From 3b1f3f90d1acb805dbaae75d25c6e654fd445bcc Mon Sep 17 00:00:00 2001
From: Ilya Zhitomirskiy <iz268@nyu.edu>
Date: Wed, 26 Oct 2011 14:24:35 -0700
Subject: [PATCH] removing duplicate tag followings

---
 ...3547_add_missing_tag_followings_indices.rb | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/db/migrate/20111026173547_add_missing_tag_followings_indices.rb b/db/migrate/20111026173547_add_missing_tag_followings_indices.rb
index 15a44410c..c15d0198b 100644
--- a/db/migrate/20111026173547_add_missing_tag_followings_indices.rb
+++ b/db/migrate/20111026173547_add_missing_tag_followings_indices.rb
@@ -1,5 +1,26 @@
 class AddMissingTagFollowingsIndices < ActiveRecord::Migration
+  def self.delete_duplicate_tag_followings
+    duplicate_rows = execute <<SQL
+      SELECT COUNT(tf.user_id), tf.user_id, tf.tag_id from tag_followings AS tf
+        GROUP BY tf.user_id, tf.tag_id
+          HAVING COUNT(*)>1;
+SQL
+    duplicate_rows.each do |row|
+      count = row.first
+      user_id = row[1]
+      tag_id = row.last
+
+      execute <<SQL
+        DELETE FROM tag_followings
+        WHERE tag_followings.user_id = #{user_id} AND tag_followings.tag_id = #{tag_id}
+        LIMIT #{count-1}
+SQL
+    end
+  end
+
   def self.up
+    delete_duplicate_tag_followings
+
     add_index :tag_followings, :tag_id
     add_index :tag_followings, :user_id
     add_index :tag_followings, [:tag_id, :user_id], :unique => true