Extra history row when deleting from self-referenced table

--source include/have_innodb.inc

create table t1 (

  f1 int, f2 int,

  key(f1),

  foreign key (f2) references t1 (f1) on delete set null)

with system versioning engine innodb;

insert into t1 values (1, 1), (1, 1);

delete from t1;

select f1, f2, row_start, row_end from t1 for system_time all;

# cleanup

drop table t1;

select f1, f2, row_start, row_end from t1 for system_time all;

f1      f2      row_start       row_end

1       1       2020-12-11 19:53:57.624080      2020-12-11 19:53:57.626972

1       NULL    2020-12-11 19:53:57.626972      2020-12-11 19:53:57.626972

1       1       2020-12-11 19:53:57.624080      2020-12-11 19:53:57.626972

select f1, f2, row_start, row_end from t1 for system_time all;

f1      f2      row_start       row_end

1       1       2020-12-11 19:53:57.624080      2020-12-11 19:53:57.626972

1       1       2020-12-11 19:53:57.624080      2020-12-11 19:53:57.626972

--source include/have_innodb.inc

create table t1 (f1 int, key(f1))

with system versioning engine innodb;

create table t2 (

  f2 int,

  foreign key (f2) references t1 (f1) on delete set null)

with system versioning engine innodb;

insert into t1 values (1), (1);

insert into t2 values (1), (1);

delete from t2;

select f1, row_start, row_end from t1 for system_time all;

select f2, row_start, row_end from t2 for system_time all;

drop tables t2, t1;

select f1, row_start, row_end from t1 for system_time all;

f1      row_start       row_end

1       2020-12-11 19:53:57.671806      2038-01-19 06:14:07.999999

1       2020-12-11 19:53:57.671806      2038-01-19 06:14:07.999999

select f2, row_start, row_end from t2 for system_time all;

f2      row_start       row_end

1       2020-12-11 19:53:57.674496      2020-12-11 19:53:57.677131

1       2020-12-11 19:53:57.674496      2020-12-11 19:53:57.677131