agrio lock

db=> \d r_locks
                 Table "public.r_locks"
 Column  |          Type           |     Modifiers
---------+-------------------------+--------------------
 code    | character varying(1024) | not null
 version | numeric(38,0)           | not null default 1
Indexes:
    "r_locks_pkey" PRIMARY KEY, btree (code)


CREATE OR REPLACE FUNCTION public.get_r_lock(codein    CHARACTER VARYING,
                                             exclusive BOOLEAN)
  RETURNS NUMERIC
LANGUAGE plpgsql
AS $function$
DECLARE
  ver NUMERIC;
BEGIN
  IF exclusive
  THEN
    SELECT
      version
    FROM r_locks
    WHERE code = codeIn
    INTO ver
    FOR UPDATE;
    IF found
    THEN
      ver := ver + 1;
      UPDATE r_locks
      SET version = ver
      WHERE code = codeIn;
    END IF;
  ELSE
    BEGIN
      SELECT
        version
      FROM r_locks
      WHERE code = codeIn
      INTO ver
      FOR SHARE NOWAIT;
      EXCEPTION WHEN lock_not_available
      THEN
        RETURN -2;
    END;
  END IF;
  IF NOT found
  THEN
    RETURN -1;
  END IF;
  RETURN ver;
END;
$function$

create or replace function
  make_r_code(tagIn numeric, blockId numeric)
  returns varchar immutable as $$
begin
  if tagIn = 0 then
    return '-' || blockId;
  else
    return blockId || '-';
  end if;
end;
$$ LANGUAGE plpgsql;