From c136a747055bd73141517692c4d5e88ef284e7a5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michal=20=C4=8Ciha=C5=99?= <michal@cihar.com>
Date: Wed, 6 Apr 2016 09:45:43 +0200
Subject: [PATCH] Cache current user information for DBI lifetime
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

We query this information quite often, so it makes sense to fetch it
only once from the MySQL server.

Signed-off-by: Michal Čihař <michal@cihar.com>
---
 libraries/DatabaseInterface.php         | 19 ++++++++++++++-----
 libraries/Util.php                      | 12 ++++--------
 libraries/check_user_privileges.lib.php |  4 ++--
 libraries/server_privileges.lib.php     |  7 +------
 user_password.php                       |  4 +---
 5 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/libraries/DatabaseInterface.php b/libraries/DatabaseInterface.php
index 85f0839dbb..900126026d 100644
--- a/libraries/DatabaseInterface.php
+++ b/libraries/DatabaseInterface.php
@@ -48,6 +48,11 @@ class DatabaseInterface
      */
     private $_table_cache;
 
+    /**
+     * @var array Current user and host cache
+     */
+    private $_current_user;
+
     /**
      * Constructor
      *
@@ -57,6 +62,7 @@ class DatabaseInterface
     {
         $this->_extension = $ext;
         $this->_table_cache = array();
+        $this->_current_user = array();
     }
 
     /**
@@ -2138,12 +2144,12 @@ class DatabaseInterface
             if ($type === 'super') {
                 $query = 'SELECT 1 FROM mysql.user LIMIT 1';
             } elseif ($type === 'create') {
-                list($user, $host) = $this->_getCurrentUserAndHost();
+                list($user, $host) = $this->getCurrentUserAndHost();
                 $query = "SELECT 1 FROM `INFORMATION_SCHEMA`.`USER_PRIVILEGES` "
                     . "WHERE `PRIVILEGE_TYPE` = 'CREATE USER' AND "
                     . "'''" . $user . "''@''" . $host . "''' LIKE `GRANTEE` LIMIT 1";
             } elseif ($type === 'grant') {
-                list($user, $host) = $this->_getCurrentUserAndHost();
+                list($user, $host) = $this->getCurrentUserAndHost();
                 $query = "SELECT 1 FROM ("
                     . "SELECT `GRANTEE`, `IS_GRANTABLE` FROM "
                     . "`INFORMATION_SCHEMA`.`COLUMN_PRIVILEGES` UNION "
@@ -2207,10 +2213,13 @@ class DatabaseInterface
      *
      * @return array array of username and hostname
      */
-    private function _getCurrentUserAndHost()
+    public function getCurrentUserAndHost()
     {
-        $user = $GLOBALS['dbi']->fetchValue("SELECT CURRENT_USER();");
-        return explode("@", $user);
+        if (count($this->_current_user) == 0) {
+            $user = $GLOBALS['dbi']->fetchValue("SELECT CURRENT_USER();");
+            $this->_current_user = explode("@", $user);
+        }
+        return $this->_current_user;
     }
 
     /**
diff --git a/libraries/Util.php b/libraries/Util.php
index 3c7ab5091a..4806972a4c 100644
--- a/libraries/Util.php
+++ b/libraries/Util.php
@@ -4036,20 +4036,16 @@ class Util
     {
         // Get the username for the current user in the format
         // required to use in the information schema database.
-        $user = $GLOBALS['dbi']->fetchValue("SELECT CURRENT_USER();");
-        if ($user === false) {
-            return false;
-        }
+        list($user, $host) = $GLOBALS['dbi']->getCurrentUserAndHost();
 
-        if ($user == '@') { // MySQL is started with --skip-grant-tables
+        if ($user === '') { // MySQL is started with --skip-grant-tables
             return true;
         }
 
-        $user = explode('@', $user);
         $username  = "''";
-        $username .= str_replace("'", "''", $user[0]);
+        $username .= str_replace("'", "''", $user);
         $username .= "''@''";
-        $username .= str_replace("'", "''", $user[1]);
+        $username .= str_replace("'", "''", $host);
         $username .= "''";
 
         // Prepare the query
diff --git a/libraries/check_user_privileges.lib.php b/libraries/check_user_privileges.lib.php
index 1d21159394..7c1f13dd63 100644
--- a/libraries/check_user_privileges.lib.php
+++ b/libraries/check_user_privileges.lib.php
@@ -306,8 +306,8 @@ function PMA_analyseShowGrant()
     PMA\libraries\Util::cacheSet('db_priv', $GLOBALS['db_priv']);
 } // end function
 
-$user = $GLOBALS['dbi']->fetchValue("SELECT CURRENT_USER();");
-if ($user == '@') { // MySQL is started with --skip-grant-tables
+list($username, $hostname) = $GLOBALS['dbi']->getCurrentUserAndHost();
+if ($username === '') { // MySQL is started with --skip-grant-tables
     $GLOBALS['is_create_db_priv'] = true;
     $GLOBALS['is_reload_priv']    = true;
     $GLOBALS['db_to_create']      = '';
diff --git a/libraries/server_privileges.lib.php b/libraries/server_privileges.lib.php
index 50c39843e6..ff32942d3a 100644
--- a/libraries/server_privileges.lib.php
+++ b/libraries/server_privileges.lib.php
@@ -1966,12 +1966,7 @@ function PMA_getCurrentAuthenticationPlugin(
             $authentication_plugin = $row['plugin'];
         }
     } elseif ($mode == 'change') {
-        $row = $GLOBALS['dbi']->fetchSingleRow(
-            'SELECT CURRENT_USER() as user;'
-        );
-        if (isset($row) && $row) {
-            list($username, $hostname) = explode('@', $row['user']);
-        }
+        list($username, $hostname) = $GLOBALS['dbi']->getCurrentUserAndHost();
 
         $row = $GLOBALS['dbi']->fetchSingleRow(
             'SELECT `plugin` FROM `mysql`.`user` WHERE '
diff --git a/user_password.php b/user_password.php
index b6d9445459..e9764e86f5 100644
--- a/user_password.php
+++ b/user_password.php
@@ -141,9 +141,7 @@ function PMA_changePassword($password, $message, $change_password_message)
 
     $hashing_function = PMA_changePassHashingFunction();
 
-    $row = $GLOBALS['dbi']->fetchSingleRow('SELECT CURRENT_USER() as user');
-    $curr_user = $row['user'];
-    list($username, $hostname) = explode('@', $curr_user);
+    list($username, $hostname) = $GLOBALS['dbi']->getCurrentUserAndHost();
 
     $serverType = PMA\libraries\Util::getServerType();