How to correctly form filter values ​​in yii2 for grid?

Question

Yii

If anyone has come across this, please, tell me, an acceptable and correct solution for such a task:
We have:
1) 2000+ - categories
2) 1000000+ - pages
3) 50 - pages at a time displayed in the grid
Additionally: The
selection is formed on the basis of different filters from the grid.
Those. it turns out such a standard grid with filters and sorting.
What you need:
In the category filter, you need to display only those categories that are used in this selection. For example - we found 10,000 pages for different filters, but they use (all together) only 5 categories, and only these 5 categories should be present in the filter.

Answer 1

/** @var ActiveQuery $query */
$query = clone $dataProvider->query;
$query->select('category_id')->asArray();
Category::find()->where(['id'=>$query])->select(['name','id'])->indexBy('id')->column();

Answer 2

While I'm considering this option:
- I take a request from the provider (clone)
- I remove LIMIT
- Modify SELECT () in such a way that it displays only the necessary value + distinct. For example - ... select('category_id')->distinct(true) ...
Thus, I will get a list of ID's for the filter and load the filter values ​​based on them.
Sounds like a good idea, but it's a bunch of requests. The situation becomes more complicated if there are several (if not all) such filters.
Of course, you can also enable caching when loading filter values ​​..
In general, maybe someone else has ideas or who has come across this?