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Server-side functions tailored for manipulating large objects from SQL are listed inTable 32.1.

There are additional server-side functions corresponding to each of the client-side functions described earlier; indeed, for the most part the client-side functions are simply interfaces to the equivalent server-side functions. The ones just as convenient to call via SQL commands arelo_creat,lo_create,lo_unlink,lo_import, andlo_export. Here are examples of their use:

CREATE TABLE image (    name            text,    raster          oid);SELECT lo_creat(-1);       -- returns OID of new, empty large objectSELECT lo_create(43213);   -- attempts to create large object with OID 43213SELECT lo_unlink(173454);  -- deletes large object with OID 173454INSERT INTO image (name, raster)    VALUES ('beautiful image', lo_import('/etc/motd'));INSERT INTO image (name, raster)  -- same as above, but specify OID to use    VALUES ('beautiful image', lo_import('/etc/motd', 68583));SELECT lo_export(image.raster, '/tmp/motd') FROM image    WHERE name = 'beautiful image';

The server-sidelo_import andlo_export functions behave considerably differently from their client-side analogs. These two functions read and write files in the server's file system, using the permissions of the database's owning user. Therefore, their use is restricted to superusers. In contrast, the client-side import and export functions read and write files in the client's file system, using the permissions of the client program. The client-side functions do not require superuser privilege.

The functionality oflo_read andlo_write is also available via server-side calls, but the names of the server-side functions differ from the client side interfaces in that they do not contain underscores. You must call these functions asloread andlowrite.