Add opt-in INSERT IGNORE support for MySQL via insert_mode option

When using on_conflict: :nothing, the MySQL adapter uses the
ON DUPLICATE KEY UPDATE x = x workaround which always reports
1 affected row regardless of actual insert.

This adds insert_mode: :ignore_errors option for insert_all that
uses INSERT IGNORE instead, providing accurate row counts (0 when
ignored, 1 when inserted).

Usage:
    Repo.insert_all(Post, posts,
      on_conflict: :nothing,
      insert_mode: :ignore_errors)

The Connection behavior is updated to accept opts in insert/8,
allowing adapter-specific options to flow through.

Author: mehiel

integration_test/myxql/upsert_all_test.exs

@@ -13,60 +13,84 @@ defmodule Ecto.Integration.UpsertAllTest do
 
   test "on conflict ignore" do
     post = [title: "first", uuid: "6fa459ea-ee8a-3ca4-894e-db77e160355e"]
-    # First insert succeeds - 1 row inserted
+    # Default :nothing behavior uses ON DUPLICATE KEY UPDATE x = x workaround
+    # which always reports rows as affected
+    assert TestRepo.insert_all(Post, [post], on_conflict: :nothing) == {1, nil}
     assert TestRepo.insert_all(Post, [post], on_conflict: :nothing) == {1, nil}
+  end
+
+  test "insert_mode: :ignore_errors" do
+    post = [title: "first", uuid: "6fa459ea-ee8a-3ca4-894e-db77e160355e"]
+    # First insert succeeds - 1 row inserted
+    assert TestRepo.insert_all(Post, [post],
+             on_conflict: :nothing,
+             insert_mode: :ignore_errors
+           ) == {1, nil}
+
     # Second insert is ignored due to duplicate - 0 rows inserted (INSERT IGNORE behavior)
-    assert TestRepo.insert_all(Post, [post], on_conflict: :nothing) == {0, nil}
+    assert TestRepo.insert_all(Post, [post],
+             on_conflict: :nothing,
+             insert_mode: :ignore_errors
+           ) == {0, nil}
   end
 
-  test "on conflict ignore with mixed records (some conflicts, some new)" do
+  test "insert_mode: :ignore_errors with mixed records (some conflicts, some new)" do
     # Insert an existing post
     existing_uuid = "6fa459ea-ee8a-3ca4-894e-db77e160355e"
     existing_post = [title: "existing", uuid: existing_uuid]
-    assert TestRepo.insert_all(Post, [existing_post], on_conflict: :nothing) == {1, nil}
+
+    assert TestRepo.insert_all(Post, [existing_post],
+             on_conflict: :nothing,
+             insert_mode: :ignore_errors
+           ) == {1, nil}
 
     # Now insert a batch with one duplicate and two new records
     new_uuid1 = "7fa459ea-ee8a-3ca4-894e-db77e160355f"
     new_uuid2 = "8fa459ea-ee8a-3ca4-894e-db77e160355a"
 
     posts = [
-      [title: "new post 1", uuid: new_uuid1],     # new - should be inserted
-      [title: "duplicate", uuid: existing_uuid],   # duplicate - should be ignored
-      [title: "new post 2", uuid: new_uuid2]       # new - should be inserted
+      [title: "new post 1", uuid: new_uuid1],
+      [title: "duplicate", uuid: existing_uuid],
+      [title: "new post 2", uuid: new_uuid2]
     ]
 
     # With INSERT IGNORE, only 2 rows should be inserted (the non-duplicates)
-    assert TestRepo.insert_all(Post, posts, on_conflict: :nothing) == {2, nil}
+    assert TestRepo.insert_all(Post, posts,
+             on_conflict: :nothing,
+             insert_mode: :ignore_errors
+           ) == {2, nil}
 
     # Verify the data - should have 3 posts total (1 existing + 2 new)
     assert length(TestRepo.all(Post)) == 3
 
     # Verify the existing post was not modified
     [original] = TestRepo.all(from p in Post, where: p.uuid == ^existing_uuid)
-    assert original.title == "existing"  # title unchanged
+    assert original.title == "existing"
 
     # Verify new posts were inserted
     assert TestRepo.exists?(from p in Post, where: p.uuid == ^new_uuid1)
     assert TestRepo.exists?(from p in Post, where: p.uuid == ^new_uuid2)
   end
 
-  test "on conflict ignore with all duplicates" do
+  test "insert_mode: :ignore_errors with all duplicates" do
     # Insert initial posts
     uuid1 = "1fa459ea-ee8a-3ca4-894e-db77e160355e"
     uuid2 = "2fa459ea-ee8a-3ca4-894e-db77e160355e"
-    initial_posts = [
-      [title: "first", uuid: uuid1],
-      [title: "second", uuid: uuid2]
-    ]
-    assert TestRepo.insert_all(Post, initial_posts, on_conflict: :nothing) == {2, nil}
+    initial_posts = [[title: "first", uuid: uuid1], [title: "second", uuid: uuid2]]
+
+    assert TestRepo.insert_all(Post, initial_posts,
+             on_conflict: :nothing,
+             insert_mode: :ignore_errors
+           ) == {2, nil}
 
     # Try to insert all duplicates
-    duplicate_posts = [
-      [title: "dup1", uuid: uuid1],
-      [title: "dup2", uuid: uuid2]
-    ]
+    duplicate_posts = [[title: "dup1", uuid: uuid1], [title: "dup2", uuid: uuid2]]
+
     # All are duplicates, so 0 rows inserted
-    assert TestRepo.insert_all(Post, duplicate_posts, on_conflict: :nothing) == {0, nil}
+    assert TestRepo.insert_all(Post, duplicate_posts,
+             on_conflict: :nothing,
+             insert_mode: :ignore_errors
+           ) == {0, nil}
 
     # Verify count unchanged
     assert length(TestRepo.all(Post)) == 2

lib/ecto/adapters/myxql.ex

@@ -103,6 +103,25 @@ defmodule Ecto.Adapters.MyXQL do
   automatically commits after some commands like CREATE TABLE.
   Therefore MySQL migrations does not run inside transactions.
 
+  ### Upserts
+
+  When using `on_conflict: :nothing`, the adapter uses the
+  `ON DUPLICATE KEY UPDATE x = x` workaround to simulate "do nothing"
+  behavior. This always reports 1 affected row regardless of whether
+  the row was actually inserted or ignored.
+
+  If you need accurate row counts (0 when ignored, 1 when inserted),
+  you can opt into MySQL's `INSERT IGNORE` by specifying:
+
+      Repo.insert_all(Post, posts,
+        on_conflict: :nothing,
+        insert_mode: :ignore_errors)
+
+  Note that `INSERT IGNORE` has broader semantics in MySQL - it also
+  ignores certain type conversion errors, not just duplicate key conflicts.
+  The `insert_mode: :ignore_errors` option only affects the behavior of
+  `on_conflict: :nothing`.
+
   ## Old MySQL versions
 
   ### JSON support
@@ -319,7 +338,10 @@ defmodule Ecto.Adapters.MyXQL do
 
     key = primary_key!(schema_meta, returning)
     {fields, values} = :lists.unzip(params)
-    sql = @conn.insert(prefix, source, fields, [fields], on_conflict, [], [])
+
+    # Extract insert_mode and pass it to the connection's insert function
+    insert_opts = if opts[:insert_mode], do: [insert_mode: opts[:insert_mode]], else: []
+    sql = @conn.insert(prefix, source, fields, [fields], on_conflict, [], [], insert_opts)
 
     opts =
       if is_nil(Keyword.get(opts, :cache_statement)) do
@@ -330,16 +352,14 @@ defmodule Ecto.Adapters.MyXQL do
 
     case Ecto.Adapters.SQL.query(adapter_meta, sql, values ++ query_params, opts) do
       {:ok, %{num_rows: 0}} ->
-        # With INSERT IGNORE (on_conflict: :nothing), 0 rows means the row was
-        # ignored due to a conflict, which is expected behavior
-        case on_conflict do
-          {:nothing, _, _} ->
-            {:ok, []}
-
-          _ ->
-            raise "insert operation failed to insert any row in the database. " <>
-                    "This may happen if you have trigger or other database conditions rejecting operations. " <>
-                    "The emitted SQL was: #{sql}"
+        # With INSERT IGNORE (insert_mode: :ignore_errors), 0 rows means the row
+        # was ignored due to a conflict, which is expected behavior
+        if opts[:insert_mode] == :ignore_errors do
+          {:ok, []}
+        else
+          raise "insert operation failed to insert any row in the database. " <>
+                  "This may happen if you have trigger or other database conditions rejecting operations. " <>
+                  "The emitted SQL was: #{sql}"
         end
 
       # We were used to check if num_rows was 1 or 2 (in case of upserts)

lib/ecto/adapters/myxql/connection.ex

@@ -179,45 +179,61 @@ if Code.ensure_loaded?(MyXQL) do
     end
 
     @impl true
-    def insert(prefix, table, header, rows, on_conflict, [], []) do
+    def insert(prefix, table, header, rows, on_conflict, returning, placeholders, opts \\ [])
+
+    def insert(prefix, table, header, rows, on_conflict, [], [], opts) do
       fields = quote_names(header)
-      insert_keyword = insert_keyword(on_conflict)
+      insert_keyword = insert_keyword(on_conflict, opts)
 
       [
         insert_keyword,
         quote_table(prefix, table),
         " (",
         fields,
         ") ",
-        insert_all(rows) | on_conflict(on_conflict, header)
+        insert_all(rows) | on_conflict(on_conflict, header, opts)
       ]
     end
 
-    defp insert_keyword({:nothing, _, []}), do: "INSERT IGNORE INTO "
-    defp insert_keyword(_), do: "INSERT INTO "
-
-    def insert(_prefix, _table, _header, _rows, _on_conflict, _returning, []) do
+    def insert(_prefix, _table, _header, _rows, _on_conflict, _returning, [], _opts) do
       error!(nil, ":returning is not supported in insert/insert_all by MySQL")
     end
 
-    def insert(_prefix, _table, _header, _rows, _on_conflict, _returning, _placeholders) do
+    def insert(_prefix, _table, _header, _rows, _on_conflict, _returning, _placeholders, _opts) do
       error!(nil, ":placeholders is not supported by MySQL")
     end
 
-    defp on_conflict({_, _, [_ | _]}, _header) do
+    # INSERT IGNORE when insert_mode: :ignore_errors is passed
+    defp insert_keyword({:nothing, _, _}, opts) do
+      if Keyword.get(opts, :insert_mode) == :ignore_errors do
+        "INSERT IGNORE INTO "
+      else
+        "INSERT INTO "
+      end
+    end
+
+    defp insert_keyword(_, _opts), do: "INSERT INTO "
+
+    defp on_conflict({_, _, [_ | _]}, _header, _opts) do
       error!(nil, ":conflict_target is not supported in insert/insert_all by MySQL")
     end
 
-    defp on_conflict({:raise, _, []}, _header) do
+    defp on_conflict({:raise, _, []}, _header, _opts) do
       []
     end
 
-    defp on_conflict({:nothing, _, []}, _header) do
-      # Handled by INSERT IGNORE
-      []
+    # With insert_mode: :ignore_errors, INSERT IGNORE handles conflicts - no ON DUPLICATE KEY needed
+    defp on_conflict({:nothing, _, []}, [field | _], opts) do
+      if Keyword.get(opts, :insert_mode) == :ignore_errors do
+        []
+      else
+        # Default :nothing - uses workaround to simulate "do nothing" behavior
+        quoted = quote_name(field)
+        [" ON DUPLICATE KEY UPDATE ", quoted, " = " | quoted]
+      end
     end
 
-    defp on_conflict({fields, _, []}, _header) when is_list(fields) do
+    defp on_conflict({fields, _, []}, _header, _opts) when is_list(fields) do
       [
         " ON DUPLICATE KEY UPDATE "
         | Enum.map_intersperse(fields, ?,, fn field ->
@@ -227,11 +243,11 @@ if Code.ensure_loaded?(MyXQL) do
       ]
     end
 
-    defp on_conflict({%{wheres: []} = query, _, []}, _header) do
+    defp on_conflict({%{wheres: []} = query, _, []}, _header, _opts) do
       [" ON DUPLICATE KEY " | update_all(query, "UPDATE ")]
     end
 
-    defp on_conflict({_query, _, []}, _header) do
+    defp on_conflict({_query, _, []}, _header, _opts) do
       error!(
         nil,
         "Using a query with :where in combination with the :on_conflict option is not supported by MySQL"

lib/ecto/adapters/postgres/connection.ex

@@ -229,7 +229,7 @@ if Code.ensure_loaded?(Postgrex) do
     end
 
     @impl true
-    def insert(prefix, table, header, rows, on_conflict, returning, placeholders) do
+    def insert(prefix, table, header, rows, on_conflict, returning, placeholders, _opts \\ []) do
       counter_offset = length(placeholders) + 1
 
       values =

lib/ecto/adapters/sql.ex

@@ -970,7 +970,7 @@ defmodule Ecto.Adapters.SQL do
         rows -> unzip_inserts(header, rows)
       end
 
-    sql = conn.insert(prefix, source, header, rows, on_conflict, returning, placeholders)
+    sql = conn.insert(prefix, source, header, rows, on_conflict, returning, placeholders, opts)
 
     opts =
       if is_nil(Keyword.get(opts, :cache_statement)) do

lib/ecto/adapters/sql/connection.ex

@@ -94,7 +94,8 @@ defmodule Ecto.Adapters.SQL.Connection do
               rows :: [[atom | nil]],
               on_conflict :: Ecto.Adapter.Schema.on_conflict(),
               returning :: [atom],
-              placeholders :: [term]
+              placeholders :: [term],
+              opts :: Keyword.t()
             ) :: iodata
 
   @doc """

lib/ecto/adapters/tds/connection.ex

@@ -220,7 +220,7 @@ if Code.ensure_loaded?(Tds) do
     end
 
     @impl true
-    def insert(prefix, table, header, rows, on_conflict, returning, placeholders) do
+    def insert(prefix, table, header, rows, on_conflict, returning, placeholders, _opts \\ []) do
       counter_offset = length(placeholders) + 1
       [] = on_conflict(on_conflict, header)
       returning = returning(returning, "INSERTED")

test/ecto/adapters/myxql_test.exs

@@ -56,8 +56,8 @@ defmodule Ecto.Adapters.MyXQLTest do
   defp delete_all(query), do: query |> SQL.delete_all() |> IO.iodata_to_binary()
   defp execute_ddl(query), do: query |> SQL.execute_ddl() |> Enum.map(&IO.iodata_to_binary/1)
 
-  defp insert(prefx, table, header, rows, on_conflict, returning) do
-    IO.iodata_to_binary(SQL.insert(prefx, table, header, rows, on_conflict, returning, []))
+  defp insert(prefx, table, header, rows, on_conflict, returning, opts \\ []) do
+    IO.iodata_to_binary(SQL.insert(prefx, table, header, rows, on_conflict, returning, [], opts))
   end
 
   defp update(prefx, table, fields, filter, returning) do
@@ -1465,10 +1465,12 @@ defmodule Ecto.Adapters.MyXQLTest do
     end
   end
 
-  test "insert with on conflict" do
-    # Using INSERT IGNORE for :nothing on_conflict
+  test "insert with on duplicate key" do
+    # Default :nothing uses ON DUPLICATE KEY UPDATE workaround
     query = insert(nil, "schema", [:x, :y], [[:x, :y]], {:nothing, [], []}, [])
-    assert query == ~s{INSERT IGNORE INTO `schema` (`x`,`y`) VALUES (?,?)}
+
+    assert query ==
+             ~s{INSERT INTO `schema` (`x`,`y`) VALUES (?,?) ON DUPLICATE KEY UPDATE `x` = `x`}
 
     update = from("schema", update: [set: [z: "foo"]]) |> plan(:update_all)
     query = insert(nil, "schema", [:x, :y], [[:x, :y]], {update, [], []}, [])
@@ -1498,6 +1500,22 @@ defmodule Ecto.Adapters.MyXQLTest do
                  end
   end
 
+  test "insert with insert_mode: :ignore_errors" do
+    # INSERT IGNORE via insert_mode: :ignore_errors option
+    query =
+      insert(
+        nil,
+        "schema",
+        [:x, :y],
+        [[:x, :y]],
+        {:nothing, [], []},
+        [],
+        insert_mode: :ignore_errors
+      )
+
+    assert query == ~s{INSERT IGNORE INTO `schema` (`x`,`y`) VALUES (?,?)}
+  end
+
   test "insert with query" do
     select_query = from("schema", select: [:id]) |> plan(:all)