Gerhard Wiesinger wrote:
Hello Craig,
Are you sure this is correct?
The test program (see below) with autocommit=0 counts up when an insert
is done in another session and there is no commit done.
I think with each new select a new implicit transaction is done when no
explicit "BEGIN" has been established.
Sorry, I should have been more specific. A transaction starts when you do something that will alter data in the database, such as insert, update, alter table, create sequence, and so forth. The Perl DBI won't start a transaction for a select.
But my basic point is still valid: Some languages like Perl can implicitely start a transaction, so if programmers aren't familiar with this behavior, they can accidentally create long-running transactions.
Craig
Can one confirm this behavior?
Thnx.
Ciao,
Gerhard
# Disable autocommit!
my $dbh = DBI->connect($con, $dbuser, $dbpass, {RaiseError => 1,
AutoCommit=>0}) || die "Unable to access Database '$dbname' on host
'$dbhost' as user '$dbuser'. Error returned was: ". $DBI::errstr ."";
my $sth = $dbh->prepare('SELECT COUNT(*) FROM employee;');
for (;;)
{
$sth->execute();
my ($count) = $sth->fetchrow();
print "count=$count\n";
$sth->finish();
# $dbh->commit;
sleep(3);
}
$dbh->disconnect;
--
http://www.wiesinger.com/
On Thu, 24 Sep 2009, Craig James wrote:
Dave Dutcher wrote:
You need a COMMIT for every BEGIN. If you just run a SELECT statement
without first beginning a transaction, then you should not end up with a
connection that is Idle in Transaction. If you are beginning a
transaction,
doing a select, and then not committing, then yes that is a bug.
The BEGIN can be hidden, though. For example, if the application is
written in Perl,
$dbh = DBI->connect($dsn, $user, $pass, {AutoCommit => 0});
will automatically start a transaction the first time you do
anything. Under the covers, the Perl DBI issues the BEGIN for you,
and you have to do an explicit
$dbh->commit();
to commit it.
Craig
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