On lucene you can query+filter+sort on a single shard, so it should be better than MV/sasi. The index building is a little async though.
On Tue, Oct 4, 2016 at 2:29 PM, Benjamin Roth <benjamin.r...@jaumo.com> wrote: > Thanks guys! > > Good to know, that my approach is basically right, but I will check that > lucene indices by time. > > 2016-10-04 14:22 GMT+02:00 DuyHai Doan <doanduy...@gmail.com>: > >> "What scatter/gather? " >> >> http://www.slideshare.net/doanduyhai/sasi-cassandra-on-the- >> full-text-search-ride-voxxed-daybelgrade-2016/23 >> >> "If you partition your data by user_id then you query only 1 shard to >> get sorted by time visitors for a user" >> >> Exact, but in this case, you're using a 2nd index only for sorting right >> ? For SASI it's not even possible. Maybe it can work with Statrio Lucene >> impl >> >> On Tue, Oct 4, 2016 at 2:15 PM, Dorian Hoxha <dorian.ho...@gmail.com> >> wrote: >> >>> @DuyHai >>> >>> What scatter/gather? If you partition your data by user_id then you >>> query only 1 shard to get sorted by time visitors for a user. >>> >>> On Tue, Oct 4, 2016 at 2:09 PM, DuyHai Doan <doanduy...@gmail.com> >>> wrote: >>> >>>> MV is right now your best choice for this kind of sorting behavior. >>>> >>>> Secondary index (whatever the impl, SASI or Lucene) has a cost of >>>> scatter-gather if your cluster scale out. With MV you're at least >>>> guaranteed to hit a single node everytime >>>> >>>> On Tue, Oct 4, 2016 at 1:56 PM, Dorian Hoxha <dorian.ho...@gmail.com> >>>> wrote: >>>> >>>>> Can you use the lucene index https://github.com/Stratio/cas >>>>> sandra-lucene-index ? >>>>> >>>>> On Tue, Oct 4, 2016 at 1:27 PM, Benjamin Roth <benjamin.r...@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 >
