Il 12/04/2011 7.50, karolbieniaszewski ha scritto:

>
> --- In firebird-support@yahoogroups.com, Ann Harrison<aharrison@...> wrote:
>>
>>> --- In firebird-support@yahoogroups.com, "karolbieniaszewski"<liviuslivius@> wrote:
>>>>
>>>> is some API to get generator value?
>>>> or only possible way is
>>>> select GEN_ID(gen_name, 0) from RDB$Database
>>>>
>>>> i ask because this is stupid to start transaction to get non transactional object value
>>
>>
>> On Mon, Apr 11, 2011 at 3:56 PM, emb_blaster<EMB_Blaster@...> wrote:
>>
>>> AFAICR, no. There's not.
>>>
>>> If you are using ISQL, you could use "SHOW GENERATOR xxxxx;" or "SHOW SEQUENCE xxxxxx;", or yet "SHOW GENERATORS;" or "SHOW SEQUENCES;" to list all. (see http://www.firebirdsql.org/refdocs/langrefupd21-ddl-sequence.html)
>>
>> Any of those statements will either open a transaction or use the DDL
>> transaction.
>>>
>>> Also, I can agree that seems make no sense at all that. But I've learned to do not call stupid something I did not understand at all. Maybe in the time it was made, a "no transaction request" would make no sense too.
>>> So, if someone else could explain, I would be glad to learn too. But don't think this is a bug or a missing feature at all. :)
>>>
>>
>> Since you can neither write nor read the contents of the database
>> without an open
>> transaction, it may be that the designers assumed that there would be
>> a transaction
>> started or about to start when someone wanted the current contents of
>> a generator.
>> Note that in a multi-user application, the value returned by GEN_ID
>> (<generator>,0)
>> may well not be the value most recently stored by the transaction that
>> gets the value.
>>
>> Good luck,
>>
>> Ann
>>
>
> Generator is non transactional and next unique value is generated by mutex locking for multiuser use. And starting database context transaction is unnecessary, time costs, resource costs ..
>
> and i say "stupid" in condition as "unnecessary"
> may English is bad so sorry for some mistakes..
>
> Karol Bieniaszewski
>

As far as I know, generators are used to get primary keys values for new
rows. Inserting a row requires a transaction, so you will need it anyway.

Are there real situations when you might need to know a generator value
without using it in a transaction?

Fulvio Senore