=== modified file 'database/updates.inc'
--- database/updates.inc	
+++ database/updates.inc	
@@ -1806,7 +1806,7 @@ function system_update_178() {
         $args[] = $node->vid;
         db_query('UPDATE {node_revisions} SET '. implode(', ', $set) .' WHERE vid = %d', $args);
       }
-      
+
     }
 
     if ($_SESSION['system_update_178_comment'] == $_SESSION['system_update_178_comment_max'] &&
@@ -1828,3 +1828,20 @@ function system_update_178() {
 
   return array();
 }
+
+function system_update_179() {
+  $ret = array();
+
+  switch ($GLOBALS['db_type']) {
+    case 'mysql':
+    case 'mysqli':
+      db_lock_table('sequences');
+      $new_id = db_result(db_query('SELECT MAX(id) FROM {sequences}'));
+      $ret[] = update_sql('DROP TABLE {sequences}');
+      $ret[] = update_sql('CREATE TABLE {sequences} (id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY)');
+      db_query('INSERT INTO {sequences} VALUES (%d)', $new_id);
+      db_unlock_table('sequences');
+  }
+
+  return $ret;
+}
=== modified file 'includes/bootstrap.inc'
--- includes/bootstrap.inc	
+++ includes/bootstrap.inc	
@@ -234,10 +234,10 @@ function variable_get($name, $default) {
 function variable_set($name, $value) {
   global $conf;
 
-  db_lock_table('variable');
-  db_query("DELETE FROM {variable} WHERE name = '%s'", $name);
-  db_query("INSERT INTO {variable} (name, value) VALUES ('%s', '%s')", $name, serialize($value));
-  db_unlock_tables();
+  $serialized_value = serialize($value);
+  db_query_replace(array(
+    'update' => array("UPDATE {variable} SET value = '%s' WHERE name = '%s'", $serialized_value, $name),
+    'insert' => array("{variable} (name, value) VALUES ('%s', '%s')", $name, $serialized_value)));
 
   cache_clear_all('variables');
 
@@ -321,12 +321,9 @@ function cache_get($key) {
  *   A string containing HTTP header information for cached pages.
  */
 function cache_set($cid, $data, $expire = CACHE_PERMANENT, $headers = NULL) {
-  db_lock_table('cache');
-  db_query("UPDATE {cache} SET data = %b, created = %d, expire = %d, headers = '%s' WHERE cid = '%s'", $data, time(), $expire, $headers, $cid);
-  if (!db_affected_rows()) {
-    @db_query("INSERT INTO {cache} (cid, data, created, expire, headers) VALUES ('%s', %b, %d, %d, '%s')", $cid, $data, time(), $expire, $headers);
-  }
-  db_unlock_tables();
+  db_query_replace(array(
+    'update' => array("UPDATE {cache} SET data = %b, created = %d, expire = %d, headers = '%s' WHERE cid = '%s'", $data, time(), $expire, $headers, $cid),
+    'insert' => array("{cache} (cid, data, created, expire, headers) VALUES ('%s', %b, %d, %d, '%s')", $cid, $data, time(), $expire, $headers)));
 }
 
 /**
=== modified file 'includes/database.mysql.inc'
--- includes/database.mysql.inc	
+++ includes/database.mysql.inc	
@@ -203,13 +203,8 @@ function db_error() {
  * will be created.
  */
 function db_next_id($name) {
-  $name = db_prefix_tables($name);
-  db_query('LOCK TABLES {sequences} WRITE');
-  $id = db_result(db_query("SELECT id FROM {sequences} WHERE name = '%s'", $name)) + 1;
-  db_query("REPLACE INTO {sequences} VALUES ('%s', %d)", $name, $id);
-  db_query('UNLOCK TABLES');
-
-  return $id;
+  db_query('INSERT INTO {sequences} VALUES (NULL)');
+  return mysq_insert_id();
 }
 
 /**
@@ -317,6 +312,24 @@ function db_query_temporary($query) {
 }
 
 /**
+ * Try an update and if that fails, do an INSERT.
+ *
+ * @param $queries
+ *   An associative array, containing exactly two keys: update and insert.
+ *   The value of update is an update query, in the same format as db_query
+ *   expects. The value of insert is an insert query without the INSERT INTO,
+ *   just begin with the table name.
+ * @return
+ *   A database query result resource, or FALSE if the query was not executed
+ *   correctly.
+ */
+function db_query_replace($queries) {
+  $queries['insert'][0] = 'REPLACE '. $queries['insert'][0];
+  return call_user_func_array('db_query', $queries['insert']);
+}
+
+
+/**
  * Returns a properly formatted Binary Large OBject value.
  *
  * @param $data
=== modified file 'includes/database.mysqli.inc'
--- includes/database.mysqli.inc	
+++ includes/database.mysqli.inc	
@@ -319,6 +319,23 @@ function db_query_temporary($query) {
 }
 
 /**
+ * Try an update and if that fails, do an INSERT.
+ *
+ * @param $queries
+ *   An associative array, containing exactly two keys: update and insert.
+ *   The value of update is an update query, in the same format as db_query
+ *   expects. The value of insert is an insert query without the INSERT INTO,
+ *   just begin with the table name.
+ * @return
+ *   A database query result resource, or FALSE if the query was not executed
+ *   correctly.
+ */
+function db_query_replace($queries) {
+  $queries['insert'][0] = 'REPLACE '. $queries['insert'][0];
+  return call_user_func_array('db_query', $queries['insert']);
+}
+
+/**
  * Returns a properly formatted Binary Large Object value.
  *
  * @param $data
=== modified file 'includes/database.pgsql.inc'
--- includes/database.pgsql.inc	
+++ includes/database.pgsql.inc	
@@ -327,6 +327,34 @@ function db_escape_string($text) {
 }
 
 /**
+ * Performs an INSERT but if an old row in the table has the same value as a
+ * new row for a PRIMARY KEY or a UNIQUE index, the old row is deleted before
+ * the new row is inserted.
+ *
+ * @param $queries
+ *   An associative array, containing exactly two keys: update and insert.
+ *   The value of update is an update query, in the same format as db_query
+ *   expects. The value of insert is an insert query without the INSERT INTO,
+ *   just begin with the table name.
+ * @return
+ *   A database query result resource, or FALSE if the query was not executed
+ *   correctly.
+ */
+function db_query_replace($queries) {
+  $args = func_get_args();
+
+  db_query('BEGIN');
+  $result = call_user_func_array('db_query', $queries['update']);
+  if (!db_affected_rows()) {
+    $queries['insert'][0] = 'INSERT '. $queries['insert'][0]
+    $result = call_user_func_array('db_query', $queries['insert']);
+  }
+  db_query('COMMIT');
+  return $result;
+}
+
+
+/**
  * Lock a table.
  * This function automatically starts a transaction.
  */