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Aleksey Yeschenko commented on CASSANDRA-7423:
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- there is more or less a consensus about UDTs as blobs in its current form
being of very limited usefulness
- making UDTs sub-field resolvable would most likely require the fields to be
stored in separate cells
- thus a rather painful migration will be required (like supercolumns,
CASSANDRA-3237, bugs from which we are still occasionally finding)
- a lot of other huge changes are planned for 3.0. Tackling them all at once,
and UDT migrations on top, might end up being a hellish experience
So I have a controversial suggesting here, especially with 2.1.0 being so
close. Maybe (maybe) we should delay UDTs altogether until 3.0, where we'll
make them properly sub-field resolvable. The native protocol part won't have to
change - we can just remove CREATE/ALTER/DROP TYPE from Cql.g and the docs for
2.1.0, and remove the rest of the code (that needs removal) in 2.1.1+.
> Allow updating individual subfields of UDT
> ------------------------------------------
>
> Key: CASSANDRA-7423
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7423
> Project: Cassandra
> Issue Type: Improvement
> Components: API, Core
> Reporter: Tupshin Harper
> Labels: cql
>
> Since user defined types were implemented in CASSANDRA-5590 as blobs (you
> have to rewrite the entire type in order to make any modifications), they
> can't be safely used without LWT for any operation that wants to modify a
> subset of the UDT's fields by any client process that is not authoritative
> for the entire blob.
> When trying to use UDTs to model complex records (particularly with nesting),
> this is not an exceptional circumstance, this is the totally expected normal
> situation.
> The use of UDTs for anything non-trivial is harmful to either performance or
> consistency or both.
> edit: to clarify, i believe that most potential uses of UDTs should be
> considered anti-patterns until/unless we have field-level r/w access to
> individual elements of the UDT, with individual timestamps and standard LWW
> semantics
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