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While this is true, i don't personally think Percona tools alone makes these changes 'safe'. You can create scenarios where performance is so degraded that you
by verelo 10y ago
While this is true, i don't personally think Percona tools alone makes these changes 'safe'. You can create scenarios where performance is so degraded that you introduce replication delay or service interruptions (and yes the tools have ways to work around that, but it's a significant challenge to tune this correctly on production), data can be lost during the table switch over, and the complication of managing a product / database with a table in an extended migration is very difficult.
This space is far from done, until we can change data structures on the fly...we're going to find there to be a constant struggle between schema and schema-less and neither side will be right or wrong.
Solution: Quantum states; We suspect every possible scenario is happening already, so we should just migrate our database to the appropriate quantum state, where the data is in the structure we desire. Sounds insane, it probably is.
- spotman 10y agoYour absolutely correct that it is not risk free, however, if you do not use foreign keys (which no huge scale mysql install like schemaless does) and you know what your doing (read: calculating the expected load, adding throttles and sanity checks, backups, etc) online alters are extremely feasible with mysql and folks have been doing them for years. I know first hand shops like FB use a similar method in production. Also, big note, the whole point of "schemaless" (And other things, like fb's friend feed architecture) is that you don't make schema changes.