RE: Suddenly $dbh->{AutoCommit}=0 => "Transactions notsupported by database"

> Some users of the Debian packages I create recently reported that
after
> the
> upgrade from MySQL 5.0.22 to 5.0.24 Perl scripts that try to
explicitly
> set
> $dbh->{AutoCommit} =3D 0;
> die with the error message:
> "Transactions not supported by database"
>=20
> I could verify this but failed to trace down the exact reason due to
the
> confusing perl-xs code :) At least I figured out that
> * ethereal tells me that the greeting and login request both set the
> "client knows transactions" flag to 1
> * the default for imp_dbh->has_transactions is TRUE in dbdimp.c of
> DBD::mysql and
> * that set variable setting triggers dbd_db_STORE_attrib() from
dbdimp.c
> which for some reason thinks that imp_dbh->has_transactions is
FALSE.
>=20
> Has anybody a clue if this really is a recent change or if it should
work?

From the docs... (http://dev.mysql.com/doc/refman/5.1/en/commit.html)

To disable autocommit mode for a single series of statements, use the
START TRANSACTION statement:

START TRANSACTION;
SELECT @A:=3DSUM(salary) FROM table1 WHERE type=3D1;
UPDATE table2 SET summary=3D@A WHERE type=3D1;
COMMIT;

With START TRANSACTION, autocommit remains disabled until you end the
transaction with COMMIT or ROLLBACK. The autocommit mode then reverts to
its previous state.

---
Kevin Benton
Perl/Bugzilla Developer/Administrator, Perforce SCM Administrator
AMD - ECSD Software Validation and Tools
=20
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Re: Suddenly $dbh->{AutoCommit}=0 => "Transactions not supported bydatabase"

Hello

On 2006-08-24 Benton, Kevin wrote:
> > Some users of the Debian packages I create recently reported that after
> > the upgrade from MySQL 5.0.22 to 5.0.24 Perl scripts that try to
> > explicitly set
> > $dbh->{AutoCommit} = 0;
> > die with the error message:
> > "Transactions not supported by database"
....

> From the docs... (http://dev.mysql.com/doc/refman/5.1/en/commit.html)
>
> To disable autocommit mode for a single series of statements, use the
> START TRANSACTION statement:

Although this is true, the "perldoc DBI" specification not only allows
the explicit use of the AutoCommit flag, it even recommends using it
this way:
$dbh = DBI->connect($dsn, $user, $password,
{ RaiseError => 1, AutoCommit => 0 });
...
Explicitly defining the required "AutoCommit" behaviour is strongly
recommended and may become mandatory in a later version. This deter-
mines whether changes are automatically committed to the database when
executed, or need to be explicitly committed later.

But this is not even the point, DBD::mysql understands this flag but
it suddenly says that the MySQL installations had no transaction support
in which case it would be allowed to issue a fatal error but which is
definitely not the case here as I have innodb enabled.
So how does it come to that conclusion?

bye,

-christian-


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