Improve indexes on sent_emails, better column ordering, removed dupli…

…cates.

db/migrate/20130820193236_update_sent_emails_indexes.rb

@@ -0,0 +1,20 @@
+class UpdateSentEmailsIndexes < ActiveRecord::Migration
+  def up
+    add_index :sent_emails, [:created_at, :type], algorithm: :concurrently
+
+    #   Using raw sql for 'IF EXISTS'
+    execute 'DROP INDEX IF EXISTS index_sent_emails_on_type_and_created_at'
+    execute 'DROP INDEX IF EXISTS index_sent_emails_on_created_at'
+
+    # These indexes exist on production and duplicate other indexes
+    execute 'DROP INDEX IF EXISTS sent_emails_member_id_idx'
+    execute 'DROP INDEX IF EXISTS sent_emails_created_idx'
+  end
+
+  def down
+    add_index :sent_emails, [:type, :created_at], algorithm: :concurrently
+    add_index :sent_emails, [:created_at], algorithm: :concurrently
+    #   Using raw sql for 'IF EXISTS'
+    execute 'DROP INDEX IF EXISTS index_sent_emails_on_created_at_and_type'
+  end
+end