18th October 2018: PostgreSQL 11 Released!
Unsupported versions: 6.5

Built in registered functions

There are two built-in registered functions, lo_import and lo_export which are convenient for use in SQL queries. Here is an example of their use

CREATE TABLE image (
    name            text,
    raster          oid
);

INSERT INTO image (name, raster)
    VALUES ('beautiful image', lo_import('/etc/motd'));

SELECT lo_export(image.raster, "/tmp/motd") from image
    WHERE name = 'beautiful image';