From 13959e7be9a2a45a65bfffb97d4185d5f59e19b6 Mon Sep 17 00:00:00 2001
From: Kazuyoshi Kato <kato.kazuyoshi@gmail.com>
Date: Sat, 10 Aug 2024 00:26:55 -0700
Subject: [PATCH 1/3] Full-text search on Postgres

---
 app/controllers/messages_controller.rb         | 13 +++++++++++--
 app/views/messages/index.html.erb              |  9 +++------
 db/migrate/20240810063115_add_pg_trgm.rb       |  5 +++++
 db/migrate/20240810064037_add_trigram_index.rb | 15 +++++++++++++++
 db/schema.rb                                   |  3 ++-
 5 files changed, 36 insertions(+), 9 deletions(-)
 create mode 100644 db/migrate/20240810063115_add_pg_trgm.rb
 create mode 100644 db/migrate/20240810064037_add_trigram_index.rb

diff --git a/app/controllers/messages_controller.rb b/app/controllers/messages_controller.rb
index ec84559..13afd85 100644
--- a/app/controllers/messages_controller.rb
+++ b/app/controllers/messages_controller.rb
@@ -3,12 +3,21 @@ class MessagesController < ApplicationController
 
   # GET /messages or /messages.json
   def index
-    @messages = Message.all
+    query = params[:q]
+    if query
+      @messages = Message.where('body like ?', "%#{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
diff --git a/app/views/messages/index.html.erb b/app/views/messages/index.html.erb
index 809266a..4b5d127 100644
--- a/app/views/messages/index.html.erb
+++ b/app/views/messages/index.html.erb
@@ -2,13 +2,10 @@
 
 <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 %></li>
   <% end %>
-</div>
+</ul>
 
 <%= link_to "New message", new_message_path %>
diff --git a/db/migrate/20240810063115_add_pg_trgm.rb b/db/migrate/20240810063115_add_pg_trgm.rb
new file mode 100644
index 0000000..9629962
--- /dev/null
+++ b/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
diff --git a/db/migrate/20240810064037_add_trigram_index.rb b/db/migrate/20240810064037_add_trigram_index.rb
new file mode 100644
index 0000000..291a602
--- /dev/null
+++ b/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
diff --git a/db/schema.rb b/db/schema.rb
index 3330b7b..fcde555 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,13 +10,14 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2024_08_10_040807) do
+ActiveRecord::Schema[7.1].define(version: 2024_08_10_064037) do
   create_table "messages", force: :cascade do |t|
     t.string "subject"
     t.string "from"
     t.text "body"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.index ["body"], name: "index_messages_on_body"
   end
 
 end

From 41f1822ad7d39e7cae87a2bb24223f536ffd94f7 Mon Sep 17 00:00:00 2001
From: Kazuyoshi Kato <kato.kazuyoshi@gmail.com>
Date: Fri, 9 Aug 2024 23:18:00 -0700
Subject: [PATCH 2/3] Handle invalid UTF-8 chars

---
 app/models/message.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/app/models/message.rb b/app/models/message.rb
index 87d0bf4..56c9368 100644
--- a/app/models/message.rb
+++ b/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

From 38fd78006a8c7f182de81e8a99d1d229c69dcee5 Mon Sep 17 00:00:00 2001
From: Kazuyoshi Kato <kato.kazuyoshi@gmail.com>
Date: Sat, 10 Aug 2024 00:46:15 -0700
Subject: [PATCH 3/3] Use pg_trgm's operator to sort results correctly

---
 app/controllers/messages_controller.rb | 7 ++++++-
 app/views/messages/index.html.erb      | 5 ++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/app/controllers/messages_controller.rb b/app/controllers/messages_controller.rb
index 13afd85..2c38c38 100644
--- a/app/controllers/messages_controller.rb
+++ b/app/controllers/messages_controller.rb
@@ -5,7 +5,12 @@ class MessagesController < ApplicationController
   def index
     query = params[:q]
     if query
-      @messages = Message.where('body like ?', "%#{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
diff --git a/app/views/messages/index.html.erb b/app/views/messages/index.html.erb
index 4b5d127..0d32916 100644
--- a/app/views/messages/index.html.erb
+++ b/app/views/messages/index.html.erb
@@ -4,7 +4,10 @@
 
 <ul>
   <% @messages.each do |message| %>
-    <li><%= link_to message.subject, message %></li>
+    <li>
+      <%= link_to message.subject, message %>
+      <small><%= message.body %></small>
+    </li>
   <% end %>
 </ul>