MDEV-19229 Allow innodb_undo_tablespaces to be changed after database creationbb-10.6-MDEV-19229

trx_sys_t::undo_log_empty: Set to true if there are no undo log
to rollback and purge.

The algorithm for re-creating the undo tablespace when
trx_sys_t::undo_log_empty is enabled:

1) Free the rollback segment header page of system tablespace
for the slots 1..127

2) trx_sys_t::reset_page(): Reset the TRX_SYS page and assign all
rollback segment slots from 1..127 to FIL_NULL

3) Update the binlog and WSREP information in system tablespace
rollback segment header
Step (2) and Step (3) should happen atomically within a
single mini-transaction.

4) srv_undo_delete_old_tablespaces(): Delete the old undo tablespaces
present in the undo log directory

5) Make checkpoint to get rid of old undo log tablespaces redo logs

6) Assign new start space id for the undo log tablespaces

7) Re-create the specified undo log tablespaces. InnoDB uses same
mtr for above (6), (7)

8) Make checkpoint again, so that server or mariabackup
can read the undo log tablespace page0 before applying
the redo logs

9) Assign the rollback segment header page for each rollback
segment slots

srv_undo_tablespaces_reinit(): Recreate the undo log tablespaces.
It does reset trx_sys page, delete the old undo tablespaces,
update the binlog offset, write set replication checkpoint
in system rollback segment page

trx_rseg_update_binlog_offset(): Added 2 new parameters to pass
binlog file name and binlog offset

trx_rseg_array_init(): Return error if the rollback segment
slot points to non-existent tablespace

srv_undo_tablespaces_init(): Added new parameter mtr that can be
used for reinitialization of undo tablespaces

wf_incremental_process(): Detects whether TRX_SYS page has been
modified since last backup. If it is then incremental backup
fails and throws the information about taking full backup again

xb_assign_undo_space_start(): Removed the function. Because
undo001 has first undo space id value in page0

trx_assign_rseg_low(): Even user mentioned the innodb_undo_tablespace
value as 0, allow the transaction to use the other undo tablespace
rollback segment slots

srv_start(): Override the user specified value of
innodb_undo_tablespaces variable with already existing actual
undo tablespaces

Added test case to test the scenario during startup and mariabackup
incremental process too.

1 files changed, 4 insertions, 3 deletions

diff --git a/storage/innobase/include/srv0start.h b/storage/innobase/include/srv0start.h
index 44b19aa666b..1372959d184 100644
--- a/storage/innobase/include/srv0start.h
+++ b/storage/innobase/include/srv0start.h
@@ -33,10 +33,11 @@ Created 10/10/1995 Heikki Tuuri
 struct dict_table_t;
 
 /** Open the configured number of dedicated undo tablespaces.
-@param[in]	create_new_db	whether the database is being initialized
+@param[in]      create_new_undo whether the undo tablespaces has to be created
+@param[in]      mtr             mini-transaction in case of reinitialize
+                                of undo tablespaces
 @return DB_SUCCESS or error code */
-dberr_t
-srv_undo_tablespaces_init(bool create_new_db);
+dberr_t srv_undo_tablespaces_init(bool create_new_undo, mtr_t *mtr= nullptr);
 
 /** Start InnoDB.
 @param[in]	create_new_db	whether to create a new database