IS NOT NULL shouldn't be allowed on columns
which are outside of the materialized view's primary key.
It's currently allowed to create views with such restrictions,
but they're silently ignored, it's a bug.
In the following commits restricting regular columns
with IS NOT NULL will be forbidden.
This is a breaking change.
Some users might have existing code that creates
views with such restrictions, we don't want to break it.
To deal with this a new feature flag is introduced:
strict_is_not_null_in_views.
By default it's set to `warn`. If a user tries to create
a view with such invalid restrictions they will get a warning
saying that this is invalid, but the query will still go through,
it's just a warning.
The default value in scylla.yaml will be `true`. This way new clusters
will have strict enforcement enabled and they'll throw errors when the
user tries to create such an invalid view,
Old clusters without the flag present in scylla.yaml will
have the flag set to warn, so they won't break on an update.
There's also the option to set the flag to `false`. It's dangerous,
as it silences information about a bug, but someone might want it
to silence the warnings for a moment.
Signed-off-by: Jan Ciolek <jan.ciolek@scylladb.com>
c67d65987e