<?php
/* vim: set expandtab sw=4 ts=4 sts=4: */
/**
 * Main interface for database interactions
 *
 * @package PhpMyAdmin-DBI
 */
if (! defined('PHPMYADMIN')) {
    exit;
}

/**
 * Main interface for database interactions
 *
 * @package PhpMyAdmin-DBI
 */
class PMA_DatabaseInterface
{
    /**
     * Force STORE_RESULT method, ignored by classic MySQL.
     */
    const QUERY_STORE = 1;
    /**
     * Do not read whole query.
     */
    const QUERY_UNBUFFERED = 2;
    /**
     * Get session variable.
     */
    const GETVAR_SESSION = 1;
    /**
     * Get global variable.
     */
    const GETVAR_GLOBAL = 2;

    /**
     * @var PMA_DBI_Extension
     */
    private $_extension;

    /**
     * Constructor
     *
     * @param PMA_DBI_Extension $ext Object to be used for database queries
     */
    public function __construct(PMA_DBI_Extension $ext)
    {
        $this->_extension = $ext;
    }

    /**
     * Checks whether database extension is loaded
     *
     * @param string $extension mysql extension to check
     *
     * @return bool
     */
    public static function checkDbExtension($extension = 'mysql')
    {
        if ($extension == 'drizzle' && function_exists('drizzle_create')) {
            return true;
        } else if (function_exists($extension . '_connect')) {
            return true;
        }
        return false;
    }

    /**
     * runs a query
     *
     * @param string $query               SQL query to execute
     * @param mixed  $link                optional database link to use
     * @param int    $options             optional query options
     * @param bool   $cache_affected_rows whether to cache affected rows
     *
     * @return mixed
     */
    public function query($query, $link = null, $options = 0,
        $cache_affected_rows = true
    ) {
        $res = $this->tryQuery($query, $link, $options, $cache_affected_rows)
            or PMA_Util::mysqlDie($this->getError($link), $query);
        return $res;
    }


    /**
     * Caches table data so PMA_Table does not require to issue
     * SHOW TABLE STATUS again
     *
     * @param array       $tables information for tables of some databases
     * @param string|bool $table  table name or false
     *
     * @return void
     */
    private function _cacheTableData($tables, $table)
    {
        // Note: I don't see why we would need array_merge_recursive() here,
        // as it creates double entries for the same table (for example a double
        // entry for Comment when changing the storage engine in Operations)
        // Note 2: Instead of array_merge(), simply use the + operator because
        //  array_merge() renumbers numeric keys starting with 0, therefore
        //  we would lose a db name thats consists only of numbers

        foreach ($tables as $one_database => $its_tables) {
            if (isset(PMA_Table::$cache[$one_database])) {
                // the + operator does not do the intended effect
                // when the cache for one table already exists
                if ($table
                    && isset(PMA_Table::$cache[$one_database][$table])
                ) {
                    unset(PMA_Table::$cache[$one_database][$table]);
                }
                PMA_Table::$cache[$one_database]
                    = PMA_Table::$cache[$one_database] + $tables[$one_database];
            } else {
                PMA_Table::$cache[$one_database] = $tables[$one_database];
            }
        }
    }

    /**
     * Stores query data into session data for debugging purposes
     *
     * @param string   $query  Query text
     * @param resource $link   database link
     * @param resource $result Query result
     * @param integer  $time   Time to execute query
     *
     * @return void
     */
    private function _dbgQuery($query, $link, $result, $time)
    {
        $hash = md5($query);

        if (isset($_SESSION['debug']['queries'][$hash])) {
            $_SESSION['debug']['queries'][$hash]['count']++;
        } else {
            $_SESSION['debug']['queries'][$hash] = array();
            if ($result == false) {
                $_SESSION['debug']['queries'][$hash]['error']
                    = '<b style="color:red">'
                        . htmlspecialchars(mysqli_error($link)) . '</b>';
            }
            $_SESSION['debug']['queries'][$hash]['count'] = 1;
            $_SESSION['debug']['queries'][$hash]['query'] = htmlspecialchars($query);
            $_SESSION['debug']['queries'][$hash]['time'] = $time;
        }

        $trace = array();
        foreach (debug_backtrace() as $trace_step) {
            $trace[]
                = (isset($trace_step['file'])
                    ? PMA_Error::relPath($trace_step['file'])
                    : '')
                . (isset($trace_step['line'])
                    ?  '#' . $trace_step['line'] . ': '
                    : '')
                . (isset($trace_step['class']) ? $trace_step['class'] : '')
                . (isset($trace_step['type']) ? $trace_step['type'] : '')
                . (isset($trace_step['function']) ? $trace_step['function'] : '')
                . '('
                . (isset($trace_step['params'])
                    ? implode(', ', $trace_step['params'])
                    : ''
                )
                . ')'
                ;
        }
        $_SESSION['debug']['queries'][$hash]['trace'][] = $trace;
    }

    /**
     * runs a query and returns the result
     *
     * @param string   $query               query to run
     * @param resource $link                mysql link resource
     * @param integer  $options             query options
     * @param bool     $cache_affected_rows whether to cache affected row
     *
     * @return mixed
     */
    public function tryQuery($query, $link = null, $options = 0,
        $cache_affected_rows = true
    ) {
        if (empty($link)) {
            if (isset($GLOBALS['userlink'])) {
                $link = $GLOBALS['userlink'];
            } else {
                return false;
            }
        }

        if ($GLOBALS['cfg']['DBG']['sql']) {
            $time = microtime(true);
        }

        $result = $this->_extension->realQuery($query, $link, $options);

        if ($cache_affected_rows) {
            $GLOBALS['cached_affected_rows'] = $this->affectedRows($link, false);
        }

        if ($GLOBALS['cfg']['DBG']['sql']) {
            $time = microtime(true) - $time;
            $this->_dbgQuery($query, $link, $result, $time);
        }
        if ($result != false && PMA_Tracker::isActive() == true ) {
            PMA_Tracker::handleQuery($query);
        }

        return $result;
    }

    /**
     * Run multi query statement and return results
     *
     * @param string $multi_query multi query statement to execute
     * @param mysqli $link        mysqli object
     *
     * @return mysqli_result collection | boolean(false)
     */
    public function tryMultiQuery($multi_query = '', $link = null)
    {
        if (empty($link)) {
            if (isset($GLOBALS['userlink'])) {
                $link = $GLOBALS['userlink'];
            } else {
                return false;
            }
        }

        return $this->_extension->realMultiQuery($link, $multi_query);
    }

    /**
     * converts charset of a mysql message, usually coming from mysql_error(),
     * into PMA charset, usually UTF-8
     * uses language to charset mapping from mysql/share/errmsg.txt
     * and charset names to ISO charset from information_schema.CHARACTER_SETS
     *
     * @param string $message the message
     *
     * @return string  $message
     */
    public function convertMessage($message)
    {
        // latin always last!
        $encodings = array(
            'japanese'      => 'EUC-JP', //'ujis',
            'japanese-sjis' => 'Shift-JIS', //'sjis',
            'korean'        => 'EUC-KR', //'euckr',
            'russian'       => 'KOI8-R', //'koi8r',
            'ukrainian'     => 'KOI8-U', //'koi8u',
            'greek'         => 'ISO-8859-7', //'greek',
            'serbian'       => 'CP1250', //'cp1250',
            'estonian'      => 'ISO-8859-13', //'latin7',
            'slovak'        => 'ISO-8859-2', //'latin2',
            'czech'         => 'ISO-8859-2', //'latin2',
            'hungarian'     => 'ISO-8859-2', //'latin2',
            'polish'        => 'ISO-8859-2', //'latin2',
            'romanian'      => 'ISO-8859-2', //'latin2',
            'spanish'       => 'CP1252', //'latin1',
            'swedish'       => 'CP1252', //'latin1',
            'italian'       => 'CP1252', //'latin1',
            'norwegian-ny'  => 'CP1252', //'latin1',
            'norwegian'     => 'CP1252', //'latin1',
            'portuguese'    => 'CP1252', //'latin1',
            'danish'        => 'CP1252', //'latin1',
            'dutch'         => 'CP1252', //'latin1',
            'english'       => 'CP1252', //'latin1',
            'french'        => 'CP1252', //'latin1',
            'german'        => 'CP1252', //'latin1',
        );

        $server_language = $this->fetchValue(
            'SHOW VARIABLES LIKE \'language\';',
            0,
            1
        );
        if ($server_language) {
            $found = array();
            $match = preg_match(
                '&(?:\\\|\\/)([^\\\\\/]*)(?:\\\|\\/)$&i',
                $server_language,
                $found
            );
            if ($match) {
                $server_language = $found[1];
            }
        }

        if (! empty($server_language) && isset($encodings[$server_language])) {
            $encoding = $encodings[$server_language];
        } else {
            /* Fallback to CP1252 if we can not detect */
            $encoding = 'CP1252';
        }

        return PMA_convertString($encoding, 'utf-8', $message);
    }

    /**
     * returns array with table names for given db
     *
     * @param string $database name of database
     * @param mixed  $link     mysql link resource|object
     *
     * @return array   tables names
     */
    public function getTables($database, $link = null)
    {
        return $this->fetchResult(
            'SHOW TABLES FROM ' . PMA_Util::backquote($database) . ';',
            null,
            0,
            $link,
            self::QUERY_STORE
        );
    }

    /**
     * returns a segment of the SQL WHERE clause regarding table name and type
     *
     * @param string|bool $table        table or false
     * @param boolean     $tbl_is_group $table is a table group
     * @param string      $tble_type    whether table or view
     *
     * @return string a segment of the WHERE clause
     */
    private function _getTableCondition($table, $tbl_is_group, $tble_type)
    {
        // get table information from information_schema
        if ($table) {
            if (true === $tbl_is_group) {
                $sql_where_table = 'AND t.`TABLE_NAME` LIKE \''
                    . PMA_Util::escapeMysqlWildcards(
                        PMA_Util::sqlAddSlashes($table)
                    )
                    . '%\'';
            } else {
                $sql_where_table = 'AND t.`TABLE_NAME` = \''
                    . PMA_Util::sqlAddSlashes($table) . '\'';
            }
        } else {
            $sql_where_table = '';
        }

        if ($tble_type) {
            if ($tble_type == 'view') {
                if (PMA_DRIZZLE) {
                    $sql_where_table .= " AND t.`TABLE_TYPE` != 'BASE'";
                } else {
                    $sql_where_table .= " AND t.`TABLE_TYPE` != 'BASE TABLE'";
                }
            } else if ($tble_type == 'table') {
                if (PMA_DRIZZLE) {
                    $sql_where_table .= " AND t.`TABLE_TYPE` = 'BASE'";
                } else {
                    $sql_where_table .= " AND t.`TABLE_TYPE` = 'BASE TABLE'";
                }
            }
        }
        return $sql_where_table;
    }

    /**
     * returns the beginning of the SQL statement to fetch the list of tables
     *
     * @param array  $this_databases  databases to list
     * @param string $sql_where_table additional condition
     *
     * @return string the SQL statement
     */
    private function _getSqlForTablesFull($this_databases, $sql_where_table)
    {
        if (PMA_DRIZZLE) {
            $engine_info = PMA_Util::cacheGet('drizzle_engines', null);
            $stats_join = "LEFT JOIN (SELECT 0 NUM_ROWS) AS stat ON false";
            if (isset($engine_info['InnoDB'])
                && $engine_info['InnoDB']['module_library'] == 'innobase'
            ) {
                $stats_join = "LEFT JOIN data_dictionary.INNODB_SYS_TABLESTATS"
                    . " stat ON (t.ENGINE = 'InnoDB' AND stat.NAME"
                    . " = (t.TABLE_SCHEMA || '/') || t.TABLE_NAME)";
            }

            // data_dictionary.table_cache may not contain any data
            // for some tables, it's just a table cache
            // auto_increment == 0 is cast to NULL because currently
            // (2011.03.13 GA)
            // Drizzle doesn't provide correct value
            $sql = "
                SELECT t.*,
                    t.TABLE_SCHEMA        AS `Db`,
                    t.TABLE_NAME          AS `Name`,
                    t.TABLE_TYPE          AS `TABLE_TYPE`,
                    t.ENGINE              AS `Engine`,
                    t.ENGINE              AS `Type`,
                    t.TABLE_VERSION       AS `Version`,-- VERSION
                    t.ROW_FORMAT          AS `Row_format`,
                    coalesce(tc.ROWS, stat.NUM_ROWS)
                                          AS `Rows`,-- TABLE_ROWS,
                    coalesce(tc.ROWS, stat.NUM_ROWS)
                                          AS `TABLE_ROWS`,
                    tc.AVG_ROW_LENGTH     AS `Avg_row_length`, -- AVG_ROW_LENGTH
                    tc.TABLE_SIZE         AS `Data_length`, -- DATA_LENGTH
                    NULL                  AS `Max_data_length`, -- MAX_DATA_LENGTH
                    NULL                  AS `Index_length`, -- INDEX_LENGTH
                    NULL                  AS `Data_free`, -- DATA_FREE
                    nullif(t.AUTO_INCREMENT, 0)
                                          AS `Auto_increment`,
                    t.TABLE_CREATION_TIME AS `Create_time`, -- CREATE_TIME
                    t.TABLE_UPDATE_TIME   AS `Update_time`, -- UPDATE_TIME
                    NULL                  AS `Check_time`, -- CHECK_TIME
                    t.TABLE_COLLATION     AS `Collation`,
                    NULL                  AS `Checksum`, -- CHECKSUM
                    NULL                  AS `Create_options`, -- CREATE_OPTIONS
                    t.TABLE_COMMENT       AS `Comment`
                FROM data_dictionary.TABLES t
                    LEFT JOIN data_dictionary.TABLE_CACHE tc
                        ON tc.TABLE_SCHEMA = t.TABLE_SCHEMA AND tc.TABLE_NAME
                        = t.TABLE_NAME
                    $stats_join
                WHERE t.TABLE_SCHEMA IN ('" . implode("', '", $this_databases) . "')
                    " . $sql_where_table;
        } else {
            $sql = '
                SELECT *,
                    `TABLE_SCHEMA`       AS `Db`,
                    `TABLE_NAME`         AS `Name`,
                    `TABLE_TYPE`         AS `TABLE_TYPE`,
                    `ENGINE`             AS `Engine`,
                    `ENGINE`             AS `Type`,
                    `VERSION`            AS `Version`,
                    `ROW_FORMAT`         AS `Row_format`,
                    `TABLE_ROWS`         AS `Rows`,
                    `AVG_ROW_LENGTH`     AS `Avg_row_length`,
                    `DATA_LENGTH`        AS `Data_length`,
                    `MAX_DATA_LENGTH`    AS `Max_data_length`,
                    `INDEX_LENGTH`       AS `Index_length`,
                    `DATA_FREE`          AS `Data_free`,
                    `AUTO_INCREMENT`     AS `Auto_increment`,
                    `CREATE_TIME`        AS `Create_time`,
                    `UPDATE_TIME`        AS `Update_time`,
                    `CHECK_TIME`         AS `Check_time`,
                    `TABLE_COLLATION`    AS `Collation`,
                    `CHECKSUM`           AS `Checksum`,
                    `CREATE_OPTIONS`     AS `Create_options`,
                    `TABLE_COMMENT`      AS `Comment`
                FROM `information_schema`.`TABLES` t
                WHERE ' . (PMA_IS_WINDOWS ? '' : 'BINARY') . ' `TABLE_SCHEMA`
                    IN (\'' . implode("', '", $this_databases) . '\')
                    ' . $sql_where_table;
        }
        return $sql;
    }

    /**
     * returns array of all tables in given db or dbs
     * this function expects unquoted names:
     * RIGHT: my_database
     * WRONG: `my_database`
     * WRONG: my\_database
     * if $tbl_is_group is true, $table is used as filter for table names
     *
     * <code>
     * $GLOBALS['dbi']->getTablesFull('my_database');
     * $GLOBALS['dbi']->getTablesFull('my_database', 'my_table'));
     * $GLOBALS['dbi']->getTablesFull('my_database', 'my_tables_', true));
     * </code>
     *
     * @param string          $database     database
     * @param string|bool     $table        table name or false
     * @param boolean         $tbl_is_group $table is a table group
     * @param mixed           $link         mysql link
     * @param integer         $limit_offset zero-based offset for the count
     * @param boolean|integer $limit_count  number of tables to return
     * @param string          $sort_by      table attribute to sort by
     * @param string          $sort_order   direction to sort (ASC or DESC)
     * @param string          $tble_type    whether table or view
     *
     * @todo    move into PMA_Table
     *
     * @return array           list of tables in given db(s)
     */
    public function getTablesFull($database, $table = false,
        $tbl_is_group = false,  $link = null, $limit_offset = 0,
        $limit_count = false, $sort_by = 'Name', $sort_order = 'ASC',
        $tble_type = null
    ) {
        if (true === $limit_count) {
            $limit_count = $GLOBALS['cfg']['MaxTableList'];
        }
        // prepare and check parameters
        if (! is_array($database)) {
            $databases = array($database);
        } else {
            $databases = $database;
        }

        $tables = array();

        $sql_where_table = $this->_getTableCondition(
            $table, $tbl_is_group, $tble_type
        );

        // for PMA bc:
        // `SCHEMA_FIELD_NAME` AS `SHOW_TABLE_STATUS_FIELD_NAME`
        //
        // on non-Windows servers,
        // added BINARY in the WHERE clause to force a case sensitive
        // comparison (if we are looking for the db Aa we don't want
        // to find the db aa)
        $this_databases = array_map('PMA_Util::sqlAddSlashes', $databases);

        $sql = $this->_getSqlForTablesFull($this_databases, $sql_where_table);
        unset($sql_where_table);

        // Sort the tables
        $sql .= " ORDER BY $sort_by $sort_order";

        if ($limit_count) {
            $sql .= ' LIMIT ' . $limit_count . ' OFFSET ' . $limit_offset;
        }

        $tables = $this->fetchResult(
            $sql, array('TABLE_SCHEMA', 'TABLE_NAME'), null, $link
        );
        unset($sql);

        if (PMA_DRIZZLE) {
            // correct I_S and D_D names returned by D_D.TABLES -
            // Drizzle generally uses lower case for them,
            // but TABLES returns uppercase
            foreach ((array)$database as $db) {
                $db_upper = strtoupper($db);
                if (!isset($tables[$db]) && isset($tables[$db_upper])) {
                    $tables[$db] = $tables[$db_upper];
                    unset($tables[$db_upper]);
                }
            }
        }

        if ($sort_by == 'Name' && $GLOBALS['cfg']['NaturalOrder']) {
            // here, the array's first key is by schema name
            foreach ($tables as $one_database_name => $one_database_tables) {
                uksort($one_database_tables, 'strnatcasecmp');

                if ($sort_order == 'DESC') {
                    $one_database_tables = array_reverse($one_database_tables);
                }
                $tables[$one_database_name] = $one_database_tables;
            }
        } else if ($sort_by == 'Data_length') { // Size = Data_length + Index_length
            foreach ($tables as $one_database_name => $one_database_tables) {
                uasort(
                    $one_database_tables,
                    function ($a, $b) {
                        $aLength = $a['Data_length'] + $a['Index_length'];
                        $bLength = $b['Data_length'] + $b['Index_length'];
                        return ($aLength == $bLength)
                            ? 0
                            : ($aLength < $bLength) ? -1 : 1;
                    }
                );

                if ($sort_order == 'DESC') {
                    $one_database_tables = array_reverse($one_database_tables);
                }
                $tables[$one_database_name] = $one_database_tables;
            }
        }
        // end (get information from table schema)

        // If permissions are wrong on even one database directory,
        // information_schema does not return any table info for any database
        // this is why we fall back to SHOW TABLE STATUS even for MySQL >= 50002
        if (empty($tables) && !PMA_DRIZZLE) {
            foreach ($databases as $each_database) {
                if ($table || (true === $tbl_is_group) || $tble_type) {
                    $sql = 'SHOW TABLE STATUS FROM '
                        . PMA_Util::backquote($each_database)
                        . ' WHERE';
                    $needAnd = false;
                    if ($table || (true === $tbl_is_group)) {
                        $sql .= " `Name` LIKE '"
                            . PMA_Util::escapeMysqlWildcards(
                                PMA_Util::sqlAddSlashes($table, true)
                            )
                            . "%'";
                        $needAnd = true;
                    }
                    if ($tble_type) {
                        if ($needAnd) {
                            $sql .= " AND";
                        }
                        if ($tble_type == 'view') {
                            $sql .= " `Comment` = 'VIEW'";
                        } else if ($tble_type == 'table') {
                            $sql .= " `Comment` != 'VIEW'";
                        }
                    }
                } else {
                    $sql = 'SHOW TABLE STATUS FROM '
                        . PMA_Util::backquote($each_database);
                }

                $useStatusCache = false;

                if (extension_loaded('apc')
                    && isset($GLOBALS['cfg']['Server']['StatusCacheDatabases'])
                    && ! empty($GLOBALS['cfg']['Server']['StatusCacheLifetime'])
                ) {
                    $statusCacheDatabases
                        = (array) $GLOBALS['cfg']['Server']['StatusCacheDatabases'];
                    if (in_array($each_database, $statusCacheDatabases)) {
                        $useStatusCache = true;
                    }
                }

                $each_tables = null;

                if ($useStatusCache) {
                    $cacheKey = 'phpMyAdmin_tableStatus_'
                        . sha1($GLOBALS['cfg']['Server']['host'] . '_' . $sql);

                    $each_tables = apc_fetch($cacheKey);
                }

                if (! $each_tables) {
                    $each_tables = $this->fetchResult($sql, 'Name', null, $link);
                }

                if ($useStatusCache) {
                    apc_store(
                        $cacheKey, $each_tables,
                        $GLOBALS['cfg']['Server']['StatusCacheLifetime']
                    );
                }

                // Sort naturally if the config allows it and we're sorting
                // the Name column.
                if ($sort_by == 'Name' && $GLOBALS['cfg']['NaturalOrder']) {
                    uksort($each_tables, 'strnatcasecmp');

                    if ($sort_order == 'DESC') {
                        $each_tables = array_reverse($each_tables);
                    }
                } else {
                    // Prepare to sort by creating array of the selected sort
                    // value to pass to array_multisort

                    // Size = Data_length + Index_length
                    if ($sort_by == 'Data_length') {
                        foreach ($each_tables as $table_name => $table_data) {
                            ${$sort_by}[$table_name] = strtolower(
                                $table_data['Data_length']
                                + $table_data['Index_length']
                            );
                        }
                    } else {
                        foreach ($each_tables as $table_name => $table_data) {
                            ${$sort_by}[$table_name]
                                = strtolower($table_data[$sort_by]);
                        }
                    }

                    if ($sort_order == 'DESC') {
                        array_multisort($$sort_by, SORT_DESC, $each_tables);
                    } else {
                        array_multisort($$sort_by, SORT_ASC, $each_tables);
                    }

                    // cleanup the temporary sort array
                    unset($$sort_by);
                }

                if ($limit_count) {
                    $each_tables = array_slice(
                        $each_tables, $limit_offset, $limit_count
                    );
                }

                $tables[$each_database] = $this->copyTableProperties(
                    $each_tables, $each_database
                );
            }
        }

        $this->_cacheTableData($tables, $table);

        if (! is_array($database)) {
            if (isset($tables[$database])) {
                return $tables[$database];
            } elseif (isset($tables[strtolower($database)])) {
                // on windows with lower_case_table_names = 1
                // MySQL returns
                // with SHOW DATABASES or information_schema.SCHEMATA: `Test`
                // but information_schema.TABLES gives `test`
                // bug #2036
                // https://sourceforge.net/p/phpmyadmin/bugs/2036/
                return $tables[strtolower($database)];
            } else {
                // one database but inexact letter case match
                // as Drizzle is always case insensitive,
                // we can safely return the only result
                if (PMA_DRIZZLE && count($tables) == 1) {
                    $keys = array_keys($tables);
                    if (strlen(array_pop($keys)) == strlen($database)) {
                        return array_pop($tables);
                    }
                }
                return $tables;
            }
        } else {
            return $tables;
        }
    }

    /**
     * Copies the table properties to the set of property names used by PMA.
     *
     * @param array  $tables   array of table properties
     * @param string $database database name
     *
     * @return array array with added properties
     */
    public function copyTableProperties($tables, $database)
    {
        foreach ($tables as $table_name => $each_table) {
            if (! isset($tables[$table_name]['Type'])
                && isset($tables[$table_name]['Engine'])
            ) {
                // pma BC, same parts of PMA still uses 'Type'
                $tables[$table_name]['Type']
                    =& $tables[$table_name]['Engine'];
            } elseif (! isset($tables[$table_name]['Engine'])
                && isset($tables[$table_name]['Type'])
            ) {
                // old MySQL reports Type, newer MySQL reports Engine
                $tables[$table_name]['Engine']
                    =& $tables[$table_name]['Type'];
            }

            // MySQL forward compatibility
            // so pma could use this array as if every server
            // is of version >5.0
            // todo : remove and check usage in the rest of the code,
            // MySQL 5.0 is required by current PMA version
            $tables[$table_name]['TABLE_SCHEMA']
                = $database;
            $tables[$table_name]['TABLE_NAME']
                =& $tables[$table_name]['Name'];
            $tables[$table_name]['ENGINE']
                =& $tables[$table_name]['Engine'];
            $tables[$table_name]['VERSION']
                =& $tables[$table_name]['Version'];
            $tables[$table_name]['ROW_FORMAT']
                =& $tables[$table_name]['Row_format'];
            $tables[$table_name]['TABLE_ROWS']
                =& $tables[$table_name]['Rows'];
            $tables[$table_name]['AVG_ROW_LENGTH']
                =& $tables[$table_name]['Avg_row_length'];
            $tables[$table_name]['DATA_LENGTH']
                =& $tables[$table_name]['Data_length'];
            $tables[$table_name]['MAX_DATA_LENGTH']
                =& $tables[$table_name]['Max_data_length'];
            $tables[$table_name]['INDEX_LENGTH']
                =& $tables[$table_name]['Index_length'];
            $tables[$table_name]['DATA_FREE']
                =& $tables[$table_name]['Data_free'];
            $tables[$table_name]['AUTO_INCREMENT']
                =& $tables[$table_name]['Auto_increment'];
            $tables[$table_name]['CREATE_TIME']
                =& $tables[$table_name]['Create_time'];
            $tables[$table_name]['UPDATE_TIME']
                =& $tables[$table_name]['Update_time'];
            $tables[$table_name]['CHECK_TIME']
                =& $tables[$table_name]['Check_time'];
            $tables[$table_name]['TABLE_COLLATION']
                =& $tables[$table_name]['Collation'];
            $tables[$table_name]['CHECKSUM']
                =& $tables[$table_name]['Checksum'];
            $tables[$table_name]['CREATE_OPTIONS']
                =& $tables[$table_name]['Create_options'];
            $tables[$table_name]['TABLE_COMMENT']
                =& $tables[$table_name]['Comment'];

            if (strtoupper($tables[$table_name]['Comment']) === 'VIEW'
                && $tables[$table_name]['Engine'] == null
            ) {
                $tables[$table_name]['TABLE_TYPE'] = 'VIEW';
            } else {
                /**
                 * @todo difference between 'TEMPORARY' and 'BASE TABLE'
                 * but how to detect?
                 */
                $tables[$table_name]['TABLE_TYPE'] = 'BASE TABLE';
            }
        }
        return $tables;
    }

    /**
     * Get VIEWs in a particular database
     *
     * @param string $db Database name to look in
     *
     * @return array $views Set of VIEWs inside the database
     */
    public function getVirtualTables($db)
    {

        $tables_full = $this->getTablesFull($db);
        $views = array();

        foreach ($tables_full as $table=>$tmp) {

            if (PMA_Table::isView($db, $table)) {
                $views[] = $table;
            }

        }

        return $views;

    }


    /**
     * returns array with databases containing extended infos about them
     *
     * @param string   $database     database
     * @param boolean  $force_stats  retrieve stats also for MySQL < 5
     * @param resource $link         mysql link
     * @param string   $sort_by      column to order by
     * @param string   $sort_order   ASC or DESC
     * @param integer  $limit_offset starting offset for LIMIT
     * @param bool|int $limit_count  row count for LIMIT or true
     *                               for $GLOBALS['cfg']['MaxDbList']
     *
     * @todo    move into PMA_List_Database?
     *
     * @return array $databases
     */
    public function getDatabasesFull($database = null, $force_stats = false,
        $link = null, $sort_by = 'SCHEMA_NAME', $sort_order = 'ASC',
        $limit_offset = 0, $limit_count = false
    ) {
        $sort_order = strtoupper($sort_order);

        if (true === $limit_count) {
            $limit_count = $GLOBALS['cfg']['MaxDbList'];
        }

        $apply_limit_and_order_manual = true;

        /**
         * if $GLOBALS['cfg']['NaturalOrder'] is enabled, we cannot use LIMIT
         * cause MySQL does not support natural ordering,
         * we have to do it afterward
         */
        $limit = '';
        if (! $GLOBALS['cfg']['NaturalOrder']) {
            if ($limit_count) {
                $limit = ' LIMIT ' . $limit_count . ' OFFSET ' . $limit_offset;
            }

            $apply_limit_and_order_manual = false;
        }

        // get table information from information_schema
        if ($database) {
            $sql_where_schema = 'WHERE `SCHEMA_NAME` LIKE \''
                . PMA_Util::sqlAddSlashes($database) . '\'';
        } else {
            $sql_where_schema = '';
        }

        if (PMA_DRIZZLE) {
            // data_dictionary.table_cache may not contain any data for some
            // tables, it's just a table cache
            $sql = 'SELECT
                s.SCHEMA_NAME,
                s.DEFAULT_COLLATION_NAME';
            if ($force_stats) {
                // no TABLE_CACHE data, stable results are better than
                // constantly changing
                $sql .= ',
                    COUNT(t.TABLE_SCHEMA) AS SCHEMA_TABLES,
                    SUM(stat.NUM_ROWS)    AS SCHEMA_TABLE_ROWS';
            }
            $sql .= '
                   FROM data_dictionary.SCHEMAS s';
            if ($force_stats) {
                $engine_info = PMA_Util::cacheGet('drizzle_engines', null);
                $stats_join = "LEFT JOIN (SELECT 0 NUM_ROWS) AS stat ON false";
                if (isset($engine_info['InnoDB'])
                    && $engine_info['InnoDB']['module_library'] == 'innobase'
                ) {
                    $stats_join
                        = "LEFT JOIN data_dictionary.INNODB_SYS_TABLESTATS stat"
                        . " ON (t.ENGINE = 'InnoDB' AND stat.NAME"
                        . " = (t.TABLE_SCHEMA || '/') || t.TABLE_NAME)";
                }

                $sql .= "
                    LEFT JOIN data_dictionary.TABLES t
                        ON t.TABLE_SCHEMA = s.SCHEMA_NAME
                    $stats_join";
            }
            $sql .= $sql_where_schema . '
                GROUP BY s.SCHEMA_NAME
                ORDER BY ' . PMA_Util::backquote($sort_by) . ' ' . $sort_order
                . $limit;
        } else {
            $sql = 'SELECT
                s.SCHEMA_NAME,
                s.DEFAULT_COLLATION_NAME';
            if ($force_stats) {
                $sql .= ',
                    COUNT(t.TABLE_SCHEMA)  AS SCHEMA_TABLES,
                    SUM(t.TABLE_ROWS)      AS SCHEMA_TABLE_ROWS,
                    SUM(t.DATA_LENGTH)     AS SCHEMA_DATA_LENGTH,
                    SUM(t.MAX_DATA_LENGTH) AS SCHEMA_MAX_DATA_LENGTH,
                    SUM(t.INDEX_LENGTH)    AS SCHEMA_INDEX_LENGTH,
                    SUM(t.DATA_LENGTH + t.INDEX_LENGTH)
                                           AS SCHEMA_LENGTH,
                    SUM(t.DATA_FREE)       AS SCHEMA_DATA_FREE';
            }
            $sql .= '
                   FROM `information_schema`.SCHEMATA s';
            if ($force_stats) {
                $sql .= '
                    LEFT JOIN `information_schema`.TABLES t
                        ON BINARY t.TABLE_SCHEMA = BINARY s.SCHEMA_NAME';
            }
            $sql .= $sql_where_schema . '
                    GROUP BY BINARY s.SCHEMA_NAME
                    ORDER BY BINARY ' . PMA_Util::backquote($sort_by)
                . ' ' . $sort_order
                . $limit;
        }

        $databases = $this->fetchResult($sql, 'SCHEMA_NAME', null, $link);

        $mysql_error = $this->getError($link);
        if (! count($databases) && $GLOBALS['errno']) {
            PMA_Util::mysqlDie($mysql_error, $sql);
        }

        // display only databases also in official database list
        // f.e. to apply hide_db and only_db
        $drops = array_diff(
            array_keys($databases), (array) $GLOBALS['pma']->databases
        );
        if (count($drops)) {
            foreach ($drops as $drop) {
                unset($databases[$drop]);
            }
            unset($drop);
        }
        unset($sql_where_schema, $sql, $drops);

        /**
         * apply limit and order manually now
         * (caused by older MySQL < 5 or $GLOBALS['cfg']['NaturalOrder'])
         */
        if ($apply_limit_and_order_manual) {
            $GLOBALS['callback_sort_order'] = $sort_order;
            $GLOBALS['callback_sort_by'] = $sort_by;
            usort(
                $databases,
                array('PMA_DatabaseInterface', '_usortComparisonCallback')
            );
            unset($GLOBALS['callback_sort_order'], $GLOBALS['callback_sort_by']);

            /**
             * now apply limit
             */
            if ($limit_count) {
                $databases = array_slice($databases, $limit_offset, $limit_count);
            }
        }

        return $databases;
    }

    /**
     * usort comparison callback
     *
     * @param string $a first argument to sort
     * @param string $b second argument to sort
     *
     * @return integer  a value representing whether $a should be before $b in the
     *                   sorted array or not
     *
     * @access  private
     */
    private static function _usortComparisonCallback($a, $b)
    {
        if ($GLOBALS['cfg']['NaturalOrder']) {
            $sorter = 'strnatcasecmp';
        } else {
            $sorter = 'strcasecmp';
        }
        /* No sorting when key is not present */
        if (! isset($a[$GLOBALS['callback_sort_by']])
            || ! isset($b[$GLOBALS['callback_sort_by']])
        ) {
            return 0;
        }
        // produces f.e.:
        // return -1 * strnatcasecmp($a["SCHEMA_TABLES"], $b["SCHEMA_TABLES"])
        return ($GLOBALS['callback_sort_order'] == 'ASC' ? 1 : -1) * $sorter(
            $a[$GLOBALS['callback_sort_by']], $b[$GLOBALS['callback_sort_by']]
        );
    } // end of the '_usortComparisonCallback()' method

    /**
     * returns detailed array with all columns for given table in database,
     * or all tables/databases
     *
     * @param string $database name of database
     * @param string $table    name of table to retrieve columns from
     * @param string $column   name of specific column
     * @param mixed  $link     mysql link resource
     *
     * @return array
     */
    public function getColumnsFull($database = null, $table = null,
        $column = null, $link = null
    ) {
        $columns = array();

        $sql_wheres = array();
        $array_keys = array();

        // get columns information from information_schema
        if (null !== $database) {
            $sql_wheres[] = '`TABLE_SCHEMA` = \''
                . PMA_Util::sqlAddSlashes($database) . '\' ';
        } else {
            $array_keys[] = 'TABLE_SCHEMA';
        }
        if (null !== $table) {
            $sql_wheres[] = '`TABLE_NAME` = \''
                . PMA_Util::sqlAddSlashes($table) . '\' ';
        } else {
            $array_keys[] = 'TABLE_NAME';
        }
        if (null !== $column) {
            $sql_wheres[] = '`COLUMN_NAME` = \''
                . PMA_Util::sqlAddSlashes($column) . '\' ';
        } else {
            $array_keys[] = 'COLUMN_NAME';
        }

        // for PMA bc:
        // `[SCHEMA_FIELD_NAME]` AS `[SHOW_FULL_COLUMNS_FIELD_NAME]`
        if (PMA_DRIZZLE) {
            $sql = "SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME,
                column_name        AS `Field`,
                (CASE
                    WHEN character_maximum_length > 0
                    THEN concat(lower(data_type), '(', character_maximum_length, ')')
                    WHEN numeric_precision > 0 OR numeric_scale > 0
                    THEN concat(lower(data_type), '(', numeric_precision,
                        ',', numeric_scale, ')')
                    WHEN enum_values IS NOT NULL
                        THEN concat(lower(data_type), '(', enum_values, ')')
                    ELSE lower(data_type) END)
                                   AS `Type`,
                collation_name     AS `Collation`,
                (CASE is_nullable
                    WHEN 1 THEN 'YES'
                    ELSE 'NO' END) AS `Null`,
                (CASE
                    WHEN is_used_in_primary THEN 'PRI'
                    ELSE '' END)   AS `Key`,
                column_default     AS `Default`,
                (CASE
                    WHEN is_auto_increment THEN 'auto_increment'
                    WHEN column_default_update
                    THEN 'on update ' || column_default_update
                    ELSE '' END)   AS `Extra`,
                NULL               AS `Privileges`,
                column_comment     AS `Comment`
            FROM data_dictionary.columns";
        } else {
            $sql = '
                 SELECT *,
                        `COLUMN_NAME`       AS `Field`,
                        `COLUMN_TYPE`       AS `Type`,
                        `COLLATION_NAME`    AS `Collation`,
                        `IS_NULLABLE`       AS `Null`,
                        `COLUMN_KEY`        AS `Key`,
                        `COLUMN_DEFAULT`    AS `Default`,
                        `EXTRA`             AS `Extra`,
                        `PRIVILEGES`        AS `Privileges`,
                        `COLUMN_COMMENT`    AS `Comment`
                   FROM `information_schema`.`COLUMNS`';
        }
        if (count($sql_wheres)) {
            $sql .= "\n" . ' WHERE ' . implode(' AND ', $sql_wheres);
        }
        return $this->fetchResult($sql, $array_keys, null, $link);
    }

    /**
     * Returns SQL query for fetching columns for a table
     *
     * The 'Key' column is not calculated properly, use $GLOBALS['dbi']->getColumns()
     * to get correct values.
     *
     * @param string  $database name of database
     * @param string  $table    name of table to retrieve columns from
     * @param string  $column   name of column, null to show all columns
     * @param boolean $full     whether to return full info or only column names
     *
     * @see getColumns()
     *
     * @return string
     */
    public function getColumnsSql($database, $table, $column = null, $full = false)
    {
        if (PMA_DRIZZLE) {
            // `Key` column:
            // * used in primary key => PRI
            // * unique one-column => UNI
            // * indexed, one-column or first in multi-column => MUL
            // Promotion of UNI to PRI in case no promary index exists
            // is done after query is executed
            $sql = "SELECT
                    column_name        AS `Field`,
                    (CASE
                        WHEN character_maximum_length > 0
                        THEN concat(
                            lower(data_type), '(', character_maximum_length, ')'
                        )
                        WHEN numeric_precision > 0 OR numeric_scale > 0
                        THEN concat(lower(data_type), '(', numeric_precision,
                            ',', numeric_scale, ')')
                        WHEN enum_values IS NOT NULL
                            THEN concat(lower(data_type), '(', enum_values, ')')
                        ELSE lower(data_type) END)
                                       AS `Type`,
                    " . ($full ? "
                    collation_name     AS `Collation`," : '') . "
                    (CASE is_nullable
                        WHEN 1 THEN 'YES'
                        ELSE 'NO' END) AS `Null`,
                    (CASE
                        WHEN is_used_in_primary THEN 'PRI'
                        WHEN is_unique AND NOT is_multi THEN 'UNI'
                        WHEN is_indexed
                        AND (NOT is_multi OR is_first_in_multi) THEN 'MUL'
                        ELSE '' END)   AS `Key`,
                    column_default     AS `Default`,
                    (CASE
                        WHEN is_auto_increment THEN 'auto_increment'
                        WHEN column_default_update <> ''
                        THEN 'on update ' || column_default_update
                        ELSE '' END)   AS `Extra`
                    " . ($full ? " ,
                    NULL               AS `Privileges`,
                    column_comment     AS `Comment`" : '') . "
                FROM data_dictionary.columns
                WHERE table_schema = '" . PMA_Util::sqlAddSlashes($database) . "'
                    AND table_name = '" . PMA_Util::sqlAddSlashes($table) . "'
                    " . (
                        ($column != null)
                            ? "
                    AND column_name = '" . PMA_Util::sqlAddSlashes($column) . "'"
                            : ''
                        );
            // ORDER BY ordinal_position
        } else {
            $sql = 'SHOW ' . ($full ? 'FULL' : '') . ' COLUMNS FROM '
                . PMA_Util::backquote($database) . '.' . PMA_Util::backquote($table)
                . (($column != null) ? "LIKE '"
                . PMA_Util::sqlAddSlashes($column, true) . "'" : '');
        }
        return $sql;
    }

    /**
     * Returns descriptions of columns in given table (all or given by $column)
     *
     * @param string  $database name of database
     * @param string  $table    name of table to retrieve columns from
     * @param string  $column   name of column, null to show all columns
     * @param boolean $full     whether to return full info or only column names
     * @param mixed   $link     mysql link resource
     *
     * @return false|array   array indexed by column names or,
     *                        if $column is given, flat array description
     */
    public function getColumns($database, $table, $column = null, $full = false,
        $link = null
    ) {
        $sql = $this->getColumnsSql($database, $table, $column, $full);
        $fields = $this->fetchResult($sql, 'Field', null, $link);
        if (! is_array($fields) || count($fields) == 0) {
            return null;
        }
        if (PMA_DRIZZLE) {
            // fix Key column, it's much simpler in PHP than in SQL
            $has_pk = false;
            $has_pk_candidates = false;
            foreach ($fields as $f) {
                if ($f['Key'] == 'PRI') {
                    $has_pk = true;
                    break;
                } else if ($f['Null'] == 'NO'
                    && ($f['Key'] == 'MUL'
                    || $f['Key'] == 'UNI')
                ) {
                    $has_pk_candidates = true;
                }
            }
            if (! $has_pk && $has_pk_candidates) {
                $secureDatabase = PMA_Util::sqlAddSlashes($database);
                // check whether we can promote some unique index to PRI
                $sql = "
                    SELECT i.index_name, p.column_name
                    FROM data_dictionary.indexes i
                        JOIN data_dictionary.index_parts p
                        USING (table_schema, table_name)
                    WHERE i.table_schema = '" . $secureDatabase . "'
                        AND i.table_name = '" . PMA_Util::sqlAddSlashes($table) . "'
                        AND i.is_unique
                            AND NOT i.is_nullable";
                $result = $this->fetchResult($sql, 'index_name', null, $link);
                $result = $result ? array_shift($result) : array();
                foreach ($result as $f) {
                    $fields[$f]['Key'] = 'PRI';
                }
            }
        }

        return ($column != null) ? array_shift($fields) : $fields;
    }

    /**
     * Returns all column names in given table
     *
     * @param string $database name of database
     * @param string $table    name of table to retrieve columns from
     * @param mixed  $link     mysql link resource
     *
     * @return null|array
     */
    public function getColumnNames($database, $table, $link = null)
    {
        $sql = $this->getColumnsSql($database, $table);
        // We only need the 'Field' column which contains the table's column names
        $fields = array_keys($this->fetchResult($sql, 'Field', null, $link));

        if ( ! is_array($fields) || count($fields) == 0 ) {
            return null;
        }
        return $fields;
    }

    /**
    * Returns SQL for fetching information on table indexes (SHOW INDEXES)
    *
    * @param string $database name of database
    * @param string $table    name of the table whose indexes are to be retreived
    * @param string $where    additional conditions for WHERE
    *
    * @return array   $indexes
    */
    public function getTableIndexesSql($database, $table, $where = null)
    {
        if (PMA_DRIZZLE) {
            $sql = "SELECT
                    ip.table_name          AS `Table`,
                    (NOT ip.is_unique)     AS Non_unique,
                    ip.index_name          AS Key_name,
                    ip.sequence_in_index+1 AS Seq_in_index,
                    ip.column_name         AS Column_name,
                    (CASE
                        WHEN i.index_type = 'BTREE' THEN 'A'
                        ELSE NULL END)     AS Collation,
                    NULL                   AS Cardinality,
                    compare_length         AS Sub_part,
                    NULL                   AS Packed,
                    ip.is_nullable         AS `Null`,
                    i.index_type           AS Index_type,
                    NULL                   AS Comment,
                    i.index_comment        AS Index_comment
                FROM data_dictionary.index_parts ip
                    LEFT JOIN data_dictionary.indexes i
                    USING (table_schema, table_name, index_name)
                WHERE table_schema = '" . PMA_Util::sqlAddSlashes($database) . "'
                    AND table_name = '" . PMA_Util::sqlAddSlashes($table) . "'
            ";
            if ($where) {
                $sql = "SELECT * FROM (" . $sql . ") A WHERE (" . $where . ")";
            }
        } else {
            $sql = 'SHOW INDEXES FROM ' . PMA_Util::backquote($database) . '.'
                . PMA_Util::backquote($table);
            if ($where) {
                $sql .= ' WHERE (' . $where . ')';
            }
        }
        return $sql;
    }

    /**
     * Returns indexes of a table
     *
     * @param string $database name of database
     * @param string $table    name of the table whose indexes are to be retrieved
     * @param mixed  $link     mysql link resource
     *
     * @return array   $indexes
     */
    public function getTableIndexes($database, $table, $link = null)
    {
        $sql = $this->getTableIndexesSql($database, $table);
        $indexes = $this->fetchResult($sql, null, null, $link);

        if (! is_array($indexes) || count($indexes) < 1) {
            return array();
        }
        return $indexes;
    }

    /**
     * returns value of given mysql server variable
     *
     * @param string $var  mysql server variable name
     * @param int    $type PMA_DatabaseInterface::GETVAR_SESSION |
     *                     PMA_DatabaseInterface::GETVAR_GLOBAL
     * @param mixed  $link mysql link resource|object
     *
     * @return mixed   value for mysql server variable
     */
    public function getVariable(
        $var, $type = self::GETVAR_SESSION, $link = null
    ) {
        if ($link === null) {
            if (isset($GLOBALS['userlink'])) {
                $link = $GLOBALS['userlink'];
            } else {
                return false;
            }
        }

        switch ($type) {
        case self::GETVAR_SESSION:
            $modifier = ' SESSION';
            break;
        case self::GETVAR_GLOBAL:
            $modifier = ' GLOBAL';
            break;
        default:
            $modifier = '';
        }
        return $this->fetchValue(
            'SHOW' . $modifier . ' VARIABLES LIKE \'' . $var . '\';', 0, 1, $link
        );
    }

    /**
     * Function called just after a connection to the MySQL database server has
     * been established. It sets the connection collation, and determines the
     * version of MySQL which is running.
     *
     * @param mixed   $link           mysql link resource|object
     * @param boolean $is_controluser whether link is for control user
     *
     * @return void
     */
    public function postConnect($link, $is_controluser = false)
    {
        if ($is_controluser) {
            /*
             * FIXME: Not sure if this is right approach, but we can not
             * define constants multiple time.
             */
            return;
        }
        if (! defined('PMA_MYSQL_INT_VERSION')) {
            if (PMA_Util::cacheExists('PMA_MYSQL_INT_VERSION', null)) {
                define(
                    'PMA_MYSQL_INT_VERSION',
                    PMA_Util::cacheGet('PMA_MYSQL_INT_VERSION', null)
                );
                define(
                    'PMA_MYSQL_MAJOR_VERSION',
                    PMA_Util::cacheGet('PMA_MYSQL_MAJOR_VERSION', null)
                );
                define(
                    'PMA_MYSQL_STR_VERSION',
                    PMA_Util::cacheGet('PMA_MYSQL_STR_VERSION', null)
                );
                define(
                    'PMA_MYSQL_VERSION_COMMENT',
                    PMA_Util::cacheGet('PMA_MYSQL_VERSION_COMMENT', null)
                );
                define(
                    'PMA_DRIZZLE',
                    PMA_Util::cacheGet('PMA_DRIZZLE', null)
                );
            } else {
                $version = $this->fetchSingleRow(
                    'SELECT @@version, @@version_comment',
                    'ASSOC',
                    $link
                );

                if ($version) {
                    $match = explode('.', $version['@@version']);
                    define('PMA_MYSQL_MAJOR_VERSION', (int)$match[0]);
                    define(
                        'PMA_MYSQL_INT_VERSION',
                        (int) sprintf(
                            '%d%02d%02d', $match[0], $match[1], intval($match[2])
                        )
                    );
                    define('PMA_MYSQL_STR_VERSION', $version['@@version']);
                    define(
                        'PMA_MYSQL_VERSION_COMMENT',
                        $version['@@version_comment']
                    );
                } else {
                    define('PMA_MYSQL_INT_VERSION', 50015);
                    define('PMA_MYSQL_MAJOR_VERSION', 5);
                    define('PMA_MYSQL_STR_VERSION', '5.00.15');
                    define('PMA_MYSQL_VERSION_COMMENT', '');
                }
                PMA_Util::cacheSet(
                    'PMA_MYSQL_INT_VERSION',
                    PMA_MYSQL_INT_VERSION,
                    null
                );
                PMA_Util::cacheSet(
                    'PMA_MYSQL_MAJOR_VERSION',
                    PMA_MYSQL_MAJOR_VERSION,
                    null
                );
                PMA_Util::cacheSet(
                    'PMA_MYSQL_STR_VERSION',
                    PMA_MYSQL_STR_VERSION,
                    null
                );
                PMA_Util::cacheSet(
                    'PMA_MYSQL_VERSION_COMMENT',
                    PMA_MYSQL_VERSION_COMMENT,
                    null
                );

                /* Detect Drizzle - it does not support charsets */
                $charset_result = $this->query(
                    "SHOW VARIABLES LIKE 'character_set_results'",
                    $link
                );
                if ($this->numRows($charset_result) == 0) {
                    define('PMA_DRIZZLE', true);
                } else {
                    define('PMA_DRIZZLE', false);
                }
                $this->freeResult($charset_result);

                PMA_Util::cacheSet(
                    'PMA_DRIZZLE',
                    PMA_DRIZZLE,
                    null
                );
            }
        }

        // Skip charsets for Drizzle
        if (!PMA_DRIZZLE) {
            if (PMA_MYSQL_INT_VERSION >  50503) {
                $default_charset = 'utf8mb4';
                $default_collation = 'utf8mb4_general_ci';
            } else {
                $default_charset = 'utf8';
                $default_collation = 'utf8_general_ci';
            }
            if (! empty($GLOBALS['collation_connection'])) {
                $this->query(
                    "SET CHARACTER SET '$default_charset';",
                    $link,
                    self::QUERY_STORE
                );
                /* Automatically adjust collation to mb4 variant */
                if ($default_charset == 'utf8mb4'
                    && strncmp('utf8_', $GLOBALS['collation_connection'], 5) == 0
                ) {
                    $GLOBALS['collation_connection'] = 'utf8mb4_' . substr(
                        $GLOBALS['collation_connection'],
                        5
                    );
                }
                $this->query(
                    "SET collation_connection = '"
                    . PMA_Util::sqlAddSlashes($GLOBALS['collation_connection'])
                    . "';",
                    $link,
                    self::QUERY_STORE
                );
            } else {
                $this->query(
                    "SET NAMES '$default_charset' COLLATE '$default_collation';",
                    $link,
                    self::QUERY_STORE
                );
            }
        }

        // Cache plugin list for Drizzle
        if (PMA_DRIZZLE && !PMA_Util::cacheExists('drizzle_engines', null)) {
            $sql = "SELECT p.plugin_name, m.module_library
                FROM data_dictionary.plugins p
                    JOIN data_dictionary.modules m USING (module_name)
                WHERE p.plugin_type = 'StorageEngine'
                    AND p.plugin_name NOT IN ('FunctionEngine', 'schema')
                    AND p.is_active = 'YES'";
            $engines = $this->fetchResult($sql, 'plugin_name', null, $link);
            PMA_Util::cacheSet('drizzle_engines', $engines, null);
        }
    }

    /**
     * returns a single value from the given result or query,
     * if the query or the result has more than one row or field
     * the first field of the first row is returned
     *
     * <code>
     * $sql = 'SELECT `name` FROM `user` WHERE `id` = 123';
     * $user_name = $GLOBALS['dbi']->fetchValue($sql);
     * // produces
     * // $user_name = 'John Doe'
     * </code>
     *
     * @param string|mysql_result $result     query or mysql result
     * @param integer             $row_number row to fetch the value from,
     *                                        starting at 0, with 0 being default
     * @param integer|string      $field      field to fetch the value from,
     *                                        starting at 0, with 0 being default
     * @param resource            $link       mysql link
     *
     * @return mixed value of first field in first row from result
     *               or false if not found
     */
    public function fetchValue($result, $row_number = 0, $field = 0, $link = null)
    {
        $value = false;

        if (is_string($result)) {
            $result = $this->tryQuery(
                $result,
                $link,
                self::QUERY_STORE,
                false
            );
        }

        // return false if result is empty or false
        // or requested row is larger than rows in result
        if ($this->numRows($result) < ($row_number + 1)) {
            return $value;
        }

        // if $field is an integer use non associative mysql fetch function
        if (is_int($field)) {
            $fetch_function = 'fetchRow';
        } else {
            $fetch_function = 'fetchAssoc';
        }

        // get requested row
        for ($i = 0; $i <= $row_number; $i++) {
            $row = $this->$fetch_function($result);
        }
        $this->freeResult($result);

        // return requested field
        if (isset($row[$field])) {
            $value = $row[$field];
        }
        unset($row);

        return $value;
    }

    /**
     * returns only the first row from the result
     *
     * <code>
     * $sql = 'SELECT * FROM `user` WHERE `id` = 123';
     * $user = $GLOBALS['dbi']->fetchSingleRow($sql);
     * // produces
     * // $user = array('id' => 123, 'name' => 'John Doe')
     * </code>
     *
     * @param string|mysql_result $result query or mysql result
     * @param string              $type   NUM|ASSOC|BOTH
     *                                    returned array should either numeric
     *                                    associativ or booth
     * @param resource            $link   mysql link
     *
     * @return array|boolean first row from result
     *                       or false if result is empty
     */
    public function fetchSingleRow($result, $type = 'ASSOC', $link = null)
    {
        if (is_string($result)) {
            $result = $this->tryQuery(
                $result,
                $link,
                self::QUERY_STORE,
                false
            );
        }

        // return null if result is empty or false
        if (! $this->numRows($result)) {
            return false;
        }

        switch ($type) {
        case 'NUM' :
            $fetch_function = 'fetchRow';
            break;
        case 'ASSOC' :
            $fetch_function = 'fetchAssoc';
            break;
        case 'BOTH' :
        default :
            $fetch_function = 'fetchArray';
            break;
        }

        $row = $this->$fetch_function($result);
        $this->freeResult($result);
        return $row;
    }

    /**
     * returns all rows in the resultset in one array
     *
     * <code>
     * $sql = 'SELECT * FROM `user`';
     * $users = $GLOBALS['dbi']->fetchResult($sql);
     * // produces
     * // $users[] = array('id' => 123, 'name' => 'John Doe')
     *
     * $sql = 'SELECT `id`, `name` FROM `user`';
     * $users = $GLOBALS['dbi']->fetchResult($sql, 'id');
     * // produces
     * // $users['123'] = array('id' => 123, 'name' => 'John Doe')
     *
     * $sql = 'SELECT `id`, `name` FROM `user`';
     * $users = $GLOBALS['dbi']->fetchResult($sql, 0);
     * // produces
     * // $users['123'] = array(0 => 123, 1 => 'John Doe')
     *
     * $sql = 'SELECT `id`, `name` FROM `user`';
     * $users = $GLOBALS['dbi']->fetchResult($sql, 'id', 'name');
     * // or
     * $users = $GLOBALS['dbi']->fetchResult($sql, 0, 1);
     * // produces
     * // $users['123'] = 'John Doe'
     *
     * $sql = 'SELECT `name` FROM `user`';
     * $users = $GLOBALS['dbi']->fetchResult($sql);
     * // produces
     * // $users[] = 'John Doe'
     *
     * $sql = 'SELECT `group`, `name` FROM `user`'
     * $users = $GLOBALS['dbi']->fetchResult($sql, array('group', null), 'name');
     * // produces
     * // $users['admin'][] = 'John Doe'
     *
     * $sql = 'SELECT `group`, `name` FROM `user`'
     * $users = $GLOBALS['dbi']->fetchResult($sql, array('group', 'name'), 'id');
     * // produces
     * // $users['admin']['John Doe'] = '123'
     * </code>
     *
     * @param string|mysql_result  $result  query or mysql result
     * @param string|integer|array $key     field-name or offset
     *                                      used as key for array
     * @param string|integer       $value   value-name or offset
     *                                      used as value for array
     * @param resource             $link    mysql link
     * @param mixed                $options query options
     *
     * @return array resultrows or values indexed by $key
     */
    public function fetchResult($result, $key = null, $value = null,
        $link = null, $options = 0
    ) {
        $resultrows = array();

        if (is_string($result)) {
            $result = $this->tryQuery($result, $link, $options, false);
        }

        // return empty array if result is empty or false
        if (! $result) {
            return $resultrows;
        }

        $fetch_function = 'fetchAssoc';

        // no nested array if only one field is in result
        if (null === $key && 1 === $this->numFields($result)) {
            $value = 0;
            $fetch_function = 'fetchRow';
        }

        // if $key is an integer use non associative mysql fetch function
        if (is_int($key)) {
            $fetch_function = 'fetchRow';
        }

        if (null === $key && null === $value) {
            while ($row = $this->$fetch_function($result)) {
                $resultrows[] = $row;
            }
        } elseif (null === $key) {
            while ($row = $this->$fetch_function($result)) {
                $resultrows[] = $row[$value];
            }
        } elseif (null === $value) {
            if (is_array($key)) {
                while ($row = $this->$fetch_function($result)) {
                    $result_target =& $resultrows;
                    foreach ($key as $key_index) {
                        if (null === $key_index) {
                            $result_target =& $result_target[];
                            continue;
                        }

                        if (! isset($result_target[$row[$key_index]])) {
                            $result_target[$row[$key_index]] = array();
                        }
                        $result_target =& $result_target[$row[$key_index]];
                    }
                    $result_target = $row;
                }
            } else {
                while ($row = $this->$fetch_function($result)) {
                    $resultrows[$row[$key]] = $row;
                }
            }
        } else {
            if (is_array($key)) {
                while ($row = $this->$fetch_function($result)) {
                    $result_target =& $resultrows;
                    foreach ($key as $key_index) {
                        if (null === $key_index) {
                            $result_target =& $result_target[];
                            continue;
                        }

                        if (! isset($result_target[$row[$key_index]])) {
                            $result_target[$row[$key_index]] = array();
                        }
                        $result_target =& $result_target[$row[$key_index]];
                    }
                    $result_target = $row[$value];
                }
            } else {
                while ($row = $this->$fetch_function($result)) {
                    $resultrows[$row[$key]] = $row[$value];
                }
            }
        }

        $this->freeResult($result);
        return $resultrows;
    }

    /**
     * Get supported SQL compatibility modes
     *
     * @return array supported SQL compatibility modes
     */
    public function getCompatibilities()
    {
        // Drizzle doesn't support compatibility modes
        if (PMA_DRIZZLE) {
            return array();
        }

        $compats = array('NONE');
        $compats[] = 'ANSI';
        $compats[] = 'DB2';
        $compats[] = 'MAXDB';
        $compats[] = 'MYSQL323';
        $compats[] = 'MYSQL40';
        $compats[] = 'MSSQL';
        $compats[] = 'ORACLE';
        // removed; in MySQL 5.0.33, this produces exports that
        // can't be read by POSTGRESQL (see our bug #1596328)
        //$compats[] = 'POSTGRESQL';
        $compats[] = 'TRADITIONAL';

        return $compats;
    }

    /**
     * returns warnings for last query
     *
     * @param resource $link mysql link resource
     *
     * @return array warnings
     */
    public function getWarnings($link = null)
    {
        if (empty($link)) {
            if (isset($GLOBALS['userlink'])) {
                $link = $GLOBALS['userlink'];
            } else {
                return array();
            }
        }

        return $this->fetchResult('SHOW WARNINGS', null, null, $link);
    }

    /**
     * returns an array of PROCEDURE or FUNCTION names for a db
     *
     * @param string   $db    db name
     * @param string   $which PROCEDURE | FUNCTION
     * @param resource $link  mysql link
     *
     * @return array the procedure names or function names
     */
    public function getProceduresOrFunctions($db, $which, $link = null)
    {
        if (PMA_DRIZZLE) {
            // Drizzle doesn't support functions and procedures
            return array();
        }
        $shows = $this->fetchResult(
            'SHOW ' . $which . ' STATUS;', null, null, $link
        );
        $result = array();
        foreach ($shows as $one_show) {
            if ($one_show['Db'] == $db && $one_show['Type'] == $which) {
                $result[] = $one_show['Name'];
            }
        }
        return($result);
    }

    /**
     * returns the definition of a specific PROCEDURE, FUNCTION, EVENT or VIEW
     *
     * @param string $db    db name
     * @param string $which PROCEDURE | FUNCTION | EVENT | VIEW
     * @param string $name  the procedure|function|event|view name
     *
     * @return string the definition
     */
    public function getDefinition($db, $which, $name)
    {
        $returned_field = array(
            'PROCEDURE' => 'Create Procedure',
            'FUNCTION'  => 'Create Function',
            'EVENT'     => 'Create Event',
            'VIEW'      => 'Create View'
        );
        $query = 'SHOW CREATE ' . $which . ' '
            . PMA_Util::backquote($db) . '.'
            . PMA_Util::backquote($name);
        return($this->fetchValue($query, 0, $returned_field[$which]));
    }

    /**
     * returns details about the TRIGGERs for a specific table or database
     *
     * @param string $db        db name
     * @param string $table     table name
     * @param string $delimiter the delimiter to use (may be empty)
     *
     * @return array information about triggers (may be empty)
     */
    public function getTriggers($db, $table = '', $delimiter = '//')
    {
        if (PMA_DRIZZLE) {
            // Drizzle doesn't support triggers
            return array();
        }

        $result = array();
        // Note: in http://dev.mysql.com/doc/refman/5.0/en/faqs-triggers.html
        // their example uses WHERE TRIGGER_SCHEMA='dbname' so let's use this
        // instead of WHERE EVENT_OBJECT_SCHEMA='dbname'
        $query = 'SELECT TRIGGER_SCHEMA, TRIGGER_NAME, EVENT_MANIPULATION'
            . ', EVENT_OBJECT_TABLE, ACTION_TIMING, ACTION_STATEMENT'
            . ', EVENT_OBJECT_SCHEMA, EVENT_OBJECT_TABLE, DEFINER'
            . ' FROM information_schema.TRIGGERS'
            . ' WHERE TRIGGER_SCHEMA ' . PMA_Util::getCollateForIS() . '='
            . ' \'' . PMA_Util::sqlAddSlashes($db) . '\'';

        if (! empty($table)) {
            $query .= " AND EVENT_OBJECT_TABLE = '"
                . PMA_Util::sqlAddSlashes($table) . "';";
        }

        if ($triggers = $this->fetchResult($query)) {
            foreach ($triggers as $trigger) {
                $one_result = array();
                $one_result['name'] = $trigger['TRIGGER_NAME'];
                $one_result['table'] = $trigger['EVENT_OBJECT_TABLE'];
                $one_result['action_timing'] = $trigger['ACTION_TIMING'];
                $one_result['event_manipulation'] = $trigger['EVENT_MANIPULATION'];
                $one_result['definition'] = $trigger['ACTION_STATEMENT'];
                $one_result['definer'] = $trigger['DEFINER'];

                // do not prepend the schema name; this way, importing the
                // definition into another schema will work
                $one_result['full_trigger_name'] = PMA_Util::backquote(
                    $trigger['TRIGGER_NAME']
                );
                $one_result['drop'] = 'DROP TRIGGER IF EXISTS '
                    . $one_result['full_trigger_name'];
                $one_result['create'] = 'CREATE TRIGGER '
                    . $one_result['full_trigger_name'] . ' '
                    . $trigger['ACTION_TIMING'] . ' '
                    . $trigger['EVENT_MANIPULATION']
                    . ' ON ' . PMA_Util::backquote($trigger['EVENT_OBJECT_TABLE'])
                    . "\n" . ' FOR EACH ROW '
                    . $trigger['ACTION_STATEMENT'] . "\n" . $delimiter . "\n";

                $result[] = $one_result;
            }
        }

        // Sort results by name
        $name = array();
        foreach ($result as $value) {
            $name[] = $value['name'];
        }
        array_multisort($name, SORT_ASC, $result);

        return($result);
    }

    /**
     * Formats database error message in a friendly way.
     * This is needed because some errors messages cannot
     * be obtained by mysql_error().
     *
     * @param int    $error_number  Error code
     * @param string $error_message Error message as returned by server
     *
     * @return string HML text with error details
     */
    public function formatError($error_number, $error_message)
    {
        if (! empty($error_message)) {
            $error_message = $this->convertMessage($error_message);
        }

        $error_message = htmlspecialchars($error_message);

        $error = '#' . ((string) $error_number);

        if ($error_number == 2002) {
            $error .= ' - ' . $error_message;
            $error .= '<br />';
            $error .= __(
                'The server is not responding (or the local server\'s socket'
                . ' is not correctly configured).'
            );
        } elseif ($error_number == 2003) {
            $error .= ' - ' . $error_message;
            $error .= '<br />' . __('The server is not responding.');
        } elseif ($error_number == 1005) {
            if (strpos($error_message, 'errno: 13') !== false) {
                $error .= ' - ' . $error_message;
                $error .= '<br />'
                    . __('Please check privileges of directory containing database.');
            } else {
                /* InnoDB contraints, see
                 * http://dev.mysql.com/doc/refman/5.0/en/
                 *  innodb-foreign-key-constraints.html
                 */
                $error .= ' - ' . $error_message .
                    ' (<a href="server_engines.php' .
                    PMA_URL_getCommon(
                        array('engine' => 'InnoDB', 'page' => 'Status')
                    ) . '">' . __('Details…') . '</a>)';
            }
        } else {
            $error .= ' - ' . $error_message;
        }

        return $error;
    }

    /**
     * returns true (int > 0) if current user is superuser
     * otherwise 0
     *
     * @return bool Whether use is a superuser
     */
    public function isSuperuser()
    {
        if (PMA_Util::cacheExists('is_superuser', null)) {
            return PMA_Util::cacheGet('is_superuser', null);
        }

        // when connection failed we don't have a $userlink
        if (isset($GLOBALS['userlink'])) {
            if (PMA_DRIZZLE) {
                // Drizzle has no authorization by default, so when no plugin is
                // enabled everyone is a superuser
                // Known authorization libraries: regex_policy, simple_user_policy
                // Plugins limit object visibility (dbs, tables, processes), we can
                // safely assume we always deal with superuser
                $result = true;
            } else {
                // check access to mysql.user table
                $result = (bool) $GLOBALS['dbi']->tryQuery(
                    'SELECT COUNT(*) FROM mysql.user',
                    $GLOBALS['userlink'],
                    self::QUERY_STORE
                );
            }
            PMA_Util::cacheSet('is_superuser', $result, null);
        } else {
            PMA_Util::cacheSet('is_superuser', false, null);
        }

        return PMA_Util::cacheGet('is_superuser', null);
    }

    /**
     * Checks whether given schema is a system schema: information_schema
     * (MySQL and Drizzle) or data_dictionary (Drizzle)
     *
     * @param string $schema_name        Name of schema (database) to test
     * @param bool   $testForMysqlSchema Whether 'mysql' schema should
     *                                   be treated the same as IS and DD
     *
     * @return bool
     */
    public function isSystemSchema($schema_name, $testForMysqlSchema = false)
    {
        return strtolower($schema_name) == 'information_schema'
            || (!PMA_DRIZZLE && strtolower($schema_name) == 'performance_schema')
            || (PMA_DRIZZLE && strtolower($schema_name) == 'data_dictionary')
            || ($testForMysqlSchema && !PMA_DRIZZLE && $schema_name == 'mysql');
    }

    /**
     * connects to the database server
     *
     * @param string $user                 user name
     * @param string $password             user password
     * @param bool   $is_controluser       whether this is a control user connection
     * @param array  $server               host/port/socket/persistent
     * @param bool   $auxiliary_connection (when true, don't go back to login if
     *                                     connection fails)
     *
     * @return mixed false on error or a connection object on success
     */
    public function connect(
        $user, $password, $is_controluser = false, $server = null,
        $auxiliary_connection = false
    ) {
        return $this->_extension->connect(
            $user, $password, $is_controluser, $server, $auxiliary_connection
        );
    }

    /**
     * selects given database
     *
     * @param string $dbname database name to select
     * @param object $link   connection object
     *
     * @return boolean
     */
    public function selectDb($dbname, $link = null)
    {
        return $this->_extension->selectDb($dbname, $link);
    }

    /**
     * returns array of rows with associative and numeric keys from $result
     *
     * @param object $result result set identifier
     *
     * @return array
     */
    public function fetchArray($result)
    {
        return $this->_extension->fetchArray($result);
    }

    /**
     * returns array of rows with associative keys from $result
     *
     * @param object $result result set identifier
     *
     * @return array
     */
    public function fetchAssoc($result)
    {
        return $this->_extension->fetchAssoc($result);
    }

    /**
     * returns array of rows with numeric keys from $result
     *
     * @param object $result result set identifier
     *
     * @return array
     */
    public function fetchRow($result)
    {
        return $this->_extension->fetchRow($result);
    }

    /**
     * Adjusts the result pointer to an arbitrary row in the result
     *
     * @param object  $result database result
     * @param integer $offset offset to seek
     *
     * @return bool true on success, false on failure
     */
    public function dataSeek($result, $offset)
    {
        return $this->_extension->dataSeek($result, $offset);
    }

    /**
     * Frees memory associated with the result
     *
     * @param object $result database result
     *
     * @return void
     */
    public function freeResult($result)
    {
        $this->_extension->freeResult($result);
    }

    /**
     * Check if there are any more query results from a multi query
     *
     * @param object $link the connection object
     *
     * @return bool true or false
     */
    public function moreResults($link = null)
    {
        return $this->_extension->moreResults($link = null);
    }

    /**
     * Prepare next result from multi_query
     *
     * @param object $link the connection object
     *
     * @return bool true or false
     */
    public function nextResult($link = null)
    {
        return $this->_extension->nextResult($link = null);
    }

    /**
     * Store the result returned from multi query
     *
     * @return mixed false when empty results / result set when not empty
     */
    public function storeResult()
    {
        return $this->_extension->storeResult();
    }

    /**
     * Returns a string representing the type of connection used
     *
     * @param object $link mysql link
     *
     * @return string type of connection used
     */
    public function getHostInfo($link = null)
    {
        return $this->_extension->getHostInfo($link);
    }

    /**
     * Returns the version of the MySQL protocol used
     *
     * @param object $link mysql link
     *
     * @return integer version of the MySQL protocol used
     */
    public function getProtoInfo($link = null)
    {
        return $this->_extension->getProtoInfo($link);
    }

    /**
     * returns a string that represents the client library version
     *
     * @return string MySQL client library version
     */
    public function getClientInfo()
    {
        return $this->_extension->getClientInfo();
    }

    /**
     * returns last error message or false if no errors occurred
     *
     * @param object $link connection link
     *
     * @return string|bool $error or false
     */
    public function getError($link = null)
    {
        return $this->_extension->getError($link);
    }

    /**
     * returns the number of rows returned by last query
     *
     * @param object $result result set identifier
     *
     * @return string|int
     */
    public function numRows($result)
    {
        return $this->_extension->numRows($result);
    }

    /**
     * returns last inserted auto_increment id for given $link
     * or $GLOBALS['userlink']
     *
     * @param object $link the connection object
     *
     * @return string|int
     */
    public function insertId($link = null)
    {
        return $this->_extension->insertId($link);
    }

    /**
     * returns the number of rows affected by last query
     *
     * @param object $link           the connection object
     * @param bool   $get_from_cache whether to retrieve from cache
     *
     * @return string|int
     */
    public function affectedRows($link = null, $get_from_cache = true)
    {
        return $this->_extension->affectedRows($link, $get_from_cache);
    }

    /**
     * returns metainfo for fields in $result
     *
     * @param object $result result set identifier
     *
     * @return array meta info for fields in $result
     */
    public function getFieldsMeta($result)
    {
        return $this->_extension->getFieldsMeta($result);
    }

    /**
     * return number of fields in given $result
     *
     * @param object $result result set identifier
     *
     * @return int field count
     */
    public function numFields($result)
    {
        return $this->_extension->numFields($result);
    }

    /**
     * returns the length of the given field $i in $result
     *
     * @param object $result result set identifier
     * @param int    $i      field
     *
     * @return int length of field
     */
    public function fieldLen($result, $i)
    {
        return $this->_extension->fieldLen($result, $i);
    }

    /**
     * returns name of $i. field in $result
     *
     * @param object $result result set identifier
     * @param int    $i      field
     *
     * @return string name of $i. field in $result
     */
    public function fieldName($result, $i)
    {
        return $this->_extension->fieldName($result, $i);
    }

    /**
     * returns concatenated string of human readable field flags
     *
     * @param object $result result set identifier
     * @param int    $i      field
     *
     * @return string field flags
     */
    public function fieldFlags($result, $i)
    {
        return $this->_extension->fieldFlags($result, $i);
    }
}
?>
