Index: modules/comment/comment.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/comment/comment.module,v
retrieving revision 1.503
diff -u -p -r1.503 comment.module
--- modules/comment/comment.module	26 Nov 2006 23:10:29 -0000	1.503
+++ modules/comment/comment.module	28 Nov 2006 00:05:36 -0000
@@ -172,10 +172,49 @@ function comment_block($op = 'list', $de
   }
 }
 
+/**
+ * Find a number of recent comments.
+ *
+ * @param $number
+ * (optional) The maximum number of comments to find.
+ * @return
+ * An array of comment objects each contaning all the comment's data, 
+ * including nid, cid, subject, and timestamp, or an
+ * empty array if there are no recent comments visible to the current user.
+ */
+function comment_get_recent($number = 10) {
+
+  // Select the $number nodes (visible to the current user) with the most recent comments.  This is efficient due to the index on last_comment_timestamp.
+  $result = db_query_range(db_rewrite_sql("SELECT n.nid from {node_comment_statistics} n WHERE n.comment_count > 0 ORDER BY n.last_comment_timestamp DESC"), 0, $number);
+
+  $nids = array();
+
+  while ($cnode = db_fetch_object($result)) {
+    $nids[] = $cnode->nid;
+  }
+
+  $recent = array();
+
+  if (!empty($nids)) {
+    // From among the comments on the nodes selected in the first query, find the $number most recent comments.
+    $result = db_query_range('SELECT c.* FROM {comments} c INNER JOIN {node} n ON n.nid = c.nid WHERE c.nid IN ('. implode(',', $nids) .') AND n.status = 1 AND c.status = %d ORDER BY c.timestamp DESC', COMMENT_PUBLISHED, 0, $number);
+    while ($comment = db_fetch_object($result)) {
+      $recent[] = $comment;
+    }
+  }
+  return $recent;
+}
+
+/**
+ * Returns a formatted list of recent comments to be displayed in the comment block.
+ *
+ * @ingroup themeable
+ */
 function theme_comment_block() {
-  $result = db_query_range(db_rewrite_sql('SELECT c.nid, c.subject, c.cid, c.timestamp FROM {comments} c INNER JOIN {node} n ON n.nid = c.nid WHERE n.status = 1 AND c.status = %d ORDER BY c.timestamp DESC', 'c'), COMMENT_PUBLISHED, 0, 10);
+  
+  $recent = comment_get_recent();
   $items = array();
-  while ($comment = db_fetch_object($result)) {
+  foreach ($recent as $comment) {
     $items[] = l($comment->subject, 'node/'. $comment->nid, NULL, NULL, 'comment-'. $comment->cid) .'<br />'. t('@time ago', array('@time' => format_interval(time() - $comment->timestamp)));
   }
   return theme('item_list', $items);