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From Sylvain Lebresne <>
Subject Re: DyanmicCompositeType bug?
Date Mon, 05 Dec 2011 09:31:01 GMT
On Mon, Dec 5, 2011 at 8:19 AM, Boris Yen <> wrote:
> Hi,
> I am using 0.8.7.
> I was trying to use DynamicComposite column. After I intentional added a
> column (string:string:uuid) into a record which has previous columns
> inserted with comparator (string:uuid:uuid). I got an exception on the
> cassandra side and an timeout exception on the client (I was actually
> expecting an validation exception on the client).

By design, the DynamicComposite comparator cannot return a validation
exception in that case. Or rather, since there is nothing specifying how
a column should look like, the only way we could ever hope to return a
validation exception would be to scan the entire row on insertion (which
is out of question).

> After that when I re-started cassandra, cassandra kept saying that
> "comparator mismatch while comparing two dynamicCompositeType column..." and
> cassandra never really got started.
> Is this a bug?

No. As said above, this is something we cannot do anything about.
The DynamicCompositeType comparator is by nature a very dangerous
one. One column inserted in the wrong row can corrupt that row (with
recovery involving losing data).
In other words, don't use DynamicCompositeType. Don't use it unless
you are absolutely sure you won't ever insert the wrong column in the
wrong row *and* you absolutely need the DynamicCompositeType (by
opposition to the faster, cheaper and safe CompositeType). And if you
do, you have to assume the consequence if you do mess up.



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