Question

Given two tables: (incoming greatly reduced/simplified example that exhibits the key problem)

app_data represents applications that can be subscribed to

id   app_name
 1   apple
 2   berry
 3   cherry

app_sub maps email addresses to applications

id   email
 1   alex
 2   bob
 2   coby

I’d like to generate a table from a single-user point-of-view showing which applications the current user is subscribed to and not.

For example, from Alex’s perspective I’d like to get:

desired_table

id    app_name    is_subscribed
 1    apple       true
 2    berry       false
 3    cherry      false

The following pure SQL query seems to be fine:

select id, app_name, email
  from app_data left join ( select *
                              from app_sub
                             where email='alex'
                          ) as subquery
                          on app_name.id=app_data.id;

However I’m having great difficulty getting that to work in dbix-class.

Alternatively, I tried to eliminate the subquery like so:

$app_data_resultset->search( { -or => [ { email => 'alex' },
                                        { email => undef },
                                      ],
                             },
                             { select => [ qw{ me.id
                                               me.app_name
                                               app_sub.email
                                             },
                                         ],
                               as => [ qw{ id
                                           app_name
                                           email
                                         },
                                     ],
                               join => 'app_sub',
                           );

However, this (now expectedly) results in the following (after treating both 0 and null as false):

bad_table

id    app_name    is_subscribed
 1    apple       true
 3    cherry      false

Since ‘bob’ and ‘coby’ are subscribed to id 2, the where clause completely eliminates the second id.

Any help would be greatly appreciated!

Answer 1

Vincent, I am trying to join to a subquery now myself. I cannot find anyone succeeding so far.

An alternative is to just do it in plain SQL with $c->model(‘blah’)->storage->dbh->prepare(“query”) OR the ‘Arbitrary SQL through a custom ResultSource’ section of the DBIx Class Cookbook, which also seems like a reasonable way.