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> In the old methodology, any schema change requires the entire application to be shut down MySQL perhaps, when even the addition of nullable columns without d
by bsg75 8y ago
> In the old methodology, any schema change requires the entire application to be shut down
MySQL perhaps, when even the addition of nullable columns without defaults or constraints requires a full table lock and copy?
That seems to be a common reason for stating online schema migrations are difficult (not impossible), but not a problem with many other RDBMS engines.
- dub 8y agoWhile it's clear that the author of the linked article isn't familiar with MySQL administration, it's worth noting that the most recent versions of MySQL finally support instant column adds: https://mysqlserverteam.com/mysql-8-0-innodb-now-supports-instant-add-column/ https://mysqlserverteam.com/mysql-8-0-innodb-now-supports-in... That won't save us from needing extra tooling like pt-online-schema-change or gh-ost for other types of schema changes in high availability environments, but it's a step in the right direction.
- VintageCool 8y agoMySQL has supported algorithm=online since the release of MySQL 5.6 in 2013. MySQL builds a shadow copy off the new table in the background, then swaps the new table in for the old table once the copy is complete.