Subversion-Projekte lars-tiefland.prado

<?php
/**
 * TMsssqlCommandBuilder class file.
 *
 * @author Wei Zhuo <weizhuo[at]gmail[dot]com>
 * @link http://www.pradosoft.com/
 * @copyright Copyright &copy; 2005-2008 PradoSoft
 * @license http://www.pradosoft.com/license/
 * @version $Id: TDbCommandBuilder.php 1863 2007-04-12 12:43:49Z wei $
 * @package System.Data.Common
 */

Prado::using('System.Data.Common.TDbCommandBuilder');

/**
 * TMssqlCommandBuilder provides specifics methods to create limit/offset query commands
 * for MSSQL servers.
 *
 * @author Wei Zhuo <weizho[at]gmail[dot]com>
 * @version $Id: TDbCommandBuilder.php 1863 2007-04-12 12:43:49Z wei $
 * @package System.Data.Common
 * @since 3.1
 */
class TMssqlCommandBuilder extends TDbCommandBuilder
{
        /**
         * Overrides parent implementation. Uses "SELECT @@Identity".
         * @return integer last insert id, null if none is found.
         */
        public function getLastInsertID()
        {
                foreach($this->getTableInfo()->getColumns() as $column)
                {
                        if($column->hasSequence())
                        {
                                $command = $this->getDbConnection()->createCommand('SELECT @@Identity');
                                return intval($command->queryScalar());
                        }
                }
        }

        /**
         * Overrides parent implementation. Alters the sql to apply $limit and $offset.
         * The idea for limit with offset is done by modifying the sql on the fly
         * with numerous assumptions on the structure of the sql string.
         * The modification is done with reference to the notes from
         * http://troels.arvin.dk/db/rdbms/#select-limit-offset
         *
         * <code>
         * SELECT * FROM (
         *  SELECT TOP n * FROM (
         *    SELECT TOP z columns      -- (z=n+skip)
         *    FROM tablename
         *    ORDER BY key ASC
         *  ) AS FOO ORDER BY key DESC -- ('FOO' may be anything)
         * ) AS BAR ORDER BY key ASC    -- ('BAR' may be anything)
         * </code>
         *
         * <b>Regular expressions are used to alter the SQL query. The resulting SQL query
         * may be malformed for complex queries.</b> The following restrictions apply
         *
         * <ul>
         *   <li>
         * In particular, <b>commas</b> should <b>NOT</b>
         * be used as part of the ordering expression or identifier. Commas must only be
         * used for separating the ordering clauses.
         *  </li>
         *  <li>
         * In the ORDER BY clause, the column name should NOT be be qualified
         * with a table name or view name. Alias the column names or use column index.
         * </li>
         * <li>
         * No clauses should follow the ORDER BY clause, e.g. no COMPUTE or FOR clauses.
         * </li>
         *
         * @param string SQL query string.
         * @param integer maximum number of rows, -1 to ignore limit.
         * @param integer row offset, -1 to ignore offset.
         * @return string SQL with limit and offset.
         */
        public function applyLimitOffset($sql, $limit=-1, $offset=-1)
        {
                $limit = $limit!==null ? intval($limit) : -1;
                $offset = $offset!==null ? intval($offset) : -1;
                if ($limit > 0 && $offset <= 0) //just limit
                        $sql = preg_replace('/^([\s(])*SELECT( DISTINCT)?(?!\s*TOP\s*\()/i',"\\1SELECT\\2 TOP $limit", $sql);
                else if($limit > 0 && $offset > 0)
                        $sql = $this->rewriteLimitOffsetSql($sql, $limit,$offset);
                return $sql;
        }

        /**
         * Rewrite sql to apply $limit > and $offset > 0 for MSSQL database.
         * See http://troels.arvin.dk/db/rdbms/#select-limit-offset
         * @param string sql query
         * @param integer $limit > 0
         * @param integer $offset > 0
         * @return sql modified sql query applied with limit and offset.
         */
        protected function rewriteLimitOffsetSql($sql, $limit, $offset)
        {
                $fetch = $limit+$offset;
                $sql = preg_replace('/^([\s(])*SELECT( DISTINCT)?(?!\s*TOP\s*\()/i',"\\1SELECT\\2 TOP $fetch", $sql);
                $ordering = $this->findOrdering($sql);

                $orginalOrdering = $this->joinOrdering($ordering);
                $reverseOrdering = $this->joinOrdering($this->reverseDirection($ordering));
                $sql = "SELECT * FROM (SELECT TOP {$limit} * FROM ($sql) as [__inner top table__] {$reverseOrdering}) as [__outer top table__] {$orginalOrdering}";
                return $sql;
        }

        /**
         * Base on simplified syntax http://msdn2.microsoft.com/en-us/library/aa259187(SQL.80).aspx
         *
         * @param string $sql
         * @return array ordering expression as key and ordering direction as value
         */
        protected function findOrdering($sql)
        {
                if(!preg_match('/ORDER BY/i', $sql))
                        return array();
                $matches=array();
                $ordering=array();
                preg_match_all('/(ORDER BY)[\s"\[](.*)(ASC|DESC)?(?:[\s"\[]|$|COMPUTE|FOR)/i', $sql, $matches);
                if(count($matches)>1 && count($matches[2]) > 0)
                {
                        $parts = explode(',', $matches[2][0]);
                        foreach($parts as $part)
                        {
                                $subs=array();
                                if(preg_match_all('/(.*)[\s"\]](ASC|DESC)$/i', trim($part), $subs))
                                {
                                        if(count($subs) > 1 && count($subs[2]) > 0)
                                        {
                                                $ordering[$subs[1][0]] = $subs[2][0];
                                        }
                                        //else what?
                                }
                                else
                                        $ordering[trim($part)] = 'ASC';
                        }
                }
                return $ordering;
        }

        /**
         * @param array ordering obtained from findOrdering()
         * @return string concat the orderings
         */
        protected function joinOrdering($orders)
        {
                if(count($orders)>0)
                {
                        $str=array();
                        foreach($orders as $column => $direction)
                                $str[] = $column.' '.$direction;
                        return 'ORDER BY '.implode(', ', $str);
                }
        }

        /**
         * @param array original ordering
         * @return array ordering with reversed direction.
         */
        protected function reverseDirection($orders)
        {
                foreach($orders as $column => $direction)
                        $orders[$column] = strtolower(trim($direction))==='desc' ? 'ASC' : 'DESC';
                return $orders;
        }
}