mdcreate():

    fd = FileNameOpenFile(path, O_RDWR|O_CREAT|O_EXCL, 0600);

    /*
     *  If the file already exists and is empty, we pretend that the
     *  create succeeded.  During bootstrap processing, we skip that check,
     *  because pg_time, pg_variable, and pg_log get created before their
     *  .bki file entries are processed.
     *
>    *  As the result of this pretence it was possible to have in
>    *  pg_class > 1 records with the same relname. Actually, it
>    *  should be fixed in upper levels, too, but... -  vadim 05/06/97
>    */