Merged pull request https://github.com/scylladb/scylla/pull/5567
from Calle Wilund:
Fixes#5314
Instead of tying CDC handling into cql statement objects, this patch set
moves it to storage proxy, i.e. shared code for mutating stuff. This means
we automatically handle cdc for code paths outside cql (i.e. alternator).
It also adds api handling (though initially inefficient) for batch statements.
CDC is tied into storage proxy by giving the former a ref to the latter (per
shard). Initially this is not a constructor parameter, because right now we
have chicken and egg issues here. Hopefully, Pavels refactoring of migration
manager and notifications will untie these and this relationship can become
nicer.
The actual augmentation can (as stated above) be made much more efficient.
Hopefully, the stream management refactoring will deal with expensive stream
lookup, and eventually, we can maybe coalesce pre-image selects for batches.
However, that is left as an exercise for when deemed needed.
The augmentation API has an optional return value for a "post-image handler"
to be used iff returned after mutation call is finished (and successful).
It is not yet actually invoked from storage_proxy, but it is at least in the
call chain.
1ed21d70dc