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From Benjamin Roth <benjamin.r...@jaumo.com>
Subject Re: Efficient model for a sorting
Date Tue, 04 Oct 2016 17:10:27 GMT
I started off with 3.0.6 and for my personal use case(s) they had the same
bugs as tick tock.

2016-10-04 19:03 GMT+02:00 Jonathan Haddad <jon@jonhaddad.com>:

> I strongly recommend avoiding tick tock. You'll be one of the only people
> putting it in prod and will likely hit a number of weird issues nobody will
> be able to help you with.
> On Tue, Oct 4, 2016 at 12:40 PM Benjamin Roth <benjamin.roth@jaumo.com>
> wrote:
>
>> I have the impression, that not the tick-tock is the real problem but MVs
>> are not really battle-tested yet.
>> Depending on the model, they put much more complexity on a cluster and
>> it's behaviour under heavy load. Especially if you are going to create an
>> MV with a different partition key than the base table this might be a shot
>> in the head.
>> At least I was able to bring my cluster down many times just by throwing
>> a few queries too much at it or by running some big repairs with reaper.
>> Only since some days, things seem to go smoothly after having struggled
>> about 2 months with very different kind of issues.
>>
>> We'll see ... most probably I will stick with the latest version. After
>> all it seems to work ok, I gained a lot of experience in running and
>> troubleshooting and to deal with bugs and maybe I am so able to contribute
>> a bit to further development.
>>
>> 2016-10-04 18:26 GMT+02:00 Vladimir Yudovin <vladyu@winguzone.com>:
>>
>> >Would you consider 3.0.x to be more stable than 3.x?
>> I guess yes, but there are some discussion on this list:
>>
>> (C)* stable version after 3.5
>> <https://lists.apache.org/thread.html/4e4e67175efd1207965eb528e098f35dd268fba0f66632924d8bd0a2@%3Cuser.cassandra.apache.org%3E>
>> Upgrade from 3.0.6 to 3.7.
>> <https://lists.apache.org/thread.html/14e383fabe1ea1750a3e3eec78a1490ae27484ed2d3424d9c3aeb9e2@%3Cuser.cassandra.apache.org%3E>
>>
>> It seems to be eternal topic till tick-tock approach stabilizes.
>>
>>
>> Best regards, Vladimir Yudovin,
>>
>>
>> *Winguzone Inc <https://winguzone.com?from=list> - Hosted Cloud Cassandra
>> on Azure and SoftLayer.Launch your cluster in minutes.*
>>
>>
>> ---- On Tue, 04 Oct 2016 12:19:13 -0400 *Benjamin
>> Roth<benjamin.roth@jaumo.com <benjamin.roth@jaumo.com>>* wrote ----
>>
>> I use the self-compiled master (3.10, ticktock). I had to fix a severe
>> bug on my own and decided to go with the latest code.
>> Would you consider 3.0.x to be more stable than 3.x?
>>
>> 2016-10-04 18:14 GMT+02:00 Vladimir Yudovin <vladyu@winguzone.com>:
>>
>> Hi Benjamin!
>>
>> >we now use CS 3.x and have been advised that 3.x is still not considered
>> really production ready.
>>
>> Did you consider using of 3.0.9? Actually it's 3.0 with almost an year
>> fixes.
>>
>>
>> Best regards, Vladimir Yudovin,
>>
>>
>> *Winguzone Inc <https://winguzone.com?from=list> - Hosted Cloud Cassandra
>> on Azure and SoftLayer.Launch your cluster in minutes.*
>>
>>
>> ---- On Tue, 04 Oct 2016 07:27:54 -0400 *Benjamin Roth
>> <benjamin.roth@jaumo.com <benjamin.roth@jaumo.com>>* wrote ----
>>
>> Hi!
>>
>> I have a frequently used pattern which seems to be quite costly in CS.
>> The pattern is always the same: I have a unique key and a sorting by a
>> different field.
>>
>> To give an example, here a real life example from our model:
>> CREATE TABLE visits.visits_in (
>>     user_id int,
>>     user_id_visitor int,
>>     created timestamp,
>>     PRIMARY KEY (user_id, user_id_visitor)
>> ) WITH CLUSTERING ORDER BY (user_id_visitor ASC)
>>
>> CREATE MATERIALIZED VIEW visits.visits_in_sorted_mv AS
>>     SELECT user_id, created, user_id_visitor
>>     FROM visits.visits_in
>>     WHERE user_id IS NOT NULL AND created IS NOT NULL AND user_id_visitor
>> IS NOT NULL
>>     PRIMARY KEY (user_id, created, user_id_visitor)
>>     WITH CLUSTERING ORDER BY (created DESC, user_id_visitor DESC)
>>
>> This simply represents people, that visited my profile sorted by date
>> desc but only one entry per visitor.
>> Other examples with the same pattern could be a whats-app-like inbox
>> where the last message of each sender is shown by date desc. There are lots
>> of examples for that pattern.
>>
>> E.g. in redis I'd just use a sorted set, where the key could be like
>> "visits_${user_id}", set key would be user_id_visitor and score
>> the created timestamp.
>> In MySQL I'd create the table with PK on user_id + user_id_visitor and
>> create an index on user_id + created
>> In C* i use an MV.
>>
>> Is this the most efficient approach?
>> I also could have done this without an MV but then the situation in our
>> app would be far more complex.
>> I know that denormalization is a common pattern in C* and I don't
>> hesitate to use it but in this case, it is not as simple as it's not an
>> append-only case but updates have to be handled correctly.
>> If it is the first visit of a user, it's that simple, just 2 inserts in
>> base table + denormalized table. But on a 2nd or 3rd visit, the 1st or 2nd
>> visit has to be deleted from the denormalized table before. Otherwise the
>> visit would not be unique any more.
>> Handling this case without an MV requires a lot more effort, I guess even
>> more effort than just using an MV.
>> 1. You need kind of app-side locking to deal with race conditions
>> 2. Read before write is required to determine if an old record has to be
>> deleted
>> 3. At least CL_QUORUM is required to make sure that read before write is
>> always consistent
>> 4. Old record has to be deleted on update
>>
>> I guess, using an MV here is more efficient as there is less roundtrip
>> between C* and the app to do all that and the MV does not require strong
>> consistency as MV updates are always local and are eventual consistent when
>> the base table is. So there is also no need for distributed locks.
>>
>> I ask all this as we now use CS 3.x and have been advised that 3.x is
>> still not considered really production ready.
>>
>> I guess in a perfect world, this wouldn't even require an MV if SASI
>> indexes could be created over more than 1 column. E.g. in MySQL this case
>> is nothing else than a BTree. AFAIK SASI indices are also BTrees, filtering
>> by Partition Key (which should to be done anyway) and sorting by a field
>> would perfectly do the trick. But from the docs, this is not possible right
>> now.
>>
>> Does anyone see a better solution or are all my assumptions correct?
>>
>> --
>> Benjamin Roth
>> Prokurist
>>
>> Jaumo GmbH · www.jaumo.com
>> Wehrstraße 46 · 73035 Göppingen · Germany
>> Phone +49 7161 304880-6 · Fax +49 7161 304880-1
>> AG Ulm · HRB 731058 · Managing Director: Jens Kammerer
>>
>>
>>
>>
>>
>>
>> --
>> Benjamin Roth
>> Prokurist
>>
>> Jaumo GmbH · www.jaumo.com
>> Wehrstraße 46 · 73035 Göppingen · Germany
>> Phone +49 7161 304880-6 · Fax +49 7161 304880-1
>> AG Ulm · HRB 731058 · Managing Director: Jens Kammerer
>>
>>
>>
>>
>>
>>
>> --
>> Benjamin Roth
>> Prokurist
>>
>> Jaumo GmbH · www.jaumo.com
>> Wehrstraße 46 · 73035 Göppingen · Germany
>> Phone +49 7161 304880-6 · Fax +49 7161 304880-1
>> AG Ulm · HRB 731058 · Managing Director: Jens Kammerer
>>
>


-- 
Benjamin Roth
Prokurist

Jaumo GmbH · www.jaumo.com
Wehrstraße 46 · 73035 Göppingen · Germany
Phone +49 7161 304880-6 · Fax +49 7161 304880-1
AG Ulm · HRB 731058 · Managing Director: Jens Kammerer

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