MDEV-24408 Crash-safe DROP DATABASE
Description of how DROP DATABASE works after this patch - Collect list of tables - DDL log tables as they are dropped - DDL log drop database - Delete db.opt - Delete data directory - Log either DROP TABLE or DROP DATABASE to binary log - De active ddl log entry This is in line of how things where before (minus ddl logging) except that we delete db.opt file last to not loose it if DROP DATABASE fails. On recovery we have to ensure that all dropped tables are logged in binary log and that they are properly dropped (as with atomic drop table). No new tables be dropped as part of recovery. Recovery of active drop database ddl log entry: - If drop database was logged to ddl log but was not found in the binary log: - drop the db.opt file and database directory. - Log DROP DATABASE to binary log - If drop database was not logged to ddl log - Update binary log with DROP TABLE of the dropped tables. If table list is longer than max_allowed_packet, then the query will be split into multiple DROP TABLE/VIEW queries. Other things: - Added DDL_LOG_STATE and 'current database' as arguments to mysql_rm_table_no_locks(). This was needed to be able to combine ddl logging of DROP DATABASE and DROP TABLE and make the generated DROP TABLE statements shorter. - To make the DROP TABLE statement created by ddl log shorter, I changed the binlogged query to use current directory and omit the directory part for all tables in the current directory. - Merged some DROP TABLE and DROP VIEW code in ddl logger. This was done to be able get separate DROP VIEW and DROP TABLE statements in the binary log. - Added a 'recovery_state' variable to remember the state of dropped tables and views. - Moved out code that drops database objects (stored procedures) from mysql_rm_db_internal() to drop_database_objects() for better code reuse. - Made mysql_rm_db_internal() global so that could be used by the ddl recovery code.
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