Changing data that affects an expression index that contains references to null date fields fails in Firebird 2.5
Here is an isql script to show the effect:
-------
create database 'bugtest.fdb';
show version;
CREATE GENERATOR GEN_POLICEN_ORDER_ID;
CREATE TABLE POLICEN_ORDER (
    ID INTEGER NOT NULL,
    VSTATUS INTEGER,
    ABLAUF DATE,
    VSTORNO INTEGER,
    STORNO DATE
);
ALTER TABLE POLICEN_ORDER ADD CONSTRAINT PK_NEW_TABLE PRIMARY KEY (ID);

SET TERM ^ ;
CREATE OR ALTER TRIGGER POLICEN_ORDER_BI FOR POLICEN_ORDER
ACTIVE BEFORE INSERT POSITION 0
as
begin
  if (new.id is null) then
    new.id = gen_id(gen_policen_order_id,1);
end
^
SET TERM ; ^


-- insert some data with null dates

INSERT INTO POLICEN_ORDER (ID, VSTATUS, ABLAUF, VSTORNO, STORNO)
                   VALUES (2, 1, NULL, NULL, NULL);
INSERT INTO POLICEN_ORDER (ID, VSTATUS, ABLAUF, VSTORNO, STORNO)
                   VALUES (3, 2, NULL, NULL, NULL);
INSERT INTO POLICEN_ORDER (ID, VSTATUS, ABLAUF, VSTORNO, STORNO)
                   VALUES (4, 3, NULL, NULL, NULL);

COMMIT;

-- now let's create an obscure index

CREATE INDEX IDX_POLICEN_ORDER_BIT_VSTATUS ON POLICEN_ORDER COMPUTED BY (case
    when POLICEN_ORDER.VSTATUS=1 then 64 -- Anbahnung
    when POLICEN_ORDER.VSTATUS=7 then 32 -- DA
    when POLICEN_ORDER.VSTATUS=8 then 16 -- Angebot
    when POLICEN_ORDER.VSTATUS=0 then 8 -- Vertrag
    when POLICEN_ORDER.VSTATUS=3 then 8 -- Vertrag
    when POLICEN_ORDER.VSTATUS=4 then 8 -- Vertrag
    when POLICEN_ORDER.VSTATUS=5 then 8 -- Vertrag
    when POLICEN_ORDER.VSTATUS=6 then 8 -- Vertrag
    when POLICEN_ORDER.VSTATUS=2 then 4 -- Fremdvertrag
    else 0
  end +
  case when coalesce(POLICEN_ORDER.ABLAUF, current_date+1)<=current_date or
  POLICEN_ORDER.VSTORNO=1 and coalesce(POLICEN_ORDER.STORNO,
   current_date+1)<=current_date then 2 else 0 end);
-- and do some work with the data that will fail miserably in 2.5

update POLICEN_ORDER
        set VSTATUS = 8
        where (ID = 2);
commit;

-- this works in 2.0

select * from policen_order;

update POLICEN_ORDER
        set VSTATUS = 2
        where (ID = 2);
commit;


exit;
--------

Here is what happens in 2.0:

-------
....
update POLICEN_ORDER
        set VSTATUS = 8
        where (ID = 2);
commit;

-- this works in 2.0

select * from policen_order;

          ID VSTATUS ABLAUF VSTORNO STORNO
============ ============ =========== ============ ===========
           2 8 <null> <null> <null>
           3 2 <null> <null> <null>
           4 3 <null> <null> <null>
-----

and this is from 2.5

------
.....
update POLICEN_ORDER
        set VSTATUS = 8
        where (ID = 2);
Statement failed, SQLSTATE = 22008
value exceeds the range for valid dates
After line 52 in file bugtest.sql
commit;

-- this works in 2.1

select * from policen_order;

          ID VSTATUS ABLAUF VSTORNO STORNO
============ ============ =========== ============ ===========
           2 1 <null> <null> <null>
           3 2 <null> <null> <null>
           4 3 <null> <null> <null>


update POLICEN_ORDER
        set VSTATUS = 2
        where (ID = 2);
Statement failed, SQLSTATE = 22008
value exceeds the range for valid dates
After line 62 in file bugtest.sql
commit;


exit;



hth

fsg