improvements to importer

- improve perf of test for existing posts
- always use a system guardian when importing posts
- for lithuim importer requery raw (transform is not repeatable)

script/import_scripts/base.rb

@@ -197,13 +197,20 @@ class ImportScripts::Base
   def all_records_exist?(type, import_ids)
     return false if import_ids.empty?
 
+    Post.exec_sql('create temp table import_ids(val varchar(200) primary key)')
+
+    import_id_clause = import_ids.map{|id| "('#{PG::Connection.escape_string(id)}')"}.join(",")
+    Post.exec_sql("insert into import_ids values #{import_id_clause}")
+
     existing = "#{type.to_s.classify}CustomField".constantize.where(name: 'import_id')
-    existing = existing.where('value in (?)', import_ids.map(&:to_s))
+    existing = existing.joins('JOIN import_ids ON val=value')
 
     if existing.count == import_ids.length
-      # puts "Skipping #{import_ids.length} already imported #{type}"
-      true
+      puts "Skipping #{import_ids.length} already imported #{type}"
+      return true
     end
+  ensure
+    Post.exec_sql('drop table import_ids')
   end
 
   # Iterate through a list of user records to be imported.
@@ -444,6 +451,8 @@ class ImportScripts::Base
     [created, skipped]
   end
 
+  STAFF_GUARDIAN = Guardian.new(User.find(-1))
+
   def create_post(opts, import_id)
     user = User.find(opts[:user_id])
     post_create_action = opts.delete(:post_create_action)
@@ -452,6 +461,7 @@ class ImportScripts::Base
     opts[:custom_fields] ||= {}
     opts[:custom_fields]['import_id'] = import_id
 
+    opts[:guardian] = STAFF_GUARDIAN
     if @bbcode_to_md
       opts[:raw] = opts[:raw].bbcode_to_md(false) rescue opts[:raw]
     end