mysqli auto rollback on script termination

Hi,

In case the PHP script dies (from fatal error, die() or similar), is any
started transaction (BEGIN TRANSACTION) automatically rolled back
(ROLLBACK) by PHP then?

I can't find any documentation about this.

Thanks in advance for hints, links etc.

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Re: mysqli auto rollback on script termination

Martin Koch Andersen wrote:
> Hi,
>
> In case the PHP script dies (from fatal error, die() or similar), is any
> started transaction (BEGIN TRANSACTION) automatically rolled back
> (ROLLBACK) by PHP then?

It should be rolled back when a connection is lost or a transaction
isn't explicitly committed.

Whether that's a php script dying or the server being shut down
mid-transaction or anything similar (eg a remote server's lan connection
goes down).

Of course this assumes you're using innodb tables and not myisam -
myisam doesn't support transactions..

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Re: mysqli auto rollback on script termination

Chris skrev:
> It should be rolled back when a connection is lost or a transaction
> isn't explicitly committed.

Can you find documentation on this specific issue anywhere?

I think the same as you, but I find it odd, it is not documented.

Reason I'm asking is, I've seen some deadlock issues in a script (using
FOR UPDATE and LOCK IN SHARE MODE), that looks like they are caused by
transactions not being rolled back (releasing locks) correctly.

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Re: mysqli auto rollback on script termination

Martin Koch Andersen wrote:
> Chris skrev:
>> It should be rolled back when a connection is lost or a transaction
>> isn't explicitly committed.
>
> Can you find documentation on this specific issue anywhere?
>
> I think the same as you, but I find it odd, it is not documented.
>
> Reason I'm asking is, I've seen some deadlock issues in a script (using
> FOR UPDATE and LOCK IN SHARE MODE), that looks like they are caused by
> transactions not being rolled back (releasing locks) correctly.

This suggests they should be released:
http://dev.mysql.com/doc/refman/4.1/en/innodb-locking-reads. html

Locks set by IN SHARE MODE and FOR UPDATE reads are released when the
transaction is committed or rolled back.


It doesn't explicitly say anything about when a connection is lost but
I'm guessing it would rollback the transaction (well I'd sure hope so).

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Re: mysqli auto rollback on script termination

Chris skrev:
> It doesn't explicitly say anything about when a connection is lost but
> I'm guessing it would rollback the transaction (well I'd sure hope so).

Me too. In any case, I'm now also using register_shutdown_function,
which calls a function that does rollback of not committed transations.

Thanks.

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Re: mysqli auto rollback on script termination

> Reason I'm asking is, I've seen some deadlock issues in a script (using
> FOR UPDATE and LOCK IN SHARE MODE), that looks like they are caused by
> transactions not being rolled back (releasing locks) correctly.
Do you use pconnect? If I right remember there was a bug in some version
of mysql that in the case of using pconnect in some cases the automatic
rollback didn't happen. The solution was: after pconnect one had to
start with a rollback command.


Regards,
Felhő

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