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bc7b5926d2
In an earlier patch, we introduced regular_column_transformation, a new type of computed column that does a computation on a cell in regular column in the base and returns a potentially transformed cell (value or deletion, timestamp and ttl). In *this* patch, we wire the materialized view code to support this new kind of computed column that is usable as a materialized-view key column. This new type of computed column is not yet used in this patch - this will come in the next patch, where we will use it for Alternator GSIs. Before this patch, the logic of deciding when the view update needs to create a new row or delete a new one, and which timestamp and ttl to give to the new row, could depend on one (or two - in Alternator) cells read from base-table regular columns. In this patch, this logic is rewritten - the notion of "base table regular columns" is generalized to the notion of "updatable view key columns" - these are view key columns that an update may change - because they really are base regular columns, or a computed function of one (regular_column_transformation). In some sense, the new code is easier to understand - there is no longer a separate "compute_row_marker()" function, rather the top-level generate_update() is now in charge of finding the "updatable view key columns" and calculate the row marker (timestamp and ttl) as part of deciding what needs to be done. But unfortunately the code still has separate code paths for "collection secondary indexing", and also for old-style column_computation (basically, only token_column_computation). Perhaps in the future this can be further simplified. Signed-off-by: Nadav Har'El <nyh@scylladb.com>