This used to be possible to hit, but I think now that Distinct on a
set field returns a *Row rather than a SignedRow it isn't an issue. (I
wasn't able to trigger it in the tests). Adding the fix anyway as it
seems safer than not.
The rest of the changes are test infrastructure to make it easy to
call GRPC queries and verify the results as CSV.
This PR adds a `StatusError` to the `pproto.RowResponse` type, which
allows a stream to pass an error on the stream (encoded into
the `RowResponse.StatusError`). This can be checked downstream
for matching `EOF` or `err != nil` and handled appropriately.
This is helpful mainly with the `RowResponse` reducers which run in
goroutines. Instead of trying to manage a separate channel of errors
from those goroutines, we just follow the grpc model and send the
error with the stream.
In order to standardize results as streams of RowResponse,
this PR introduces two interfaces `StreamClient` and
`StreamServer`) which mirror the grpc stream interfaces.
Upstream users (sqlmapper, vdsm, etc) can implement
instances of these interfaces to ensure that results can
stream through the entire sytem in an expected way.
This PR also fixes a couple of missing data types.
