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app/controllers/messages_controller.rb

@@ -3,12 +3,26 @@ class MessagesController < ApplicationController
 
   # GET /messages or /messages.json
   def index
-    @messages = Message.all
+    query = params[:q]
+    if query
+      # %> and <-> are defined by pg_trgm.
+      # https://www.postgresql.org/docs/17/pgtrgm.html
+      @messages = Message.find_by_sql([
+        'SELECT * FROM messages WHERE body %> ? ORDER BY body <-> ? LIMIT 20',
+        query, query,
+      ])
+    else
+      @messages = Message.all
+    end
   end
 
   # GET /messages/1 or /messages/1.json
   def show
-    @message = Message.from_s3(params[:list_name], params[:list_seq])
+    if params[:id]
+      @message = Message.find(params[:id])
+    else
+      @message = Message.from_s3(params[:list_name], params[:list_seq])
+    end
   end
 
   # GET /messages/new

app/models/message.rb

@@ -9,7 +9,7 @@ def self.from_s3(list_name, list_seq)
     end
 
     def self.from_string(str)
-        hs, body = str.split(/\n\n/, 2)
+        hs, body = str.encode('utf-8', invalid: :replace).split(/\n\n/, 2)
         headers = hs.split(/\n/).map { |line|
           line.split(/:\s+/, 2)
         }.to_h

app/views/messages/index.html.erb

@@ -2,13 +2,13 @@
 
 <h1>Messages</h1>
 
-<div id="messages">
+<ul>
   <% @messages.each do |message| %>
-    <%= render message %>
-    <p>
-      <%= link_to "Show this message", message %>
-    </p>
+    <li>
+      <%= link_to message.subject, message %>
+      <small><%= message.body %></small>
+    </li>
   <% end %>
-</div>
+</ul>
 
 <%= link_to "New message", new_message_path %>

db/migrate/20240810063115_add_pg_trgm.rb

@@ -0,0 +1,5 @@
+class AddPgTrgm < ActiveRecord::Migration[7.1]
+  def change
+    enable_extension 'pg_trgm'
+  end
+end

db/migrate/20240810064037_add_trigram_index.rb

@@ -0,0 +1,15 @@
+class AddTrigramIndex < ActiveRecord::Migration[7.1]
+  def up
+    # According to https://www.postgresql.org/docs/9.1/textsearch-indexes.html
+    #
+    # > As a rule of thumb, GIN indexes are best for static data because
+    # > lookups are faster. For dynamic data, GiST indexes are faster to update.
+    #
+    # So we use GIN here instead of GiST.
+    add_index(:messages, :body, using: :gin, opclass: { body: :gin_trgm_ops })
+  end
+
+  def down
+    remove_index(:messages, :body)
+  end
+end