XF 2.2 XFES / Enhanced Search: I need to search also on an extra column

[Scandal]

Hello all!
I have the following issue for which I need some help.

I have this part of code to make a search for nodes (I use also Enhanced Search / Elastic Search).

        $input = [
            'search_type' => 'node',
            'keywords' => $keywords,
            'c' => [],
            'c.title_only' => 1,
            'c.newer_than' => 0,
            'c.older_than' => 0,
            'c.users' => '',
            'c.content' => '',
            'c.type' => 'node',
            'c.thread_type' => '',
            'grouped' => false,
            'order' => 'relevance'
        ];
       
        $constraints = [];
       
        $searchRequest = new \XF\Http\Request($this->app->inputFilterer(), $input, [], []);

        $urlConstraints = $input['c'];

        $searcher = $this->app()->search();
        $query = $searcher->getQuery();

        if ($input['search_type'] && $searcher->isValidContentType($input['search_type']))
        {
            $typeHandler = $searcher->handler($input['search_type']);
            $query->forTypeHandler($typeHandler, $searchRequest, $urlConstraints);
        }

        $input['keywords'] = $this->app->stringFormatter()->censorText($input['keywords'], '');
        if ($input['keywords'])
        {
            $query->withKeywords($input['keywords'], $input['c.title_only']);
        }

        $searchRepo = $this->repository('XF:Search');
        $search = $searchRepo->runSearch($query, $constraints, false);

        if (!$search)
        {
            return $this->message(\XF::phrase('no_results_found'));
        }      

        $nodeIds = [];
       
        if (!empty($search->search_results))
        {
            foreach ($search->search_results AS $r)
            {
                $nodeIds[] = $r[1];
            }
        }

What I need to do?
On xf_forum db table (entity XF:Forum / not XF:Node), I have a text column, let's call it "title_new".

I need via the same search code, to detect the $nodeIds which are closer to $keywords, by search the xf_forum "title_new" column.

I know that I could made it with a finder->where LIKE %%, but currently I need to use the elastic search and maybe to do the search via the same $query.
As you know xf_forum and xf_node are joined via the node_id column.

Any idea?
If I need to make indexable my "title_new" column, some instructions would be very helpful!

 

[Scandal]

Any idea?