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From Ali Akhtar <ali.rac...@gmail.com>
Subject Re: Consistency when adding data to collections concurrently?
Date Sat, 12 Nov 2016 12:06:03 GMT
Thanks DuyHai, I will switch to using a set.

But I'm still not sure how to resolve the original question.

- Original labels = []
- Request 1 arrives with label = 1, and request 2 arrives with label = 2
- Updates are sent to c* with labels = [1] and labels = [2] simultaneously.

What will happen in the above case? Will it cause the labels to end up as
[1,2] (what I want) or either [1] or [2]?

If I use consistency level = all, will that cause it to end up with [1,2]?

On Sat, Nov 12, 2016 at 4:59 PM, DuyHai Doan <doanduyhai@gmail.com> wrote:

> 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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