create or alter procedure FIAS$GET_HOUSES_SOURCE
returns (
    OBJECT_ID D$GUID,
    OBJECT_FK D$GUID,
    HOUSENUM D$PREFIX_NAME,
    BUILDNUM D$PREFIX_NAME,
    STRUCNUM D$PREFIX_NAME,
    STRUCTYPE D$SMALLINT,
    DSTART D$SMALLINT,
    DEND D$SMALLINT,
    DTYPE D$SMALLINT,
    POSTALCODE D$POSTALCODE,
    OKATO D$OKATO,
    OKTMO D$OKTMO)
as
declare variable OLD_OID D$GUID;
BEGIN
  -- FIAS$HOUSES_SOURCE
  OLD_OID = NULL;
  FOR
    SELECT
      T.HOUSEGUID, T.AOGUID, T.HOUSENUM, T.BUILDNUM, T.STRUCNUM, IIF(T.STRUCNUM IS NULL, 0, T.STRUCTYPE),
      T.INTSTART, T.INTEND, T.INTSTATUS, T.POSTALCODE, T.OKATO, T.OKTMO
    FROM (
      SELECT
        CHAR_TO_UUID(HOUSEGUID) AS HOUSEGUID,
        CHAR_TO_UUID(AOGUID) AS AOGUID,
        NULLIF(UPPER(TRIM(HOUSENUM)), '') AS HOUSENUM,
        NULLIF(UPPER(TRIM(BUILDNUM)), '') AS BUILDNUM,
        NULLIF(UPPER(TRIM(STRUCNUM)), '') AS STRUCNUM,
        CAST(STRSTATUS AS SMALLINT) AS STRUCTYPE,
        NULL AS INTSTART,
        NULL AS INTEND,
        0 AS INTSTATUS,
        NULLIF(TRIM(POSTALCODE), '') AS POSTALCODE,
        NULLIF(TRIM(OKATO), '') AS OKATO,
        NULLIF(TRIM(OKTMO), '') AS OKTMO,
        STARTDATE,
        ENDDATE
      FROM FIAS$HOUSES_SOURCE
    ) T
    WHERE (
          T.HOUSENUM IS NOT NULL 
       OR T.BUILDNUM IS NOT NULL 
       OR T.STRUCNUM IS NOT NULL)
      AND CHAR_LENGTH(COALESCE(T.OKTMO, '')) IN (0, 8, 11)
    ORDER BY T.HOUSEGUID, T.ENDDATE DESC, T.STARTDATE DESC
  INTO :OBJECT_ID, :OBJECT_FK, :HOUSENUM, :BUILDNUM, :STRUCNUM, :STRUCTYPE, :DSTART, :DEND, :DTYPE, :POSTALCODE, :OKATO, :OKTMO DO
  BEGIN
    IF (OLD_OID IS DISTINCT FROM OBJECT_ID) THEN
    BEGIN
      SUSPEND;
      OLD_OID = OBJECT_ID;
    END
  END
END

План
PLAN MERGE (SORT (FIAS$HOUSES_SOURCE NATURAL), SORT (SORT (FIAS$HOUSES_SOURCE NATURAL)))

------ Информация о производительности ------
Время подготовки запроса = 1s 903ms
Время выполнения запроса = 7m 24s 431ms
Среднее время на получение одной записи = 444 431,00 ms
Current memory = 35 258 872
Max memory = 0
Memory buffers = 2 048
Reads from disk to cache = 0
Writes from cache to disk = 0
Чтений из кэша = 6