statement_restrictions: forbid IS NOT NULL on columns outside the primary key
IS NOT NULL is currently allowed only when creating materialized views.
It's used to convey that the view will not include any rows that would make the view's primary key columns NULL.
Generally materialized views allow to place restrictions on the primary key columns, but restrictions on the regular columns are forbidden. The exception was IS NOT NULL - it was allowed to write regular_col IS NOT NULL. The problem is that this restriction isn't respected, it's just silently ignored (see #10365).
Supporting IS NOT NULL on regular columns seems to be as hard as supporting any other restrictions on regular columns.
It would be a big effort, and there are some reasons why we don't support them.
For now let's forbid such restrictions, it's better to fail than be wrong silently.
Throwing a hard error would be a breaking change.
To avoid breaking existing code the reaction to an invalid IS NOT NULL restrictions is controlled by the `strict_is_not_null_in_views` flag.
This flag can have the following values:
* `true` - strict checking. Having an `IS NOT NULL` restriction on a column that doesn't belong to the view's primary key causes an error to be thrown.
* `warn` - allow invalid `IS NOT NULL` restrictions, but throw a warning. The invalid restrictions are silently ignored.
* `false` - allow invalid `IS NOT NULL` restricitons, without any warnings or errors. The invalid restrictions are silently ignored.
The default values for this flag are `warn` in `db::config` and `true` in scylla.yaml.
This way the existing clusters will have `warn` by default, so they'll get a warning if they try to create such an invalid view.
New clusters with fresh scylla.yaml will have the flag set to `true`, as scylla.yaml overwrites the default value in `db::config`.
New clusters will throw a hard error for invalid views, but in older existing clusters it will just be a warning.
This way we can maintain backwards compatibility, but still move forward by rejecting invalid queries on new clusters.
Fixes: #10365Closes#13013
* github.com:scylladb/scylladb:
boost/restriction_test: test the strict_is_not_null_in_views flag
docs/cql/mv: columns outside of view's primary key can't be restricted
cql-pytest: enable test_is_not_null_forbidden_in_filter
statement_restrictions: forbid IS NOT NULL on columns outside the primary key
schema_altering_statement: return warnings from prepare_schema_mutations()
db/config: add strict_is_not_null_in_views config option
statement_restrictions: add get_not_null_columns()
test: remove invalid IS NOT NULL restrictions from tests
5984db047d