Enum DataControllerOp 

pub enum DataControllerOp {
    Nop,
    Insert,
    Revoke,
    Drop,
}

What the cache controller should do with the initial value that was submitted for data controller processing.

Variants

Nop

Do nothing, only put the returned update record into the update pool.

Insert

Insert the value into the cache. This is possible for “immutable” records, i.e., those for which it can be guaranteed that they won’t be changed by the backend. For example, if the primary key field is pre-generated by the client application, then inserting the record into the database won’t change it. If the same guarantee can be made for all other fields as well, it means that injecting the value into the cache immediately would have the same effect as inserting it into the database and then reading it back.

Contrary, if there is an auto-increment field in the record, then sending it to the backend and reading it back is mandatory to achieve a consistent final state.

Revoke

Revoke the value from the cache. Useful for cases when the data controller knows that the value must undergo a flushing operation either to be deleted from the backend or to be updated.

Note: There is a nuance in how the cache controller decides to flush an individual record when necessary: if there is an update record for its key but the data record itself is not cached, then it is time to flush that key under certain circumstances. Such circumstances may include, for example, a request to update the data record. Since the cache controller does not know how to apply the update (and the data controller may also be uncertain about this), the only way to provide the user with a valid data record is to flush the update first.

Drop

An extreme case of the Revoke operation. The value is not only revoked from the cache, but the corresponding entry is also removed from the update pool. This would be an ideal case of an “immutable” record which is inserted and deleted sufficiently fast to not require being written back to the backend.

Trait Implementations

impl Clone for DataControllerOp

fn clone(&self) -> DataControllerOp

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for DataControllerOp

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Copy for DataControllerOp