Hi, Sergei! Thanks for you review. 04.02.2019, 21:59, "Sergei Golubchik" :

Hi, Eugene!

On Feb 04, Eugene Kosov wrote:

...

 revision-id: f93af1f93e2 (mariadb-10.3.12-19-gf93af1f93e2)  parent(s): d4144c8e010  author: Eugene Kosov  committer: Eugene Kosov  timestamp: 2019-01-23 19:32:02 +0300  message:

 MDEV-12836 Avoid table rebuild when adding or removing of auto_increment settings

 ALTER_AUTO_INC: this flag indicates that ALTER operation  adds or removes AUTO_INCREMENT from some field

 Field::is_equal(): now sometime returns IS_EQUAL_BUT_AUTO_INC  which means that only AUTO_INCREMENT was changed for that field

You enable instant alter for adding auto_inc. This is not what Valerii asked for in MDEV-12836, and for a reason. Consider this test case:

  create table t1 (a int unique);   insert t1 values (NULL),(NULL),(NULL);   alter table t1 modify a int auto_increment;

Here we ha_alter_info->handler_flags are: ALTER_CHANGE_COLUMN_DEFAULT ALTER_DROP_UNIQUE_INDEX ALTER_ADD_PK_INDEX ALTER_COLUMN_NOT_NULLABLE This is in a tt-10.3-MDEV-12836-instant-auto-inc branch. F.ex ALTER_COLUMN_NOT_NULLABLE requires rebuild in InnoDB not counting AUTO_INCREMENT at all. So, I think this is not related to MDEV-12836 create table t1 (a int not null, unique key a_key (a)) engine=innodb; insert into t1 values (19), (1), (100500); alter table t1 modify a int not null auto_increment,algorithm=instant; drop table t1; In this modified test case we have ALTER_CHANGE_COLUMN_DEFAULT and ALTER_AUTO_INC which is can be done instantly now. And this is now the subject of MDEV-12836.

here `alter table` modifies the data, actually generating auto-inc values for all NULL columns. I don't think you can do that instantly. You can only remove auto-inc instantly. And for that you don't need any big changes, just modify Field::is_equal() to allow it:

diff --git a/sql/field.cc b/sql/field.cc --- a/sql/field.cc +++ b/sql/field.cc @@ -3507,7 +3507,7 @@ uint Field_new_decimal::is_equal(Create_field *new_field)    return ((new_field->type_handler() == type_handler()) &&            ((new_field->flags & UNSIGNED_FLAG) ==             (uint) (flags & UNSIGNED_FLAG)) && - ((new_field->flags & AUTO_INCREMENT_FLAG) == + ((new_field->flags & AUTO_INCREMENT_FLAG) <=             (uint) (flags & AUTO_INCREMENT_FLAG)) &&            (new_field->length == max_display_length()) &&            (new_field->decimals == dec)); @@ -9508,7 +9508,7 @@ uint Field_num::is_equal(Create_field *new_field)    return ((new_field->type_handler() == type_handler()) &&            ((new_field->flags & UNSIGNED_FLAG) ==             (uint) (flags & UNSIGNED_FLAG)) && - ((new_field->flags & AUTO_INCREMENT_FLAG) == + ((new_field->flags & AUTO_INCREMENT_FLAG) <=            (uint) (flags & AUTO_INCREMENT_FLAG)) &&            (new_field->pack_length == pack_length()));  }

And this should be enough.

Regards, Sergei Chief Architect MariaDB and security@mariadb.org

-- Eugene