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From "Ekaterina Dimitrova (Jira)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-16217) Minimal 4.0 COMPACT STORAGE backport
Date Wed, 21 Oct 2020 14:03:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-16217?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17218304#comment-17218304
] 

Ekaterina Dimitrova commented on CASSANDRA-16217:
-------------------------------------------------

Hi @Alex, 

Thanks for pinging.

??Possible solutions are to document these behaviours, or to bring back a minimal set of COMPACT
STORAGE to keep supporting these.??

I am +1 on adding the minimal support and not having breaking changes. 

> Minimal 4.0 COMPACT STORAGE backport
> ------------------------------------
>
>                 Key: CASSANDRA-16217
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-16217
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Alex Petrov
>            Assignee: Alex Petrov
>            Priority: Normal
>
> There are several behavioural changes related to compact storage, and these differences
are larger than most of us have anticipated: we first thought there’ll be that “appearing
column”, but there’s implicit nulls in clusterings thing, and row vs column deletion.
> Some of the recent issues on the subject are: CASSANDRA-16048, which allows to ignore
these differences. The other one was trying to improve user experience of anyone still using
compact storage: CASSANDRA-15811.
> Easily reproducible differernces 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)
>  (3) INSERT allows skipping clusterings, which are filled with nulls by default.
> Some of these are tricky to support, as 15811 has shown. Anyone on OSS side 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 to keep supporting these.
> 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 direrclty visible) cases.
> [~e.dimitrova] since you were working on removal on compact storage, wanted to reassure
that this is not a revert of your patch. On contrary: your patch was instrumental in identifying
the right places.
> cc [~slebresne] [~aleksey] [~benedict] [~marcuse]
> Preliminary patch: [https://github.com/apache/cassandra/pull/785]



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