I am in favor of bringing it back, but I do feel we should also plan how to get it removed as well.
Few examples, would love to see fleshed out * when you drop compact storage and have some SSTables stored in compact storage and some SSTables stored normally, how do we present data correctly? * does upgradesstables and/or compaction migrate off the compact storage format into the normal format? * how do we know it is safe to remove? On Thu, Oct 22, 2020 at 6:55 AM Ekaterina Dimitrova <e.dimitr...@gmail.com> wrote: > Hi Alex, > Thanks for bringing this up. > I am with you for returning part of the code back and considering this as a > bug. > I truly believe it is too late in the release to document changed behavior. > I think this contradicts with the project’s promise for no breaking > changes. This should have been documented in alpha. > Best regards, > Ekaterina > > On Thu, 22 Oct 2020 at 3:20, Oleksandr Petrov <oleksandr.pet...@gmail.com> > wrote: > > > Since this is an important subject, I thought it also makes sense to > start > > a mailing list thread. > > > > You may know that in 4.0 there was a plan to drop compact storage and > > related code. However, there are several behavioural changes related to > > compact storage, and difference in visible behaviour between "normal" and > > compact tables are larger than most of us have anticipated: we first > > thought there’ll be only “appearing column” in dense case, but there’s > > implicit nulls in clusterings thing, and row vs column deletion now, TTL, > > and more. > > > > Some of the recent issues on the subject are: CASSANDRA-16048 > > <https://issues.apache.org/jira/browse/CASSANDRA-16048>, which allows to > > ignore these differences. The other one was an attempt to improve the > user > > experience of anyone still using compact storage: CASSANDRA-15811 > > <https://issues.apache.org/jira/browse/CASSANDRA-15811>. > > > > Easily reproducible differences are: > > > > (1) hidden columns show up, which breaks SELECT * queries > > (2) DELETE v and UPDATE v WITH TTL would result into row removals in > > non-dense compact tables (CASSANDRA-16069 > > <https://issues.apache.org/jira/browse/CASSANDRA-16069>) > > (3) INSERT allows skipping clusterings, which are filled with nulls by > > default. > > > > Some of these are tricky to support, as 15811 has shown. Anyone who might > > want to upgrade to 4.0 while still using compact storage might be > affected > > by being forced into one of these behaviours. > > > > Possible solutions are to document these behaviours, or to bring back a > > minimal set of COMPACT STORAGE and keep supporting these in 4.0 > > > > It looks like it is possible to leave some of the functionality related > to > > DENSE flag and allow it to be present in 4.0, but only for these three > (and > > potential related, however not directly visible) cases. > > > > You can find more details on the subject here: > > https://issues.apache.org/jira/browse/CASSANDRA-16217 > > > > Thank you, > > > > -- Alex > > >
