Re: Catching errors with Perl DBI

Stan:

On Thu, Jul 2, 2020 at 5:03 PM stan <stanb(at)panix(dot)com> wrote:

> How can I catch the errors generated whne I call an INSERT that violates a
> constraint? I have coded like this:
>
> my $sth = $dbh->prepare($stmt);
> my $rv = $sth->execute() or die $DBI::errstr;
> if ( $rv < 0 ) {
> print $DBI::errstr;
> }
>
> But, if the INSERT violates a constraint, it never gets the the evaluation
> of the $rv

I assume you mean the if($rv<0) is what it is not executed.

In perl this happens because something died. I assume it is not the
one you coded. This means some of your handles have the RaiseError
attribute, lookit up in the perldoc.

> Is this a setting for the DBI?

I do not remember if it has a global setting, but it sure has a
database handle setting ( which percolates down ). I use it routinely
for easier error handling.

I'm not sure if you know how to from your message, but if something is
dying you can use the block eval construct:

eval {
# potentially dying code...
my $sth = $dbh->prepare($stmt);
my $rv = $sth->execute() or die $DBI::errstr;
if ( $rv < 0 ) {
print $DBI::errstr;
}
1; # This forces the eval to return true if execution gets here.
} or do {
# Whatever you want, $@ has the codes.
}

to trap it in perl.

About RaiseError, it is common to set it to true in the handle, put
all your code in a sub() and catch it, in programs where you donot
have easy recovery of errors, and use local eval if needed to catch
this kind of prim. key violation things.

Francisco Olarte.