Questo errore può verificarsi a seguito dello spegnimento forzato di un server.
Soluzione: https://stackoverflow.com/questions/33829888/innodb-attempted-to-open-a-previously-opened-tablespace

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* Open my.ini (my.cnf on linux-based systems and Mac)
* Look for [mysqld]
* Just below [mysqld] insert innodb_force_recovery = 1
* Start MySQL Service
* Stop MySQL Service
* Remove the line from my.ini (innodb_force_recovery = 1)
* Start MySQL Service