[jira] [Commented] (CASSANDRA-7857) Ability to froze UDT

["Sylvain Lebresne (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-7857?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14117494#comment-14117494 ] 

Sylvain Lebresne commented on CASSANDRA-7857:
---------------------------------------------

As a side node, [~iamaleksey] suggested {{packed}} instead of {{frozen}} and so far this new proposition seems to achieve consensus. It has been further suggested that we use
{noformat}
CREATE TABLE (
    k foo packed PRIMARY KEY
)
{noformat}
instead of
{noformat}
CREATE TABLE (
    k packed<foo> PRIMARY KEY
)
{noformat}
though I don't thing a consensus on that has been reached yet (I think I sligthy prefer sticking to {{packed<foo>}} personally).

> Ability to froze UDT
> --------------------
>
>                 Key: CASSANDRA-7857
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7857
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>             Fix For: 2.1.0
>
>         Attachments: 7857.txt
>
>
> Currently, UDT are serialized into a single value. For 3.0, we want to change that somewhat and allow updating individual subfields: CASSANDRA-7423 (and ultimately, we'll probably allow querying subpart of UDT to some extend). Also for 3.0, we want to allow some nesting of collections (CASSANDRA-7826).
> However, migrating the currently serialized UDT would be challenging. Besides that, even with nested collections, we probably won't be able to support nesting within map keys and sets without serializing (at the very least, not initially). Also, it can be useful in some specific case to have UDT or collections for PK columns, even if those are serialized.
> So we need a better way to distinguish when a composite types (collections & UDT) are serialized (which imply you can't update subpart of the value, you have to rewrite it fully) and when they are not. The suggestion is then to introduce a new keyword, {{frozen}}, to indicate that a type is serialized:
> {noformat}
> CREATE TYPE foo (a int, b int);
> CREATE TABLE bar (
>     k frozen<foo> PRIMARY KEY,
>     m map<frozen<set<int>>, text>
> )
> {noformat}
> A big advantage is that it makes the downside (you can't update the value without rewriting it all) clear and upfront.
> Now, as of 2.1, we only support frozen UDT, and so we should make this clear by 1) adding the frozen keyword and 2) don't allow use of UDT unless they are "frozen" (since that's all we really support). This is what this ticket proposes to do. And this should be done in 2.1.0 or this will be a breaking change.
> We will have a follow-up ticket that will extend {{frozen}} to collection, but this is less urgent since this will be strictly an improvement.
> I'll note that in term of syntax, {{serialized}} was suggested as an alternative to {{frozen}}. I personally have a minor preference for {{serialized}} but it was argued that it had a "sequential" connotation which {{frozen}} don't have. Changing that is still up for discussion, but we need to reach a decision quickly.



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