diff --git a/script/import_scripts/askbot.rb b/script/import_scripts/askbot.rb
index c6af92b4eae..ec0cfc7cb8c 100644
--- a/script/import_scripts/askbot.rb
+++ b/script/import_scripts/askbot.rb
@@ -73,7 +73,7 @@ class ImportScripts::MyAskBot < ImportScripts::Base
         LIMIT #{BATCH_SIZE}
         OFFSET #{offset}
       SQL
-      ) 
+      )
       break if tags.ntuples() < 1
       tags.each do |tag|
         tid = tag["thread_id"].to_i
@@ -110,6 +110,8 @@ class ImportScripts::MyAskBot < ImportScripts::Base
 
       break if users.ntuples() < 1
 
+      next if all_records_exist? :users, users.map {|u| u["id"].to_i}
+
       create_users(users, total: total_count, offset: offset) do |user|
         {
           id:           user["id"],
@@ -153,6 +155,8 @@ class ImportScripts::MyAskBot < ImportScripts::Base
 
       break if posts.ntuples() < 1
 
+      next if all_records_exist? :posts, posts.map {|p| p["id"].to_i}
+
       create_posts(posts, total: post_count, offset: offset) do |post|
         pid = post["id"]
         tid = post["thread_id"].to_i
@@ -206,6 +210,8 @@ class ImportScripts::MyAskBot < ImportScripts::Base
 
       break if posts.ntuples() < 1
 
+      next if all_records_exist? :posts, posts.map {|p| p["id"].to_i}
+
       create_posts(posts, total: post_count, offset: offset) do |post|
         tid = post["thread_id"].to_i
         next unless thread = @thread_parents[tid]
@@ -267,4 +273,4 @@ class ImportScripts::MyAskBot < ImportScripts::Base
     end
   end
 
-ImportScripts::MyAskBot.new.perform 
+ImportScripts::MyAskBot.new.perform
diff --git a/script/import_scripts/base.rb b/script/import_scripts/base.rb
index 0bc796c7301..57bbc24e9d9 100644
--- a/script/import_scripts/base.rb
+++ b/script/import_scripts/base.rb
@@ -194,6 +194,23 @@ class ImportScripts::Base
     g.tap(&:save)
   end
 
+  def all_records_exist?(type, import_ids)
+    return false if import_ids.empty?
+
+    existing = "#{type.to_s.classify}CustomField".constantize.where(name: 'import_id')
+
+    if Fixnum === import_ids.first
+      existing = existing.where('cast(value as int) in (?)', import_ids)
+    else
+      existing = existing.where('value in (?)', import_ids)
+    end
+
+    if existing.count == import_ids.length
+      # puts "Skipping #{import_ids.length} already imported #{type}"
+      true
+    end
+  end
+
   # Iterate through a list of user records to be imported.
   # Takes a collection, and yields to the block for each element.
   # Block should return a hash with the attributes for the User model.
@@ -258,9 +275,8 @@ class ImportScripts::Base
     if opts[:username].blank? ||
       opts[:username].length < User.username_length.begin ||
       opts[:username].length > User.username_length.end ||
-      opts[:username] =~ /[^A-Za-z0-9_]/ ||
-      opts[:username][0] =~ /[^A-Za-z0-9]/ ||
-      !User.username_available?(opts[:username])
+      !User.username_available?(opts[:username]) ||
+      !UsernameValidator.new(opts[:username]).valid_format?
       opts[:username] = UserNameSuggester.suggest(opts[:username] || opts[:name] || opts[:email])
     end
     opts[:email] = opts[:email].downcase
@@ -289,13 +305,18 @@ class ImportScripts::Base
       if opts[:active] && opts[:password].present?
         u.activate
       end
-    rescue
+    rescue => e
       # try based on email
-      existing = User.find_by(email: opts[:email].downcase)
-      if existing
-        existing.custom_fields["import_id"] = import_id
-        existing.save!
-        u = existing
+      if e.record.errors.messages[:email].present?
+        existing = User.find_by(email: opts[:email].downcase)
+        if existing
+          existing.custom_fields["import_id"] = import_id
+          existing.save!
+          u = existing
+        end
+      else
+        puts "Error on record: #{opts}"
+        raise e
       end
     end
     post_create_action.try(:call, u) if u.persisted?
diff --git a/script/import_scripts/bbpress.rb b/script/import_scripts/bbpress.rb
index 066c9c23d5b..aba552d11e0 100644
--- a/script/import_scripts/bbpress.rb
+++ b/script/import_scripts/bbpress.rb
@@ -85,6 +85,8 @@ class ImportScripts::Bbpress < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :posts, results.map {|p| p["id"].to_i}
+
       create_posts(results, total: total_count, offset: offset) do |post|
         skip = false
         mapped = {}
diff --git a/script/import_scripts/discuz_x.rb b/script/import_scripts/discuz_x.rb
index 68f1738061d..f252ddb861d 100644
--- a/script/import_scripts/discuz_x.rb
+++ b/script/import_scripts/discuz_x.rb
@@ -98,6 +98,8 @@ class ImportScripts::DiscuzX < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :users, users.map {|u| u["id"].to_i}
+
       create_users(results, total: total_count, offset: offset) do |user|
         { id: user['id'],
           email: user['email'],
@@ -205,6 +207,8 @@ class ImportScripts::DiscuzX < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :posts, results.map {|p| p["id"].to_i}
+
       create_posts(results, total: total_count, offset: offset) do |m|
         skip = false
         mapped = {}
@@ -281,6 +285,8 @@ class ImportScripts::DiscuzX < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :posts, results.map {|m| "pm:#{m['id']}"}
+
       create_posts(results, total: total_count, offset: offset) do |m|
         skip = false
         mapped = {}
diff --git a/script/import_scripts/drupal.rb b/script/import_scripts/drupal.rb
index 82266d77ca8..a15933b10c1 100644
--- a/script/import_scripts/drupal.rb
+++ b/script/import_scripts/drupal.rb
@@ -121,6 +121,8 @@ class ImportScripts::Drupal < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :posts, results.map {|p| "nid:#{p['nid']}"}
+
       create_posts(results, total: total_count, offset: offset) do |row|
         {
           id: "nid:#{row['nid']}",
@@ -167,6 +169,8 @@ class ImportScripts::Drupal < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :posts, results.map {|p| "cid:#{p['cid']}"}
+
       create_posts(results, total: total_count, offset: offset) do |row|
         topic_mapping = topic_lookup_from_imported_post_id("nid:#{row['nid']}")
         if topic_mapping && topic_id = topic_mapping[:topic_id]
diff --git a/script/import_scripts/drupal_qa.rb b/script/import_scripts/drupal_qa.rb
index 9ce0b556e81..9899f73ad5e 100644
--- a/script/import_scripts/drupal_qa.rb
+++ b/script/import_scripts/drupal_qa.rb
@@ -56,6 +56,8 @@ class ImportScripts::DrupalQA < ImportScripts::Drupal
 
       break if results.size < 1
 
+      next if all_records_exist? :posts, results.map {|p| "nid:#{p['nid']}"}
+
       create_posts(results, total: total_count, offset: offset) do |row|
         {
           id: "nid:#{row['nid']}",
@@ -100,6 +102,8 @@ class ImportScripts::DrupalQA < ImportScripts::Drupal
 
       break if results.size < 1
 
+      next if all_records_exist? :posts, results.map {|p| "cid:#{p['cid']}"}
+
       create_posts(results, total: total_count, offset: offset) do |row|
         topic_mapping = topic_lookup_from_imported_post_id("nid:#{row['nid']}")
         if topic_mapping && topic_id = topic_mapping[:topic_id]
@@ -151,6 +155,8 @@ class ImportScripts::DrupalQA < ImportScripts::Drupal
 
       break if results.size < 1
 
+      next if all_records_exist? :posts, results.map {|p| "cid:#{p['cid']}"}
+
       create_posts(results, total: total_count, offset: offset) do |row|
         topic_mapping = topic_lookup_from_imported_post_id("nid:#{row['nid']}")
         if topic_mapping && topic_id = topic_mapping[:topic_id]
@@ -201,6 +207,8 @@ class ImportScripts::DrupalQA < ImportScripts::Drupal
 
       break if results.size < 1
 
+      next if all_records_exist? :posts, results.map {|p| "cid:#{p['cid']}"}
+
       create_posts(results, total: total_count, offset: offset) do |row|
         topic_mapping = topic_lookup_from_imported_post_id("nid:#{row['nid']}")
         if topic_mapping && topic_id = topic_mapping[:topic_id]
diff --git a/script/import_scripts/kunena.rb b/script/import_scripts/kunena.rb
index 8e1f6275b38..3cb52e7b38a 100644
--- a/script/import_scripts/kunena.rb
+++ b/script/import_scripts/kunena.rb
@@ -109,6 +109,8 @@ class ImportScripts::Kunena < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :posts, results.map {|p| p['id'].to_i}
+
       create_posts(results, total: total_count, offset: offset) do |m|
         skip = false
         mapped = {}
diff --git a/script/import_scripts/kunena3.rb b/script/import_scripts/kunena3.rb
index 56103861fd4..49b3f24e917 100644
--- a/script/import_scripts/kunena3.rb
+++ b/script/import_scripts/kunena3.rb
@@ -109,6 +109,8 @@ class ImportScripts::Kunena < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :posts, results.map {|p| p['id'].to_i}
+
       create_posts(results, total: total_count, offset: offset) do |m|
         skip = false
         mapped = {}
diff --git a/script/import_scripts/lithium.rb b/script/import_scripts/lithium.rb
index 4d7a84366c8..795f04f366a 100644
--- a/script/import_scripts/lithium.rb
+++ b/script/import_scripts/lithium.rb
@@ -101,6 +101,8 @@ class ImportScripts::Lithium < ImportScripts::Base
 
       break if users.size < 1
 
+      next if all_records_exist? :users, users.map {|u| u["id"].to_i}
+
       create_users(users, total: user_count, offset: offset) do |user|
 
         {
@@ -274,9 +276,10 @@ class ImportScripts::Lithium < ImportScripts::Base
           OFFSET #{offset}
       SQL
 
-
       break if topics.size < 1
 
+      next if all_records_exist? :posts, topics.map {|topic| "#{topic["node_id"]} #{topic["id"]}"}
+
       create_posts(topics, total: topic_count, offset: offset) do |topic|
 
         category_id = category_id_from_imported_category_id(topic["node_id"])
@@ -322,6 +325,8 @@ class ImportScripts::Lithium < ImportScripts::Base
 
       break if posts.size < 1
 
+      next if all_records_exist? :posts, posts.map {|post| "#{post["node_id"]} #{post["root_id"]} #{post["id"]}"}
+
       create_posts(posts, total: post_count, offset: offset) do |post|
         raw = post["raw"]
         next unless topic = topic_lookup_from_imported_post_id("#{post["node_id"]} #{post["root_id"]}")
@@ -593,6 +598,8 @@ class ImportScripts::Lithium < ImportScripts::Base
 
       break if topics.size < 1
 
+      next if all_records_exist? :posts, topics.map {|topic| "pm_#{topic["note_id"]}"}
+
       create_posts(topics, total: topic_count, offset: offset) do |topic|
 
         user_id = user_id_from_imported_user_id(topic["sender_user_id"]) || Discourse::SYSTEM_USER_ID
diff --git a/script/import_scripts/mbox.rb b/script/import_scripts/mbox.rb
index 78549ae909a..d47b5553fc7 100755
--- a/script/import_scripts/mbox.rb
+++ b/script/import_scripts/mbox.rb
@@ -69,6 +69,7 @@ class ImportScripts::Mbox < ImportScripts::Base
     batches(BATCH_SIZE) do |offset|
       users = user_keys[offset..offset+BATCH_SIZE-1]
       break if users.nil?
+      next if all_records_exist? :users, users
 
       create_users(users, total: total_count, offset: offset) do |email|
         {
@@ -99,6 +100,8 @@ class ImportScripts::Mbox < ImportScripts::Base
       topics = all_topics[offset..offset+BATCH_SIZE-1]
       break if topics.nil?
 
+      next if all_records_exist? :posts, topics.map {|t| t['id'].to_i}
+
       create_posts(topics, total: topic_count, offset: offset) do |t|
         raw_email = File.read(t['file'])
         receiver = Email::Receiver.new(raw_email, skip_sanity_check: true)
@@ -136,6 +139,8 @@ class ImportScripts::Mbox < ImportScripts::Base
       posts = replies[offset..offset+BATCH_SIZE-1]
       break if posts.nil?
 
+      next if all_records_exist? :posts, posts.map {|p| p['id'].to_i}
+
       create_posts(posts, total: post_count, offset: offset) do |p|
         parent_id = p['topic']
         id = p['id']
diff --git a/script/import_scripts/mybb.rb b/script/import_scripts/mybb.rb
index c2337d56a14..b76e1e0d919 100644
--- a/script/import_scripts/mybb.rb
+++ b/script/import_scripts/mybb.rb
@@ -48,6 +48,8 @@ class ImportScripts::MyBB < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :users, users.map {|u| u["id"].to_i}
+
       create_users(results, total: total_count, offset: offset) do |user|
         { id: user['id'],
           email: user['email'],
@@ -100,6 +102,8 @@ class ImportScripts::MyBB < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :posts, results.map {|m| m['id'].to_i}
+
       create_posts(results, total: total_count, offset: offset) do |m|
         skip = false
         mapped = {}
diff --git a/script/import_scripts/nabble.rb b/script/import_scripts/nabble.rb
index 607772da418..78e48497509 100644
--- a/script/import_scripts/nabble.rb
+++ b/script/import_scripts/nabble.rb
@@ -40,6 +40,8 @@ class ImportScripts::Nabble < ImportScripts::Base
 
       break if users.ntuples() < 1
 
+      next if all_records_exist? :users, users.map {|u| u["user_id"].to_i}
+
       create_users(users, total: total_count, offset: offset) do |user|
         {
           id:           user["user_id"],
@@ -80,6 +82,8 @@ class ImportScripts::Nabble < ImportScripts::Base
 
       break if topics.ntuples() < 1
 
+      next if all_records_exist? :posts, topics.map {|t| t['node_id'].to_i}
+
       create_posts(topics, total: topic_count, offset: offset) do |t|
         raw = body_from(t)
         next unless raw
@@ -122,6 +126,8 @@ class ImportScripts::Nabble < ImportScripts::Base
 
       break if posts.ntuples() < 1
 
+      next if all_records_exist? :posts, posts.map {|p| p['node_id'].to_i}
+
       create_posts(posts, total: post_count, offset: offset) do |p|
         parent_id = p['parent_id']
         id = p['node_id']
diff --git a/script/import_scripts/phpbb3/importer.rb b/script/import_scripts/phpbb3/importer.rb
index 28c2ed6fa63..11592b40d18 100644
--- a/script/import_scripts/phpbb3/importer.rb
+++ b/script/import_scripts/phpbb3/importer.rb
@@ -56,6 +56,8 @@ module ImportScripts::PhpBB3
         rows = @database.fetch_users(offset)
         break if rows.size < 1
 
+        next if all_records_exist? :users, importer.map_to_import_ids(rows)
+
         create_users(rows, total: total_count, offset: offset) do |row|
           importer.map_user(row)
         end
diff --git a/script/import_scripts/phpbb3/importers/user_importer.rb b/script/import_scripts/phpbb3/importers/user_importer.rb
index be0321d48ef..aeef5ec8627 100644
--- a/script/import_scripts/phpbb3/importers/user_importer.rb
+++ b/script/import_scripts/phpbb3/importers/user_importer.rb
@@ -9,6 +9,10 @@ module ImportScripts::PhpBB3
       @settings = settings
     end
 
+    def map_to_import_ids(array)
+      array.map {|u| u[:user_id]}
+    end
+
     def map_user(row)
       is_active_user = row[:user_inactive_reason] != Constants::INACTIVE_REGISTER
 
diff --git a/script/import_scripts/punbb.rb b/script/import_scripts/punbb.rb
index 08ecc883130..a5d54372f1e 100644
--- a/script/import_scripts/punbb.rb
+++ b/script/import_scripts/punbb.rb
@@ -43,6 +43,8 @@ class ImportScripts::PunBB < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :users, users.map {|u| u["id"].to_i}
+
       create_users(results, total: total_count, offset: offset) do |user|
         { id: user['id'],
           email: user['email'],
@@ -118,6 +120,7 @@ class ImportScripts::PunBB < ImportScripts::Base
       ").to_a
 
       break if results.size < 1
+      next if all_records_exist? :posts, results.map {|m| m['id'].to_i}
 
       create_posts(results, total: total_count, offset: offset) do |m|
         skip = false
diff --git a/script/import_scripts/sfn.rb b/script/import_scripts/sfn.rb
index f8a14f00d93..14e54196cdb 100644
--- a/script/import_scripts/sfn.rb
+++ b/script/import_scripts/sfn.rb
@@ -77,6 +77,7 @@ class ImportScripts::Sfn < ImportScripts::Base
       SQL
 
       break if users.size < 1
+      next if all_records_exist? :users, users.map {|u| u["id"].to_i}
 
       create_users(users, total: user_count, offset: offset) do |user|
         external_user = @external_users[user["id"]]
@@ -231,6 +232,7 @@ class ImportScripts::Sfn < ImportScripts::Base
       SQL
 
       break if topics.size < 1
+      next if all_records_exist? :posts, topics.map {|t| t['id'].to_i}
 
       create_posts(topics, total: topic_count, offset: offset) do |topic|
         next unless category_id = CATEGORY_MAPPING[topic["category_id"]]
@@ -282,6 +284,8 @@ class ImportScripts::Sfn < ImportScripts::Base
 
       break if posts.size < 1
 
+      next if all_records_exist? :posts, posts.map {|p| p['id'].to_i}
+
       create_posts(posts, total: posts_count, offset: offset) do |post|
         next unless parent = topic_lookup_from_imported_post_id(post["topic_id"])
 
diff --git a/script/import_scripts/tnation.rb b/script/import_scripts/tnation.rb
index b8563997e71..438327c7b0e 100644
--- a/script/import_scripts/tnation.rb
+++ b/script/import_scripts/tnation.rb
@@ -173,6 +173,8 @@ class ImportScripts::Tnation < ImportScripts::Base
 
       break if users.size < 1
 
+      next if all_records_exist? :users, users.map {|u| u["id"].to_i}
+
       user_bios = {}
       user_avatars = {}
       user_properties = {}
@@ -317,6 +319,7 @@ class ImportScripts::Tnation < ImportScripts::Base
       posts = posts.to_a
 
       break if posts.size < 1
+      next if all_records_exist? :posts, posts.map {|p| p['id'].to_i}
 
       # load images
       forum_images = {}
diff --git a/script/import_scripts/vanilla_mysql.rb b/script/import_scripts/vanilla_mysql.rb
index 841bf1478a7..e472ce525b7 100644
--- a/script/import_scripts/vanilla_mysql.rb
+++ b/script/import_scripts/vanilla_mysql.rb
@@ -42,6 +42,8 @@ class ImportScripts::VanillaSQL < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :users, users.map {|u| u['UserID'].to_i}
+
       create_users(results, total: total_count, offset: offset) do |user|
         next if user['Email'].blank?
         next if user['Name'].blank?
@@ -92,6 +94,7 @@ class ImportScripts::VanillaSQL < ImportScripts::Base
          OFFSET #{offset};")
 
       break if discussions.size < 1
+      next if all_records_exist? :posts, discussions.map {|t| "discussion#" + t['DiscussionID'].to_s}
 
       create_posts(discussions, total: total_count, offset: offset) do |discussion|
         {
@@ -121,6 +124,7 @@ class ImportScripts::VanillaSQL < ImportScripts::Base
          OFFSET #{offset};")
 
       break if comments.size < 1
+      next if all_records_exist? :posts, comments.map {|comment| "comment#" + comment['CommentID'].to_s}
 
       create_posts(comments, total: total_count, offset: offset) do |comment|
         next unless t = topic_lookup_from_imported_post_id("discussion#" + comment['DiscussionID'].to_s)
diff --git a/script/import_scripts/vbulletin.rb b/script/import_scripts/vbulletin.rb
index 6d3ac4415f8..22e5883db38 100644
--- a/script/import_scripts/vbulletin.rb
+++ b/script/import_scripts/vbulletin.rb
@@ -71,6 +71,8 @@ class ImportScripts::VBulletin < ImportScripts::Base
 
       break if users.size < 1
 
+      next if all_records_exist? :users, users.map {|u| u["userid"].to_i}
+
       create_users(users, total: user_count, offset: offset) do |user|
         username = @htmlentities.decode(user["username"]).strip
 
@@ -208,6 +210,7 @@ class ImportScripts::VBulletin < ImportScripts::Base
       SQL
 
       break if topics.size < 1
+      next if all_records_exist? :posts, topics.map {|t| "thread-#{topic["threadid"]}" }
 
       create_posts(topics, total: topic_count, offset: offset) do |topic|
         raw = preprocess_post_raw(topic["raw"]) rescue nil
@@ -249,6 +252,7 @@ class ImportScripts::VBulletin < ImportScripts::Base
       SQL
 
       break if posts.size < 1
+      next if all_records_exist? :posts, posts.map {|p| p["postid"] }
 
       create_posts(posts, total: post_count, offset: offset) do |post|
         raw = preprocess_post_raw(post["raw"]) rescue nil
diff --git a/script/import_scripts/xenforo.rb b/script/import_scripts/xenforo.rb
index 536c03ec144..41f7cd15874 100644
--- a/script/import_scripts/xenforo.rb
+++ b/script/import_scripts/xenforo.rb
@@ -42,6 +42,8 @@ class ImportScripts::XenForo < ImportScripts::Base
 
       break if results.size < 1
 
+      next if all_records_exist? :users, users.map {|u| u["id"].to_i}
+
       create_users(results, total: total_count, offset: offset) do |user|
         next if user['username'].blank?
         { id: user['id'],
@@ -98,6 +100,7 @@ class ImportScripts::XenForo < ImportScripts::Base
       ").to_a
 
       break if results.size < 1
+      next if all_records_exist? :posts, results.map {|p| p['id'] }
 
       create_posts(results, total: total_count, offset: offset) do |m|
         skip = false