[jira] [Commented] (CASSANDRA-7423) Allow updating individual subfields of UDT

["Robert Stupp (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-7423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14123474#comment-14123474 ] 

Robert Stupp commented on CASSANDRA-7423:
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One question (just for understanding):
Would this mean that each deeply nested field is persisted individually?
For a user-type in a user-type it would lead to a column-name {{upperTypeCol:fieldA:deepTypeFieldA}} (with imaginary column "upperTypeCol" of type "upperType".
But a {{set}} or {{list}} or {{map}} with user types or collections - wouldn't these require "blob serialization"?
AFAIK are {{set}}s serialized with column names like "columnName:setElementValue".
I think "blob serialization" must occur at a certain nesting/usage level - for example when a UDT is used as a map value - or when a UDT is used in a {{list}} (for convenience, when list elements are inserted/removed).

> 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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