• Allow bytea values to be written in hex notation (Peter Eisentraut)

The server parameter bytea_output controls whether hex or traditional
format is used for bytea output. Libpq’s PQescapeByteaConn() function
automatically uses the hex format when connected to Postgresql 9.0 or
newer servers. However,pre-9.0 libpq versions will not correctly
process hex format from newer servers.

The new hex format will be directly compatible with more applications
that use binary data,allowing them to store and retrieve it without
extra conversion. It is also significantly faster to read and write
than the traditional format.

你似乎已经意识到了bytea_output.