Raise if using an in memory database with pool_size != 1

CHANGELOG.md

@@ -7,6 +7,8 @@ project adheres to [Semantic Versioning][semver].
 
 ## Unreleased
 
+- changed: raise if an in memory database is opened with a pool_size != 1
+
 ## v0.11.0
 
 - added: Support for DDL transactions.

lib/ecto/adapters/sqlite3.ex

@@ -210,6 +210,7 @@ defmodule Ecto.Adapters.SQLite3 do
   @impl Ecto.Adapter.Storage
   def storage_up(options) do
     database = Keyword.get(options, :database)
+    pool_size = Keyword.get(options, :pool_size)
 
     cond do
       is_nil(database) ->
@@ -226,6 +227,11 @@ defmodule Ecto.Adapters.SQLite3 do
       File.exists?(database) ->
         {:error, :already_up}
 
+      database == ":memory:" && pool_size != 1 ->
+        raise ArgumentError, """
+        In memory databases must have a pool_size of 1
+        """
+
       true ->
         {:ok, state} = Exqlite.Connection.connect(options)
         :ok = Exqlite.Connection.disconnect(:normal, state)

test/ecto/adapters/sqlite3_test.exs

@@ -47,6 +47,20 @@ defmodule Ecto.Adapters.SQLite3ConnTest do
         fn -> SQLite3.storage_up(mumble: "no database here") == :ok end
       )
     end
+
+    test "can create an in memory database" do
+      assert SQLite3.storage_up(database: ":memory:", pool_size: 1) == :ok
+    end
+
+    test "fails if in memory database does not have a pool size of 1" do
+      assert_raise(
+        ArgumentError,
+        """
+        In memory databases must have a pool_size of 1
+        """,
+        fn -> SQLite3.storage_up(database: ":memory:", pool_size: 2) end
+      )
+    end
   end
 
   describe ".storage_down/2" do