lib/MyAppMerge.pm 

my $table_handlers = [     # row_count_estimates
    al_links                        => [ 'skip_empty'  ],
    schema_migrations               => [ 'skip'        ],
    issue_statuses                  => [ 'skip_subset' ],

    users             => [ 'build_mapping', 'email' => 'id' ],
    projects          => [ 'mapping_table', 'project_desc' => 'id' ],

    tasks             => [ copy_rows => {
        condition         => "WHERE task_status <> 'CANCELLED'",
        order_by          => 'id',
        pre_map_method    => 'pre_map_tasks',
        column_mappings   => [
            id              => 'map_task_id(id)',
            owner_user_id   => 'users.id',
            project_id      => 'projects.id',
        ],
    }],