mysql_upgrade issue for libmysqld and amarok

[Ian Monroe]

On Fri, Mar 18, 2011 at 05:44, Kristian Nielsen
<knielsen at knielsen-hq.org> wrote:
> This is a follow up on a discussion I had with eean on Freenode IRC #maria.
>
> The issue is how to upgrade libmysqd from MySQL version 5.1 to version 5.5 (or
> more generally any major version upgrade), in particular as relates to
> Amarok's use of libmysqld.
>
> The procedure for upgrading a normal MySQL server is to run the mysql_upgrade
> command. However, this requires a running mysqld server, so it is not
> appropriate for libmysqld, or at least very inconvenient.
>
> We discussed this briefly at our MariaDB meeting in Lisbon, and here is what
> we came up with:
>
> One idea is to also build mysql_upgrade_embedded; this would be a variant of
> mysql_upgrade linked with libmysqld, so it does not depend on the mysqld
> server. Similarly, we would need mysqlcheck_embedded (mysqlcheck is called
> from mysql_upgrade). These two binaries could be included in the libmysqld
> package (they are small).

wouldn't they be huge? libmysqld is a static library, so anything
linking to them is going to be at least 50mb.

> The upgrade procedure for amarok would then be to stop amarok linked with 5.1,
> then run mysql_upgrade_embedded (from 5.5) against the amarok libmysqld data
> directory, then start amarok linked with 5.5.

There can't be any procedure that the user has to do.

But if there is some way for us to determine if mysql_upgrade_embedded
needs to be run, I don't see why this would a problem. Amarok could
run it before initializing the database.

> Does that sound useful?
>
> The other idea that came up was to add this as extra calls in the library. So
> that the amarok application could just call some mysql_upgrade() function
> instead of having to run an external upgrade binary. Would this be more useful
> for amarok?

This sounds much more straightforward.

> Either way, we then need to think on how to implement this change.
>
> We could offer to implement this (either solution I think) in MariaDB (a
> version of MariaDB that includes MySQL 5.5 is in the works). This would allow
> to use the above to upgrade Amarok to using MariaDB 5.5. Would this work?

Sounds good.

> (I think it would even work to keep Amarok using MySQL 5.5 libmysqld, but
> using MariaDB 5.5 mysql_upgrade_embedded, though that is kind of a strange
> solution. Or we could provide the patch for MariaDB and you could patch
> libmysqld similarly to provide the same functionality in relevant distros.)

We really could care less about maria vs. mysql, we just want
something that works.

> Does this sound like a feasible way forward?
>
> One question about how Amarok uses libmysqld, which will help understand what
> is needed to solve the upgrade issue:
>
> Does Amarok use libmysqld built with the --with-embedded-privilege-control
> option, or use stored procedures, or other things that require the `mysql'
> database schema to be available in MySQL?
>
> If this does not make sense, the answer is probably "no" :-)

Doesn't make sense. :)

> The background: When a normal standalone mysql database server is installed,
> it is necessary to create the `mysql' database schema using
> mysql_create_db. This database schema contains such things as user accounts
> and passwords, stored procedure code, etc.
>
> Normally, libmysqld does not do any access control on accounts, and it is
> possible to use it without running mysql_install_db. In fact it's a bit hard
> to run mysql_install_db, as it has the same issue as mysql_upgrade. So I
> assume that Amarok does not do this and just does not use account privileges
> or stored procedures/functions, but just wanted to check?
>
> This affects how much mysql_upgrade_embedded has to do, as part of the upgrade
> is to add any missing columns in tables in the `mysql' database schema.

Since I talked to you last time, I've had reports of people going from
mysql 5.1 to 5.5 without needing mysql_upgrade. mysql_upgrade seemed
to fix things for me, but maybe it was just a coincidence.

Either way though, relying on newer versions of mysql simply not
needing to do any upgrade procedures seems like poor planning.

Ian