Marko Mäkelä 8ea923f55b MDEV-24818: Optimize multi-statement INSERT into an empty table ...

If the user "opts in" (as in the parent
commit 92b2a911e5),
we can optimize multiple INSERT statements to use table-level locking
and undo logging.

There will be a change of behavior:

    CREATE TABLE t(a PRIMARY KEY) ENGINE=InnoDB;
    SET foreign_key_checks=0, unique_checks=0;
    BEGIN; INSERT INTO t SET a=1; INSERT INTO t SET a=1; COMMIT;

will end up with an empty table, because in case of an error,
the entire transaction will be rolled back, instead of rolling
back the failing statement. Previously, the second INSERT statement
would have been logged row by row, and only that second statement
would have been rolled back, leaving the first INSERT intact.

lock_table_x_unlock(), trx_mod_table_time_t::WAS_BULK: Remove.
Because we cannot really support statement rollback in this
optimized mode, we will not optimize the locking. The exclusive
table lock will be held until the end of the transaction.

2021-03-16 15:21:34 +02:00

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