Is there any thing like In-Memory sequence manager - That will improve the performance.

Only for the first time an uid request,we need to go to the database for the value of the target column in the table which stores custom sequences(for example: talbe_sequence), update it with adding a custom INCREMENT value (configure it in the specified hbm.xml), and store the currentID and maxID in memory, then all following request were performed in memory util the currentID > maxID.

Just as Jive's Sequence Manager.

Which document will tell me how can I do in this case. (ie) Will Hibernate query the DB in specified situation to get an ID and will it have some thing in memory.

Please let me know how to begin, thank u

<generator class="increment"/>

Oh, not this I want.

What I need is A table to store sequences,like this:

table_sequence (block increment is 15)
=========================
tablename ---+--- id_sequence
user -----------+--- 105
company -----+---- 45
....

=========================

And there are table User and Company in DB, which ID generated in memory base on column sequence of table_sequence. Only for the time that currentID > maxID in memory, we need to go to the database for the value of next block sequence. The size of block can initialize in a file,just as hbm.xml .

Is this as well as "increment"? I don't think so...

Thanks for your reply ,gavin. I am a beginner of Hibernate, please tell me more, thanks a lot.

oh, its "hilo", except we use multiple tables, not multiple rows of the same table. (or you can use seqhilo)

yes! I have checked the source of Hibernate. The case I mentioned is similar to hilo. But I don't want multiple tables and hi/lo algorithm, I want the ID is continuous.

Is that means I must custom my own generator? if true, How can I begin?
implement PersistentIdentifierGenerator ? It seem that I can't extend the TableGenerator class.

But I have an unsuccessful try to do so...

Would u tell me more detail about how to think over this case? thank u gavin!