I'm writing some code which, amongst other things, utilities MySQL server-side prepare statements to ensure the validity of chunks of SQL. However, I have to wrap the prepare in an eval because it dies when it encounters bad SQL:

eval {
    $dbh->prepare( $statement, { mysql_server_prepare => 1 } ) 
};
if ( my $error = $@ ) { ... }

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Well, that seems pretty reasonable, except for one tiny problem. I trap the exception, but it still gets sent to STDERR unless I do this:

eval {
    local $SIG{__WARN__} = sub {};
    $dbh->prepare( $statement, { mysql_server_prepare => 1 } ) 
};
if ( my $error = $@ ) { ... }

[download]

Why the heck do I need to do that? Am I have a total brain-cramp and missing something obvious here? A complete example of how I'm doing this is below, though I think all of the relevant bits are above.

use DBI;
use DBD::mysql 3.0002_1;    # so we have have server-side prepares
use Data::Record;
use Regexp::Common;

my $dbh = DBI->connect(
    "DBI:mysql:$database:$server",
    $user,
    $pass,
    {   AutoCommit => 0,
        RaiseError => 1,
    }
);

my $sql = <<'END_SQL';
SELECT 1;
ALTER TABLET foo;
END_SQL

use Data::Dumper;
my @errors = invalid_sql($dbh, $sql);
print Dumper(\@errors);

sub invalid_sql {
    my ( $dbh, $sql ) = @_;
    my @errors;
    foreach my $statement ( split_sql($sql) ) {
        next unless $statement =~ /\S/;
        local $SIG{__WARN__} = sub {}; # XXX Why do I need this?
        eval { $dbh->prepare( $statement, { mysql_server_prepare => 1 
+} ) };
        if ( my $error = $@ ) {
            push @errors => [ $statement => $error ];
        }
    }
    return wantarray ? @errors : \@errors;
}

sub split_sql {
    my $sql = shift;
    my $record = Data::Record->new(
        {   split  => ';',
            unless => $RE{quoted},
        }
    );
    return $record->records($sql);
}

[download]

Cheers,
Ovid

New address of my CGI Course.

In reply to DBD::mysql warns *and* dies? by Ovid

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