Use timestamp-based IDs

This change introduces timestamp-based (Snowflake/Cornflake/Waspflake)
identifier.

Rakefile

@@ -430,3 +430,32 @@ namespace :justask do
     end
   end
 end
+
+namespace :db do
+  namespace :schema do
+    task :create_timestampid_function do
+      conn = ActiveRecord::Base.connection
+      have_func = conn.execute("SELECT EXISTS(SELECT * FROM pg_proc WHERE proname = 'gen_timestamp_id');").values.first.first
+      next if have_func
+
+      statement = File.read(File.join(__dir__, 'db/migrate/20200704163504_use_timestamped_ids.rb')).match(/<~SQL(?<stmt>.+)SQL$/m)[:stmt]
+      conn.execute(statement)
+    end
+
+    task :create_id_sequences do
+      conn = ActiveRecord::Base.connection
+
+      # required for the timestampid function to work properly
+      %i[questions answers comments smiles comment_smiles users].each do |tbl|
+        conn.execute("CREATE SEQUENCE IF NOT EXISTS #{tbl}_id_seq")
+      end
+    end
+  end
+
+  # create timestampid before loading schema
+  Rake::Task['db:schema:load'].enhance ['db:schema:create_timestampid_function']
+  # create id_sequences after loading schema
+  Rake::Task['db:schema:load'].enhance do
+    Rake::Task['db:schema:create_id_sequences'].invoke
+  end
+end

db/migrate/20200704163504_use_timestamped_ids.rb

@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+require 'securerandom'
+
+# This migration changes the IDs of several tables from serial to a
+# timestamped/"snowflake" one.
+#
+# Instead of "snowflakes" we shall call those IDs Cornflakes or Waspflakes
+# instead.
+#
+# Implementation somewhat lifted from Mastodon.
+class UseTimestampedIds < ActiveRecord::Migration[5.2]
+  def up
+    # PL/pgSQL is just spicy pascal
+    # don't @ me
+    execute <<~SQL
+      CREATE or replace FUNCTION gen_timestamp_id(tblname text) RETURNS bigint AS $$
+      DECLARE
+        timepart bigint;
+        seqpart  bigint;
+      BEGIN
+        timepart := (date_part('epoch', now()) * 1000)::bigint << 16;
+        seqpart := ('x' || substr(md5(tblname ||
+                                      '#{SecureRandom.hex(16)}' ||
+                                      timepart::text), 1, 4))::bit(16)::bigint;
+        RETURN timepart | ((seqpart + nextval(tblname || '_id_seq')) & 65535);
+      END;
+      $$ LANGUAGE plpgsql VOLATILE;
+    SQL
+
+    # we need to migrate related columns to bigints for this to work
+    {
+      question: %i[answers inboxes],
+      answer: %i[comments smiles subscriptions],
+      comment: %i[comment_smiles],
+      user: %i[announcements answers comment_smiles comments inboxes list_members lists moderation_comments moderation_votes questions reports services smiles subscriptions themes users_roles],
+
+      # polymorphic tables go brrr
+      recipient: %i[notifications],
+      source: %i[relationships],
+      target: %i[notifications relationships reports],
+    }.each do |ref, tbls|
+      tbls.each do |tbl|
+        say "Migrating #{tbl}.#{ref}_id to bigint"
+        change_column(tbl, :"#{ref}_id", :bigint)
+      end
+    end
+
+    %i[questions answers comments smiles comment_smiles users].each do |tbl|
+      say "Migrating #{tbl} to use timestamped ids"
+      change_column(tbl, :id, :bigint, default: -> { "gen_timestamp_id('#{tbl}'::text)" })
+    end
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2020_05_25_145144) do
+ActiveRecord::Schema.define(version: 2020_07_04_163504) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -27,11 +27,11 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
     t.index ["user_id"], name: "index_announcements_on_user_id"
   end
 
-  create_table "answers", id: :serial, force: :cascade do |t|
+  create_table "answers", id: :bigint, default: -> { "gen_timestamp_id('answers'::text)" }, force: :cascade do |t|
     t.text "content"
-    t.integer "question_id"
+    t.bigint "question_id"
     t.integer "comment_count", default: 0, null: false
-    t.integer "user_id"
+    t.bigint "user_id"
     t.datetime "created_at"
     t.datetime "updated_at"
     t.integer "smile_count", default: 0, null: false
@@ -39,9 +39,9 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
     t.index ["user_id", "created_at"], name: "index_answers_on_user_id_and_created_at"
   end
 
-  create_table "comment_smiles", id: :serial, force: :cascade do |t|
+  create_table "comment_smiles", id: :bigint, default: -> { "gen_timestamp_id('comment_smiles'::text)" }, force: :cascade do |t|
-    t.integer "user_id"
+    t.bigint "user_id"
-    t.integer "comment_id"
+    t.bigint "comment_id"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.index ["comment_id"], name: "index_comment_smiles_on_comment_id"
@@ -49,10 +49,10 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
     t.index ["user_id"], name: "index_comment_smiles_on_user_id"
   end
 
-  create_table "comments", id: :serial, force: :cascade do |t|
+  create_table "comments", id: :bigint, default: -> { "gen_timestamp_id('comments'::text)" }, force: :cascade do |t|
     t.string "content"
-    t.integer "answer_id"
+    t.bigint "answer_id"
-    t.integer "user_id"
+    t.bigint "user_id"
     t.datetime "created_at"
     t.datetime "updated_at"
     t.integer "smile_count", default: 0, null: false
@@ -61,8 +61,8 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
   end
 
   create_table "inboxes", id: :serial, force: :cascade do |t|
-    t.integer "user_id"
+    t.bigint "user_id"
-    t.integer "question_id"
+    t.bigint "question_id"
     t.boolean "new"
     t.datetime "created_at"
     t.datetime "updated_at"
@@ -71,14 +71,14 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
 
   create_table "list_members", id: :serial, force: :cascade do |t|
     t.integer "list_id", null: false
-    t.integer "user_id", null: false
+    t.bigint "user_id", null: false
     t.datetime "created_at"
     t.datetime "updated_at"
     t.index ["list_id", "user_id"], name: "index_list_members_on_list_id_and_user_id", unique: true
   end
 
   create_table "lists", id: :serial, force: :cascade do |t|
-    t.integer "user_id", null: false
+    t.bigint "user_id", null: false
     t.string "name"
     t.string "display_name"
     t.boolean "private", default: true
@@ -89,7 +89,7 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
 
   create_table "moderation_comments", id: :serial, force: :cascade do |t|
     t.integer "report_id"
-    t.integer "user_id"
+    t.bigint "user_id"
     t.string "content"
     t.datetime "created_at"
     t.datetime "updated_at"
@@ -98,7 +98,7 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
 
   create_table "moderation_votes", id: :serial, force: :cascade do |t|
     t.integer "report_id", null: false
-    t.integer "user_id", null: false
+    t.bigint "user_id", null: false
     t.boolean "upvote", default: false, null: false
     t.datetime "created_at"
     t.datetime "updated_at"
@@ -109,19 +109,19 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
 
   create_table "notifications", id: :serial, force: :cascade do |t|
     t.string "target_type"
-    t.integer "target_id"
+    t.bigint "target_id"
-    t.integer "recipient_id"
+    t.bigint "recipient_id"
     t.boolean "new"
     t.datetime "created_at"
     t.datetime "updated_at"
   end
 
-  create_table "questions", id: :serial, force: :cascade do |t|
+  create_table "questions", id: :bigint, default: -> { "gen_timestamp_id('questions'::text)" }, force: :cascade do |t|
     t.string "content"
     t.boolean "author_is_anonymous"
     t.string "author_name"
     t.string "author_email"
-    t.integer "user_id"
+    t.bigint "user_id"
     t.datetime "created_at"
     t.datetime "updated_at"
     t.integer "answer_count", default: 0, null: false
@@ -129,8 +129,8 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
   end
 
   create_table "relationships", id: :serial, force: :cascade do |t|
-    t.integer "source_id"
+    t.bigint "source_id"
-    t.integer "target_id"
+    t.bigint "target_id"
     t.datetime "created_at"
     t.datetime "updated_at"
     t.index ["source_id", "target_id"], name: "index_relationships_on_source_id_and_target_id", unique: true
@@ -140,8 +140,8 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
 
   create_table "reports", id: :serial, force: :cascade do |t|
     t.string "type", null: false
-    t.integer "target_id", null: false
+    t.bigint "target_id", null: false
-    t.integer "user_id", null: false
+    t.bigint "user_id", null: false
     t.datetime "created_at"
     t.datetime "updated_at"
     t.boolean "deleted", default: false
@@ -162,7 +162,7 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
 
   create_table "services", id: :serial, force: :cascade do |t|
     t.string "type", null: false
-    t.integer "user_id", null: false
+    t.bigint "user_id", null: false
     t.string "uid"
     t.string "access_token"
     t.string "access_secret"
@@ -172,9 +172,9 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
     t.index ["user_id"], name: "index_services_on_user_id"
   end
 
-  create_table "smiles", id: :serial, force: :cascade do |t|
+  create_table "smiles", id: :bigint, default: -> { "gen_timestamp_id('smiles'::text)" }, force: :cascade do |t|
-    t.integer "user_id"
+    t.bigint "user_id"
-    t.integer "answer_id"
+    t.bigint "answer_id"
     t.datetime "created_at"
     t.datetime "updated_at"
     t.index ["answer_id"], name: "index_smiles_on_answer_id"
@@ -183,8 +183,8 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
   end
 
   create_table "subscriptions", id: :serial, force: :cascade do |t|
-    t.integer "user_id", null: false
+    t.bigint "user_id", null: false
-    t.integer "answer_id", null: false
+    t.bigint "answer_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.boolean "is_active", default: true
@@ -192,7 +192,7 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
   end
 
   create_table "themes", id: :serial, force: :cascade do |t|
-    t.integer "user_id", null: false
+    t.bigint "user_id", null: false
     t.integer "primary_color", default: 6174129
     t.integer "primary_text", default: 16777215
     t.integer "danger_color", default: 14431557
@@ -219,7 +219,7 @@ ActiveRecord::Schema.define(version: 2020_05_25_145144) do
     t.index ["user_id", "created_at"], name: "index_themes_on_user_id_and_created_at"
   end
 
-  create_table "users", id: :serial, force: :cascade do |t|
+  create_table "users", id: :bigint, default: -> { "gen_timestamp_id('users'::text)" }, force: :cascade do |t|
     t.string "email", default: "", null: false
     t.string "encrypted_password", default: "", null: false
     t.string "reset_password_token"