How to get distinct values from object's property with Drift (ex Moor); Flutter

Question

TLDR: "SELECT DISTINCT category FROM items" efficiently in Drift

There is Item (or ItemsCompanion) data class that among others has 'String category' property. I'd like to get a list of distinct categories efficiently.

I'm failing to found a way

to get in result property of object without object itself
to filter out only unique values

Any help would be appreciated.

I can get a list of Items, iterate through and put it's categories in List, transform a List into a Set but it seems way too inefficient.

Please provide enough code so others can better understand or reproduce the problem. — Community, Dec 19 '22 at 10:58

score 1 · Answer 1 · answered Dec 19 '22 at 08:25

Using the answer from simolus3 https://stackoverflow.com/a/62359317/8108153 I got this:

 Future<List<String>> getItemsCategories() {
    final query = selectOnly(items, distinct: true)
          ..addColumns([items.category])
          ..where(items.category.isNotNull());
        ;

    return query.map((row) => row.read(items.category)).get();
  }

Whether it's the optimal approach or not yet it's way better anything I've come up with

How to get distinct values from object's property with Drift (ex Moor); Flutter

1 Answers1