From 7d8dfccf70da047b68f974b7e63610f5c7bf1a43 Mon Sep 17 00:00:00 2001
From: Valery Sizov <vsv2711@gmail.com>
Date: Mon, 8 Dec 2014 15:15:11 +0200
Subject: [PATCH] speed up migration to identities

---
 .../20141121161704_add_identity_table.rb      | 24 ++++++++++++-------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/db/migrate/20141121161704_add_identity_table.rb b/db/migrate/20141121161704_add_identity_table.rb
index 243958039af..6fe63637dfe 100644
--- a/db/migrate/20141121161704_add_identity_table.rb
+++ b/db/migrate/20141121161704_add_identity_table.rb
@@ -8,9 +8,11 @@ class AddIdentityTable < ActiveRecord::Migration
 
     add_index :identities, :user_id
 
-    User.where("provider IS NOT NULL").find_each do |user|
-      execute "INSERT INTO identities(provider, extern_uid, user_id) VALUES('#{user.provider}', '#{user.extern_uid}', '#{user.id}')"
-    end
+    execute <<eos
+INSERT INTO identities (provider, extern_uid, user_id)
+SELECT provider, extern_uid, id FROM users
+WHERE provider IS NOT NULL
+eos
 
     remove_column :users, :extern_uid
     remove_column :users, :provider
@@ -20,12 +22,16 @@ class AddIdentityTable < ActiveRecord::Migration
     add_column :users, :extern_uid, :string
     add_column :users, :provider, :string
 
-    User.where("id IN(SELECT user_id FROM identities)").find_each do |user|
-      identity = user.identities.last
-      user.extern_uid = identity.extern_uid
-      user.provider = identity.provider
-      user.save
-    end
+    if ActiveRecord::Base.connection.adapter_name == 'PostgreSQL'
+      execute <<eos
+UPDATE users u
+SET provider = i.provider, extern_uid = i.extern_uid
+FROM identities i
+WHERE i.user_id = u.id
+eos
+      else
+        execute "UPDATE users u, identities i SET u.provider = i.provider, u.extern_uid = i.extern_uid WHERE u.id = i.user_id"
+      end
 
     drop_table :identities
   end