Apache::DBI , Transactions and Warnings ... Oh my!

BMaximus has asked for the wisdom of the Perl Monks concerning the following question:

While working on my site tonight I put in some transactions just to play around with it. Now I have a mixed set of tables in my MySQL database. Some are regular MyISAM tables and some are InnoDB tables, which have the transaction abilities. Now when AutoCommit is set to 0 on the connection to the database. The transaction tables work great. However I come up with an error when a non-transaction table is worked on.

DBD::mysql::db rollback failed: Warning:  Some non-transactional chang
+ed tables couldn't be rolled back at /usr/lib/perl5/site_perl/5.6.1/A
+pache/DBI.pm line 153.
[download]

now since Apache::DBI basically overloads DBI to create a connection pool. Here is the code around line 153 on Apache::DBI.

# The PerlCleanupHandler is supposed to initiate a rollback after the 
+script has finished if AutoCommit is off.
# Note: the PerlCleanupHandler runs after the response has been sent t
+o the client

sub cleanup {
    my $prefix = "$$ Apache::DBI            ";
    print STDERR "$prefix PerlCleanupHandler \n" if $Apache::DBI::DEBU
+G > 1;
    my $dbh = $Connected{$Idx};
    if ($Rollback{$Idx} and $dbh and $dbh->{Active} and !$dbh->{AutoCo
+mmit} and eval {$dbh->rollback}) {
        print STDERR "$prefix PerlCleanupHandler rollback for $Idx \n"
+ if $Apache::DBI::DEBUG > 1;
    }
    delete $Rollback{$Idx};
    1;
}
[download]

line 153 has eval {$dbh->rollback} which executes whenever AutoCommit is set to 0. Isn't DBI supposed to be told by MySQL whether the table is a transaction based table or not? I've gotten around the warning by setting $dbi->{AutoCommit} to 1 in the non-transaction section of the code that communicates with the DB. However I believe that this is a kludgy way of doing it and it should be handled in DBI somewhere/somehow. In any case, I thought MySQL sets AutoCommit according to the table being accesed by type. Could this be a bug in Apache::DBI or Apache::DBI breaking something on DBI?

BMaximus

Comment on Apache::DBI , Transactions and Warnings ... Oh my! Select or Download Code

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Re: Apache::DBI , Transactions and Warnings ... Oh my! by lachoy (Parson) on Feb 26, 2002 at 13:39 UTC
How could DBI or MySQL even know whether the affected tables are transaction based? What if you mixed them up in your transaction? `$dbh->do( "INSERT INTO nontrans VALUES ( 'hi' )" ); $dbh->do( "UPDATE trans SET name = 'hey' WHERE id = 4" ); $dbh->commit;` [download] How could either MySQL or DBI deal with this? It's probably a good idea to create two separate connections: one for transactions, one for non-transactions. And is it a good idea to even mix transaction and non-transactional tables in a database? This seems ripe for mistakes to me... but I haven't used transactions in MySQL before, so maybe this is recommended behavior? Chris M-x auto-bs-mode	[reply] [d/l]
Re: Apache::DBI , Transactions and Warnings ... Oh my! by perrin (Chancellor) on Feb 26, 2002 at 15:58 UTC
Apache::DBI does that in case your program crashes with some uncomitted changes active. It's a good thing. That warning can probably be turned off somehow at the MySQL level.	[reply]
Re: Apache::DBI , Transactions and Warnings ... Oh my! by zakzebrowski (Curate) on May 03, 2004 at 13:25 UTC
Mysql on a non-transactional table can't rollback anything, so anytime it sees that issued on a non-rollback table, the transaction is lost and it always gives that warning. DBI was not designed explicitly for certain databases, so it's a feature I believe you have to live with (if you can't modify the mysql configuration which may have an option to turn the warning off... i don't thinks so though.) ---- Zak - the office	[reply]


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