Ecto: a database wrapper and language integrated query for Elixir

Transcript

1. ecto
   a database wrapper and language
   integrated query for Elixir
   

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2. defmodule Weather do
   use Ecto.Model
   schema "weather" do
   field :city # Defaults to type :string
   field :temp_lo, :integer
   field :temp_hi, :integer
   field :prcp, :float, default: 0.0
   end
   end
   query = from w in Weather,
   where: w.prcp > 0 or is_nil(w.prcp),
   select: w
   Repo.all(query)
   

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3. simplicity over
   convenience
   

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4. “If you want Ecto to get something, you
   have to explicitly ask for it. This
   feature will probably seem a little
   tedious to you…”
   

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5. “…but it is the only way to guarantee
   your application has predictable
   performance when the amount of
   data grows.”
   

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6. defmodule Weather do
   use Ecto.Model
   schema "weather" do
   field :city # Defaults to type :string
   field :temp_lo, :integer
   field :temp_hi, :integer
   field :prcp, :float, default: 0.0
   end
   end
   query = from w in Weather,
   where: w.prcp > 0 or is_nil(w.prcp),
   select: w
   Repo.all(query)
   

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7. defmodule Weather do
   use Ecto.Model
   schema "weather" do
   field :city # Defaults to type :string
   field :temp_lo, :integer
   field :temp_hi, :integer
   field :prcp, :float, default: 0.0
   end
   end
   query = from w in Weather,
   where: w.prcp > 0 or is_nil(w.prcp),
   select: w
   Repo.all(query)
   

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8. defmodule Weather do
   use Ecto.Model
   schema "weather" do
   field :city # Defaults to type :string
   field :temp_lo, :integer
   field :temp_hi, :integer
   field :prcp, :float, default: 0.0
   end
   end
   query = from w in Weather,
   where: w.prcp > 0 or is_nil(w.prcp),
   select: w
   Repo.all(query)
   

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9. defmodule Weather do
   use Ecto.Model
   schema "weather" do
   field :city # Defaults to type :string
   field :temp_lo, :integer
   field :temp_hi, :integer
   field :prcp, :float, default: 0.0
   end
   end
   query = from w in Weather,
   where: w.prcp > 0 or is_nil(w.prcp),
   select: w
   Repo.all(query)
   

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10. defmodule Weather do
    use Ecto.Model
    schema "weather" do
    field :city # Defaults to type :string
    field :temp_lo, :integer
    field :temp_hi, :integer
    field :prcp, :float, default: 0.0
    end
    end
    query = from w in Weather,
    where: w.prcp > 0 or is_nil(w.prcp),
    select: w
    Repo.all(query)
    

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11. ‣ data mapper
    ‣ query language
    ‣ associations
    ‣ filtering
    ‣ validations
    ‣ lifecycle callbacks
    ‣ changesets
    ‣ migrations
    ‣ custom types
    ‣ embedded structs
    

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12. compose queries
    

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13. # Create a query
    query = from w in Weather, where: w.prcp > 0
    # Extend the query
    query = from w in query, select: w.city
    

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14. repository
    

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15. Repo.get_by(Post, title: "My post")
    Repo.transaction(fn ->
    Repo.update!(%{alice | balance: alice.balance - 10})
    Repo.update!(%{bob | balance: bob.balance + 10})
    end)
    post = Repo.get!(Post, 42)
    post = %{post | title: "New title"}
    case Repo.update post do
    {:ok, model} -> # Updated with success
    {:error, changeset} -> # Something went wrong
    end
    

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16. Repo.get_by(Post, title: "My post")
    Repo.transaction(fn ->
    Repo.update!(%{alice | balance: alice.balance - 10})
    Repo.update!(%{bob | balance: bob.balance + 10})
    end)
    post = Repo.get!(Post, 42)
    post = %{post | title: "New title"}
    case Repo.update post do
    {:ok, model} -> # Updated with success
    {:error, changeset} -> # Something went wrong
    end
    

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17. Repo.get_by(Post, title: "My post")
    Repo.transaction(fn ->
    Repo.update!(%{alice | balance: alice.balance - 10})
    Repo.update!(%{bob | balance: bob.balance + 10})
    end)
    post = Repo.get!(Post, 42)
    post = %{post | title: "New title"}
    case Repo.update post do
    {:ok, model} -> # Updated with success
    {:error, changeset} -> # Something went wrong
    end
    

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18. changesets
    

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19. defmodule User do
    use Ecto.Model
    import Ecto.Changeset
    schema "users" do
    field :name
    field :email
    field :age, :integer
    end
    def changeset(user, params \\ :empty) do
    user
    |> cast(params, ~w(name email), ~w(age))
    |> validate_format(:email, ~r/@/)
    |> unique_constraint(:email)
    |> validate_inclusion(:age, 18..100)
    end
    end
    

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20. defmodule User do
    use Ecto.Model
    import Ecto.Changeset
    schema "users" do
    field :name
    field :email
    field :age, :integer
    end
    def changeset(user, params \\ :empty) do
    user
    |> cast(params, ~w(name email), ~w(age))
    |> validate_format(:email, ~r/@/)
    |> unique_constraint(:email)
    |> validate_inclusion(:age, 18..100)
    end
    end
    

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21. defmodule User do
    use Ecto.Model
    import Ecto.Changeset
    schema "users" do
    field :name
    field :email
    field :age, :integer
    end
    def changeset(user, params \\ :empty) do
    user
    |> cast(params, ~w(name email), ~w(age))
    |> validate_format(:email, ~r/@/)
    |> unique_constraint(:email)
    |> validate_inclusion(:age, 18..100)
    end
    end
    

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22. defmodule User do
    use Ecto.Model
    import Ecto.Changeset
    schema "users" do
    field :name
    field :email
    field :age, :integer
    end
    def changeset(user, params \\ :empty) do
    user
    |> cast(params, ~w(name email), ~w(age))
    |> validate_format(:email, ~r/@/)
    |> unique_constraint(:email)
    |> validate_inclusion(:age, 18..100)
    end
    end
    

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23. defmodule User do
    use Ecto.Model
    import Ecto.Changeset
    schema "users" do
    field :name
    field :email
    field :age, :integer
    end
    def changeset(user, params \\ :empty) do
    user
    |> cast(params, ~w(name email), ~w(age))
    |> validate_format(:email, ~r/@/)
    |> unique_constraint(:email)
    |> validate_inclusion(:age, 18..100)
    end
    end
    

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24. defmodule User do
    use Ecto.Model
    import Ecto.Changeset
    schema "users" do
    field :name
    field :email
    field :age, :integer
    end
    def changeset(user, params \\ :empty) do
    user
    |> cast(params, ~w(name email), ~w(age))
    |> validate_format(:email, ~r/@/)
    |> unique_constraint(:email)
    |> validate_inclusion(:age, 18..100)
    end
    end
    

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25. def registration_changeset(model, params) do
    model
    |> changeset(params)
    |> cast(params, ~w(password), [])
    |> validate_length(:password, min: 6, max: 100)
    |> put_pass_hash()
    end
    

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26. associations
    

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27. query = from p in Post, preload: [:comments]
    query = from p in Post,
    join: c in assoc(p, :comments),
    where: c.published_at > p.updated_at,
    preload: [comments: c]
    query |> Repo.all
    

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28. familiar
    different
    pragmatic
    fun
    

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