 5.7 slaves to perform your tests, and later, when all your servers will be upgraded to 5.7, activate GTIDs on both master and slaves.

see http://dev.mysql.com/doc/refman/5.7/en/replication-upgrade.html for more information.

If you are upgrading an existing replication setup from a version of MySQL that does not support global transaction identifiers to a version that does, you should not enable GTIDs on either the master or the slave before making sure that the setup meets all the requirements for GTID-based replication. For example server_uuid, which was added in MySQL 5.6, must exist for GTIDs to function correctly. See Section 18.1.3.2, “Setting Up Replication Using GTIDs”, which contains information about converting existing replication setups to use GTID-based replication.

I was finally successful restoring the data. My problem was, that I tried to restore the data with a docker-compose, which somehow didn't work.

So I took a different approach

1. Run a docker image of mysql:8 and mounted the "corrupt" folder to it

docker run -d -e MYSQL_ROOT_PASSWORD=root -v /path/to/corrupt/folder:/var/lib/mysql --name mrestore mysql:8

The mysql-server started without any problems and I was able to run mysql with

mysql -u root -p.

But when I run the command mysql>show databases; It gave me an error like:

The user specified as a definer ('mysql.infoschema'@'localhost') does not exist

2. Fix user does not exist error

A quick google search led me to the answer of someone having the same problem: https://stackoverflow.com/questions/49992868/mysql-errorthe-user-specified-as-a-definer-mysql-infoschemalocalhost-doe

Which is:

mysql -u root -p
mysql> SET GLOBAL innodb_fast_shutdown = 1;
mysql_upgrade -u root -p

3. Dump databse

Finally I was able to start mysql and dump the database that I thought I've lost

mysqldump -u root -p databasename > databasename.sql