Using binary encoding can save a lot of CPU cycles, both on the sender
and on the receiver. Since the walsender and walreceiver processes are
single threaded, this can matter a lot for the throughput if they are
bottlenecked on CPU.
This feature is only available in PG14, not PG13. It should be safe to
always enable because it's only used for types that support binary
encoding according to the PG docs:
> Even when this option is enabled, only data types that have binary
> send and receive functions will be transferred in binary.
But in case it causes problems, it can still be disabled by setting
`citus.enable_binary_protocol` to `false`.
Since PG14 we can now use binary encoding for arrays and composite types
that contain user defined types. This was fixed in this commit in
Postgres: 670c0a1d47
This change starts using that knowledge, by not necessarily falling back
to text encoding anymore for those types.
While doing this and testing a bit more I found various cases where
binary encoding would fail that our checks didn't cover. This fixes
those cases and adds tests for those. It also fixes EXPLAIN ANALYZE
never using binary encoding, which was a leftover of workaround that
was not necessary anymore.
Finally, it changes the default for both `citus.enable_binary_protocol`
and `citus.binary_worker_copy_format` to `true` for PG14 and up. In our
cloud offering `binary_worker_copy_format` already was true by default.
`enable_binary_protocol` had some bug with MX and user defined types,
this bug was fixed by the above mentioned fixes.
Sadly this does not actually work yet for binary protocol data, because
when doing EXPLAIN ANALYZE we send two commands at the same time. This
means we cannot use `SendRemoteCommandParams`, and thus cannot use the
binary protocol. This can still be useful though when using the text
protocol, to find out that a lot of data is being sent.
This can save a lot of data to be sent in some cases, thus improving
performance for which inter query bandwidth is the bottleneck.
There's some issues with enabling this as default, so that's currently not done.
Jelte Fennema
Nils Dijk