Datum
sub_fp_compress(PG_FUNCTION_ARGS)
{
    GISTENTRY  *entry = (GISTENTRY *)PG_GETARG_POINTER(0);
    // Column and Storage data types are the same (bytea)
    // so no compression is required.
    GISTENTRY  *retval = entry;

    PG_RETURN_POINTER(retval);
}