Maybe you should use my Achilles mapper, which does generates UPDATE statements on collections and not only INSERT Le 12 nov. 2016 13:08, "Ali Akhtar" <ali.rac...@gmail.com> a écrit :
> I am using the Java Cassandra mapper for all of these cases, so my code > looks like this: > > Item myItem = myaccessor.get( itemId ); > Mapper<Item> mapper = mappingManager.create( Item.class ); > > myItem.labels.add( newLabel ); > mapper.save( myItem ); > > On Sat, Nov 12, 2016 at 5:06 PM, Ali Akhtar <ali.rac...@gmail.com> wrote: > >> 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 <doanduy...@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.rac...@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? >>>> >>> >>> >> >
