How can I see the raw SQL generated for an Ecto.Qu

问题:

I have an Ecto.Query and a Repo, such that I can call Repo.all(query) and get results. However, the results are not what I expect.

How can I see the raw SQL the Repo will generate from the Ecto.Query?

回答1:

You can use Ecto.Adapters.SQL.to_sql/3:

iex> Ecto.Adapters.SQL.to_sql(:all, Repo, Post)
{"SELECT p.id, p.title, p.inserted_at, p.created_at FROM posts as p", []}

The query can be any struct that implements the Ecto.Queryable protocol like Post above(which is a module that imports Ecto.Schema). An Ecto.Query can also be passed:

iex> query = Ecto.Query.where(Post, [p], p.views > 10)
iex> Ecto.Adapters.SQL.to_sql(:all, Repo, query)
{"SELECT p.id, p.title, p.inserted_at, p.created_at FROM posts as p WHERE p.views > $1", [10]}

回答2:

A convenient helper method for printing raw SQL

def print_sql(queryable) do
  IO.inspect(Ecto.Adapters.SQL.to_sql(:all, Repo, queryable))
  queryable
end

def list_new_foos() do
  Foo
  |> where([foo], foo.bar == 1337)
  |> limit(100)
  |> print_sql
  |> Repo.all()
end

回答3:

It's basically Gazlers answer, but modified to use in code:

query = from p in Post
{query, params} = Ecto.Adapters.SQL.to_sql(:all, Repo, query)
IO.puts("#{query}, #{inspect(params)}")

You could use simple IO.inspect, but it'll output a query with backslashes.