[Pljava-dev] Explicit transaction control

Not sure what advantage a subtransaction would bring besides non-standard calls. JDBC has savepoints and PL/Java
supports them. What do you need besides this?

Savepoint sp = conn.setSavepoint();
try {
...
conn.releaseSavepoint(sp);
} catch(SQLException e) {
conn.rollback(sp);
}

- thomas

On 2013-11-29 02:38, Altaf, Muhammad wrote:
>
> Agreed, let's consider *Connection.setAutocommit(true) *which is nothing more than user informing the connection
> object to automatically commit each statement as it executes, it does not matter how we achieve this. We can
> internally create savepoints/start subtransactions and commit/rollback them depending upon how they execute. Even in
> normal JDBC setAutocommit(false) means issue another *BEGIN *statement with the next call, and when user issues a
> commit/rollback, we send another *BEGIN *with next query to automatically start another transaction. This is to ease
> the pain on user's end, otherwise he has the Savepoint option in JDBC as well.
>
> Similarly when we are not in autocommit mode (and we are not in pljava), the user's action to
> connection.commit()/rollback() could be responded with a similar way -- end the current SUBTRANSACTION and start a new
> one.
>
> See www.postgresql.org/docs/9.2/static/plpython-subtransaction.html the function call is still in transaction, but
> they do allow exolicit transaction control with the same backend.
>
> -- Altaf
>
> *From:*Hal Hildebrand [mailto:hal.hildebrand at me.com]
> *Sent:* Friday, 29 November 2013 12:19 PM
> *To:* Altaf, Muhammad
> *Cc:* pljava-dev at lists.pgfoundry.org
> *Subject:* Re: [Pljava-dev] Explicit transaction control
>
> By definition, you're *already* in a transaction because you're running your Java inside of a database session. You
> can use save points <http://is.gd/mQ5ytc> (haven't tried them in pl/java). You can save/rollback to them. But you
> can't nest transitions in PostgreSQL, irregardless of the stored procedure language, or DB driver (afaik).
>
> On Nov 28, 2013, at 4:21 PM, Altaf, Muhammad <Muhammad.Altaf at au.fujitsu.com <mailto:Muhammad.Altaf at au.fujitsu.com>> wrote:
>
>
>
> Hi,
>
> Currently connection.commit/rollback in pljava throw FeatureNotSupportedException because the function call is already
> in a transaction so the explicit transaction control is not allowed. I was comparing this with pl/python and found
> that the later actually allows this by creating sub-transactions, which means technically it should be possible to
> handle this in pljava but there should be other reasons not to implement it.
>
> I am willing to implement this feature if there is no philosophical reason that discourages use of explicit
> transaction controls in pljava, or some backend limitation that does not permit these controls without putting some
> **hacks**.
>
> Thoughts?
>
> Muhammad Altaf
>
> Fujitsu Australia Software Technology
>
> www.fastware.com.au <http://www.fastware.com.au/>
>
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