MDEV-29069 ER_KEY_NOT_FOUND on online autoinc addition + concurrent DELETE

We can't rely on keys formed with columns that were added during this
ALTER. These columns can be set with non-deterministic values, which can
end up with broken or incorrect search.

The same applies to the keys that contain reliable columns, but also have
bogus ones. Using them can narrow the search, but they're also ignored.

Also, added columns shouldn't be considered during the record match. To
determine them, table->has_value_set bitmap is used.

To fill has_value_set bitmap in the find_key call, extra unpack_row call
has been added.

For replication case, extra replica columns can be considered for this
case. We try to ignore them, too.

mysql-test/main/alter_table_online_debug.test

@@ -1152,6 +1152,144 @@ xa commit 'xid' one phase;
 drop table t;
 set debug_sync= reset;
 
+--echo #
+--echo # MDEV-29069 ER_KEY_NOT_FOUND upon online autoinc addition and
+--echo # concurrent DELETE
+--echo #
+set @old_dbug=@@debug_dbug;
+set debug_dbug="+d,rpl_report_chosen_key";
+
+create table t (a int);
+insert into t values (10),(20),(30);
+
+set debug_sync= 'alter_table_online_downgraded signal downgraded wait_for goforit';
+--send
+alter table t add pk int auto_increment primary key, algorithm=copy, lock=none;
+--connection con2
+set debug_sync= 'now wait_for downgraded';
+delete from t where a = 20;
+update t set a = a + 1 where a = 10;
+set debug_sync= 'now signal goforit';
+
+--connection default
+--reap
+select * from t;
+
+--echo #
+--echo # Add clumsy DEFAULT
+--echo #
+create or replace table t (a int);
+insert into t values (10),(20),(30);
+
+set debug_sync= 'alter_table_online_downgraded signal downgraded wait_for goforit';
+--send
+alter table t add b int default(RAND() * 20), add key(b),
+              algorithm=copy, lock=none;
+--connection con2
+set debug_sync= 'now wait_for downgraded';
+delete from t where a = 20;
+update t set a = a + 1 where a = 10;
+set debug_sync= 'now signal goforit';
+--connection default
+--reap
+select a from t;
+
+--echo # CURRENT_TIMESTAMP
+create or replace table t (a int);
+insert into t values (10),(20),(30);
+
+set debug_sync= 'alter_table_online_downgraded signal downgraded wait_for goforit';
+--send
+alter table t add b timestamp default CURRENT_TIMESTAMP, add key(b),
+              algorithm=copy, lock=none;
+--connection con2
+set debug_sync= 'now wait_for downgraded';
+delete from t where a = 20;
+update t set a = a + 1 where a = 10;
+set debug_sync= 'now signal goforit';
+--connection default
+--reap
+select a from t;
+
+--echo # CURRENT_TIMESTAMP, mixed key
+create or replace table t (a int);
+insert into t values (10),(20),(30);
+
+set debug_sync= 'alter_table_online_downgraded signal downgraded wait_for goforit';
+--send
+alter table t add b timestamp default CURRENT_TIMESTAMP, add key(a, b),
+              algorithm=copy, lock=none;
+--connection con2
+set debug_sync= 'now wait_for downgraded';
+delete from t where a = 20;
+update t set a = a + 1 where a = 10;
+set debug_sync= 'now signal goforit';
+
+--connection default
+--reap
+select a from t;
+
+--echo # Mixed primary key
+create or replace table t (a int);
+insert into t values (10),(20),(30);
+
+set debug_sync= 'alter_table_online_downgraded signal downgraded wait_for goforit';
+--send
+alter table t add b int default (a+1), add primary key(b, a),
+              algorithm=copy, lock=none;
+--connection con2
+set debug_sync= 'now wait_for downgraded';
+delete from t where a = 20;
+update t set a = a + 1 where a = 10;
+set debug_sync= 'now signal goforit';
+
+--connection default
+--reap
+select a from t;
+
+--echo #
+--echo # Normal row, could be used as a key
+--echo #
+create or replace table t (a int);
+insert into t values (10),(20),(30);
+
+set debug_sync= 'alter_table_online_downgraded signal downgraded wait_for goforit';
+--send
+alter table t add b int as (a * 10) unique, algorithm=copy, lock=none;
+--connection con2
+set debug_sync= 'now wait_for downgraded';
+delete from t where a = 20;
+update t set a = a + 1 where a = 10;
+set debug_sync= 'now signal goforit';
+
+--connection default
+--reap
+
+--echo #
+--echo # Add key for old row
+--echo #
+create or replace table t (a int);
+insert into t values (10),(20),(30);
+
+set debug_sync= 'alter_table_online_downgraded signal downgraded wait_for goforit';
+--send
+alter table t add unique(a), algorithm=copy, lock=none;
+--connection con2
+set debug_sync= 'now wait_for downgraded';
+delete from t where a = 20;
+update t set a = a + 1 where a = 10;
+set debug_sync= 'now signal goforit';
+
+--connection default
+--reap
+
+
+# Cleanup
+drop table t;
+set debug_sync= reset;
+set debug_dbug= @old_debug;
+--connection default
+
 --echo #
 --echo # End of 11.2 tests
 --echo #