Allow literal struct in insert_all + add recent changes to docs

lib/ecto/repo.ex

@@ -1490,16 +1490,19 @@ defmodule Ecto.Repo do
   ## Source query
 
   A query can be given instead of a list with entries. This query needs to select
-  into a map containing only keys that are available as writeable columns in the
-  schema. This will query and insert the values all inside one query, without
-  another round trip to the application.
+  into a map, struct or source containing only keys that are available as writeable
+  columns in the schema. This will query and insert the values all inside one query,
+  without another round trip to the application.
 
   ## Examples
 
+      # List of keyword lists
       MyRepo.insert_all(Post, [[title: "My first post"], [title: "My second post"]])
 
+      # List of maps
       MyRepo.insert_all(Post, [%{title: "My first post"}, %{title: "My second post"}])
 
+      # Query selecting into a map
       query = from p in Post,
         join: c in assoc(p, :comments),
         select: %{
@@ -1508,8 +1511,29 @@ defmodule Ecto.Repo do
           interactions: sum(p.likes) + count(c.id)
         },
         group_by: p.author_id
+
       MyRepo.insert_all(AuthorStats, query)
 
+      query = from p in Post, select: map(p, [:author_id, :title])
+      MyRepo.insert_all(PostAuthors, query)
+
+      # Query selecting into a struct
+      query = from p in Post, select: %Post{author_id: p.author_id, title: p.title}
+      MyRepo.insert_all(PostAuthors, query)
+
+      query = from p in Post, select: struct(p, [:author_id, :title])
+      MyRepo.insert_all(PostAuthors, query)
+
+      # Query selecting into a source
+      query = from p in Post, select: p
+      MyRepo.insert_all(PostBackup, query)
+
+      query = from p in Post, select: %{p | public: false}
+      MyRepo.insert_all(PostBackup, query)
+
+      query = from p in Post, join: c in assoc(p, :comments), where: p.public, select: c
+      MyRepo.insert_all(PublicCommentBackup, query)
+
   ## Upserts
 
   `c:insert_all/3` provides upserts (update or inserts) via the `:on_conflict`

lib/ecto/repo/schema.ex

@@ -142,6 +142,9 @@ defmodule Ecto.Repo.Schema do
         %Ecto.Query.SelectExpr{expr: {:&, _, [_ix]}, fields: fields} ->
           Enum.map(fields, &insert_all_select_dump!(&1))
 
+        %Ecto.Query.SelectExpr{expr: {:%, _, [_, {:%{}, _, args}]}} ->
+          Enum.map(args, fn {field, _} -> insert_all_select_dump!(field, dumper) end)
+
         _ ->
           raise ArgumentError, """
           cannot generate a fields list for insert_all from the given source query:
@@ -154,10 +157,8 @@ defmodule Ecto.Repo.Schema do
             * A single `struct/2` or several `struct/2` expressions combined with `select_merge`
             * A source such as `p` in the query `from p in Post`
             * A single literal map or several literal maps combined with `select_merge`. If
-              combining several literal maps, there cannot be any query interpolations
-              except in the last `select_merge`. Consider using `Ecto.Query.exclude/2`
-              to rebuild the select expression from scratch if you need multiple `select_merge`
-              statements with interpolations
+              combining several literal maps, there cannot be any overwrites to keys containing
+              query interpolations.
 
           All keys must exist in the schema that is being inserted into
           """

test/ecto/repo_test.exs

@@ -670,6 +670,25 @@ defmodule Ecto.RepoTest do
       assert ["ten"] = params
     end
 
+    test "takes query selecting on struct" do
+      threshold = "ten"
+
+      query =
+        from s in MySchema,
+          where: s.x > ^threshold,
+          select: %MySchema{
+            x: s.x,
+            y: "bar",
+            z: nil
+          }
+
+      TestRepo.insert_all(MySchema, query)
+
+      assert_received {:insert_all, %{source: "my_schema"}, {%Ecto.Query{} = query, params}}
+      assert [{{:., _, [{:&, [], [0]}, :x]}, _, []}, "bar", nil] = query.select.fields
+      assert ["ten"] = params
+    end
+
     test "takes query selecting on struct/2" do
       query =
         from s in MySchema,