I'd do something like this:
CREATE TABLE questions (
question_id timeuuid primary key,
question text
);
CREATE TABLE answers (
question_id timeuuid,
answer_id timeuuid,
answer text,
primary key(question_id, answer_id)
);
CREATE TABLE comments (
answer_id timeuuid,
comment_id timeuuid,
comment text,
primary key(question_id, answer_id)
);
You can select all the answers for a given question (ordered by the time
they appeared, yay) with :
SELECT * from answers where question_id = ?
Same applies to comments.
If you want to do categories as well, you'd want to modify the question
table to have category_id as the partition key. Again, I suggest you watch
the videos in Datastax Academy and not try to shortcut your data modeling
knowledge as it's really, really important and screwing it up will cost you
100x the time as well as about a million headaches.
On Tue, Mar 1, 2016 at 9:59 AM Sandeep Kalra <sandeep.ka...@gmail.com>
wrote:
> I do not have limit of number of Answers or its comments. Assume it to
> be clone of StackOverflow..
>
>
>
> Best Regards,
> Sandeep Kalra
>
>
> On Tue, Mar 1, 2016 at 11:29 AM, Jack Krupansky <jack.krupan...@gmail.com>
> wrote:
>
>> Clustering columns are your friends.
>>
>> But the first question is how you need to query the data. Queries drive
>> data models in Cassandra.
>>
>> What is the cardinality of this data - how many answers per question and
>> how many comments per answer?
>>
>>
>> -- Jack Krupansky
>>
>> On Tue, Mar 1, 2016 at 12:23 PM, Sandeep Kalra <sandeep.ka...@gmail.com>
>> wrote:
>>
>>> Hi all.
>>>
>>> I am beginner in Cassandra.
>>>
>>> I am working on Q&A project where I have to maintain a list of list for
>>> objects.
>>>
>>> For e.g. A Question can have list of Answers, and each Answer can then
>>> have list of Comments.
>>>
>>> --
>>> As of now I have 3 tables. Questions, Answers, and Comments. I have
>>> stored UID of Answers in List<uid of answers> for question, and then each
>>> answer has List<UID of comments> in separate table. [Optionally a Comment
>>> may have replies]
>>>
>>> I do multiple queries to find the complete answers-list and then its
>>> related comments.
>>>
>>> This whole thing looks inefficient to me.
>>> --
>>>
>>> Question:
>>> *Is there a better way to do it in Cassandra*. What can I do as far as
>>> re-designing database to have lesser queries.
>>>
>>>
>>>
>>> Best Regards,
>>> Sandeep Kalra
>>>
>>>
>>
>
