- optimization : representative picture becomes mandatory for a non empty

category. So, at each insertion in images table for a category, a new
  representative element is elected (by rand). This must be improved by not
  reelcting a random picture admin set an element as representative
  manually.

- optimization : recent cats page only needs 2 queries instead of 3*N (N
  categories to display). The bad point is that it shows representative
  element of recent cat and not a random element among recently added.

- optimization : empty cats page only needs 1 query per non empty sub
  category instead of... a lot. For each sub category, PhpWebGallery shows
  the representative element of a category chosen randomly in sub
  cats. Thus, get_non_empty_subcat_ids and get_first_non_empty_cat_id
  becomes obsolete.

- new function get_cat_display_name_cache to show category names with a
  caching for all gallery categories names. This function, to the contrary
  of get_cat_display_name shows names in the correct order...


git-svn-id: http://piwigo.org/svn/trunk@610 68402e56-0260-453c-a942-63ccdbb3a9ee

admin/include/functions.php

@@ -486,8 +486,8 @@ SELECT id, representative_picture_id
   WHERE representative_picture_id IS NOT NULL
     AND id IN ('.implode(',', $cat_ids).')
 ;';
-    $result = pwg_query( $query );
-    while ( $row = mysql_fetch_array( $result ) )
+    $result = pwg_query($query);
+    while ($row = mysql_fetch_array($result))
     {
       $query = '
 SELECT image_id
@@ -495,15 +495,37 @@ SELECT image_id
   WHERE category_id = '.$row['id'].'
     AND image_id = '.$row['representative_picture_id'].'
 ;';
-      $result = pwg_query( $query );
-      if (mysql_num_rows($result) == 0)
+      $sub_result = pwg_query($query);
+      if (mysql_num_rows($sub_result) == 0)
       {
+        // set a new representative element for this category
         $query = '
+SELECT image_id
+  FROM '.IMAGE_CATEGORY_TABLE.'
+  WHERE category_id = '.$row['id'].'
+  ORDER BY RAND()
+  LIMIT 0,1
+;';
+        $sub_sub_result = pwg_query($query);
+        if (mysql_num_rows($sub_sub_result) > 0)
+        {
+          list($representative) = mysql_fetch_array(pwg_query($query));
+          $query = '
+UPDATE '.CATEGORIES_TABLE.'
+  SET representative_picture_id = '.$representative.'
+  WHERE id = '.$row['id'].'
+;';
+          pwg_query($query);
+        }
+        else
+        {
+          $query = '
 UPDATE '.CATEGORIES_TABLE.'
   SET representative_picture_id = NULL
   WHERE id = '.$row['id'].'
 ;';
-        pwg_query( $query );
+          pwg_query($query);
+        }
       }
     }
   }