In the codepath when no encoding conversion is required, the check for incomplete character at the end of input incorrectly used server encoding's max character length, instead of the client's. Usually the server and client encodings are the same when we're not performing encoding conversion, but SQL_ASCII is an exception.
In the passing, also fix some outdated comments that still talked about the old COPY protocol. It was removed in v14.
Per bug #17501 from Vitaly Voronov. Backpatch to v14 where this was introduced.
fc36ac52eb Fix COPY FROM when database encoding is SQL_ASCII.
src/backend/commands/copyfromparse.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)