Use the mysql bulk insert statement format if possible.

We found that using the traditional prepare/execute cycle was about 10 times slower to insert 2 million records, than using several bulk sql statements of about 500K.

my @rows = (
    [qw(a b c d)],
    [qw(e f g h)],
    [qw(i j k l)],
    [qw(m n o p)],
    [qw(q r s t)],
    [qw(u v w x)],
    [qw(y z a b)],
    [qw(c d e f)],
    [qw(h i j k)],
    [qw(l m n o)],
  );
  
# -------------------------------------
# slower
# -------------------------------------
my $sth = $db->prepare("INSERT INTO mytable VALUES(?,?,?,?)")
  or die "prepare failed: " . $db->errstr;
 
for my $row ( @rows ) {
 $sth->execute(@$row);
}

# -------------------------------------
# faster
# -------------------------------------
my $sql = "INSERT INTO mytable VALUES ";
for my $row ( @rows ) {
 $sql .= "('" . join("','",@$row) . '),";
}
substr($sql,-1)='';

$db->do( $sql );
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