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From "Aleksey Yeschenko (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-5590) User defined types for CQL3
Date Thu, 31 Oct 2013 12:21:18 GMT


Aleksey Yeschenko commented on CASSANDRA-5590:

1. UserType.isCompatibleWith() has redundant logic - (duplicates CT.isCompatibleWith() except
for the type name comparison bit)
2. DefsTables.mergeTypes() 'extension' check is wrong for for equal-sized yet compatible user
types (will simply pick u1 even if u2 is the most recent one, timestamp-wise)
3. UserTypes.Literal.toString() is slightly wrong
4. the cf name for user types should probably be schema_usertypes or schema_user_types - for
consistency's sake (and to be able to continue to reference them as system.schema_* cfs)
5. ALTER TYPE RENAME for the complete type seems to just make a copy of the original type
with a new name. Should drop the original type. Also, should update all the user types that
have the type that's being renamed, updated.. and all the cfs that were using that. IMHO the
complexity is not worth it and we should just drop ALTER TYPE RENAME (the full type rename
variant) entirely. There is always CREATE/DROP/ALTER if a user has to perform a rename, which
should be rare.
6. For auth, we should create a new Resource object and not reuse DataResouce (GRANT/REVOKE
for now). And/or check for ALTER on all the affected by a rename/add tables. Will create a
separate ticket for that.

Attaching a patch that corrects 1-4, with a dose of OCD on top (feel free to ignore the OCD
part or the whole patch if you've got better versions in mind).

Will also create tickets for cqlsh support (DESCRIBE, SELECT, completion for create/alter/drop
type, updated grant/revoke, etc.)

> User defined types for CQL3
> ---------------------------
>                 Key: CASSANDRA-5590
>                 URL:
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: API, Core
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>             Fix For: 2.1
>         Attachments: ocd-and-corrections-patch.txt
> A typical use case for a collection could be to store a bunch of addresses in a user
profile. An address could typically be composed of a few properties: say a street, a city,
a postal code and maybe a few phone numbers associated to it.
> To model that currently with collections, you might use a {{map<string, blob>}},
where the map key could be a string identifying the address, and the value would be all the
infos of an address serialized manually (you can use {{text}} instead of {{blob}} and shove
everything in a string if you prefer but the principle is the same).
> This ticket suggests to make this more user friendly by allowing:
> {noformat}
> CREATE TYPE address (
>   street text,
>   city text,
>   zip_code int,
>   phones set<text>
> )
> CREATE TABLE users (
>   id uuid PRIMARY KEY,
>   name text,
>   addresses map<string, address>
> )
> {noformat}
> Under the hood, that type declaration would just be metadata on top of CompositeType
(which does mean a limitation would be that we wouldn't allow re-ordering or removal of fields
in a custom TYPE). Namely, the {{address}} type would be in practice a {{CompositeType(UTF8Type,
UTF8Type, Int32Type, SetType(UTF8Type))}} + some metadata that records the name of each component.
 In other words, this would mostly be user-friendly syntactic sugar to create composite blobs.
> I'll note that this would also be useful outside collections, as it might sometimes be
more efficient/useful to have such simple composite blob. For instance, you could imagine
to have a:
> {noformat}
> CREATE TYPE fullname (
>   firstname text,
>   lastname text
> )
> {noformat}
> and to rewrite the {{users}} table above as
> {noformat}
> CREATE TABLE users (
>   id uuid PRIMARY KEY,
>   name fullname,
>   addresses map<string, address>
> )
> {noformat}
> In terms of inserts we'd need a syntax for those new "struct". Could be:
> {noformat}
> INSERT INTO users (id, name)
>            VALUES (2ad..., { firstname: 'Paul', lastname: 'smith'});
> UPDATE users
>    SET addresses = address + { 'home': { street: '...', city: 'SF', zip_code: 94102,
phones: {} } }
>    WHERE id=2ad...;
> {noformat}
> where the difference with a map is that the "key" would be a column name (in the CQL3
sense), not a value/literal. Though we might find that a bit confusing and find some other
> On the query side, we could optionally allow things like:
> {noformat}
> SELECT name.firstname, name.lastname FROM users WHERE id=2ad...;
> {noformat}
> One open question however is what type do we send back in the result set
> for a query like:
> {noformat}
> SELECT name FROM users WHERE id=2ad...;
> {noformat}
> We could:
> # return just that it's the user defined type named {{address}}, but that imply the client
has to query the cluster metadata to find out the definition of the type.
> # return the full definition of the type every time.
> I also note that client side, it might be a tad harder to support such types cleanly
in statically type languages than in dynamically typed ones, but that's not the end of the
world either. 

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