That sounds perfect.
On Mar 3, 3:42 pm, Thomas Mueller <[email protected]>
wrote:
> Hi,
>
> > A function would be perfect! A String would work for SymmetricDS.
>
> I'm currently implementing such a function. I have a question: if
> there is currently no uncommitted change (that is, a transaction is
> not started, or one is started, but no changes have been made so far),
> is it OK if NULL is returned? My plan is to return:
>
> - NULL if there is no uncommitted change currently
> - Otherwise the position of the first uncommitted change in the
> transaction log file, and session id. Format:
> <logFileId>-<position>-<sessionId>.
>
> TRANSACTION_ID() returns a VARCHAR
>
> Returns the current transaction id for this session. This method returns NULL
> if there is no uncommitted change, or if the the database is not persisted.
> Otherwise a value of the following form is returned:
> logFileId-position-sessionId.
> The value is unique across database restarts (values are not re-used).
>
> Example:
> CALL TRANSACTION_ID()
>
> Regards,
> Thomas
>
> > The value needs to be unique across database restarts. The faster the
> > better. We use it to track changes that need to be 'synchronized'
> > atomically. I am really looking for the equivalent of
> > DBMS_TRANSACTION.local_transaction_id(false) on Oracle. I would think
> > the name could be as simple as TRANSACTION_ID() ??
>
> > Thank you.
>
> > On Feb 6, 2:10 pm, Thomas Mueller <[email protected]>
> > wrote:
> >> Hi,
>
> >> > I am currently implementing an H2 'database dialect' for SymmetricDS
> >> > (www.symmetricds.org). I am trying to figure out the best way to
> >> > access a 'transaction id' from an H2 trigger. The following is the
> >> > Java code I have come up with. Does anybody have suggestions for
> >> > improvements (or more likely can they poke holes in my approach)?
>
> >> > protected String getTransactionId(Connection c) {
> >> > JdbcConnection con = (JdbcConnection) c;
> >> > Session session = (Session) con.getSession();
> >> > return StringUtils.leftPad(Integer.toString(session.getId
> >> > ()), 3, "0") + "-"
> >> > + session.getFirstUncommittedLog() + "-" +
> >> > session.getFirstUncommittedPos();
> >> > }
>
> >> There is currently no good way to do that. How unique does the
> >> transaction id need to be? I mean, is it a problem if the id starts
> >> from 0 when you restart the application? Is there a sort requirements
> >> (larger transaction ids means later)?
>
> >> Your solution doesn't work for remote connections. I suggest I add a
> >> SQL system function that returns the current transaction id. What is
> >> your preferred function name?
>
> >> Is a String good enough, or is a byte array better? How fast does it
> >> need to be?
>
> >> Regards,
> >> Thomas
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups "H2
Database" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/h2-database?hl=en
-~----------~----~----~----~------~----~------~--~---
