All the explanation for why just 1 non PK column can be used as PK for MV is here:
https://skillsmatter.com/skillscasts/7446-cassandra-udf-and-materialised-views-in-depth Skip to 19:18 for the explanation On Mon, May 8, 2017 at 8:08 PM, Fridtjof Sander < fridtjof.san...@googlemail.com> wrote: > Hi, > > I'm struggling to understand some problems with respect to materialized > views. > > First, I want to understand the example mentioned in > https://issues.apache.org/jira/browse/CASSANDRA-9928 explaining how > multiple non-PK columns in the view PK can lead to unrepairable/orphanized > entries. I understand that only happens if a node dies that pushed an > "intermediate" state (the result of only one of several updates affecting > the same entry) to it's view replica. The case mentioned looks like the > following: initially all nodes have (p=1, a=1, b=1). Then two concurrent > updates are send: a=2 and b=2. One node gets b=2, deletes view (a=1, b=1, > p=1) and inserts (a=1, b=2, p=1), then dies. The others get a=1, when is > why they delete (a=1, b=1, p=1) and insert (a=2, b=1, p=1). Then (a=1, > b=2, p=1) will never be deleted. > > What I don't understand is, why that can never happen with a single > column. Consider (p=1, a=1) with two updates a=2 and a=3. One node receives > a=2, deletes view entry (a=1, p=1) and inserts (a=2, p=1), then dies. The > others get a=3, delete (a=1, p=1) and insert (a=3, p=1). Now, how is (a=2, > p=1) removed from the view replica that was connected to the dying node? I > don't get what's different here. > > I would really appreciate if someone could share some insight here! > > Fridtjof >
