feature 2384: improve average rating calculation (still need to update language files)

git-svn-id: http://piwigo.org/svn/trunk@11827 68402e56-0260-453c-a942-63ccdbb3a9ee

4 files changed, 95 insertions, 25 deletions

diff --git a/include/functions_category.inc.php b/include/functions_category.inc.php
index 30cf7d2e7..23509a684 100644
--- a/include/functions_category.inc.php
+++ b/include/functions_category.inc.php
@@ -290,7 +290,7 @@ function get_category_preferred_image_orders()
   return trigger_event('get_category_preferred_image_orders',
     array(
     array(l10n('Default'), '', true),
-    array(l10n('Average rate'), 'average_rate DESC', $conf['rate']),
+    array(l10n('Rating score'), 'average_rate DESC', $conf['rate']),
     array(l10n('Most visited'), 'hit DESC', true),
     array(l10n('Creation date'), 'date_creation DESC', true),
     array(l10n('Post date'), 'date_available DESC', true),
diff --git a/include/functions_rate.inc.php b/include/functions_rate.inc.php
index a5c6084c8..de52c37f3 100644
--- a/include/functions_rate.inc.php
+++ b/include/functions_rate.inc.php
@@ -116,21 +116,88 @@ INSERT
 ;';
   pwg_query($query);
 
-  // update of images.average_rate field
+  return update_rating_score($image_id);
+}
+
+
+/* update images.average_rate field
+  * we use a bayesian average (http://en.wikipedia.org/wiki/Bayesian_average) with
+C = average number of rates per item
+m = global average rate (all rates)
+
+ * param int $element_id optional, otherwise applies to all
+ * @return array(average_rate, count) if element_id is specified
+*/
+function update_rating_score($element_id = false)
+{
   $query = '
-SELECT COUNT(rate) AS count
-     , ROUND(AVG(rate),2) AS average
+SELECT element_id,
+    COUNT(rate) AS rcount,
+    SUM(rate) AS rsum
   FROM '.RATE_TABLE.'
-  WHERE element_id = '.$image_id.'
-;';
-  $row = pwg_db_fetch_assoc(pwg_query($query));
-  $query = '
-UPDATE '.IMAGES_TABLE.'
-  SET average_rate = '.$row['average'].'
-  WHERE id = '.$image_id.'
-;';
-  pwg_query($query);
-  return $row;
+  GROUP by element_id';
+
+  $all_rates_count = 0;
+  $all_rates_avg = 0;
+  $item_ratecount_avg = 0;
+  $by_item = array();
+
+  $result = pwg_query($query);
+  while ($row = pwg_db_fetch_assoc($result))
+  {
+    $all_rates_count += $row['rcount'];
+    $all_rates_avg += $row['rsum'];
+    $by_item[$row['element_id']] = $row;
+  }
+
+  $all_rates_avg /= $all_rates_count;
+  $item_ratecount_avg = $all_rates_count / count($by_item);
+
+  $updates = array();
+  foreach ($by_item as $id => $rate_summary )
+  {
+    $score = ( $item_ratecount_avg * $all_rates_avg + $rate_summary['rsum'] ) / ($item_ratecount_avg + $rate_summary['rcount']);
+    $score = round($score,2);
+    if ($id==$element_id)
+    {
+      $return = array(
+        'score' => $score,
+        'average' => round($rate_summary['rsum'] / $rate_summary['rcount'], 2),
+        'count' => $rate_summary['rcount'],
+        );
+    }
+    $updates[] = array( 'id'=>$id, 'average_rate'=>$score );
+  }
+  mass_updates(
+    IMAGES_TABLE,
+    array(
+      'primary' => array('id'),
+      'update' => array('average_rate')
+      ),
+    $updates
+    );
+
+  //set to null all items with no rate
+  if ( !isset($by_item[$element_id]) )
+  {
+    $query='
+SELECT id FROM '.IMAGES_TABLE .'
+  LEFT JOIN '.RATE_TABLE.' ON id=element_id
+  WHERE element_id IS NULL AND average_rate IS NOT NULL';
+
+    $to_update = array_from_query( $query, 'id');
+
+    if ( !empty($to_update) )
+    {
+      $query='
+UPDATE '.IMAGES_TABLE .'
+  SET average_rate=NULL
+  WHERE id IN (' . implode(',',$to_update) . ')';
+    pwg_query($query);
+    }
+  }
+
+  return isset($return) ? $return : array('score'=>null, 'average'=>null, 'count'=>0 );
 }
 
 ?>
\ No newline at end of file
diff --git a/include/picture_rate.inc.php b/include/picture_rate.inc.php
index 2c0d9dd3f..086287c81 100644
--- a/include/picture_rate.inc.php
+++ b/include/picture_rate.inc.php
@@ -28,7 +28,8 @@
 
 if ($conf['rate'])
 {
-  if ( NULL != $picture['current']['average_rate'] )
+  $rate_summary = array( 'count'=>0, 'score'=>$picture['current']['average_rate'], 'average'=>null );
+  if ( NULL != $rate_summary['score'] )
   {
     $query = '
 SELECT COUNT(rate) AS count
@@ -36,18 +37,14 @@ SELECT COUNT(rate) AS count
   FROM '.RATE_TABLE.'
   WHERE element_id = '.$picture['current']['id'].'
 ;';
-    $row = pwg_db_fetch_assoc(pwg_query($query));
+		list($rate_summary['count'], $rate_summary['average']) = pwg_db_fetch_row(pwg_query($query));
   }
-  else
-  { // avg rate null -> no rate -> no need to query db
-    $row = array( 'count'=>0, 'average'=>NULL );
-  }
-  $template->assign('rate_summary', $row);
+  $template->assign('rate_summary', $rate_summary);
 
   $user_rate = null;
   if ($conf['rate_anonymous'] or is_autorize_status(ACCESS_CLASSIC) )
   {
-    if ($row['count']>0)
+    if ($rate_summary['count']>0)
     {
       $query = 'SELECT rate
       FROM '.RATE_TABLE.'
diff --git a/include/ws_functions.inc.php b/include/ws_functions.inc.php
index 68e90f81a..04e0dbbf3 100644
--- a/include/ws_functions.inc.php
+++ b/include/ws_functions.inc.php
@@ -781,14 +781,20 @@ SELECT id, name, permalink, uppercats, global_rank, commentable
     $related_tags[$i]=$tag;
   }
   //------------------------------------------------------------- related rates
-  $query = '
+	$rating = array('score'=>$image_row['average_rate'], 'count'=>0, 'average'=>null);
+	if (isset($rating['score']))
+	{
+		$query = '
 SELECT COUNT(rate) AS count
      , ROUND(AVG(rate),2) AS average
   FROM '.RATE_TABLE.'
   WHERE element_id = '.$image_row['id'].'
 ;';
-  $rating = pwg_db_fetch_assoc(pwg_query($query));
-  $rating['count'] = (int)$rating['count'];
+		$row = pwg_db_fetch_assoc(pwg_query($query));
+		$rating['score'] = (float)$rating['score'];
+		$rating['average'] = (float)$row['average'];
+		$rating['count'] = (int)$row['count'];
+	}
 
   //---------------------------------------------------------- related comments
   $related_comments = array();