> As another option, we could add an @Experimetal annotation (or another name)
> and a configuration parameter experimental_virtula_tables_enabled
Since these are tables we have TableProps so we could always store an
experimental = true there and if Config.experimental_virtula_tables_enabled ==
false we just skip those tables when we load them.
That way authors would just do the following…
CreateTableStatement.parse(query, keyspace)
.comment(comment)
.kind(TableMetadata.Kind.VIRTUAL)
.experimental(true)
.build();
And VirtualKeyspace would skip it when
Config.experimental_virtula_tables_enabled == false
This feels very similar to the JDK… some features require you to opt into
experimental things twice…
> What about putting such a table to system_experimental keyspace?
I like it as it makes this apart of its name, but is sad that we must break
compatibility once we mark it stable (as we move the keyspace).
> On May 29, 2024, at 1:23 PM, Štefan Miklošovič <stefan.mikloso...@gmail.com>
> wrote:
>
> I think that 2) (client warning on accessing vtable) is pretty obtrusive /
> irritating, that means that every single time I would e.g. SELECT from such a
> table, it would emit a warning to a client / cqlsh? I do not think that is
> necessary.
>
> What about putting such a table to system_experimental keyspace? Then it
> would be about deciding when it is not considered experimental anymore and
> once that happens, we just move it to the appropriate keyspace. I think that
> it is better if users (rather admins) execute a query against
> system_experimental.accord_epochs so they immediately know what they access
> (something experimental) rather than being constantly reminded about that by
> a client warning.
>
> Maxim's idea about "experimental_virtual_tables_enabled" property is also
> viable. However, I can't help it but that somehow reminds me a property for a
> guardrail. Just a thought. I do not see yet how we could leverage it, just
> saying how I perceive it.
>
> On Wed, May 29, 2024 at 9:02 PM David Capwell <dcapw...@apple.com
> <mailto:dcapw...@apple.com>> wrote:
>> We agreed a long time ago that all new features are disabled by default, but
>> I wanted to try to flesh out what we “should” do with something that might
>> still be experimental and subject to breaking changes; I would prefer we
>> keep this thread specific to vtables as the UX is different for different
>> types of things…
>>
>> So, lets say we are adding a set of vtables but we are not 100% sure what
>> the schema should be and we learn after the release that changes should be
>> made, but that would end up breaking the table… we currently define
>> everything as “don’t break this” so if we publish a table that isn’t 100%
>> baked we are kinda stuck with it for a very very long time… I would like to
>> define a way to expose vtables that are subject to change (breaking schema
>> changes) across different release and rules around them (only in minor?
>> Maybe even in patch?).
>>
>> Lets try to use a concrete example so everyone is on the same page.
>>
>> Accord is disabled by default (it is a new feature), so the vtables to
>> expose internals would be expected to be undefined and not present on the
>> instance.
>>
>> When accord is enabled (accord.enabled = true) we add a set of vtables:
>>
>> Epochs - shows what epochs are known to accord
>> Cache - shows how the internal caches are performing
>> Etc.
>>
>> Using epochs as an example it currently only shows a single column: the long
>> epoch
>>
>> CREATE VIRTUAL TABLE system_accord.epochs (epoch bigint PRIMARY KEY);
>>
>> Lets say we find that this table isn’t enough and we really need to scope it
>> to each of the “stores” (threads for processing accord tasks)
>>
>> CREATE VIRTUAL TABLE system_accord.epochs (epoch bigint, store_id int,
>> PRIMARY KEY (epoch, store_id));
>>
>> In this example the table changed the schema in a way that could break
>> users, so this normally is not allowed.
>>
>> Since we don’t really have a way to define something experimental other than
>> NEWS.txt, we kinda get stuck with this table and are forced to make new
>> versions and maintain them for a long time (in this example we would have
>> epochs and epochs_v2)… it would be nice if we could define a way to express
>> that tables are free to be changed (modified or even deleted) and the life
>> cycle for them….
>>
>> I propose that we allow such a case and make changes to the UX (as best as
>> we can) to warn about this:
>>
>> 1) update NEWS.txt to denote that the feature is experimental
>> 2) when you access an experimental table you get a ClientWarning stating
>> that this is free to change
>> 3) the tables comments starts with “[EXPERIMENTAL]”
>>
>> What do others think?
>>
>>
