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<?php

/* vim: set expandtab tabstop=4 shiftwidth=4 softtabstop=4: */

/**

 * The PEAR DB driver for PHP's oci8 extension

 * for interacting with Oracle databases

 *

 * PHP version 5

 *

 * LICENSE: This source file is subject to version 3.0 of the PHP license

 * that is available through the world-wide-web at the following URI:

 * http://www.php.net/license/3_0.txt.  If you did not receive a copy of

 * the PHP License and are unable to obtain it through the web, please

 * send a note to license@php.net so we can mail you a copy immediately.

 *

 * @category   Database

 * @package    DB

 * @author     James L. Pine <jlp@valinux.com>

 * @author     Daniel Convissor <danielc@php.net>

 * @copyright  1997-2007 The PHP Group

 * @license    http://www.php.net/license/3_0.txt  PHP License 3.0

 * @version    CVS: $Id$

 * @link       http://pear.php.net/package/DB

 */

/**

 * Obtain the DB_common class so it can be extended from

 */

require_once 'DB/common.php';

/**

 * The methods PEAR DB uses to interact with PHP's oci8 extension

 * for interacting with Oracle databases

 *

 * Definitely works with versions 8 and 9 of Oracle.

 *

 * These methods overload the ones declared in DB_common.

 *

 * Be aware...  OCIError() only appears to return anything when given a

 * statement, so functions return the generic DB_ERROR instead of more

 * useful errors that have to do with feedback from the database.

 *

 * @category   Database

 * @package    DB

 * @author     James L. Pine <jlp@valinux.com>

 * @author     Daniel Convissor <danielc@php.net>

 * @copyright  1997-2007 The PHP Group

 * @license    http://www.php.net/license/3_0.txt  PHP License 3.0

 * @version    Release: 1.9.2

 * @link       http://pear.php.net/package/DB

 */

class DB_oci8 extends DB_common

{

    // {{{ properties

    /**

     * The DB driver type (mysql, oci8, odbc, etc.)

     * @var string

     */

    var $phptype = 'oci8';

    /**

     * The database syntax variant to be used (db2, access, etc.), if any

     * @var string

     */

    var $dbsyntax = 'oci8';

    /**

     * The capabilities of this DB implementation

     *

     * The 'new_link' element contains the PHP version that first provided

     * new_link support for this DBMS.  Contains false if it's unsupported.

     *

     * Meaning of the 'limit' element:

     *   + 'emulate' = emulate with fetch row by number

     *   + 'alter'   = alter the query

     *   + false     = skip rows

     *

     * @var array

     */

    var $features = array(

        'limit'         => 'alter',

        'new_link'      => '5.0.0',

        'numrows'       => 'subquery',

        'pconnect'      => true,

        'prepare'       => true,

        'ssl'           => false,

        'transactions'  => true,

    );

    /**

     * A mapping of native error codes to DB error codes

     * @var array

     */

    var $errorcode_map = array(

        1     => DB_ERROR_CONSTRAINT,

        900   => DB_ERROR_SYNTAX,

        904   => DB_ERROR_NOSUCHFIELD,

        913   => DB_ERROR_VALUE_COUNT_ON_ROW,

        921   => DB_ERROR_SYNTAX,

        923   => DB_ERROR_SYNTAX,

        942   => DB_ERROR_NOSUCHTABLE,

        955   => DB_ERROR_ALREADY_EXISTS,

        1400  => DB_ERROR_CONSTRAINT_NOT_NULL,

        1401  => DB_ERROR_INVALID,

        1407  => DB_ERROR_CONSTRAINT_NOT_NULL,

        1418  => DB_ERROR_NOT_FOUND,

        1476  => DB_ERROR_DIVZERO,

        1722  => DB_ERROR_INVALID_NUMBER,

        2289  => DB_ERROR_NOSUCHTABLE,

        2291  => DB_ERROR_CONSTRAINT,

        2292  => DB_ERROR_CONSTRAINT,

        2449  => DB_ERROR_CONSTRAINT,

        12899 => DB_ERROR_INVALID,

    );

    /**

     * The raw database connection created by PHP

     * @var resource

     */

    var $connection;

    /**

     * The DSN information for connecting to a database

     * @var array

     */

    var $dsn = array();

    /**

     * Should data manipulation queries be committed automatically?

     * @var bool

     * @access private

     */

    var $autocommit = true;

    /**

     * Stores the $data passed to execute() in the oci8 driver

     *

     * Gets reset to array() when simpleQuery() is run.

     *

     * Needed in case user wants to call numRows() after prepare/execute

     * was used.

     *

     * @var array

     * @access private

     */

    var $_data = array();

    /**

     * The result or statement handle from the most recently executed query

     * @var resource

     */

    var $last_stmt;

    /**

     * Is the given prepared statement a data manipulation query?

     * @var array

     * @access private

     */

    var $manip_query = array();

    /**

     * Store of prepared SQL queries.

     * @var array

     * @access private

     */

    var $_prepared_queries = array();

    // }}}

    // {{{ constructor

    /**

     * This constructor calls <kbd>parent::__construct()</kbd>

     *

     * @return void

     */

    function __construct()

    {

        parent::__construct();

    }

    // }}}

    // {{{ connect()

    /**

     * Connect to the database server, log in and open the database

     *

     * Don't call this method directly.  Use DB::connect() instead.

     *

     * If PHP is at version 5.0.0 or greater:

     *   + Generally, oci_connect() or oci_pconnect() are used.

     *   + But if the new_link DSN option is set to true, oci_new_connect()

     *     is used.

     *

     * When using PHP version 4.x, OCILogon() or OCIPLogon() are used.

     *

     * PEAR DB's oci8 driver supports the following extra DSN options:

     *   + charset       The character set to be used on the connection.

     *                    Only used if PHP is at version 5.0.0 or greater

     *                    and the Oracle server is at 9.2 or greater.

     *                    Available since PEAR DB 1.7.0.

     *   + new_link      If set to true, causes subsequent calls to

     *                    connect() to return a new connection link

     *                    instead of the existing one.  WARNING: this is

     *                    not portable to other DBMS's.

     *                    Available since PEAR DB 1.7.0.

     *

     * @param array $dsn         the data source name

     * @param bool  $persistent  should the connection be persistent?

     *

     * @return int  DB_OK on success. A DB_Error object on failure.

     */

    function connect($dsn, $persistent = false)

    {

        if (!PEAR::loadExtension('oci8')) {

            return $this->raiseError(DB_ERROR_EXTENSION_NOT_FOUND);

        }

        $this->dsn = $dsn;

        if ($dsn['dbsyntax']) {

            $this->dbsyntax = $dsn['dbsyntax'];

        }

        // Backwards compatibility with DB < 1.7.0

        if (empty($dsn['database']) && !empty($dsn['hostspec'])) {

            $db = $dsn['hostspec'];

        } else {

            $db = $dsn['database'];

        }

        if (function_exists('oci_connect')) {

            if (isset($dsn['new_link'])

                && ($dsn['new_link'] == 'true' || $dsn['new_link'] === true))

            {

                $connect_function = 'oci_new_connect';

            } else {

                $connect_function = $persistent ? 'oci_pconnect'

                                    : 'oci_connect';

            }

            if (isset($this->dsn['port']) && $this->dsn['port']) {

                $db = '//'.$db.':'.$this->dsn['port'];

            }

            $char = empty($dsn['charset']) ? null : $dsn['charset'];

            $this->connection = @$connect_function($dsn['username'],

                                                   $dsn['password'],

                                                   $db,

                                                   $char);

            $error = OCIError();

            if (!empty($error) && $error['code'] == 12541) {

                // Couldn't find TNS listener.  Try direct connection.

                $this->connection = @$connect_function($dsn['username'],

                                                       $dsn['password'],

                                                       null,

                                                       $char);

            }

        } else {

            $connect_function = $persistent ? 'OCIPLogon' : 'OCILogon';

            if ($db) {

                $this->connection = @$connect_function($dsn['username'],

                                                       $dsn['password'],

                                                       $db);

            } elseif ($dsn['username'] || $dsn['password']) {

                $this->connection = @$connect_function($dsn['username'],

                                                       $dsn['password']);

            }

        }

        if (!$this->connection) {

            $error = OCIError();

            $error = (is_array($error)) ? $error['message'] : null;

            return $this->raiseError(DB_ERROR_CONNECT_FAILED,

                                     null, null, null,

                                     $error);

        }

        return DB_OK;

    }

    // }}}

    // {{{ disconnect()

    /**

     * Disconnects from the database server

     *

     * @return bool  TRUE on success, FALSE on failure

     */

    function disconnect()

    {

        if (function_exists('oci_close')) {

            $ret = @oci_close($this->connection);

        } else {

            $ret = @OCILogOff($this->connection);

        }

        $this->connection = null;

        return $ret;

    }

    // }}}

    // {{{ simpleQuery()

    /**

     * Sends a query to the database server

     *

     * To determine how many rows of a result set get buffered using

     * ocisetprefetch(), see the "result_buffering" option in setOptions().

     * This option was added in Release 1.7.0.

     *

     * @param string  the SQL query string

     *

     * @return mixed  + a PHP result resrouce for successful SELECT queries

     *                + the DB_OK constant for other successful queries

     *                + a DB_Error object on failure

     */

    function simpleQuery($query)

    {

        $this->_data = array();

        $this->last_parameters = array();

        $this->last_query = $query;

        $query = $this->modifyQuery($query);

        $result = @OCIParse($this->connection, $query);

        if (!$result) {

            return $this->oci8RaiseError();

        }

        if ($this->autocommit) {

            $success = @OCIExecute($result,OCI_COMMIT_ON_SUCCESS);

        } else {

            $success = @OCIExecute($result,OCI_DEFAULT);

        }

        if (!$success) {

            return $this->oci8RaiseError($result);

        }

        $this->last_stmt = $result;

        if ($this->_checkManip($query)) {

            return DB_OK;

        } else {

            @ocisetprefetch($result, $this->options['result_buffering']);

            return $result;

        }

    }

    // }}}

    // {{{ nextResult()

    /**

     * Move the internal oracle result pointer to the next available result

     *

     * @param a valid oci8 result resource

     *

     * @access public

     *

     * @return true if a result is available otherwise return false

     */

    function nextResult($result)

    {

        return false;

    }

    // }}}

    // {{{ fetchInto()

    /**

     * Places a row from the result set into the given array

     *

     * Formating of the array and the data therein are configurable.

     * See DB_result::fetchInto() for more information.

     *

     * This method is not meant to be called directly.  Use

     * DB_result::fetchInto() instead.  It can't be declared "protected"

     * because DB_result is a separate object.

     *

     * @param resource $result    the query result resource

     * @param array    $arr       the referenced array to put the data in

     * @param int      $fetchmode how the resulting array should be indexed

     * @param int      $rownum    the row number to fetch (0 = first row)

     *

     * @return mixed  DB_OK on success, NULL when the end of a result set is

     *                 reached or on failure

     *

     * @see DB_result::fetchInto()

     */

    function fetchInto($result, &$arr, $fetchmode, $rownum = null)

    {

        if ($rownum !== null) {

            return $this->raiseError(DB_ERROR_NOT_CAPABLE);

        }

        if ($fetchmode & DB_FETCHMODE_ASSOC) {

            $moredata = @OCIFetchInto($result,$arr,OCI_ASSOC+OCI_RETURN_NULLS+OCI_RETURN_LOBS);

            if ($this->options['portability'] & DB_PORTABILITY_LOWERCASE &&

                $moredata)

            {

                $arr = array_change_key_case($arr, CASE_LOWER);

            }

        } else {

            $moredata = OCIFetchInto($result,$arr,OCI_RETURN_NULLS+OCI_RETURN_LOBS);

        }

        if (!$moredata) {

            return null;

        }

        if ($this->options['portability'] & DB_PORTABILITY_RTRIM) {

            $this->_rtrimArrayValues($arr);

        }

        if ($this->options['portability'] & DB_PORTABILITY_NULL_TO_EMPTY) {

            $this->_convertNullArrayValuesToEmpty($arr);

        }

        return DB_OK;

    }

    // }}}

    // {{{ freeResult()

    /**

     * Deletes the result set and frees the memory occupied by the result set

     *

     * This method is not meant to be called directly.  Use

     * DB_result::free() instead.  It can't be declared "protected"

     * because DB_result is a separate object.

     *

     * @param resource $result  PHP's query result resource

     *

     * @return bool  TRUE on success, FALSE if $result is invalid

     *

     * @see DB_result::free()

     */

    function freeResult($result)

    {

        return is_resource($result) ? OCIFreeStatement($result) : false;

    }

    /**

     * Frees the internal resources associated with a prepared query

     *

     * @param resource $stmt           the prepared statement's resource

     * @param bool     $free_resource  should the PHP resource be freed too?

     *                                  Use false if you need to get data

     *                                  from the result set later.

     *

     * @return bool  TRUE on success, FALSE if $result is invalid

     *

     * @see DB_oci8::prepare()

     */

    function freePrepared($stmt, $free_resource = true)

    {

        if (!is_resource($stmt)) {

            return false;

        }

        if ($free_resource) {

            @ocifreestatement($stmt);

        }

        if (isset($this->prepare_types[(int)$stmt])) {

            unset($this->prepare_types[(int)$stmt]);

            unset($this->manip_query[(int)$stmt]);

            unset($this->_prepared_queries[(int)$stmt]);

        } else {

            return false;

        }

        return true;

    }

    // }}}

    // {{{ numRows()

    /**

     * Gets the number of rows in a result set

     *

     * Only works if the DB_PORTABILITY_NUMROWS portability option

     * is turned on.

     *

     * This method is not meant to be called directly.  Use

     * DB_result::numRows() instead.  It can't be declared "protected"

     * because DB_result is a separate object.

     *

     * @param resource $result  PHP's query result resource

     *

     * @return int  the number of rows.  A DB_Error object on failure.

     *

     * @see DB_result::numRows(), DB_common::setOption()

     */

    function numRows($result)

    {

        // emulate numRows for Oracle.  yuck.

        if ($this->options['portability'] & DB_PORTABILITY_NUMROWS &&

            $result === $this->last_stmt)

        {

            $countquery = 'SELECT COUNT(*) FROM ('.$this->last_query.')';

            $save_query = $this->last_query;

            $save_stmt = $this->last_stmt;

            $count = $this->query($countquery);

            // Restore the last query and statement.

            $this->last_query = $save_query;

            $this->last_stmt = $save_stmt;

            if (DB::isError($count) ||

                DB::isError($row = $count->fetchRow(DB_FETCHMODE_ORDERED)))

            {

                return $this->raiseError(DB_ERROR_NOT_CAPABLE);

            }

            return $row[0];

        }

        return $this->raiseError(DB_ERROR_NOT_CAPABLE);

    }

    // }}}

    // {{{ numCols()

    /**

     * Gets the number of columns in a result set

     *

     * This method is not meant to be called directly.  Use

     * DB_result::numCols() instead.  It can't be declared "protected"

     * because DB_result is a separate object.

     *

     * @param resource $result  PHP's query result resource

     *

     * @return int  the number of columns.  A DB_Error object on failure.

     *

     * @see DB_result::numCols()

     */

    function numCols($result)

    {

        $cols = @OCINumCols($result);

        if (!$cols) {

            return $this->oci8RaiseError($result);

        }

        return $cols;

    }

    // }}}

    // {{{ prepare()

    /**

     * Prepares a query for multiple execution with execute().

     *

     * With oci8, this is emulated.

     *

     * prepare() requires a generic query as string like <code>

     *    INSERT INTO numbers VALUES (?, ?, ?)

     * </code>.  The <kbd>?</kbd> characters are placeholders.

     *

     * Three types of placeholders can be used:

     *   + <kbd>?</kbd>  a quoted scalar value, i.e. strings, integers

     *   + <kbd>!</kbd>  value is inserted 'as is'

     *   + <kbd>&</kbd>  requires a file name.  The file's contents get

     *                     inserted into the query (i.e. saving binary

     *                     data in a db)

     *

     * Use backslashes to escape placeholder characters if you don't want

     * them to be interpreted as placeholders.  Example: <code>

     *    "UPDATE foo SET col=? WHERE col='over \& under'"

     * </code>

     *

     * @param string $query  the query to be prepared

     *

     * @return mixed  DB statement resource on success. DB_Error on failure.

     *

     * @see DB_oci8::execute()

     */

    function prepare($query)

    {

        $tokens   = preg_split('/((?<!\\\)[&?!])/', $query, -1,

                               PREG_SPLIT_DELIM_CAPTURE);

        $binds    = count($tokens) - 1;

        $token    = 0;

        $types    = array();

        $newquery = '';

        foreach ($tokens as $key => $val) {

            switch ($val) {

                case '?':

                    $types[$token++] = DB_PARAM_SCALAR;

                    unset($tokens[$key]);

                    break;

                case '&':

                    $types[$token++] = DB_PARAM_OPAQUE;

                    unset($tokens[$key]);

                    break;

                case '!':

                    $types[$token++] = DB_PARAM_MISC;

                    unset($tokens[$key]);

                    break;

                default:

                    $tokens[$key] = preg_replace('/\\\([&?!])/', "\\1", $val);

                    if ($key != $binds) {

                        $newquery .= $tokens[$key] . ':bind' . $token;

                    } else {

                        $newquery .= $tokens[$key];

                    }

            }

        }

        $this->last_query = $query;

        $newquery = $this->modifyQuery($newquery);

        if (!$stmt = @OCIParse($this->connection, $newquery)) {

            return $this->oci8RaiseError();

        }

        $this->prepare_types[(int)$stmt] = $types;

        $this->manip_query[(int)$stmt] = DB::isManip($query);

        $this->_prepared_queries[(int)$stmt] = $newquery;

        return $stmt;

    }

    // }}}

    // {{{ execute()

    /**

     * Executes a DB statement prepared with prepare().

     *

     * To determine how many rows of a result set get buffered using

     * ocisetprefetch(), see the "result_buffering" option in setOptions().

     * This option was added in Release 1.7.0.

     *

     * @param resource  $stmt  a DB statement resource returned from prepare()

     * @param mixed  $data  array, string or numeric data to be used in

     *                      execution of the statement.  Quantity of items

     *                      passed must match quantity of placeholders in

     *                      query:  meaning 1 for non-array items or the

     *                      quantity of elements in the array.

     *

     * @return mixed  returns an oic8 result resource for successful SELECT

     *                queries, DB_OK for other successful queries.

     *                A DB error object is returned on failure.

     *

     * @see DB_oci8::prepare()

     */

    function &execute($stmt, $data = array())

    {

        $data = (array)$data;

        $this->last_parameters = $data;

        $this->last_query = $this->_prepared_queries[(int)$stmt];

        $this->_data = $data;

        $types = $this->prepare_types[(int)$stmt];

        if (count($types) != count($data)) {

            $tmp = $this->raiseError(DB_ERROR_MISMATCH);

            return $tmp;

        }

        $i = 0;

        foreach ($data as $key => $value) {

            if ($types[$i] == DB_PARAM_MISC) {

                /*

                 * Oracle doesn't seem to have the ability to pass a

                 * parameter along unchanged, so strip off quotes from start

                 * and end, plus turn two single quotes to one single quote,

                 * in order to avoid the quotes getting escaped by

                 * Oracle and ending up in the database.

                 */

                $data[$key] = preg_replace("/^'(.*)'$/", "\\1", $data[$key]);

                $data[$key] = str_replace("''", "'", $data[$key]);

            } elseif ($types[$i] == DB_PARAM_OPAQUE) {

                $fp = @fopen($data[$key], 'rb');

                if (!$fp) {

                    $tmp = $this->raiseError(DB_ERROR_ACCESS_VIOLATION);

                    return $tmp;

                }

                $data[$key] = fread($fp, filesize($data[$key]));

                fclose($fp);

            } elseif ($types[$i] == DB_PARAM_SCALAR) {

                // Floats have to be converted to a locale-neutral

                // representation.

                if (is_float($data[$key])) {

                    $data[$key] = $this->quoteFloat($data[$key]);

                }

            }

            if (!@OCIBindByName($stmt, ':bind' . $i, $data[$key], -1)) {

                $tmp = $this->oci8RaiseError($stmt);

                return $tmp;

            }

            $this->last_query = preg_replace("/:bind$i(?!\d)/",

                    $this->quoteSmart($data[$key]), $this->last_query, 1);

            $i++;

        }

        if ($this->autocommit) {

            $success = @OCIExecute($stmt, OCI_COMMIT_ON_SUCCESS);

        } else {

            $success = @OCIExecute($stmt, OCI_DEFAULT);

        }

        if (!$success) {

            $tmp = $this->oci8RaiseError($stmt);

            return $tmp;

        }

        $this->last_stmt = $stmt;

        if ($this->manip_query[(int)$stmt] || $this->_next_query_manip) {

            $this->_last_query_manip = true;

            $this->_next_query_manip = false;

            $tmp = DB_OK;

        } else {

            $this->_last_query_manip = false;

            @ocisetprefetch($stmt, $this->options['result_buffering']);

            $tmp = new DB_result($this, $stmt);

        }

        return $tmp;

    }

    // }}}

    // {{{ autoCommit()

    /**

     * Enables or disables automatic commits

     *

     * @param bool $onoff  true turns it on, false turns it off

     *

     * @return int  DB_OK on success.  A DB_Error object if the driver

     *               doesn't support auto-committing transactions.

     */

    function autoCommit($onoff = false)

    {

        $this->autocommit = (bool)$onoff;;

        return DB_OK;

    }

    // }}}

    // {{{ commit()

    /**

     * Commits the current transaction

     *

     * @return int  DB_OK on success.  A DB_Error object on failure.

     */

    function commit()

    {

        $result = @OCICommit($this->connection);

        if (!$result) {

            return $this->oci8RaiseError();

        }

        return DB_OK;

    }

    // }}}

    // {{{ rollback()

    /**

     * Reverts the current transaction

     *

     * @return int  DB_OK on success.  A DB_Error object on failure.

     */

    function rollback()

    {

        $result = @OCIRollback($this->connection);

        if (!$result) {

            return $this->oci8RaiseError();

        }

        return DB_OK;

    }

    // }}}

    // {{{ affectedRows()

    /**

     * Determines the number of rows affected by a data maniuplation query

     *

     * 0 is returned for queries that don't manipulate data.

     *

     * @return int  the number of rows.  A DB_Error object on failure.

     */

    function affectedRows()

    {

        if ($this->last_stmt === false) {

            return $this->oci8RaiseError();

        }

        $result = @OCIRowCount($this->last_stmt);

        if ($result === false) {

            return $this->oci8RaiseError($this->last_stmt);

        }

        return $result;

    }

    // }}}

    // {{{ modifyQuery()

    /**

     * Changes a query string for various DBMS specific reasons

     *

     * "SELECT 2+2" must be "SELECT 2+2 FROM dual" in Oracle.

     *

     * @param string $query  the query string to modify

     *

     * @return string  the modified query string

     *

     * @access protected

     */

    function modifyQuery($query)

    {

        if (preg_match('/^\s*SELECT/i', $query) &&

            !preg_match('/\sFROM\s/i', $query)) {

            $query .= ' FROM dual';

        }

        return $query;

    }

    // }}}

    // {{{ modifyLimitQuery()

    /**

     * Adds LIMIT clauses to a query string according to current DBMS standards

     *

     * @param string $query   the query to modify

     * @param int    $from    the row to start to fetching (0 = the first row)

     * @param int    $count   the numbers of rows to fetch

     * @param mixed  $params  array, string or numeric data to be used in

     *                         execution of the statement.  Quantity of items

     *                         passed must match quantity of placeholders in

     *                         query:  meaning 1 placeholder for non-array

     *                         parameters or 1 placeholder per array element.

     *

     * @return string  the query string with LIMIT clauses added

     *

     * @access protected

     */

    function modifyLimitQuery($query, $from, $count, $params = array())

    {

        // Let Oracle return the name of the columns instead of

        // coding a "home" SQL parser

        if (count($params)) {

            $result = $this->prepare("SELECT * FROM ($query) "

                                     . 'WHERE NULL = NULL');

            $tmp = $this->execute($result, $params);

        } else {

            $q_fields = "SELECT * FROM ($query) WHERE NULL = NULL";

            if (!$result = @OCIParse($this->connection, $q_fields)) {

                $this->last_query = $q_fields;

                return $this->oci8RaiseError();

            }

            if (!@OCIExecute($result, OCI_DEFAULT)) {

                $this->last_query = $q_fields;

                return $this->oci8RaiseError($result);

            }

        }

        $ncols = OCINumCols($result);

        $cols  = array();

        for ( $i = 1; $i <= $ncols; $i++ ) {

            $cols[] = '"' . OCIColumnName($result, $i) . '"';

        }

        $fields = implode(', ', $cols);

        // XXX Test that (tip by John Lim)

        //if (preg_match('/^\s*SELECT\s+/is', $query, $match)) {

        //    // Introduce the FIRST_ROWS Oracle query optimizer

        //    $query = substr($query, strlen($match[0]), strlen($query));

        //    $query = "SELECT /* +FIRST_ROWS */ " . $query;

        //}

        // Construct the query

        // more at: http://marc.theaimsgroup.com/?l=php-db&m=99831958101212&w=2

        // Perhaps this could be optimized with the use of Unions

        $query = "SELECT $fields FROM".

                 "  (SELECT rownum as linenum, $fields FROM".

                 "      ($query)".

                 '  WHERE rownum <= '. ($from + $count) .

                 ') WHERE linenum >= ' . ++$from;

        return $query;

    }

    // }}}

    // {{{ nextId()

    /**

     * Returns the next free id in a sequence

     *

     * @param string  $seq_name  name of the sequence

     * @param boolean $ondemand  when true, the seqence is automatically

     *                            created if it does not exist

     *

     * @return int  the next id number in the sequence.

     *               A DB_Error object on failure.

     *

     * @see DB_common::nextID(), DB_common::getSequenceName(),

     *      DB_oci8::createSequence(), DB_oci8::dropSequence()

     */

    function nextId($seq_name, $ondemand = true)

    {

        $seqname = $this->getSequenceName($seq_name);

        $repeat = 0;

        do {

            $this->expectError(DB_ERROR_NOSUCHTABLE);

            $result = $this->query("SELECT ${seqname}.nextval FROM dual");

            $this->popExpect();

            if ($ondemand && DB::isError($result) &&

                $result->getCode() == DB_ERROR_NOSUCHTABLE) {

                $repeat = 1;

                $result = $this->createSequence($seq_name);

                if (DB::isError($result)) {

                    return $this->raiseError($result);

                }

            } else {

                $repeat = 0;

            }

        } while ($repeat);

        if (DB::isError($result)) {

            return $this->raiseError($result);

        }

        $arr = $result->fetchRow(DB_FETCHMODE_ORDERED);

        return $arr[0];

    }

    /**

     * Creates a new sequence

     *

     * @param string $seq_name  name of the new sequence

     *

     * @return int  DB_OK on success.  A DB_Error object on failure.

     *

     * @see DB_common::createSequence(), DB_common::getSequenceName(),

     *      DB_oci8::nextID(), DB_oci8::dropSequence()

     */

    function createSequence($seq_name)

    {

        return $this->query('CREATE SEQUENCE '

                            . $this->getSequenceName($seq_name));

    }

    // }}}

    // {{{ dropSequence()

    /**

     * Deletes a sequence

     *

     * @param string $seq_name  name of the sequence to be deleted

     *

     * @return int  DB_OK on success.  A DB_Error object on failure.

     *

     * @see DB_common::dropSequence(), DB_common::getSequenceName(),

     *      DB_oci8::nextID(), DB_oci8::createSequence()

     */

    function dropSequence($seq_name)

    {

        return $this->query('DROP SEQUENCE '

                            . $this->getSequenceName($seq_name));

    }

    // }}}

    // {{{ oci8RaiseError()

    /**

     * Produces a DB_Error object regarding the current problem

     *

     * @param int $errno  if the error is being manually raised pass a

     *                     DB_ERROR* constant here.  If this isn't passed

     *                     the error information gathered from the DBMS.

     *

     * @return object  the DB_Error object

     *

     * @see DB_common::raiseError(),

     *      DB_oci8::errorNative(), DB_oci8::errorCode()

     */

    function oci8RaiseError($errno = null)

    {

        if ($errno === null) {

            $error = @OCIError($this->connection);

            return $this->raiseError($this->errorCode($error['code']),

                                     null, null, null, $error['message']);

        } elseif (is_resource($errno)) {

            $error = @OCIError($errno);

            return $this->raiseError($this->errorCode($error['code']),

                                     null, null, null, $error['message']);

        }

        return $this->raiseError($this->errorCode($errno));

    }

    // }}}

    // {{{ errorNative()

    /**

     * Gets the DBMS' native error code produced by the last query

     *

     * @return int  the DBMS' error code.  FALSE if the code could not be

     *               determined

     */

    function errorNative()

    {

        if (is_resource($this->last_stmt)) {

            $error = @OCIError($this->last_stmt);

        } else {

            $error = @OCIError($this->connection);

        }

        if (is_array($error)) {

            return $error['code'];

        }