Andrew Dunstan <andrew@dunslane.net> writes:
> Does the COPY line protocol even support binary data?
The protocol, per se, just transmits a byte stream. There is a field
in the CopyInResponse/CopyOutResponse messages that indicates whether
a text or binary copy is being done. One thing we'd have to consider
is whether "raw" mode is sufficiently different from binary to justify
an additional value for this field, and if so whether that constitutes
a protocol break.
IIRC, psql wouldn't really care; it just transfers the byte stream to or
from the target file, regardless of text or binary mode. But there might
be other client libraries that are smarter and expect "binary" mode to
mean the binary file format specified in the COPY reference page. So
there may be value in being explicit about "raw" mode in these messages.
A key point in all this is that people who need "raw" transfer probably
need it in both directions, a point that your SELECT proposal cannot
satisfy, but hacking COPY could. So I lean towards the latter really.
regards, tom lane