Re: Structural Transactions

[Jonas Oreland]

Fabricio Mota wrote:
> Hi all,
> 
> In my project - as it talks about Distributed Systems and Reliability - one
> of its requirements is a feature to ensure consensus in strutuctural
> modifications (ex.: alter table, create table, etc) between machines.
> 
> So, I need a way to perform structure alterations with possibility to undo
> (such as rollback) and to confirm them (such as commit). So I ask: is there
> anything already implemented in MySQL Server (such as MySQL Cluster code)?
> Because I don't wanna reinvent the wheel... :)
> 
> Waiting
> 
> Fabricio Mota

Ndb currently support distributed schema transactions in the following way.
* Ndb internally keeps a version per table.
* Each schema operation increments the tableversion.
* Only one schema operation can be performed per object at one time.

The MySQL server then "auto discovers" the table definitions from ndb.
I.e if one mysql server creates a table, another gets it the first time it's accessed.

We have a design that will add distributed schema locks for the mysql server using ndb.
This is however not yet implemented.

> 
>>As Sanja has adviced me, many of the concepts and routines from my
>>> project could be reused from NDB...
>>> 
>>> About DDE, I have a first spec in a doc. But I'm afraid to post it on the
>>> list because of its size (aprox. 400KB).
>>> May I send it directly to you?
> 
> 
> Could you put it somewhere and send an url to the list ?

I'm interested in this to...

/Jonas