Assertion `part_id == m_last_part' failed in ha_partition::delete_row

--source include/have_innodb.inc

--source include/have_partition.inc

CREATE TABLE t1 (a CHAR(8) GENERATED ALWAYS AS ('') PERSISTENT) ENGINE=InnoDB PARTITION BY KEY(a) PARTITIONS 2;

SET SQL_MODE= 'EMPTY_STRING_IS_NULL';

INSERT INTO t1 () VALUES ();

BACKUP STAGE START;

BACKUP STAGE BLOCK_COMMIT;

--connect (con1,localhost,root,,test)

SET lock_wait_timeout= 1;

--error ER_LOCK_WAIT_TIMEOUT

DELETE FROM t1;

# Cleanup

--disconnect con1

--connection default

BACKUP STAGE END;

DROP TABLE t1;

mysqld: /data/src/10.4/sql/ha_partition.cc:4552: virtual int ha_partition::delete_row(const uchar*): Assertion `part_id == m_last_part' failed.

200720 19:22:20 [ERROR] mysqld got signal 6 ;

#7  0x00007f1cd0a83f12 in __GI___assert_fail (assertion=0x557bbd9ac81a "part_id == m_last_part", file=0x557bbd9ab770 "/data/src/10.4/sql/ha_partition.cc", line=4552, function=0x557bbd9afc00 <ha_partition::delete_row(unsigned char const*)::__PRETTY_FUNCTION__> "virtual int ha_partition::delete_row(const uchar*)") at assert.c:101

#8  0x0000557bbd4a008b in ha_partition::delete_row (this=0x7f1c7c021248, buf=0x7f1c7c020e08 "\375        ", '\245' <repeats 23 times>, "\070\016\002|\034\177") at /data/src/10.4/sql/ha_partition.cc:4552

#9  0x0000557bbcc63752 in handler::ha_delete_row (this=0x7f1c7c021248, buf=0x7f1c7c020e08 "\375        ", '\245' <repeats 23 times>, "\070\016\002|\034\177") at /data/src/10.4/sql/handler.cc:6827

#10 0x0000557bbce1e59d in TABLE::delete_row (this=0x7f1c7c01ff80) at /data/src/10.4/sql/sql_delete.cc:289

#11 0x0000557bbce1b3da in mysql_delete (thd=0x7f1c7c000af0, table_list=0x7f1c7c011ea0, conds=0x0, order_list=0x7f1c7c0054a8, limit=18446744073709551615, options=0, result=0x0) at /data/src/10.4/sql/sql_delete.cc:804

#12 0x0000557bbc8fbcd6 in mysql_execute_command (thd=0x7f1c7c000af0) at /data/src/10.4/sql/sql_parse.cc:4719

#13 0x0000557bbc90682f in mysql_parse (thd=0x7f1c7c000af0, rawbuf=0x7f1c7c011dd8 "DELETE FROM t1", length=14, parser_state=0x7f1cc5db2570, is_com_multi=false, is_next_command=false) at /data/src/10.4/sql/sql_parse.cc:7899

#14 0x0000557bbc8f2d64 in dispatch_command (command=COM_QUERY, thd=0x7f1c7c000af0, packet=0x7f1c7c0083a1 "DELETE FROM t1", packet_length=14, is_com_multi=false, is_next_command=false) at /data/src/10.4/sql/sql_parse.cc:1834

#15 0x0000557bbc8f1506 in do_command (thd=0x7f1c7c000af0) at /data/src/10.4/sql/sql_parse.cc:1352

#16 0x0000557bbca7a5c4 in do_handle_one_connection (connect=0x557bbf2f8350) at /data/src/10.4/sql/sql_connect.cc:1412

#17 0x0000557bbca7a313 in handle_one_connection (arg=0x557bbf2f8350) at /data/src/10.4/sql/sql_connect.cc:1316

#18 0x0000557bbd479c93 in pfs_spawn_thread (arg=0x557bbf2970b0) at /data/src/10.4/storage/perfschema/pfs.cc:1869

#19 0x00007f1cd2a0c4a4 in start_thread (arg=0x7f1cc5db3700) at pthread_create.c:456

#20 0x00007f1cd0b40d0f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97