MariaDB replication is not working when no database is selected - database

Question

I'm using MariaDB 10.6.8 and have one of master DB and two of slave DBs. Those DBs are set up for replication.
When I excute INSERT or UPDATE query without database selection, replication doesn't seem to work. In other words, master DB's data is changed but slave DB's data is remains intact.
/* no database is selected */
MariaDB [(none)]> show master status \G
*************************** 1. row ***************************
File: maria-bin.000007
Position: 52259873
Binlog_Do_DB:
Binlog_Ignore_DB:
1 row in set (0.000 sec)
MariaDB [(none)]> UPDATE some_database.some_tables SET some_datetime_column = now() WHERE primary_key_column = 1;
Query OK, 1 row affected (0.002 sec)
Rows matched: 1 Changed: 1 Warnings: 0
MariaDB [(none)]> show master status \G
*************************** 1. row ***************************
File: maria-bin.000007
Position: 52260068
Binlog_Do_DB:
Binlog_Ignore_DB:
1 row in set (0.000 sec)
/* only change master database's record even though the replication position is changed */
However, after selecting the database, replication work fine.
/* but, after selecting the database */
MariaDB [(none)]> USE some_database;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
MariaDB [some_database]> UPDATE some_tables SET some_datetime_column = now() WHERE primary_key_column = 1;
Query OK, 1 row affected (0.002 sec)
Rows matched: 1 Changed: 1 Warnings: 0
/* then change master and slave database's record */
Can anyone tell me what could be the cause of this situation?

Answer 1

Regardless of the binary log format (MIXED, STATEMENT, ROW) all DML commands will be written to the binary log file as soon the transaction will be committed.
When using ROW format a TABLE_MAP event will be logged first, which contains a unique ID, the database and table name. The ROW_EVENT (Delete/Insert/Update) refers to one or more table id's to identify the tables used.
The STATEMENT format logs a query event, which contains the default database name, timestamp and the SQL statement. If there is no default database, the statement itself will contain the database name.
Binlog dump example for STATEMENT format (I removed the non relevant parts such as timestamp and user variables from output)
without default database
#230210 4:42:41 server id 1 end_log_pos 474 CRC32 0x1fa4fa55 Query thread_id=5 exec_time=0 error_code=0 xid=0
insert into test.t1 values (1),(2)
/*!*/;
# at 474
#230210 4:42:41 server id 1 end_log_pos 505 CRC32 0xfecc5d48 Xid = 28
COMMIT/*!*/;
# at 505
with default database:
#230210 4:44:35 server id 1 end_log_pos 639 CRC32 0xfc862172 Query thread_id=5 exec_time=0 error_code=0 xid=0
use `test`/*!*/;
insert into t1 values (1),(2)
/*!*/;
# at 639
#230210 4:44:35 server id 1 end_log_pos 670 CRC32 0xca70b57f Xid = 56
COMMIT/*!*/;
If a session doesn't use a default database on the source server, it may not be replicated if a binary log filter was specified on the replica, e.g. replicate_do_db, since the replica doesn't parse the statement but checks if the database name applies to the filter.
To avoid inconsistent data on your replicas I would recommend to use ROW format instead.