Note:
When you SELECT bytea type, PostgreSQL returns octal byte value
prefixed by \ (e.g. \032). Users are supposed to convert back to
binary format by yourself.
This function requires PostgreSQL 7.2 or later. With PostgreSQL
7.2.0 and 7.2.1, bytea type must be casted when you enable
multi-byte support. i.e. INSERT INTO test_table (image)
VALUES ('$image_escaped'::bytea); PostgreSQL 7.2.2 or
later does not need cast. Exception is when client and backend
character encoding does not match, there may be multi-byte
stream error. User must cast to bytea to avoid this error.
Newer PostgreSQL will support unescape function. Support for
built-in unescape function will be added when it's available.
