Add namespace_id to notes

This is going to be used for partitioning the table. Also prepares the
async index on the column so we can add the foreign key constraint to
this column.

Changelog: other

db/migrate/20230718094246_add_namespace_id_to_notes.rb

+# frozen_string_literal: true
+
+class AddNamespaceIdToNotes < Gitlab::Database::Migration[2.1]
+  enable_lock_retries!
+
+  def up
+    add_column :notes, :namespace_id, :bigint
+  end
+
+  def down
+    remove_column :notes, :namespace_id
+  end
+end

db/post_migrate/20230718094501_prepare_notes_namespace_id_index.rb

+# frozen_string_literal: true
+
+class PrepareNotesNamespaceIdIndex < Gitlab::Database::Migration[2.1]
+  INDEX_NAME = 'index_notes_on_namespace_id'
+
+  # TODO: Index to be created synchronously as part of https://gitlab.com/gitlab-org/gitlab/-/issues/416127
+  def up
+    prepare_async_index :notes, :namespace_id, name: INDEX_NAME
+  end
+
+  def down
+    unprepare_async_index :notes, :namespace_id, name: INDEX_NAME
+  end
+end

db/schema_migrations/20230718094246

+8cb2cd90109dcc4f29ab34fa4caca617fe7bf42493e3a6712b66978480f06940
\ No newline at end of file

db/schema_migrations/20230718094501

+636bd7305c03f94cd161dc21deda05c289946b31a3c04805c08273f9a7067729
\ No newline at end of file

db/structure.sql

@@ -19080,7 +19080,8 @@ CREATE TABLE notes (
     confidential boolean,
     last_edited_at timestamp with time zone,
     internal boolean DEFAULT false NOT NULL,
-    id bigint NOT NULL
+    id bigint NOT NULL,
+    namespace_id bigint
 );
 CREATE SEQUENCE notes_id_seq

lib/gitlab/import_export/project/import_export.yml

@@ -984,9 +984,11 @@ excluded_attributes:
   notes:
     - :noteable_id
     - :review_id
+    - :namespace_id
   commit_notes:
     - :noteable_id
     - :review_id
+    - :namespace_id
   label_links:
     - :label_id
     - :target_id

spec/db/schema_spec.rb

@@ -14,7 +14,8 @@
     # but in Search::NamespaceIndexAssignment model, only `search_index_id` is used as foreign key and indexed
     search_namespace_index_assignments: [%w[search_index_id index_type]],
     slack_integrations_scopes: [%w[slack_api_scope_id]],
-    namespaces: %w[organization_id] # this index is added in an async manner, hence it needs to be ignored in the first phase.
+    namespaces: %w[organization_id], # this index is added in an async manner, hence it needs to be ignored in the first phase.
+    notes: %w[namespace_id] # this index is added in an async manner, hence it needs to be ignored in the first phase.
   }.with_indifferent_access.freeze
 
   TABLE_PARTITIONS = %w[ci_builds_metadata].freeze
@@ -82,7 +83,7 @@
     merge_requests_compliance_violations: %w[target_project_id],
     merge_request_diff_commits: %w[commit_author_id committer_id],
     namespaces: %w[owner_id parent_id],
-    notes: %w[author_id commit_id noteable_id updated_by_id resolved_by_id confirmed_by_id discussion_id],
+    notes: %w[author_id commit_id noteable_id updated_by_id resolved_by_id confirmed_by_id discussion_id namespace_id],
     notification_settings: %w[source_id],
     oauth_access_grants: %w[resource_owner_id application_id],
     oauth_access_tokens: %w[resource_owner_id application_id],