For InnoDB tables, parse the CREATE TABLE statement to defer index and
constraint creation until after data loading. For other storage engines,
the DISABLE/ENABLE KEYS commands achieve similar optimization.
This behavior is controlled by a new option, innodb-optimize-keys
(default: ON), compatible with mydumper.
Additionally, this commit separates the table creation phase from data
loading. Running DDL statements (such as DROP IF EXISTS) in a single
thread avoids the "table not locked" issue from MDEV-34741. As a bonus,
view creation no longer requires a separate step.
