如何在自定义混合任务中从Ecto获取数据

问题描述

我想在自定义混合任务中通过Ecto显示来自数据库的数据.如何在任务中获取(或启动)Ecto存储库?

I want to display data from my DB through Ecto in a custom mix task. How can I get the Ecto repo in my task (or start it)?

我尝试了类似的方法，但是没有用:

I tried something like this but it didn't work:

defmodule Mix.Tasks.Users.List do


use Mix.Task
  use Mix.Config
  use Ecto.Repo, otp_app: :app

  @shortdoc "List active users"
  @moduledoc """
    List active users
  """
  def run(_) do
    import Ecto.Query, only: [from: 1]

    Mix.shell.info "=== Active users ==="
    query = from u in "users"
    sync = all(query)
    Enum.each(users, fn(s) -> IO.puts(u.name) end)
  end

end

当我启动mix users.list时，这将给我以下输出:

This will give me the following output when I launch mix users.list:

** (ArgumentError) repo Mix.Tasks.Users.List is not started, please ensure it is part of your supervision tree
    lib/ecto/query/planner.ex:64: Ecto.Query.Planner.query_lookup/5
    lib/ecto/query/planner.ex:48: Ecto.Query.Planner.query_with_cache/6
    lib/ecto/repo/queryable.ex:119: Ecto.Repo.Queryable.execute/5

有什么办法解决这个问题吗?

Any idea or other way to solve this problem?

推荐答案

Ecto 3.x:

ensure_started从Ecto中删除.关于这个话题有很多困惑.在这里看到 https://github.com/elixir-ecto/ecto/拉/2829#issuecomment-456313417 了解更多. José建议使用Mix.Task.run "app.start"启动应用程序，或使用MyApp.Repo.start_link(...)运行存储库.

ensure_started has since been removed from Ecto. There has been a lot of confusion around this topic. See here https://github.com/elixir-ecto/ecto/pull/2829#issuecomment-456313417 for more. José suggests to either start the app using Mix.Task.run "app.start" or run the repo using MyApp.Repo.start_link(...).

Ecto 2.x:

该功能以前在2.x中可用，但显然Mix.Ecto未被认为是公共API的一部分.

This used to work in 2.x, but apparently Mix.Ecto was not considered part of the public API.

实际上有一个辅助模块Mix.Ecto( https://github.com/elixir-ecto/ecto/blob/master/lib/mix/ecto.ex )，这样可以更轻松地编写使用ecto的混合任务:

There is actually a helper module Mix.Ecto (https://github.com/elixir-ecto/ecto/blob/master/lib/mix/ecto.ex) that makes it easier to write mix tasks that use ecto:

defmodule Mix.Tasks.Users.List do
  use Mix.Task
  import Mix.Ecto

  def run(args) do
    repos = parse_repo(args)

    Enum.each repos, fn repo ->
      Mix.shell.info "=== Active users ==="

      ensure_repo(repo, args)
      ensure_started(repo, [])
      users = repo.all(Ectotask.User)

      Enum.each(users, fn(s) -> IO.puts(s.name) end)
    end
  end
end

此帮助程序使您可以访问parse_repo/1，ensure_repo/2，ensure_started/1. parse_repo将使您的任务与其他ecto混合任务很好地配合，例如，它将使您通过-r来指定其他回购.

This helper gives you access to parse_repo/1, ensure_repo/2, ensure_started/1. parse_repo will let your task fit in nicely with other ecto mix tasks, for example it will let you pass -r to specify a different repo.

➤ mix users.list
=== Active users ===
Adam
➤ mix users.list -r Ectotask.Repo22
=== Active users ===
** (Mix) could not load Ectotask.Repo22, error: :nofile. Please pass a repo with the -r option.

ensure_started确保您正在缺少的仓库正在运行.

ensure_started makes sure the repo is running, which you were lacking.

作为指导和灵感，您可以在 https://github.com/elixir-ecto/ecto/tree/master/lib/mix/tasks

For guidance and inspiration, you can look at how other ecto mix tasks are implemented at https://github.com/elixir-ecto/ecto/tree/master/lib/mix/tasks

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