Rewrite a message's search entry only when its body is saved

Boosting and unboosting touch the message, so after_update_commit
rewrote its row in the full-text index with the same text, loading the
rich text again to rebuild it, on every boost. The index only needs a
new row when the rich text body was saved.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0142qgjggdJ2KDdGk7RF9Xm9

app/models/message/searchable.rb

@@ -3,7 +3,7 @@ module Message::Searchable
 
   included do
     after_create_commit  :create_in_index
-    after_update_commit  :update_in_index
+    after_update_commit  :update_in_index, if: :body_saved?
     after_destroy_commit :remove_from_index
 
     scope :search, ->(query) { joins("join message_search_index idx on messages.id = idx.rowid").where("idx.body match ?", match_terms(query)).ordered }
@@ -22,6 +22,11 @@ module Message::Searchable
       execute_sql_with_binds "insert into message_search_index(rowid, body) values (?, ?)", id, plain_text_body
     end
 
+    # Boosts touch their message too: rewrite the index only when the body was saved.
+    def body_saved?
+      association(:rich_text_body).target&.saved_change_to_body?
+    end
+
     def update_in_index
       execute_sql_with_binds "update message_search_index set body = ? where rowid = ?", plain_text_body, id
     end

test/models/message/searchable_test.rb

@@ -1,6 +1,9 @@
 require "test_helper"
+require "active_record/testing/query_assertions"
 
 class Message::SearchableTest < ActiveSupport::TestCase
+  include ActionDispatch::TestProcess, ActiveRecord::Assertions::QueryAssertions
+
   test "message body is indexed and searchable" do
     message = rooms(:designers).messages.create! body: "My hovercraft is full of eels", client_message_id: "earth", creator: users(:david)
     assert_equal [ message ], rooms(:designers).messages.search("eel")
@@ -12,6 +15,28 @@ class Message::SearchableTest < ActiveSupport::TestCase
     assert_equal [], rooms(:designers).messages.search("sharks")
   end
 
+  test "boosting a message leaves the search index alone, whether or not its body is loaded" do
+    attachment_message = rooms(:designers).messages.create! attachment: fixture_file_upload("moon.jpg", "image/jpeg"), client_message_id: "moon", creator: users(:david)
+
+    [ messages(:first), Message.with_rich_text_body.find(messages(:first).id), Message.with_rich_text_body.find(attachment_message.id) ].each do |message|
+      assert_no_queries_match(/message_search_index/) do
+        message.boosts.create!(content: "🦞", booster: users(:jason)).destroy!
+      end
+    end
+  end
+
+  test "saving a new body replaces the old words in the index" do
+    message = rooms(:designers).messages.create! body: "My hovercraft is full of eels", client_message_id: "earth", creator: users(:david)
+
+    Message.find(message.id).update! body: "My hovercraft is full of sharks"
+    assert_equal [ message ], rooms(:designers).messages.search("sharks")
+    assert_equal [], rooms(:designers).messages.search("eels")
+
+    Message.find(message.id).body.update! body: "My hovercraft is full of whales"
+    assert_equal [ message ], rooms(:designers).messages.search("whales")
+    assert_equal [], rooms(:designers).messages.search("sharks")
+  end
+
   test "search results are returned in message order" do
     messages = [ "first cat", "second cat", "third cat", "cat cat cat" ].map do |body|
       rooms(:designers).messages.create! body: body, client_message_id: body, creator: users(:david)