Improve performance of widgets with large datasets

Provide database index for widgets which is used by widget queries to
fetch data way faster, e.g. 0.1 instead of > 5 seconds in one concrete
project.

Relates: #63

Documentation/Changelog/1.1.2.rst

@@ -17,7 +17,18 @@ Nothing
 Fixes
 -----
 
-Nothing
+* Improve performance of widgets with large datasets
+
+  A new database index is added which is used by widget queries.
+  This can reduce the calculation time of database based on dataset.
+  One concrete project reduced from > 5 seconds to below 0.2 seconds.
+
+  This mainly improves the PageviewsPerPage widget.
+
+  PageviewsPerDay is still way to slow, but I couldn't find a working approach to
+  improve performance.
+
+  Relates: :issue:`63`.
 
 Tasks
 -----

ext_tables.sql

@@ -3,6 +3,8 @@ CREATE TABLE tx_tracking_pageview (
     user_agent text,
     operating_system varchar(255) DEFAULT '' NOT NULL,
     type int(11) unsigned DEFAULT '0' NOT NULL,
+
+    KEY page_views_per_page (pid,uid,crdate),
 );
 
 CREATE TABLE tx_tracking_recordview (