Add $config['db']['annotate_queries'] option to include caller ID comments into queries. Comment can then be seen in process list, slow query logs on the server, aiding in tracking down unexpected slow queries.

SELECT /* queuedaemon.php Ostatus_profile->processPost */ * FROM notice WHERE ( notice.uri = 'http://stormcloud.local/mublog2/notice/479' )
INSERT /* POST Notice::saveNew */ INTO notice (profile_id , content ....

classes/Memcached_DataObject.php

@@ -330,6 +330,10 @@ class Memcached_DataObject extends Safe_DataObject
      */
     function _query($string)
     {
+        if (common_config('db', 'annotate_queries')) {
+            $string = $this->annotateQuery($string);
+        }
+
         $start = microtime(true);
         $result = parent::_query($string);
         $delta = microtime(true) - $start;
@@ -342,6 +346,70 @@ class Memcached_DataObject extends Safe_DataObject
         return $result;
     }
 
+    /**
+     * Find the first caller in the stack trace that's not a
+     * low-level database function and add a comment to the
+     * query string. This should then be visible in process lists
+     * and slow query logs, to help identify problem areas.
+     * 
+     * Also marks whether this was a web GET/POST or which daemon
+     * was running it.
+     *
+     * @param string $string SQL query string
+     * @return string SQL query string, with a comment in it
+     */
+    function annotateQuery($string)
+    {
+        $ignore = array('annotateQuery',
+                        '_query',
+                        'query',
+                        'get',
+                        'insert',
+                        'delete',
+                        'update',
+                        'find');
+        $ignoreStatic = array('staticGet',
+                              'pkeyGet',
+                              'cachedQuery');
+        $here = get_class($this); // if we get confused
+        $bt = debug_backtrace();
+
+        // Find the first caller that's not us?
+        foreach ($bt as $frame) {
+            $func = $frame['function'];
+            if (isset($frame['type']) && $frame['type'] == '::') {
+                if (in_array($func, $ignoreStatic)) {
+                    continue;
+                }
+                $here = $frame['class'] . '::' . $func;
+                break;
+            } else if (isset($frame['type']) && $frame['type'] == '->') {
+                if ($frame['object'] === $this && in_array($func, $ignore)) {
+                    continue;
+                }
+                if (in_array($func, $ignoreStatic)) {
+                    continue; // @fixme this shouldn't be needed?
+                }
+                $here = get_class($frame['object']) . '->' . $func;
+                break;
+            }
+            $here = $func;
+            break;
+        }
+
+        if (php_sapi_name() == 'cli') {
+            $context = basename($_SERVER['PHP_SELF']);
+        } else {
+            $context = $_SERVER['REQUEST_METHOD'];
+        }
+
+        // Slip the comment in after the first command,
+        // or DB_DataObject gets confused about handling inserts and such.
+        $parts = explode(' ', $string, 2);
+        $parts[0] .= " /* $context $here */";
+        return implode(' ', $parts);
+    }
+
     // Sanitize a query for logging
     // @fixme don't trim spaces in string literals
     function sanitizeQuery($string)

lib/default.php

@@ -72,6 +72,7 @@ $default =
               'quote_identifiers' => false,
               'type' => 'mysql',
               'schemacheck' => 'runtime', // 'runtime' or 'script'
+              'annotate_queries' => false, // true to add caller comments to queries, eg /* POST Notice::saveNew */
               'log_queries' => false, // true to log all DB queries
               'log_slow_queries' => 0), // if set, log queries taking over N seconds
         'syslog' =>