Create pipe.
Create databases and some data.
CREATE DATABASE db1;
CREATE DATABASE db2;
USE db1;
CREATE TABLE t1(id int);
INSERT INTO t1 VALUES(1),(2),(3),(4),(5),(6),(7),(8),(9);
INSERT INTO t1 SELECT * FROM t1;
INSERT INTO t1 SELECT * FROM t1;
INSERT INTO t1 SELECT * FROM t1;
INSERT INTO t1 SELECT * FROM t1;
USE db2;
CREATE TABLE t2(a char(5));
INSERT INTO t2 VALUES('a'),('b'),('c'),('d'),('e'),('f'),('g'),('h');
INSERT INTO t2 SELECT * FROM t2;
INSERT INTO t2 SELECT * FROM t2;
INSERT INTO t2 SELECT * FROM t2;
Start backup to pipe.
BACKUP DATABASE db1 TO 'db1_pipe';
Attempt to run a backup while another is in progress.
BACKUP DATABASE db2 TO 'db1_pipe';
ERROR HY000: Can't execute this command because another BACKUP/RESTORE operation is in progress
Cat the output to a file.
backup_id
#
Start another backup to the same pipe.
BACKUP DATABASE db2 TO 'db1_pipe';
Cat the output to a file.
backup_id
#
Cleanup
DROP DATABASE db1;
DROP DATABASE db2;