Convert a bytea column to OID while retaining values

Question

I\'m trying to alter a bytea column to have type oid and still retain the values.

I have tried using queries like:

ALTER TA         


        

Answer 1

I think the best answer can be found at Grace Batumbya's Blog, in verbis:

The algorithm is pretty simple, get the binary data, if it is null, return null. Else create a large object and in the lowrite function, pass it the binary value, instead of a path to a file.

The code for the procedure is below. Note that the lo_manage package should be installed for this to work.

create or replace function blob_write(lbytea bytea)
   returns oid
   volatile
   language plpgsql as
$f$
   declare
      loid oid;
      lfd integer;
      lsize integer;
begin
   if(lbytea is null) then
      return null;
   end if;

   loid := lo_create(0);
   lfd := lo_open(loid,131072);
   lsize := lowrite(lfd,lbytea);
   perform lo_close(lfd);
   return loid;
end;
$f$;
CREATE CAST (bytea AS oid) WITH FUNCTION blob_write(bytea) AS ASSIGNMENT;

So now the following code works: CREATE TABLE bytea_to_lo ( lo largeObj );

INSERT INTO bytea_to_lo VALUES ( DECODE('00AB','hex'));

I've tried it and works like a charm.