Online/inplace DDL operations about mysql-5.6

[alxyang]

https://dev.mysql.com/doc/refman/5.6/en/innodb-create-index-overview.html

we need to revisit exactly which of these we can/want to support.
From what I understand, we want to make CREATE INDEX fully online (still allows DML statements to occur).

Also on the roadmap would be renaming columns, default value changes, changing default auto increment value, adding/dropping columns.
For adding/dropping columns, it's unclear to me exactly how online DDL will be faster since it still needs to copy the table under the hood, even according to the documentation above for InnoDB. Need to investigate more here.

[baotiao]

hello @alxyang . what's going on with online DDL feature?

[yoshinorim]

Currently we have higher priorities for 1. supporting MyRocks in MySQL 8.0 and 2. improving MyRocks/RocksDB performance. About online schema change, there are several existing solutions like https://github.com/github/gh-ost so it is not the highest priority. We will be likely to start supporting major features like online schema change based on MySQL 8.0, not 5.6.

[baotiao]

@yoshinorim Thank you. we are going to add this feature in MySQL 5.7, if it work perfectly, we can summit a path for you

[yoshinorim]

@baotiao That is great. Please submit a pull request once it is ready!