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From DuyHai Doan <doanduy...@gmail.com>
Subject Re: Consistency when adding data to collections concurrently?
Date Sat, 12 Nov 2016 11:59:58 GMT
Don't use list, use set instead. If you need ordering of insertion, use a
map<timeuuid,text> where timeuuid is generated by the client to guarantee
insertion order

When setting a new value to a list, C* will do a read-delete-write
internally e.g. read the current list, remove all its value (by a range
tombstone) and then write the new list. Please note that prepend & append
operations on list do not require this read-delete-write and thus performs
slightly better

On Sat, Nov 12, 2016 at 11:34 AM, Ali Akhtar <ali.rac200@gmail.com> wrote:

> I have a table where each record contains a list<string> of labels.
>
> I have an endpoint which responds to new labels being added to a record by
> the user.
>
> Consider the following scenario:
>
> - Record X, labels = []
> - User selects 2 labels, clicks a button, and 2 http requests are
> generated.
> - The server receives request for Label 1 and Label 2 at the same time.
> - Both requests see the labels as empty, add 1 label to the collection,
> and send it.
> - Record state as label 1 request sees it: [1], as label 2 sees it: [2]
>
> How will the above conflict be resolved? What can I do so I end up with
> [1, 2] instead of either [1] or [2] after both requests have been processed?
>

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