Greetings wise brothers, I have a question.

I am working on a DBIx::Class table, where one row contains a regular expression stored as a plain string My current code looks like this:

package MyCompany::Result::WatchString;
use base qw/DBIx::Class::Result/;
use strict;

__PACKAGE__->table('tblWatchString');
__PACKAGE__->add_columns(
    'id',           { data_type => 'int', is_auto_increment => 1 },
    'comment',      { data_type => 'varchar', size => 30         }, # 
+Appears in logging messages
    'log_level',    { data_type => 'int',                        }, # 
+Log4perl log level.
    'match_string', { data_type => 'varchar', size => 200        }, # 
+String in the VLC output to match on.
);

sub match_re
{
    my $self = shift;

    my $match_string = $self->match_string;
    my $matcher = qr/\Q$match_string\E/;
    return $matcher;
}

[download]

In the main program, I then compare a large number of string against all the rows in the database. eg

my $logger = Log::Log4perl->get_logger();

open INPUT, '-|', '/some/program/with/verbose/output';

while( my $line <INPUT> )
{
    foreach my $watch_string ( $schema->resultset('WatchString')->all 
+)
    {
        if( $line =~ $watch_string->match_re() )
        {
            # Do stuff
            my $log_message = join(' ', 'Interesting output '. $watch_
+string->comment, $line);
            $logger->log( $watch_string->log_level, $log_message);
        }
    }
}

[download]

The problem is that $watch_string->match_re() is getting called a huge number of times, and the regular expression gets re-compiled every time. The algorithm is crying out for some sort of caching, but I can't work out how.

I have tried modifying match_re() to just cache the compiled regular expression in $self->{'_cached_re'} but the cache is not persistent between invocations.

I have read The DBIx::Class FAQ entry on this, but I could not get either the Moose or the Class::Accessor::Grouped method to work. When I tried Moose, my builder function got called every time, and the data did not appear to be cached. With Class::Accessor::Grouped the data was never stored.

I have tried using DBIx::Class::InflateColumn and creating an inflate method that returns the compiled regular expression, but it is getting called every time, and is not being cached.

I have tried DBIx::Class::VirtualColumns but when I tried to install via the CPAN client the tests failed.

There must be a way to do this, can anyone point me in the right direction, or point out what I have been doing wrong.

Thanks.

In reply to How to cache a regular expression in a DBIx::Class object by chrestomanci

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