Fix background data migrations to work with includes/eager_load o…

…n relation

Fixes #65.

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## master (unreleased)
 
+- Fix background data migrations to work with `includes`/`eager_load` on relation
 - Fix problem with running migrations for `activerecord` 8.0.0.rc2
 
 ## 0.20.0 (2024-10-21)

lib/online_migrations/batch_iterator.rb

@@ -19,7 +19,7 @@ def each_batch(of: 1000, column: relation.primary_key, start: nil, finish: nil,
       end
 
       relation = apply_limits(self.relation, column, start, finish, order)
-      base_relation = relation.reselect(column).reorder(column => order)
+      base_relation = relation.unscope(:includes, :eager_load).reselect(column).reorder(column => order)
 
       start_id = start || begin
         start_row = base_relation.uncached { base_relation.first }

test/background_migrations/background_migrations.rb

@@ -91,6 +91,16 @@ def count
     end
   end
 
+  class RelationWithIncludes < OnlineMigrations::BackgroundMigration
+    def relation
+      Project.includes(user: :commits)
+    end
+
+    def process_batch(_users)
+      # no-op
+    end
+  end
+
   class MigrationWithCount < OnlineMigrations::BackgroundMigration
     def relation
       User.all

test/background_migrations/migration_test.rb

@@ -4,9 +4,6 @@
 
 module BackgroundMigrations
   class MigrationTest < Minitest::Test
-    class User < ActiveRecord::Base
-    end
-
     def setup
       @connection = ActiveRecord::Base.connection
       @connection.create_table(:users, force: true) do |t|
@@ -18,10 +15,17 @@ def setup
         t.bigint :user_id
       end
 
+      @connection.create_table(:commits, force: true) do |t|
+        t.bigint :user_id
+      end
+
       User.reset_column_information
+      Project.reset_column_information
+      Commit.reset_column_information
     end
 
     def teardown
+      @connection.drop_table(:commits, if_exists: true)
       @connection.drop_table(:projects, if_exists: true)
       @connection.drop_table(:users, if_exists: true)
       OnlineMigrations::BackgroundMigrations::Migration.delete_all
@@ -155,6 +159,15 @@ def test_empty_relation
       assert m.enqueued?
     end
 
+    def test_relation_with_includes
+      user = User.create!
+      _project = user.projects.create!
+      m = create_migration(migration_name: "RelationWithIncludes")
+
+      run_all_migration_jobs(m)
+      assert m.succeeded?
+    end
+
     def test_progress_succeded_migration
       m = build_migration(status: :succeeded)
       assert_in_delta 100.0, m.progress

test/support/models.rb

@@ -2,9 +2,16 @@
 
 class User < ActiveRecord::Base
   has_many :projects
+  has_many :commits
 end
 
 class Project < ActiveRecord::Base
+  belongs_to :user
+  has_many :commits
+end
+
+class Commit < ActiveRecord::Base
+  belongs_to :user
 end
 
 class ShardRecord < ActiveRecord::Base