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.
Fixes#5582
... but only populate log on shard 0.
Migration manager callbacks are slightly assymetric. Notifications
for pre-create/update mutations are sent only on initiating shard
(neccesary, because we consider the mutations mutable).
But "created" callbacks are sent on all shards (immutable).
We must subscribe on all shards, but still do population of cdc table
only once, otherwise we can either miss table creat or populate
more than once.
v2:
- Add test case
Message-Id: <20200113140524.14890-1-calle@scylladb.com>
To eventually replace the free function.
Main difference is this is build to both handle batches correctly
and to eventually allow hanging cdc object on storage proxy,
and caches on the cdc object.
This allows us to create/alter/drop log and desc tables "atomically"
with the base, by including these mutations in the original mutation
set, i.e. batch create/alter tables.
Note that population does not happen until types are actually
already put into database (duh), thus there _is_ still a gap
between creating cdc and it being truly usable. This may or may
not need handling later.
The code was iterating over a collection that was modified
at the same time. Iterators were used for that and collection
modification can invalidate all iterators.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Based on a mutation, creates a pre-image select operation.
Note, this uses raw proxy query to shortcut parsing etc,
instead of trying to cache by generated query. Hypothesis is that
this is essentially faster.
The routine assumes all rows in a mutation touch same static/regular
columns. If this is not always true it will need additional
calculations.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
