Helen,
whereas I fully agree that mixing generators and other ways to assign
primary keys are bound to get you into trouble, I see Michaels code as only
an attempt to cover for stupidity in case someone should assign a PK
without using the generator. Note that he only increases the generator,
never decreases. This could lead to holes in the PK sequence, but not PK
violations due to the generator.

Set

At 09:48 08.02.2001 +1100, you wrote:

>At 04:11 PM 07-02-01 -0500, you wrote:
>>Hello Paul
>>
>>GeneratorLinks is to allow IBO to go ahead and get the
>>ID of the record before the actual insert. This allows
>>it to pass it along to Detail tables that could be connected
>>and other things. You don't have to use it for positioning,
>>I think you are talking about keylinks.
>>
>>I use the following trigger on my tables:
>>
>> create trigger TRGBEFINS_Customer for Customer
>> active before insert position 0
>> as
>> DECLARE VARIABLE Temp_ID integer;
>> begin
>> if ((new.Cus_ID is NULL) or (new.cus_ID = 0)) then
>> begin
>> new.Cus_ID = gen_id (Gen_Customer_ID, 1);
>
>END THE TRIGGER HERE !!!
>
>The following code is !!!! dangerous !!!!. Generators operate right
>outside the transaction context. In a multi-user environment, you are
>certain to get PK violations. Don't do it!!!
>
>> end else begin
>> Temp_ID = gen_id(Gen_Customer_ID,0);
>> if (new.CUS_ID > Temp_ID) then
>> begin
>> Temp_ID = gen_id(Gen_Customer_ID, new.Cus_ID-Temp_ID);
>> end
>> end
>> end
>>
>>It will update your generator if necessary and also, make
>>sure that the generator doesn't get behind if you inserted
>>records that had IDs not derived from the generator.
>
>If you are using a generator to populate a primary key, you should NEVER
>try to insert rows where the PK comes from another source that **that**
>generator.
>
>To add a further note on GeneratorLinks, you should always use it when
>inserting into a bi-directional dataset, rather than waiting until after
>the insert has committed, to ensure that the KeyLinks will work
>properly. Reserve the use of the trigger for external clients or scripts.
>
>Helen
>
>
>
>
>All for Open and Open for All
>InterBase Developer Initiative · http://www.interbase2000.org
>_______________________________________________________
>
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