You can't, iirc - if you add an autoincrement to InnoDB it MUST be the
primary key.
You *can*, however, add that, set it as PK and stick a unique index on
(cluster, file) instead. Behaviour will be identical, but be aware that
there will be some performance implications - you will now have to do an
extra primary key lookup every time you select based on the (cluster,file)
key.
On Thu, Apr 22, 2010 at 7:03 AM, Aveek Misra <aveekm@stripped> wrote:
> I have a InnoDB table which contains columns named 'cluster' and 'file'
> ('cluster' + 'file' is a primary key). I want to add a new column that
> tracks the revision number of a file for a given cluster and a file. The
> situation is tailor made for a MyIsam table where I can add a new Auto
> Increment column as a secondary column in a multiple column index. How can I
> get the same behavior in an InnoDB table? Given below is a view of how the
> records will look like
>
> --------------------------------------------------------
> | Cluster | File | Rev |
> --------------------------------------------------------
> | clusterA | fileA | 1 |
> --------------------------------------------------------
> | clusterA | fileA | 2 |
> ---------------------------------------------------------
> | clusterB | fileA | 1 |
> --------------------------------------------------------
> | clusterB | fileB | 1 |
> --------------------------------------------------------
>
>
>
> Thanks
> Aveek
>
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