Correction from previous query Thanks Ben and all experts.
I am almost a newbie to NoSQL world and thus I have a very general question how does consumer application of Cassandra/other NoSQL technologies deal with atomicity & other factors when there is need to *de-normalize *data. For example: Let us say I have requirement for queries - find all hotels by name - Find all hotels by Point of Interest (POI) - Find POI near by a hotel For these queries I would end up more or less in following tables hotels_by_name(hotel_name,hotel_id,city,........) primary key - hotel_name hotels_by_poi(poi_name,poi_id,hotel_id,hotel_name,......) primary key - poi_name poi_by_hotel(hotel_id,poi_name,poi_id,poi_loc,hotel_name,......) primary key - hotel_id So, If I have to add/remove a hotel from/into hotels_by_name , I may need to add/remove into/from tables hotels_by_poi/poi_by_hotel. So, here my assumption is these operations would need to be atomic( and may be supporting other ACID properties) . How these kind of operations/usecases being handled in Cassandra/NoSQL world? Appreciate your response. Thanks, Rajesh On Thu, Apr 26, 2018 at 8:05 AM, Rajesh Kishore <rajesh10si...@gmail.com> wrote: > Thanks Ben and all experts. > > I am almost a newbie to NoSQL world and thus I have a very general > question how does consumer application of Cassandra/other NoSQL > technologies deal with atomicity & other factors when there is need to > normalize data. For example: > > Let us say I have requirement for queries > - find all hotels by name > - Find all hotels by Point of Interest (POI) > - Find POI near by a hotel > > For these queries I would end up more or less in following tables > hotels_by_name(hotel_name,hotel_id,city,........) primary key - hotel_name > hotels_by_poi(poi_name,poi_id,hotel_id,hotel_name,......) primary key - > poi_name > poi_by_hotel(hotel_id,poi_name,poi_id,poi_loc,hotel_name,......) primary > key - hotel_id > > So, If I have to add/remove a hotel from/into hotels_by_name , I may need > to add/remove into/from tables hotels_by_poi/poi_by_hotel. So, here my > assumption is these operations would need to be atomic( and may be > supporting other ACID properties) . How these kind of operations/usecases > being handled in Cassandra/NoSQL world? > > Appreciate your response. > > Thanks, > Rajesh > > > > On Fri, Apr 20, 2018 at 11:07 AM, Ben Slater <ben.sla...@instaclustr.com> > wrote: > >> The second SO answer just says the partitions will be collocated (ie on >> the same server) not that the two tables will use the same partition. In >> any event, Cassandra does not have the kind of functionality you are >> looking for. The closest is logged batch but as Sylvain said, "all that >> guarantees is that if some operations of a batch are applied, then all >> of them will >> *eventually* get applied” and “batch have no rollback whatsoever”. >> >> As Cassandra won’t help you here, a potential (although admittedly more >> complex) option is to do implement compensating transactions at the >> application level (eg in the catch block delete the records that were >> inserted). That, however, does not provide you the isolation part of ACID. >> >> You also tend to find that if you have properly denormalised your data >> model for Cassandra there is less requirement for these type of batched >> updates. >> >> Cheers >> Ben >> >> On Fri, 20 Apr 2018 at 15:21 Rajesh Kishore <rajesh10si...@gmail.com> >> wrote: >> >>> Re-framing my question: >>> >>> So, it means that having different tables will not result into same >>> partition even though you have same partition key. >>> Ex. >>> TableA( Partionkey(id)) >>> TableB( Partionkey(id)) >>> TableC( Partionkey(id)) >>> >>> >>> and as part of batch operation I am somehow providing same id say "20" >>> It wont be considered as Atomic as it will result into different >>> partition key and there would not be any way to rollback ? >>> The same is being claimed in https://stackoverflow.com/ques >>> tions/36700859/does-the-same-partition-key-in-different- >>> cassandra-tables-add-up-to-cell-theoret >>> >>> Now, the other forum says that how we can keep two tables in same >>> partition >>> https://stackoverflow.com/questions/34294830/how-to-keep-2- >>> cassandra-tables-within-same-partition >>> >>> Which one is correct ? Please confirm >>> >>> Basically , our requirement is - we should be able to achieve similar >>> functionality as that of JDBC >>> try { >>> txn.start() >>> operation a >>> operation b >>> >>> ...... >>> operation n >>> txn.commit(); >>> } catch (Exception e) >>> { >>> txn.rollback() >>> } >>> >>> Thanks in advance. >>> >>> Regards, >>> Rajesh >>> >>> On Fri, Apr 20, 2018 at 9:38 AM, Rajesh Kishore <rajesh10si...@gmail.com >>> > wrote: >>> >>>> So, it means that having different tables will not result into same >>>> partition even though you have same partition key. >>>> Ex. >>>> TableA( Partionkey(id)) >>>> TableB( Partionkey(id)) >>>> TableC( Partionkey(id)) >>>> >>>> >>>> and as part of batch operation I am somehow providing same id say "20" >>>> It wont be considered as Atomic as it will result into different >>>> partition key and there would not be any way to rollback ? >>>> The same is being claimed in https://stackoverflow.com/ques >>>> tions/36700859/does-the-same-partition-key-in-different- >>>> cassandra-tables-add-up-to-cell-theoret >>>> >>>> Please confirm >>>> >>>> Thanks in advance. >>>> >>>> Regards, >>>> Rajesh >>>> >>>> >>>> >>>> On Thu, Apr 19, 2018 at 3:10 PM, Jacques-Henri Berthemet < >>>> jacques-henri.berthe...@genesys.com> wrote: >>>> >>>>> When using BATCH on multiple tables you’ll need to use a LOGGED >>>>> batch. When you send the request, it will be written to the batch log of >>>>> all (relevant) nodes, when this write is successful it will be “ >>>>> accepted” and nodes will try to apply the batch operations. If for >>>>> any reason a statement fails the node will keep retrying forever. In that >>>>> case you may see partially applied batch until it’s fixed. >>>>> >>>>> >>>>> >>>>> Note that you can’t mix BATCH and LWT on different tables/partitions. >>>>> >>>>> >>>>> >>>>> You can get more details here: >>>>> >>>>> http://cassandra.apache.org/doc/latest/cql/dml.html#batch >>>>> >>>>> https://inoio.de/blog/2016/01/13/cassandra-to-batch-or-not-to-batch/ >>>>> >>>>> *--* >>>>> >>>>> *Jacques-Henri Berthemet* >>>>> >>>>> >>>>> >>>>> *From:* Rajesh Kishore [mailto:rajesh10si...@gmail.com] >>>>> *Sent:* Thursday, April 19, 2018 11:13 AM >>>>> *To:* user@cassandra.apache.org >>>>> >>>>> *Subject:* Re: Does Cassandra supports ACID txn >>>>> >>>>> >>>>> >>>>> Thanks for the response. Let me put my question again wrt a example >>>>> >>>>> I want to perform a atomic txn say insert/delete/update on a set of >>>>> tables >>>>> >>>>> TableA >>>>> >>>>> TableB >>>>> >>>>> TableC >>>>> >>>>> When these are performed as batch operations and let us say something >>>>> goes wrong while doing operation at TableC >>>>> >>>>> Would the system rollback the operations done for TableA TableB ? >>>>> >>>>> -Rajesh >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> On Thu, Apr 19, 2018 at 1:25 PM, Jacques-Henri Berthemet < >>>>> jacques-henri.berthe...@genesys.com> wrote: >>>>> >>>>> Cassandra support LWT (Lightweight transactions), you may find this >>>>> doc interesting: >>>>> >>>>> https://docs.datastax.com/en/cassandra/3.0/cassandra/dml/dml >>>>> DataConsistencyTOC.html >>>>> >>>>> >>>>> >>>>> In any case, LWT or BATCH you won’t have external control on the tx, >>>>> it’s either done or not done. In case of timeout you won’t have a way >>>>> to know if it worked or not. >>>>> >>>>> There is no way to rollback a statement/batch, the only way is to send >>>>> an update to modify the partition to its previous state. >>>>> >>>>> >>>>> >>>>> Regards, >>>>> >>>>> *--* >>>>> >>>>> *Jacques-Henri Berthemet* >>>>> >>>>> >>>>> >>>>> *From:* DuyHai Doan [mailto:doanduy...@gmail.com] >>>>> *Sent:* Thursday, April 19, 2018 9:10 AM >>>>> *To:* user <user@cassandra.apache.org> >>>>> *Subject:* Re: Does Cassandra supports ACID txn >>>>> >>>>> >>>>> >>>>> No ACID transaction any soon in Cassandra >>>>> >>>>> >>>>> >>>>> On Thu, Apr 19, 2018 at 7:35 AM, Rajesh Kishore < >>>>> rajesh10si...@gmail.com> wrote: >>>>> >>>>> Hi, >>>>> >>>>> I am bit confused by reading different articles, does recent version >>>>> of Cassandra supports ACID transaction ? >>>>> >>>>> I found BATCH command , but not sure if it supports rollback, consider >>>>> that transaction I am going to perform would be on single partition. >>>>> >>>>> Also, what are the limitations if any? >>>>> >>>>> >>>>> >>>>> Thanks, >>>>> >>>>> Rajesh >>>>> >>>>> >>>>> >>>>> >>>>> >>>> >>>> >>> -- >> >> >> *Ben Slater* >> >> *Chief Product Officer <https://www.instaclustr.com/>* >> >> <https://www.facebook.com/instaclustr> >> <https://twitter.com/instaclustr> >> <https://www.linkedin.com/company/instaclustr> >> >> Read our latest technical blog posts here >> <https://www.instaclustr.com/blog/>. >> >> This email has been sent on behalf of Instaclustr Pty. Limited >> (Australia) and Instaclustr Inc (USA). >> >> This email and any attachments may contain confidential and legally >> privileged information. If you are not the intended recipient, do not copy >> or disclose its content, but please reply to this email immediately and >> highlight the error to the sender and then immediately delete the message. >> > >
