DBI: disconnect - question

Question

Would you call parts of the disconnect-code as line-noise or would you leave it as it is?

use DBI;

my $dbh = DBI->connect ...
...
...
END {
    $dbh->disconnect or die $DBI::errstr if $dbh;
}

Answer 1

Explicit disconnection from the database is not strictly necessary if you are exiting from your program after you have performed all the work. But it is a good idea, especially in programs in which you have performed multiple connections or will be carrying out multiple sequential connections.

See Programming the Perl DBI for more info.

Answer 2

Be careful. You can hit some interesting situations if you disable AutoCommit and don't commit depending on whether you disconnect:

perl -le 'use DBI;my $h = DBI->connect("dbi:ODBC:test","test","test", {AutoCommit => 0, RaiseError=>1}); $h->do(q/insert into mje values(?, ?)/, undef, 1, "fred");'

Issuing rollback() due to DESTROY without explicit disconnect() of DBD::ODBC::db handle test.

Note, because there was no explicit disconnect the insert was rolled back and we got an error.

perl -le 'use DBI;my $h = DBI->connect("dbi:ODBC:test","test","test", {AutoCommit => 0, RaiseError=>1}); $h->do(q/insert into mje values(?, ?)/, undef, 1, "fred");$h->disconnect or die $DBI::errstr;'

Here it appears there is nothing wrong even though commit was not called but the rows did not get into the database. So the disconnect masked the fact the rows were not committed.