about Switching Table operation in Gh-ost

[bckim2]

Hello, this is Bckim2.

Could you please tell us about Switching Table operation in Gh-ost ?

It Just execute "alter rename table" like this?

ex)
alter table original-table rename to original-table-backup;
alter table original-table-gho rename to original-table;

if then, What are the measures against meta-locks?

if there is long transacntion in the altering table,
Gh-ost has to occur meta-lock until finish the long transaction.

thanks.

[shlomi-noach]

The table cut-over operation is described here and here. It is not a two-step rename but a single, atomic, blocking rename of both tables.

The measures against meta-locks are #90, namely set session lock_wait_timeout which works very well (starting MySQL 5.6). The default timeout is 3 seconds.

In the event of timeout gh-ost retries multiple times, up to --default-retries times.

gh-ost does not kill queries operating on the table. If you wish to do so (the Facebook tool does that), you can use your own custom hooks.

[bckim2]

thank you for your answer.