should I commit in the following code? - perl

Question

My code:
122 #
123 my $hfpDbh = undef;
124 unless (
125 $hfpDbh = DBI->connect("dbi:Pg:host=....")#removed something
128 ) {
129 Log( ERROR, "" );
130 Exit( 1 )
131 }
132 $hfpDbh->{RaiseError} = 1;
133 $hfpDbh->{AutoCommit} = 0;
134
135 ( my $mydata, $msg ) = load_data( $hfpDbh, $DatFile );
136 unless ( defined($mydata) )
137 {
138 Log(INFO, "Calling exit...2");
139 }
140 #$hfpDbh->disconnect();
141 Exit( 0 );
142 Log(INFO, "Calling exit...4");
143
144
145 sub load_data
146 {
147 my ( $dbh, $DatFile ) = #_;
148 my $msg = '';
149 unless ( $dbh ) {
150 $msg = 'cannot load data, no DB handle';
151 Log( ERROR, $msg );
152 }
153 Log(INFO, "Call load_data...");
154 my $q = "SELECT ip as ip FROM rules WHERE active = 'true' AND isGood = 'true';";
155 my $stmt = undef;
156 unless ( $stmt = $dbh->prepare( $q ) ) {
157 $msg = "unable to prepare SQL query: $q";
158 Log( ERROR, $msg );
159 }
160
161 eval { $stmt->execute() };
162 if ( $# ) {
163 $msg = "failed to execute SQL query: $#";
164 Log( ERROR, $msg );
165 }
166
167 my $data = {};
168 while ( my $row = $stmt->fetchrow_hashref() ) {
169 #Log(INFO, "testing row");
170 }
171 $stmt->finish();
172 return $data, $msg;
173 }
The warning is:
Issuing rollback() due to DESTROY without explicit disconnect() of DBD::Pg::db handle
If I add "$dbh->commit()" after Line 171, the above warn disappeared.
If I did not add "$dbh->commit()" after Line 171 but called "$hfpDbh->disconnect();" in Line 140, the above warn disappeared too.
My question is:
The warning means that there are uncommitted transactions? That is why I need to commit or disconnect explicitly to fix the warning. But there is only SELECT operation in the code. What I am missing?
Thanks.

Answer 1

Since you aren't modifying the database at all, you don't need to enable transactions, so don't set AutoCommit to zero. That way there's no need to call commit anywhere either, and the database will be disconnected automatically when the handle goes out of dcope
Since you're handling errors yourself you shouldn't set RaiseError to 1. That will cause your program to die immediately if any error occurs and your own handling code won't get executed
There's no need to call finish. It won't do any harm here, but it's also pointless and should almost never be necessary

Answer 2

The warning means that there are uncommitted transactions?
There is an uncommitted transaction since you requested for transactions to be used, but the warning actually notifies you that a rollback was performed implicitly. It tells you this because this may result in a loss of information. Obviously, it won't result in a loss of information in this case, but the check isn't smart enough of realize this.
What I am missing?
$hfpDbh->disconnect(); or $hfpDbh->rollback();