maria-developers team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxx>]

Hi, Thirunarayanan!

On Nov 13, Thirunarayanan Balathandayuthapani wrote:
> revision-id: a04c60e6c99097c9b52f582b2af891f48b8f662d (mariadb-10.2.18-40-ga04c60e6c99)
> parent(s): ab1ce2204e959bea596817494e932754ab5cbe88
> author: Thirunarayanan Balathandayuthapani <thiru@xxxxxxxxxxx>
> committer: Thirunarayanan Balathandayuthapani <thiru@xxxxxxxxxxx>
> timestamp: 2018-11-12 16:30:34 +0530
> message:
> 
> MDEV-16849 Extending indexed VARCHAR column should be instantaneous
> 
> Analysis:
> ========
> Increasing the length of the indexed varchar column is not an instant operation for
> innodb.
> 
> diff --git a/mysql-test/suite/innodb/r/alter_varchar_change.result b/mysql-test/suite/innodb/r/alter_varchar_change.result
> new file mode 100644
> index 00000000000..b60bd7847db
> --- /dev/null
> +++ b/mysql-test/suite/innodb/r/alter_varchar_change.result
> @@ -0,0 +1,269 @@
...
> +CALL get_table_id("test/t1", @tbl1_id);
> +SELECT @tbl1_id - @tbl_id;
> +@tbl1_id - @tbl_id
> +1

That's a bit fragile, you test that table id was changed exactly by 1.
I don't think the exact difference matters here, so it'd be safer to
test for `SELECT @tbl1_id = @tbl_id` (here and everywhere).

> +SHOW CREATE TABLE t1;
> diff --git a/sql/sql_table.cc b/sql/sql_table.cc
> index 02780e7d1e0..b9668ad0979 100644
> --- a/sql/sql_table.cc
> +++ b/sql/sql_table.cc
> @@ -6687,18 +6687,29 @@ static bool fill_alter_inplace_info(THD *thd,
>           key_part < end;
>           key_part++, new_part++)
>      {
> +      new_field= get_field_by_index(alter_info, new_part->fieldnr);
> +      old_field= table->field[key_part->fieldnr - 1];
>        /*
> +        If there is a change in index length due to column expansion
> +	like varchar(X) changed to varchar(X + N) and has a compatible
> +	packed data representation, we mark it for fast/INPLACE change
> +	in index definition. InnoDB supports INPLACE for this cases

no tabs in the server code, please.

If you're using vim, I can show you my config that has different
formatting style for innodb and the rest of the server :)

> +
>          Key definition has changed if we are using a different field or
> -        if the used key part length is different. It makes sense to
> -        check lengths first as in case when fields differ it is likely
> -        that lengths differ too and checking fields is more expensive
> -        in general case.
> +	if the user key part length is different.
>        */
> -      if (key_part->length != new_part->length)
> +      if (key_part->length != new_part->length &&
> +	  new_field->field != NULL &&

can new_field->field be NULL here? when?

> +          old_field->pack_length() < new_field->pack_length &&

Do you need it? I believe IS_EQUAL_PACK_LENGTH includes this check.

> +	  (key_part->field->is_equal((Create_field*) new_field)
> +           == IS_EQUAL_PACK_LENGTH))
> +      {
> +        ha_alter_info->handler_flags |=
> +           Alter_inplace_info::ALTER_COLUMN_INDEX_LENGTH;
> +      }
> +      else if (key_part->length != new_part->length)
>          goto index_changed;
>  
> -      new_field= get_field_by_index(alter_info, new_part->fieldnr);
> -

Regards,
Sergei
Chief Architect MariaDB
and security@xxxxxxxxxxx