From 0c5d1342ae6b5ab3256848be7a83e5c3b1f21566 Mon Sep 17 00:00:00 2001 From: Sachin Date: Fri, 29 Jan 2021 11:59:14 +0000 Subject: MDEV-11675 Lag Free Alter On Slave This commit implements two phase binloggable ALTER. When a new @@session.binlog_alter_two_phase = YES ALTER query gets logged in two parts, the START ALTER and the COMMIT or ROLLBACK ALTER. START Alter is written in binlog as soon as necessary locks have been acquired for the table. The timing is such that any concurrent DML:s that update the same table are either committed, thus logged into binary log having done work on the old version of the table, or will be queued for execution on its new version. The "COMPLETE" COMMIT or ROLLBACK ALTER are written at the very point of a normal "single-piece" ALTER that is after the most of the query work is done. When its result is positive COMMIT ALTER is written, otherwise ROLLBACK ALTER is written with specific error happened after START ALTER phase. Replication of two-phase binloggable ALTER is cross-version safe. Specifically the OLD slave merely does not recognized the start alter part, still being able to process and memorize its gtid. Two phase logged ALTER is read from binlog by mysqlbinlog to produce BINLOG 'string', where 'string' contains base64 encoded Query_log_event containing either the start part of ALTER, or a completion part. The Query details can be displayed with `-v` flag, similarly to ROW format events. Notice, mysqlbinlog output containing parts of two-phase binloggable ALTER is processable correctly only by binlog_alter_two_phase server. @@log_warnings > 2 can reveal details of binlogging and slave side processing of the ALTER parts. The current commit also carries fixes to the following list of reported bugs: MDEV-27511, MDEV-27471, MDEV-27349, MDEV-27628, MDEV-27528. Thanks to all people involved into early discussion of the feature including Kristian Nielsen, those who helped to design, implement and test: Sergei Golubchik, Andrei Elkin who took the burden of the implemenation completion, Sujatha Sivakumar, Brandon Nesterenko, Alice Sherepa, Ramesh Sivaraman, Jan Lindstrom. --- sql/log.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'sql/log.h') diff --git a/sql/log.h b/sql/log.h index b55ed0f31f6..b4c82e0aed4 100644 --- a/sql/log.h +++ b/sql/log.h @@ -1266,5 +1266,8 @@ get_gtid_list_event(IO_CACHE *cache, Gtid_list_log_event **out_gtid_list); int binlog_commit(THD *thd, bool all, bool is_ro_1pc= false); int binlog_commit_by_xid(handlerton *hton, XID *xid); int binlog_rollback_by_xid(handlerton *hton, XID *xid); +bool write_bin_log_start_alter(THD *thd, bool& partial_alter, + uint64 start_alter_id, bool log_if_exists); + #endif /* LOG_H */ -- cgit v1.2.1