[Dbix-class] transactions, etc.

[Josef Karthauser]

On Wed, Jan 24, 2007 at 12:22:49PM -0600, Brandon Black wrote:
> >
> >Nope, I'm talking about the -current branch.  I think that the code when
> >it reconnections should check to see whether the internal transaction
> >count is non-zero, and if it raise an exception instead of proceeding.
> >That would be the safest thing to do.
> >
> 
> In the txn_begin/txn_end case that's true, although it needs some
> careful thought and testing.  However, txn_do is much more robust, and
> I don't believe it currently suffers from this problem.
> 

Ok. First things first.  It appears that some of the dependancy code
isn't working properly.

Look at this patch:

    === Storage/DBI/mysql.pm
    ==================================================================
    --- Storage/DBI/mysql.pm        (revision 3050)
    +++ Storage/DBI/mysql.pm        (local)
    @@ -7,6 +7,10 @@
     
     # __PACKAGE__->load_components(qw/PK::Auto/);
     
    +sub _dbh_txn_begin {
    +  print "mysql:_dbh_txn_begin\n";
    +}
    +
     sub _dbh_last_insert_id {
       my ($self, $dbh, $source, $col) = @_;
       $dbh->{mysql_insertid};
    === Storage/DBI.pm
    ==================================================================
    --- Storage/DBI.pm      (revision 3050)
    +++ Storage/DBI.pm      (local)
    @@ -741,6 +741,7 @@
     
     sub _dbh_txn_begin {
       my ($self, $dbh) = @_;
    +print "storage:_dbh_txn_begin\n";
       if ($dbh->{AutoCommit}) {
	 $self->debugobj->txn_begin()
	   if ($self->debug);
    @@ -750,8 +751,10 @@
     
     sub txn_begin {
       my $self = shift;
    -  $self->dbh_do($self->can('_dbh_txn_begin'))
    -    if $self->{transaction_depth}++ == 0;
    +print "storage:txn_begin\n";
    +#  $self->dbh_do($self->can('_dbh_txn_begin'))
    +#    if $self->{transaction_depth}++ == 0;
    +  $self->dbh_do($self->can('_dbh_txn_begin'));
     }
     
     sub _dbh_txn_commit {


The point here being to see if I can override _dbh_txn_commit in the
database specific driver file (mysql in this case).

However with this test code:

    my $schema = .... however you get your schema ...;
    $schema->txn_begin();
    print "A\n";
    $schema->txn_begin();
    print "A2\n";
    $schema->txn_begin();
    print "A3\n";
    eval { $schema->txn_rollback(); }; print Dumper $@;
    print "R3\n";
    eval { $schema->txn_rollback(); }; print Dumper $@;
    print "R2\n";
    eval { $schema->txn_rollback(); }; print Dumper $@;
    print "R1\n";

    $schema->txn_begin();
    print "A\n";
    $schema->txn_begin();
    print "A2\n";
    $schema->txn_begin();
    print "A3\n";
    eval { $schema->txn_rollback(); }; print Dumper $@;
    print "R3\n";
    eval { $schema->txn_rollback(); }; print Dumper $@;
    print "R2\n";
    eval { $schema->txn_rollback(); }; print Dumper $@;
    print "R1\n";

I get this output:


    transwarp% env DBIC_TRACE=1 ./test.pl
    storage:txn_begin
    storage:_dbh_txn_begin
    BEGIN WORK
    A
    storage:txn_begin
    mysql:_dbh_txn_begin
    A2
    storage:txn_begin
    mysql:_dbh_txn_begin
    A3
    ROLLBACK
    $VAR1 = '';
    R3
    $VAR1 = '';
    R2
    $VAR1 = '';
    R1
    storage:txn_begin
    mysql:_dbh_txn_begin
    A
    storage:txn_begin
    mysql:_dbh_txn_begin
    A2
    storage:txn_begin
    mysql:_dbh_txn_begin
    A3
    $VAR1 = '';
    R3
    $VAR1 = '';
    R2
    $VAR1 = '';
    R1


Notice that the first time that txn_begin is called it isn't calling the
code in ...::DBI::mysql, however it does subsequently.

I've not totally got my head around the auto loading code yet, but it
appears that the ...:DBI::driver code is being loaded too late.
It ought to be auto loaded when the schema object is populated, not
when the database connection is made.

Joe
-- 
=== Josef Karthauser (joe at tao.org.uk) === http://x2obuilder.com/tao ===
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