Hello, I have an Ecto query which gets me some data from the database, then I use Enum.filter to get filtered results and now I want to limit that to first 3 elements. query |> Enum.filter(fn x -> x.created_by == "user" end) |> ??? Enum.filter returns the list of elements, how do I get the first …

I just found out about Enum.slice which can help me with that… query |> Enum.filter(fn x -> x.created_by == "user" end) |> Enum.slice(0..2) Enum.take() as @NeutronStein suggested is even nicer solution. So this is the answer to my first question… if anyone can share their thoughts about getting …

query |> where([x], x.created_by == ^"user") |> order_by([x], x.id) |> limit(3)

Ecto.Query — Ecto v3.14.0 If you are not using rest of the rows - may be you can add limit directly to the query ? [image] MatijaL: I decided to get the data from the db with one larger query and then filter the data on app level as I believed this should …

[image] MatijaL: I decided to get the data from the db with one larger query and then filter the data on app level I don’t have any right to ask what I’m about to ask because I don’t know really anything about what you’re actually doing… but I’m not going to let that stop me. Why not do the …

[image] NeutronStein: query |> where([x], x.created_by == ^"user") |> order_by([x], x.id) |> limit(3) Yes, that’s the query I have in place but was thinking about changing it to a bigger query filtered by app. [image] sbuttgereit: Why not do the filtering in database query? I could, i…

[image] MatijaL: I’m thinking that having 2 queries would be slower then 1 bigger query filtered by the app I don’t see how this follows. If you can write 1 query for the database to get unfiltered data, why do you think you need 2 queries to achieve the desired filtering at the database?

I’m sorry for not making it clear enough… I have users and each user can be a project’s creator or contributor. In a user’s account page, I want to list projects where user is a creator but also list projects where user is a contributor. So, is it better to create 1 query with all user projects(bo…

That’s what I would do. Get both kinds of users with one DB query and then programmatically split the list into two – author / contributor. Super easy when you add Enum.group_by at the end of your pipe. :slight_smile:

I would need to see the actual table structures to give you the best advice. Having said that, based on my understanding of your description, I’ve heard nothing that would require you to use two queries to get the complete filtered (and even sorted) data from the database in a single query. Since …

Elixir Programming Language Forum

How to get first x elements from the list?

Questions & Help Questions

NeutronStein October 26, 2022, 12:32pm 2

... |> Enum.take(3)