Option to log slow db queries or all db queries

$config['db']['log_queries'] = true; // all
$config['db']['log_slow_queries'] = 10; // queries taking > 10 seconds

classes/Memcached_DataObject.php

@@ -315,6 +315,39 @@ class Memcached_DataObject extends DB_DataObject
         return new ArrayWrapper($cached);
     }
 
+    /**
+     * sends query to database - this is the private one that must work 
+     *   - internal functions use this rather than $this->query()
+     *
+     * Overridden to do logging.
+     *
+     * @param  string  $string
+     * @access private
+     * @return mixed none or PEAR_Error
+     */
+    function _query($string)
+    {
+        $start = microtime(true);
+        $result = parent::_query($string);
+        $delta = microtime(true) - $start;
+
+        $limit = common_config('db', 'log_slow_queries');
+        if (($limit > 0 && $delta >= $limit) || common_config('db', 'log_queries')) {
+            $clean = $this->sanitizeQuery($string);
+            common_log(LOG_DEBUG, sprintf("DB query (%0.3fs): %s", $delta, $clean));
+        }
+        return $result;
+    }
+
+    // Sanitize a query for logging
+    // @fixme don't trim spaces in string literals
+    function sanitizeQuery($string)
+    {
+        $string = preg_replace('/\s+/', ' ', $string);
+        $string = trim($string);
+        return $string;
+    }
+
     // We overload so that 'SET NAMES "utf8"' is called for
     // each connection
 

lib/default.php

@@ -67,7 +67,9 @@ $default =
               'db_driver' => 'DB', # XXX: JanRain libs only work with DB
               'quote_identifiers' => false,
               'type' => 'mysql',
-              'schemacheck' => 'runtime'), // 'runtime' or 'script'
+              'schemacheck' => 'runtime', // 'runtime' or 'script'
+              'log_queries' => false, // true to log all DB queries
+              'log_slow_queries' => 0), // if set, log queries taking over N seconds
         'syslog' =>
         array('appname' => 'statusnet', # for syslog
               'priority' => 'debug', # XXX: currently ignored