- [x] Add some more regression test coverage
- [x] Make sure returning works fine in case of
local execution + remote execution
(task->partiallyLocalOrRemote works as expected, already added tests)
- [x] Implement locking properly (and add isolation tests)
- [x] We do #shardcount round-trips on `SerializeNonCommutativeWrites`.
We made it a single round-trip.
- [x] Acquire locks for subselects on the workers & add isolation tests
- [x] Add a GUC to prevent modification from the workers, hence increase the
coordinator-only throughput
- The performance slightly drops (~%15), unless
`citus.allow_modifications_from_workers_to_replicated_tables`
is set to false
With #4338, the executor is smart enough to failover to
local node if there is not enough space in max_connections
for remote connections.
For COPY, the logic is different. With #4034, we made COPY
work with the adaptive connection management slightly
differently. The cause of the difference is that COPY doesn't
know which placements are going to be accessed hence requires
to get connections up-front.
Similarly, COPY decides to use local execution up-front.
With this commit, we change the logic for COPY on local nodes:
Try to reserve a connection to local host. This logic follows
the same logic (e.g., citus.local_shared_pool_size) as the
executor because COPY also relies on TryToIncrementSharedConnectionCounter().
If reservation to local node fails, switch to local execution
Apart from this, if local execution is disabled, we follow the
exact same logic for multi-node Citus. It means that if we are
out of the connection, we'd give an error.
After this change all the logic related to shard data fetch logic
will be removed. Planner won't plan any ShardFetchTask anymore.
Shard fetch related steps in real time executor and task-tracker
executor have been removed.
Önder Kalacı
Onder Kalaci
Philip Dubé
velioglu
Jason Petersen
Marco Slot
Eren Basak