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From Rahul Srivastava <srivastava.robi...@gmail.com>
Subject Re: how to make unique coloumns in cassandra
Date Mon, 02 Mar 2015 07:23:04 GMT
but what if i want to fetch the value using on table then this idea might
fail

On Mon, Mar 2, 2015 at 12:46 PM, Ajaya Agrawal <ajku.agr@gmail.com> wrote:

> Make a table for each of the unique keys. For e.g.
>
> If primary key for user table is user_id and you want the phone number
> column to be unique then create another table wherein the primary key is
> (phone_number, user_id). Before inserting to main table try to insert to
> this table first with "if not exists" clause. If it succeeds then go ahead
> with your insert to the user table. Similarly while deleting a row from the
> primary table delete the corresponding row in all other tables. The order
> of insertion to tables matter here otherwise you would end up inducing race
> conditions.
>
> The catch here is, you should not be updating the unique column ever. If
> you do that you would have to use locks and if there are multiple nodes
> running your application then you would need a distributed lock. I would
> suggest not to update the unique columns. In stead force your users to
> delete the entry and recreate it. If you can't do that you need to evaluate
> your choice of database. Perhaps a relational database would be better
> suited to your requirements.
>
> Hope this helps!
>
> -Ajaya
>
> Cheers,
> Ajaya
>
> On Fri, Feb 27, 2015 at 5:26 PM, ROBIN SRIVASTAVA <
> srivastava.robin71@gmail.com> wrote:
>
>> I want to make unique constraint in cassandra . As i want that all the
>> value in my column be unique in my column family ex: name-rahul phone-123
>> address-abc
>>
>> now i want that in this row no values equal to rahul ,123 and abc get
>> inserted again on searching on datastax i found that i can achieve it by
>> doing query on partition key as IF NOT EXIST ,but not getting the solution
>> for getting all the three values unique means if name- jacob phone-123
>> address-qwe
>>
>> this should also be not inserted into my database as my phone column has
>> the same value as i have shown with name-rahul.
>>
>
>

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