Abandoning models - embracing data

A gentle introduction to Ecto

Transcript

1. @michalmuskala Warszawa, 9.06.2016 Abandoning models - embracing data A gentle introduction to Ecto
4. @michalmuskala Warszawa, 9.06.2016 Abandoning models - embracing data A gentle introduction to Ecto
5. @michalmuskala Warszawa, 9.06.2016 Michał Muskała http://michal.muskala.eu/ https://github.com/michalmuskala/ @michalmuskala
11. @michalmuskala Warszawa, 9.06.2016 The Experiment
12. @michalmuskala Warszawa, 9.06.2016 Who used Elixir?
13. @michalmuskala Warszawa, 9.06.2016 Who used Ecto?
14. @michalmuskala Warszawa, 9.06.2016 Who has Ruby background?
15. @michalmuskala Warszawa, 9.06.2016 Who has C# or .NET background?
16. @michalmuskala Warszawa, 9.06.2016 Inspirations LINQ - queries ActiveRecord - associations Other Elixir projects - Moebius - pipeline queries Other Ruby projects - rom, trailblazer - focus on data
17. @michalmuskala Warszawa, 9.06.2016 Adapter-based architecture Database adapters Connection pool adapters db_connection library
18. @michalmuskala Warszawa, 9.06.2016 Ecto Ecto.Schema Ecto.Query Ecto.Repo Ecto.Changeset
19. @michalmuskala Warszawa, 9.06.2016 Ecto.Schema defmodule Weather do use Ecto.Schema schema "weather" do belongs_to :city, City field :wdate, Ecto.Date field :temp_lo, :integer field :temp_hi, :integer field :prcp, :float, default: 0.0 timestamps end end
20. @michalmuskala Warszawa, 9.06.2016 Ecto.Schema declares fields - no SELECT * FROM foos allows for custom types thin wrapper around Elixir’s structs defines data - not behaviour
21. @michalmuskala Warszawa, 9.06.2016 Ecto.Query from w in Weather, where: w.prcp <= 0.0 or is_nil(w.prcp), select: w from s in Search, where: ilike(fragment("?::text", s.name), ^name_search_term) or fragment("to_tsvector(?) @@ to_tsquery(?)", s.description, ^term)
22. @michalmuskala Warszawa, 9.06.2016 Ecto.Query from p in Post, where: fragment(position: ["$geoWithin": [...]]) def all(filter) do filter.q |> sanitize |> search |> preload(:location) |> order_by([s] asc: s.date, desc: s.type) end
23. @michalmuskala Warszawa, 9.06.2016 Ecto.Query defmacrop geo_search(coordinates, geo_point, radius) do quote do fragment("ST_DWithin(?, ?, ?)", unquote(coordinates), unquote(geo_point), unquote(radius) ) end end
24. @michalmuskala Warszawa, 9.06.2016 Ecto.Query def by_location(query, %{lat: lat, lng: lng, radius: radius}) do geo_point = %Geo.Point{coordinates: {lat, lng}} from provider in query, left_join: location_provider in assoc(provider, :location), left_join: events in assoc(provider, :events), left_join: location_event in assoc(events, :location), where: geo_search(location_provider.coordinates, ^geo_point, ^radius) or geo_search(location_event.coordinates, ^geo_point, ^radius), distinct: true, select: provider end
25. @michalmuskala Warszawa, 9.06.2016 Ecto.Query query = from p in Post, select: [:visits], order_by: [desc: :visits], limit: 10 TestRepo.all(from p in subquery(query), select: avg(p.visits))
26. @michalmuskala Warszawa, 9.06.2016 Ecto.Query Two syntaxes - keyword and pipeline No lazy-loading, explicit preloads Easily extensible via fragments and macros Translated by adapter Composable
27. @michalmuskala Warszawa, 9.06.2016 Ecto.Repo defmodule Simple.Repo do use Ecto.Repo, otp_app: :simple end def start(_type, _args) do import Supervisor.Spec tree = [supervisor(Simple.Repo, [])] opts = [name: Simple.Sup, strategy: :one_for_one] Supervisor.start_link(tree, opts) end
28. @michalmuskala Warszawa, 9.06.2016 Ecto.Repo Isolates all impure operations Is an interface to the database Outside of repo - everything is plain data
29. @michalmuskala Warszawa, 9.06.2016 Ecto.Changeset def changeset(schema, params) do schema |> cast(params, @params_required ++ @params_optional) |> validate_required(@params_required) |> validate_params |> cast_assoc(:location, required: true) |> cast_assoc(:age_group, required: true) |> cast_embed(:links) |> validate_length(:name, min: @min_length_name) |> validate_format(:image_url, @regexp_image) |> validate_inclusion(:category, Category.values) |> validate_email |> unique_constraint(:email) end
30. @michalmuskala Warszawa, 9.06.2016 Ecto.Changeset Encodes data changes as a data structure No validations are global Multiple changieret functions for different circumstances Easily extensible with functions
31. @michalmuskala Warszawa, 9.06.2016 Ecto.Multi def password_reset_multi(account, params) do account = account_password_reset(account, params) access_log = log_password_reset(account, params) Multi.new |> Multi.update(:account, account) |> Multi.insert(:log, access_log) |> Multi.delete_all(:sessions, assoc(account, :sessions)) end
32. @michalmuskala Warszawa, 9.06.2016 Ecto.Multi defmodule UserManager do def password_reset(params) do with {:ok, account} <- load_account(params), multi = password_reset_multi(account, params), {:ok, results} <- Repo.transaction(multi), :ok <- send_notification(results.account), do: {:ok, results.account} end # ... end
33. @michalmuskala Warszawa, 9.06.2016 Ecto.Multi Encodes transaction as a data structure Changesets for transactions You can test your transaction without database!
34. @michalmuskala Warszawa, 9.06.2016 Schema less queries from u in "users", join: a in "activities", on: a.user_id == u.id, where: a.start_at > type(^start_at, Ecto.DateTime) and a.end_at < type(^end_at, Ecto.DateTime), group_by: a.user_id, select: %{user_id: a.user_id, interval: a.start_at - a.end_at, count: count(u.id)}
35. @michalmuskala Warszawa, 9.06.2016 Schema less queries # insert data [%{id: id}] = MyApp.Repo.insert_all("posts", [[title: "hello"]], returning: [:id]) # use query for updates post = from p in "posts", where: p.id == ^id {1, _} = MyApp.Repo.update_all(post, set: [title: "new title"]) # and deletes {1, _} = MyApp.Repo.delete_all post
36. @michalmuskala Warszawa, 9.06.2016 Table less schemas defmoudule RegistrationSchema do use Ecto.Schema schema "" do field :foo, :string field :bar, :integer embeds_one :resource, Resource end # ... end
37. @michalmuskala Warszawa, 9.06.2016 Schema less changesets data = %{} types = %{first_name: :string, last_name: :string, email: :string} fields = Map.keys(types) changeset = {data, types} |> Ecto.Changeset.cast(params, fields) |> validate_required(...) |> validate_length(...)
38. @michalmuskala Warszawa, 9.06.2016 Concurrent, transactional tests In 1.1 - database tests sequential, 2.0 - concurrent Works with postgres, mysql has wired transaction semantics Works with Wallaby and Hound
39. @michalmuskala Warszawa, 9.06.2016 No models, no callbacks Ecto 1.1 deprecated models, embraced schemas, 2.0 removes models Ecto 1.1 deprecated callbacks, 2.0 removed them I’m forbidden by José to use the world “model” Phoenix will switch away from the model nomenclature
40. @michalmuskala Warszawa, 9.06.2016 KISS Plain CRUD interfaces are easy When you need more power - you have it We want not to force anything on the users, but keep the simplicity
41. @michalmuskala Warszawa, 9.06.2016 –José Valim “I am completely OK with taking the blame regarding Ecto 1.0. We did push folks to the wrong direction. But Ecto 2.0 no longer puts you in this place[…]. If you are using structs as your domain models, then it will be more on you than on me, since you have everything to stop doing that[…].”
42. @michalmuskala Warszawa, 9.06.2016 Ecto is less opinionated
43. @michalmuskala Warszawa, 9.06.2016 Ecto is more extensible
44. @michalmuskala Warszawa, 9.06.2016 Ecto is data centric
45. @michalmuskala Warszawa, 9.06.2016 Ecto is not a solution to the problem
46. @michalmuskala Warszawa, 9.06.2016 Ecto is a toolbox for building solutions
47. @michalmuskala Warszawa, 9.06.2016 Abandoning models - embracing data A gentle introduction to Ecto