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From:Jonas Oreland Date:May 6 2005 7:51am
Subject:Re: Alter table clarification
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Hi Nathan,

The problem with our current impl. of alter table is the following.
If using 2 mysqld's.
* One can start the the alter table. 
* But since it does not lock the table, the other can continue making
insert/update/delete.
* The first mysqld can then miss some insert/update/deletes made by the second mysqld.

And the new table (after the alter table) will be inconsistent.
So if you're only running one mysqld, your fine.
If you're using more than one, be careful when using alter table.

/Jonas

> Folks,
> 
> I would like to ask for a clarification regarding the ramifications of 
> ALTER TABLE commands against NDB tables.
> 
> In chapter 16, section 8 of the reference manual, it seems pretty clear 
> that on-line ALTER commands are not supported:
> 
> "It is not possible to make online schema changes such as those 
> accomplished using ALTER TABLE or CREATE INDEX."
> 
> Yet a few bullet points above this it states:
> 
> "ALTER TABLE is not fully locking when running multiple MySQL servers 
> (no distributed table lock)."
> 
> I also found this bit from a few days ago on this list:
> 
> "When you do an alter table, a new copy of the table is created and the
> is copied to that table, which is later renamed to the original, and the
> original table is removed."
> (http://lists.mysql.com/cluster/1864)
> 
> I did a few experiments with alterations that seemed to work and 
> propagate fine. Please clarify for me what the limitations are on table 
> alterations. Other than this small bit of confusion, I have been quite 
> pleased with the NDB cluster engine!
> 
> 
> Cheers,
> 
> Nathan
> 
> -----------------------------------
> Nathan McCall
> Senior Software Engineer
> SunRocket, Inc.
> -----------------------------------
> 
> 


-- 
Jonas Oreland, Software Engineer
MySQL AB, www.mysql.com
Thread
Alter table clarificationNathan McCall5 May
  • Re: Alter table clarificationJonas Oreland6 May
    • Re: Alter table clarificationKris Buytaert17 May
      • Re: Alter table clarificationJon Stephens17 May
        • Re: Alter table clarificationStewart Smith18 May
          • Re: Alter table clarificationJon Stephens18 May