Aran Clary Deltac > DBIx-ResultSet-0.17 > DBIx::ResultSet::Cookbook

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NAME ^

DBIx::ResultSet::Cookbook - Common recipes for DBIx::ResultSet.

RECIPES ^

JOINing

Joins are currently not supported. This is mostly because SQL::Abstract does not support them, and I've yet to have the time or impetus to try and dig in to how DBIx::Class::ResultSet does it. Also, in many cases a subselect is a better choice.

Another option is to use DBIx::ResultSet's where_sql() to produce the WHERE portion of the SQL while still being able to write the FROM/JOIN portion of the SQL with raw SQL. For example:

    my ($where_sql, @bind) = $users_rs->search({ 'u.status' => 1})->where_sql();
    
    my $sth = $dbh->prepare(qq[
        SELECT u.user_id, e.sent_date
        FROM users u
        JOIN emails e ON (e.user_id = u.user_id)
        $where_sql
    ]);
    
    $sth->execute( @bind );

Subselects

SQL::Abstract supports subselects natively, and DBIx::ResultSet provides a very elegant way to use them:

    my $emailed_users_rs = $users_rs->search({
        user_id => {-in => \[
            $emails_rs->select_sql(['user_id'])
        ]},
    });

The above example builds a SQL query like this:

    SELECT *
    FROM users
    WHERE user_id IN (
        SELECT user_id FROM emails
    );

The SQL::Abstract documentation gives a few more examples of this. Searching for a backslash and an opening square brace "\[" will give you the examples.

bind_param

See bindtype in SQL::Abstract docs. A way to easly integrate this with DBIx::ResultSet has not yet been developed.

Auto PKs

Automatically inrementing primary key values may be retrieved after an insert by calling:

    my $user_id = $users_rs->auto_pk();

This is only supported by a couple database at the moment (MySQL, and SQLte), and more are planned in the future. If you're database isn't yet supported an exception will be thrown.

Transactions

The DBIx::ResultSet::Connector class provides an interface to facilitate robust transaction management. This is done by using DBIx::Connector, which is available via the dbix_connector attribute. Several of DBIx::Connector's methods are made available directly on the DBIx::ResultSet::Connector object.

So, let's get some data and update a record within a transation:

    my $connector = DBIx::ResultSet->connect( ... );
    $connector->txn(sub{
        my $users = $connector->resultset('users');
        my $user_permissionis = $connector->resultset('user_permissions');
        my $admin_permissions = $user_permissions->search({ perm => 'ADMIN' });

        my $admin_users = $users->search({ user_id => { -in => [
            $admin_permissions->select_sql('user_id')
        ] } });

        $admin_users->update({ is_admin => 1 });
        # Executes: UPDATE users SET is_admin = ?
        #   WHERE user_id IN (SELECT user_id FROM user_permissions WHERE perm = ?);
    });

DBIx::Connector will rollback the transaction if there are any errors and then throw the error, otherwise the transaction will be commited.

Take a closer look at the DBIx::Connector docs to get an idea of what you can do.

Connection Handling

All methods in DBIx::ResultSet that need a DBI database handle get it via DBIx::Connector's run() method. It is highly recommended that you acquire a solid understanding of how DBIx::Connector works and how to use it properly. Once you have, you'll find that there are many ways in which you can control database pings, transactions, and lost connection handling.

By default the underlying DBIx::Connector object will be set with a connection mode of 'fixup'. This is typically what most people want. In this setup if the connection is disconnected from the database then it will be automatically re-connected and the code that the run block was attempting to execute will be re-executed. This means that in the following:

    $connector->run(sub{
        send_email( ... );
        $connector->resultset('email_log')->insert(...);
    });

It is possible that the e-mail would get sent TWICE if the database connection is lost. This is because the lost database connection isn't deteceted until we actually try to do something with the database, in this case an INSERT. So, when under the 'fixup' connection mode one solution is to change the order of your code to first insert the log, then send the e-mail.

Another solution is to use the 'ping' connection mode which will validate that the database connection is healthy before executing the code block. But, this still isn't 100% reliable because a database connection could potentially be lost at any time.

More details on all this can be found in the DBIx::Connector docs.

AUTHOR ^

Aran Clary Deltac <bluefeet@gmail.com>

LICENSE ^

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

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