Fixes some minor issues with the phpBB3 importer

FEATURE: Adds a link to the Howto on meta
FIX: Suppresses multiple warnings about invalid votes for the same topic
FIX: Adds missing table prefixes
FIX: Removes duplicate column from query

script/import_scripts/phpbb3.rb

@@ -1,6 +1,10 @@
+# Importer for phpBB 3.0 and 3.1
+# Documentation: https://meta.discourse.org/t/importing-from-phpbb3/30810
+
 if ARGV.length != 1 || !File.exists?(ARGV[0])
   STDERR.puts '', 'Usage of phpBB3 importer:', 'bundle exec ruby phpbb3.rb <path/to/settings.yml>'
   STDERR.puts '', "Use the settings file from #{File.expand_path('phpbb3/settings.yml', File.dirname(__FILE__))} as an example."
+  STDERR.puts '', 'Still having problems? Take a look at https://meta.discourse.org/t/importing-from-phpbb3/30810'
   exit 1
 end
 

script/import_scripts/phpbb3/database/database_3_0.rb

@@ -52,11 +52,11 @@ module ImportScripts::PhpBB3
 
     def fetch_categories
       query(<<-SQL)
-        SELECT f.forum_id, f.parent_id, f.forum_name, f.forum_name, f.forum_desc, x.first_post_time
-        FROM phpbb_forums f
+        SELECT f.forum_id, f.parent_id, f.forum_name, f.forum_desc, x.first_post_time
+        FROM #{@table_prefix}_forums f
           LEFT OUTER JOIN (
             SELECT MIN(topic_time) AS first_post_time, forum_id
-            FROM phpbb_topics
+            FROM #{@table_prefix}_topics
             GROUP BY forum_id
           ) x ON (f.forum_id = x.forum_id)
         WHERE f.forum_type != #{Constants::FORUM_TYPE_LINK}

script/import_scripts/phpbb3/importers/poll_importer.rb

@@ -122,7 +122,8 @@ module ImportScripts::PhpBB3
           end
 
           votes << option_id
-        else !warned
+        elsif !warned
+          warned = true
           Rails.logger.warn("Topic with id #{topic_id} has invalid votes.")
         end
       end