=== modified file 'includes/bootstrap.inc'
--- includes/bootstrap.inc	
+++ includes/bootstrap.inc	
@@ -286,10 +286,10 @@ 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();
+  db_replace_query(
+    array("DELETE FROM {variable} WHERE name = '%s'", $name),
+    array("INSERT INTO {variable} (name, value) VALUES ('%s', '%s')", $name, serialize($value))
+  );
 
   cache_clear_all('variables');
 
=== modified file 'includes/cache.inc'
--- includes/cache.inc	
+++ includes/cache.inc	
@@ -63,12 +63,10 @@ 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_replace_query(
+    array("DELETE FROM {cache} WHERE cid = '%s'", $cid),
+    array("INSERT INTO {cache} (cid, data, created, expire, headers) VALUES ('%s', ". DB_BLOB_PLACEHOLDER .", %d, %d, '%s')", $cid, $data, time(), $expire, $headers)
+  );
 }
 
 /**
=== modified file 'includes/database.inc'
--- includes/database.inc	
+++ includes/database.inc	
@@ -136,32 +136,6 @@ function db_set_active($name = 'default'
 }
 
 /**
- * Helper function for db_query().
- */
-function _db_query_callback($match, $init = FALSE) {
-  static $args = NULL;
-  if ($init) {
-    $args = $match;
-    return;
-  }
-
-  switch ($match[1]) {
-    case '%d': // We must use type casting to int to convert FALSE/NULL/(TRUE?)
-      return (int) array_shift($args); // We don't need db_escape_string as numbers are db-safe
-    case '%s':
-      return db_escape_string(array_shift($args));
-    case '%%':
-      return '%';
-    case '%f':
-      return (float) array_shift($args);
-    case '%b': // binary data
-      return db_encode_blob(array_shift($args));
-  }
-}
-
-define('DB_QUERY_REGEXP', '/(%d|%s|%%|%f|%b)/');
-
-/**
  * Runs a basic query in the active database.
  *
  * User-supplied arguments to the query should be passed in as separate
@@ -192,8 +166,7 @@ function db_query($query) {
   if (isset($args[0]) and is_array($args[0])) { // 'All arguments in one array' syntax
     $args = $args[0];
   }
-  _db_query_callback($args, TRUE);
-  $query = preg_replace_callback(DB_QUERY_REGEXP, '_db_query_callback', $query);
+  $query = _db_query_sprintf($query, $args);
   return _db_query($query);
 }
 
@@ -209,8 +182,7 @@ function db_queryd($query) {
   if (isset($args[0]) and is_array($args[0])) { // 'All arguments in one array' syntax
     $args = $args[0];
   }
-  _db_query_callback($args, TRUE);
-  $query = preg_replace_callback(DB_QUERY_REGEXP, '_db_query_callback', $query);
+  $query = _db_query_sprintf($query, $args);
   return _db_query($query, 1);
 }
 
=== modified file 'includes/database.mysql.inc'
--- includes/database.mysql.inc	
+++ includes/database.mysql.inc	
@@ -11,6 +11,8 @@
  * @{
  */
 
+define('DB_BLOB_PLACEHOLDER', "'%s'");
+
 /**
  * Initialize a database connection.
  *
@@ -203,21 +205,11 @@ function db_error() {
 }
 
 /**
- * Return a new unique ID in the given sequence.
- *
- * For compatibility reasons, Drupal does not use auto-numbered fields in its
- * database tables. Instead, this function is used to return a new unique ID
- * of the type requested. If necessary, a new sequence with the given name
- * 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;
+ * Return a new unique ID.
+ */
+function db_next_id() {
+  db_query('INSERT INTO {sequences} VALUES (NULL)');
+  return mysql_insert_id();
 }
 
 /**
@@ -228,6 +220,26 @@ function db_affected_rows() {
   return mysql_affected_rows($active_db);
 }
 
+function _db_query_sprintf($query, $args) {
+  return sprintf($query, $args);
+}
+
+/**
+ * Debugging version of db_query().
+ *
+ * Echoes the query to the browser.
+ */
+function db_queryd($query) {
+  $args = func_get_args();
+  array_shift($args);
+  $query = db_prefix_tables($query);
+  if (isset($args[0]) and is_array($args[0])) { // 'All arguments in one array' syntax
+    $args = $args[0];
+  }
+  $query = sprintf($query, $args);
+  return _db_query($query, 1);
+}
+
 /**
  * Runs a limited-range query in the active database.
  *
@@ -271,8 +283,7 @@ function db_query_range($query) {
   if (isset($args[0]) and is_array($args[0])) { // 'All arguments in one array' syntax
     $args = $args[0];
   }
-  _db_query_callback($args, TRUE);
-  $query = preg_replace_callback(DB_QUERY_REGEXP, '_db_query_callback', $query);
+  $query = sprintf($query, $args);
   $query .= ' LIMIT '. (int)$from .', '. (int)$count;
   return _db_query($query);
 }
@@ -319,8 +330,7 @@ function db_query_temporary($query) {
   if (isset($args[0]) and is_array($args[0])) { // 'All arguments in one array' syntax
     $args = $args[0];
   }
-  _db_query_callback($args, TRUE);
-  $query = preg_replace_callback(DB_QUERY_REGEXP, '_db_query_callback', $query);
+  $query = sprintf($query, $args);
   return _db_query($query);
 }
 
@@ -379,7 +389,20 @@ function db_table_exists($table) {
 }
 
 /**
+ * Perform a replace query.
+ *
+ * @param $delete
+ *   An array, where the first value is a query which deletes one row,
+ *   subsequent values are arguments. Same syntax as of db_query.
+ * @param
+ *   An array, where the first value is a query which inserts the new row,
+ *   subsequent values are arguments. Same syntax as of db_query.
+ */
+function db_query_replace($delete, $insert) {
+  $insert_query = array_shift($insert);
+  db_query(preg_replace('/^INSERT /', 'REPLACE ', $insert_query), $insert);
+}
+
+/**
  * @} End of "ingroup database".
  */
-
-
=== modified file 'includes/database.mysqli.inc'
--- includes/database.mysqli.inc	
+++ includes/database.mysqli.inc	
@@ -15,6 +15,8 @@
  * @{
  */
 
+define('DB_BLOB_PLACEHOLDER', "'%s'");
+
 /**
  * Initialise a database connection.
  *
@@ -198,21 +200,11 @@ function db_error() {
 }
 
 /**
- * Return a new unique ID in the given sequence.
- *
- * For compatibility reasons, Drupal does not use auto-numbered fields in its
- * database tables. Instead, this function is used to return a new unique ID
- * of the type requested. If necessary, a new sequence with the given name
- * 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;
+ * Return a new unique ID.
+ */
+function db_next_id() {
+  db_query('INSERT INTO {sequences} VALUES (NULL)');
+  return mysql_insert_id();
 }
 
 /**
@@ -223,6 +215,10 @@ function db_affected_rows() {
   return mysqli_affected_rows($active_db);
 }
 
+function _db_query_sprintf($query, $args) {
+  return sprintf($query, $args);
+}
+
 /**
  * Runs a limited-range query in the active database.
  *
@@ -266,8 +262,7 @@ function db_query_range($query) {
   if (isset($args[0]) and is_array($args[0])) { // 'All arguments in one array' syntax
     $args = $args[0];
   }
-  _db_query_callback($args, TRUE);
-  $query = preg_replace_callback(DB_QUERY_REGEXP, '_db_query_callback', $query);
+  $query = _db_query_sprintf($query, $args);
   $query .= ' LIMIT '. (int)$from .', '. (int)$count;
   return _db_query($query);
 }
@@ -314,8 +309,7 @@ function db_query_temporary($query) {
   if (isset($args[0]) and is_array($args[0])) { // 'All arguments in one array' syntax
     $args = $args[0];
   }
-  _db_query_callback($args, TRUE);
-  $query = preg_replace_callback(DB_QUERY_REGEXP, '_db_query_callback', $query);
+  $query = _db_query_sprintf($query, $args);
   return _db_query($query);
 }
 
@@ -374,6 +368,21 @@ function db_table_exists($table) {
 }
 
 /**
+ * Perform a replace query.
+ *
+ * @param $delete
+ *   An array, where the first value is a query which deletes one row,
+ *   subsequent values are arguments. Same syntax as of db_query.
+ * @param
+ *   An array, where the first value is a query which inserts the new row,
+ *   subsequent values are arguments. Same syntax as of db_query.
+ */
+function db_query_replace($delete, $insert) {
+  $insert_query = array_shift($insert);
+  db_query(preg_replace('/^INSERT /', 'REPLACE ', $insert_query), $insert);
+}
+
+/**
  * @} End of "ingroup database".
  */
 
=== modified file 'includes/database.pgsql.inc'
--- includes/database.pgsql.inc	
+++ includes/database.pgsql.inc	
@@ -11,6 +11,8 @@
  * @{
  */
 
+define('DB_BLOB_PLACEHOLDER', '%b');
+
 /**
  * Initialize a database connection.
  *
@@ -202,6 +204,53 @@ function db_affected_rows() {
 }
 
 /**
+ * Helper function for db_query().
+ */
+function _db_query_callback($match, $init = FALSE) {
+  static $args = NULL;
+  if ($init) {
+    $args = $match;
+    return;
+  }
+
+  switch ($match[1]) {
+    case '%d': // We must use type casting to int to convert FALSE/NULL/(TRUE?)
+      return (int) array_shift($args); // We don't need db_escape_string as numbers are db-safe
+    case '%s':
+      return db_escape_string(array_shift($args));
+    case '%%':
+      return '%';
+    case '%f':
+      return (float) array_shift($args);
+    case '%b': // binary data
+      return db_encode_blob(array_shift($args));
+  }
+}
+
+define('DB_QUERY_REGEXP', '/(%d|%s|%%|%f|%b)/');
+
+function _db_query_sprintf($query, $args) {
+  _db_query_callback($args, TRUE);
+  return preg_replace_callback(DB_QUERY_REGEXP, '_db_query_callback', $query);
+}
+
+/**
+ * Debugging version of db_query().
+ *
+ * Echoes the query to the browser.
+ */
+function db_queryd($query) {
+  $args = func_get_args();
+  array_shift($args);
+  $query = db_prefix_tables($query);
+  if (isset($args[0]) and is_array($args[0])) { // 'All arguments in one array' syntax
+    $args = $args[0];
+  }
+  $query = _db_query_sprintf($query, $args);
+  return _db_query($query, 1);
+}
+
+/**
  * Runs a limited-range query in the active database.
  *
  * Use this as a substitute for db_query() when a subset of the query
@@ -240,8 +289,7 @@ function db_query_range($query) {
   if (isset($args[0]) and is_array($args[0])) { // 'All arguments in one array' syntax
     $args = $args[0];
   }
-  _db_query_callback($args, TRUE);
-  $query = preg_replace_callback(DB_QUERY_REGEXP, '_db_query_callback', $query);
+  $query = _db_query_sprintf($query, $args);
   $query .= ' LIMIT '. (int)$count .' OFFSET '. (int)$from;
   return _db_query($query);
 }
@@ -361,6 +409,26 @@ function db_check_setup() {
 }
 
 /**
+ * Perform a replace query.
+ *
+ * @param $delete
+ *   An array, where the first value is a query which deletes one row,
+ *   subsequent values are arguments. Same syntax as of db_query.
+ * @param
+ *   An array, where the first value is a query which inserts the new row,
+ *   subsequent values are arguments. Same syntax as of db_query.
+ */
+function db_query_replace($delete, $insert) {
+  $delete_query = array_shift($delete);
+  db_query('BEGIN');
+  db_query(preg_replace('/^DELETE /', 'SELECT FOR UPDATE ', $delete_query), $delete);
+  db_query($delete_query, $delete);
+  $insert_query = array_shift($insert);
+  db_query($insert_query, $insert);
+  db_query('COMMIT');
+}
+
+/**
  * @} End of "ingroup database".
  */
 
=== modified file 'modules/system/system.install'
--- modules/system/system.install	
+++ modules/system/system.install	
@@ -241,9 +241,7 @@ function system_install() {
       ) /*!40100 DEFAULT CHARACTER SET UTF8 */ ");
 
       db_query("CREATE TABLE {sequences} (
-        name varchar(255) NOT NULL default '',
-        id int(10) unsigned NOT NULL default '0',
-        PRIMARY KEY (name)
+        id UNSIGNED INT NOT NULL AUTO_INCREMENT PRIMARY KEY
       ) /*!40100 DEFAULT CHARACTER SET UTF8 */ ");
 
       db_query("CREATE TABLE {node_counter} (
@@ -2908,3 +2906,18 @@ function system_update_187() {
   }
   return $ret;
 }
+
+function system_update_188() {
+  $ret = array();
+
+  switch ($GLOBALS['db_type']) {
+    case 'mysql':
+    case 'mysqli':
+      $new_id = db_result(db_query('SELECT MAX(id) FROM {sequences}'));
+      $ret[] = update_sql('DROP TABLE {sequences}');
+      $ret[] = update_sql('CREATE TABLE {sequences} (id UNSIGNED INT NOT NULL AUTO_INCREMENT PRIMARY KEY)');
+      db_query('INSERT INTO {sequences} VALUES (%d)', $new_id);
+  }
+
+  return $ret;
+}