When we create a materialized view, we consider 2 cases:
1. the view's primary key contains a column that is not
in the primary key of the base table
2. the view's primary key doesn't contain such a column
In the 2nd case, we add all columns from the base table
to the schema of the view (as virtual columns). As a result,
all of these columns are effectively "selected" in
view_updates::can_skip_view_updates. Same thing happens when
we add new columns to the base table using ALTER.
Because of this, we can never have !column_is_selected and
!has_base_non_pk_columns_in_view_pk at the same time. And
thus, the check (!column_is_selected
&& _base_info.has_base_non_pk_columns_in_view_pk) is always
the same as (!column_is_selected).
Because we immediately return after this check, the tail of
this function is also never reached - all checks after the
(column_is_selected) are affected by this. Also, the condition
(!column_is_selected && base_has_nonexpiring_marker) is always
false at the point it is called. And this in turn makes the
`base_has_nonexpiring_marker` unused, so we delete it as well.
It's worth considering, why did we even have
`base_has_nonexpiring_marker` if it's effectively unused. We
initially introduced it in bd52e05ae2 and we (incorrectly)
used it to allow skipping view updates even if the liveness of
virtual columns changed. Soon after, in 5f85a7a821, we
started categorizing virtual columns as column_is_selected == true
and we moved the liveness checks for virtual columns to the
`if (column_is_selected)` clause, before the `base_has_nonexpiring_marker`
check. We changed this because even if we have a nonexpiring marker
right now, it may be changed in the future, in which case the liveness
of the view row will depend on liveness of the virtual columns and
we'll need to have the view updates from the time the row marker was
nonexpiring.
Closesscylladb/scylladb#28838
38f02b8d76