<?php // -*-php-*-
// rcs_id('$Id: PearDB.php 7638 2010-08-11 11:58:40Z vargenau $');

require_once('lib/WikiDB/backend.php');
//require_once('lib/FileFinder.php');
//require_once('lib/ErrorManager.php');

class WikiDB_backend_PearDB
extends WikiDB_backend
{
    var $_dbh;

    function WikiDB_backend_PearDB ($dbparams) {
        // Find and include PEAR's DB.php. maybe we should force our private version again...
        // if DB would have exported its version number, it would be easier.
        @require_once('DB/common.php'); // Either our local pear copy or the system one
        // check the version!
        $name = check_php_version(5) ? "escapeSimple" : strtolower("escapeSimple");
        // TODO: apparently some Pear::Db version adds LIMIT 1,0 to getOne(),
        // which is invalid for "select version()"
        if (!in_array($name, get_class_methods("DB_common"))) {
            $finder = new FileFinder;
            $dir = dirname(__FILE__)."/../../pear";
            $finder->_prepend_to_include_path($dir);
            include_once("$dir/DB/common.php"); // use our version instead.
            if (!in_array($name, get_class_methods("DB_common"))) {
                $pearFinder = new PearFileFinder("lib/pear");
                $pearFinder->includeOnce('DB.php');
            } else {
                include_once("$dir/DB.php");
            }
        } else {
          include_once("DB.php");
        }

        // Install filter to handle bogus error notices from buggy DB.php's.
        // TODO: check the Pear_DB version, but how?
        if (DEBUG) {
            global $ErrorManager;
            $ErrorManager->pushErrorHandler(new WikiMethodCb($this, '_pear_notice_filter'));
            $this->_pearerrhandler = true;
        }
      
        // Open connection to database
        $this->_dsn = $dbparams['dsn'];
	$this->_dbparams = $dbparams;
        $this->_lock_count = 0;

        // persistent is usually a DSN option: we override it with a config value.
        //   phptype://username:password@hostspec/database?persistent=false
        $dboptions = array('persistent' => DATABASE_PERSISTENT,
                           'debug' => 2);
        //if (preg_match('/^pgsql/', $this->_dsn)) $dboptions['persistent'] = false;
        $this->_dbh = DB::connect($this->_dsn, $dboptions);
        $dbh = &$this->_dbh;
        if (DB::isError($dbh)) {
            trigger_error(sprintf("Can't connect to database: %s",
                                  $this->_pear_error_message($dbh)),
                          isset($dbparams['_tryroot_from_upgrade']) // hack!
                            ? E_USER_WARNING : E_USER_ERROR);
            if (isset($dbparams['_tryroot_from_upgrade']))
                return;              
        }
        $dbh->setErrorHandling(PEAR_ERROR_CALLBACK,
                               array($this, '_pear_error_callback'));
        $dbh->setFetchMode(DB_FETCHMODE_ASSOC);

        $prefix = isset($dbparams['prefix']) ? $dbparams['prefix'] : '';
        $this->_table_names
            = array('page_tbl'     => $prefix . 'page',
                    'version_tbl'  => $prefix . 'version',
                    'link_tbl'     => $prefix . 'link',
                    'recent_tbl'   => $prefix . 'recent',
                    'nonempty_tbl' => $prefix . 'nonempty');
        $page_tbl = $this->_table_names['page_tbl'];
        $version_tbl = $this->_table_names['version_tbl'];
        $this->page_tbl_fields = "$page_tbl.id AS id, $page_tbl.pagename AS pagename, $page_tbl.hits AS hits";
        $this->version_tbl_fields = "$version_tbl.version AS version, $version_tbl.mtime AS mtime, ".
            "$version_tbl.minor_edit AS minor_edit, $version_tbl.content AS content, $version_tbl.versiondata AS versiondata";

        $this->_expressions
            = array('maxmajor'     => "MAX(CASE WHEN minor_edit=0 THEN version END)",
                    'maxminor'     => "MAX(CASE WHEN minor_edit<>0 THEN version END)",
                    'maxversion'   => "MAX(version)",
                    'notempty'     => "<>''",
                    'iscontent'    => "content<>''");
      
    }
  
    /**
     * Close database connection.
     */
    function close () {
        if (!$this->_dbh)
            return;
        if ($this->_lock_count) {
            trigger_error( "WARNING: database still locked " . '(lock_count = $this->_lock_count)' . "\n<br />",
                          E_USER_WARNING);
        }
        $this->_dbh->setErrorHandling(PEAR_ERROR_PRINT);	// prevent recursive loops.
        $this->unlock('force');

        $this->_dbh->disconnect();

        if (!empty($this->_pearerrhandler)) {
            $GLOBALS['ErrorManager']->popErrorHandler();
        }
    }


    /*
     * Test fast wikipage.
     */
    function is_wiki_page($pagename) {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
        return $dbh->getOne(sprintf("SELECT $page_tbl.id as id"
                                    . " FROM $nonempty_tbl, $page_tbl"
                                    . " WHERE $nonempty_tbl.id=$page_tbl.id"
                                    . "   AND pagename='%s'",
                                    $dbh->escapeSimple($pagename)));
    }
      
    function get_all_pagenames() {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
        return $dbh->getCol("SELECT pagename"
                            . " FROM $nonempty_tbl, $page_tbl"
                            . " WHERE $nonempty_tbl.id=$page_tbl.id");
    }

    function numPages($filter=false, $exclude='') {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
        return $dbh->getOne("SELECT count(*)"
                            . " FROM $nonempty_tbl, $page_tbl"
                            . " WHERE $nonempty_tbl.id=$page_tbl.id");
    }
  
    function increaseHitCount($pagename) {
        $dbh = &$this->_dbh;
        // Hits is the only thing we can update in a fast manner.
        // Note that this will fail silently if the page does not
        // have a record in the page table.  Since it's just the
        // hit count, who cares?
        $dbh->query(sprintf("UPDATE %s SET hits=hits+1 WHERE pagename='%s'",
                            $this->_table_names['page_tbl'],
                            $dbh->escapeSimple($pagename)));
        return;
    }

    /**
     * Read page information from database.
     */
    function get_pagedata($pagename) {
        $dbh = &$this->_dbh;
        //trigger_error("GET_PAGEDATA $pagename", E_USER_NOTICE);
        $result = $dbh->getRow(sprintf("SELECT hits,pagedata FROM %s WHERE pagename='%s'",
                                       $this->_table_names['page_tbl'],
                                       $dbh->escapeSimple($pagename)),
                               DB_FETCHMODE_ASSOC);
        return $result ? $this->_extract_page_data($result) : false;
    }

    function  _extract_page_data($data) {
        if (empty($data)) return array();
        elseif (empty($data['pagedata'])) return $data;
        else {
            $data = array_merge($data, $this->_unserialize($data['pagedata']));
            unset($data['pagedata']);
            return $data;
        }
    }

    function update_pagedata($pagename, $newdata) {
        $dbh = &$this->_dbh;
        $page_tbl = $this->_table_names['page_tbl'];

        // Hits is the only thing we can update in a fast manner.
        if (count($newdata) == 1 && isset($newdata['hits'])) {
            // Note that this will fail silently if the page does not
            // have a record in the page table.  Since it's just the
            // hit count, who cares?
            $dbh->query(sprintf("UPDATE $page_tbl SET hits=%d WHERE pagename='%s'",
                                $newdata['hits'], $dbh->escapeSimple($pagename)));
            return;
        }

        $this->lock(array($page_tbl), true);
        $data = $this->get_pagedata($pagename);
        if (!$data) {
            $data = array();
            $this->_get_pageid($pagename, true); // Creates page record
        }
      
        $hits = !empty($data['hits']) ? (int)$data['hits'] : 0;
        unset($data['hits']);

        foreach ($newdata as $key => $val) {
            if ($key == 'hits')
                $hits = (int)$val;
            else if (empty($val))
                unset($data[$key]);
            else
                $data[$key] = $val;
        }

        /* Portability issue -- not all DBMS supports huge strings
         * so we need to 'bind' instead of building a simple SQL statment.
         * Note that we do not need to escapeSimple when we bind
        $dbh->query(sprintf("UPDATE $page_tbl"
                            . " SET hits=%d, pagedata='%s'"
                            . " WHERE pagename='%s'",
                            $hits,
                            $dbh->escapeSimple($this->_serialize($data)),
                            $dbh->escapeSimple($pagename)));
        */
        $dbh->query("UPDATE $page_tbl"
                    . " SET hits=?, pagedata=?"
                    . " WHERE pagename=?",
                    array($hits, $this->_serialize($data), $pagename));
        $this->unlock(array($page_tbl));
    }

    function get_cached_html($pagename) {
        $dbh = &$this->_dbh;
        $page_tbl = $this->_table_names['page_tbl'];
        return $dbh->GetOne(sprintf("SELECT cached_html FROM $page_tbl WHERE pagename='%s'",
                                    $dbh->escapeSimple($pagename)));
    }

    function set_cached_html($pagename, $data) {
        $dbh = &$this->_dbh;
        $page_tbl = $this->_table_names['page_tbl'];
        $dbh->query("UPDATE $page_tbl"
                    . " SET cached_html=?"
                    . " WHERE pagename=?",
                    array($data, $pagename));
    }

    function _get_pageid($pagename, $create_if_missing = false) {
      
        // check id_cache
        global $request;
        $cache =& $request->_dbi->_cache->_id_cache;
        if (isset($cache[$pagename])) {
            if ($cache[$pagename] or !$create_if_missing) {
                return $cache[$pagename];
            }
        }

	// attributes play this game.
        if ($pagename === '') return 0;

        $dbh = &$this->_dbh;
        $page_tbl = $this->_table_names['page_tbl'];
      
        $query = sprintf("SELECT id FROM $page_tbl WHERE pagename='%s'",
                         $dbh->escapeSimple($pagename));

        if (!$create_if_missing)
            return $dbh->getOne($query);

        $id = $dbh->getOne($query);
        if (empty($id)) {
            $this->lock(array($page_tbl), true); // write lock
            $max_id = $dbh->getOne("SELECT MAX(id) FROM $page_tbl");
            $id = $max_id + 1;
            // requires createSequence and on mysql lock the interim table ->getSequenceName
            //$id = $dbh->nextId($page_tbl . "_id");
            $dbh->query(sprintf("INSERT INTO $page_tbl"
                                . " (id,pagename,hits)"
                                . " VALUES (%d,'%s',0)",
                                $id, $dbh->escapeSimple($pagename)));
            $this->unlock(array($page_tbl));
        }
        return $id;
    }

    function get_latest_version($pagename) {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
        return
            (int)$dbh->getOne(sprintf("SELECT latestversion"
                                      . " FROM $page_tbl, $recent_tbl"
                                      . " WHERE $page_tbl.id=$recent_tbl.id"
                                      . "  AND pagename='%s'",
                                      $dbh->escapeSimple($pagename)));
    }

    function get_previous_version($pagename, $version) {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
      
        return
            (int)$dbh->getOne(sprintf("SELECT version"
                                      . " FROM $version_tbl, $page_tbl"
                                      . " WHERE $version_tbl.id=$page_tbl.id"
                                      . "  AND pagename='%s'"
                                      . "  AND version < %d"
                                      . " ORDER BY version DESC",
                                      /* Non portable and useless anyway with getOne
                                      . " LIMIT 1",
                                      */
                                      $dbh->escapeSimple($pagename),
                                      $version));
    }
  
    /**
     * Get version data.
     *
     * @param $version int Which version to get.
     *
     * @return hash The version data, or false if specified version does not
     *              exist.
     */
    function get_versiondata($pagename, $version, $want_content = false) {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
        extract($this->_expressions);

        assert(is_string($pagename) and $pagename != "");
        assert($version > 0);
      
        //trigger_error("GET_REVISION $pagename $version $want_content", E_USER_NOTICE);
        // FIXME: optimization: sometimes don't get page data?
        if ($want_content) {
            $fields = $this->page_tbl_fields
                . ",$page_tbl.pagedata as pagedata,"
                . $this->version_tbl_fields;
        }
        else {
            $fields = $this->page_tbl_fields . ","
                . "mtime, minor_edit, versiondata,"
                . "$iscontent AS have_content";
        }

        $result = $dbh->getRow(sprintf("SELECT $fields"
                                       . " FROM $page_tbl, $version_tbl"
                                       . " WHERE $page_tbl.id=$version_tbl.id"
                                       . "  AND pagename='%s'"
                                       . "  AND version=%d",
                                       $dbh->escapeSimple($pagename), $version),
                               DB_FETCHMODE_ASSOC);

        return $this->_extract_version_data($result);
    }

    function _extract_version_data($query_result) {
        if (!$query_result)
            return false;

        /* Earlier versions (<= 1.3.7) stored the version data in base64.
           This could be done here or in upgrade.
        */
        if (!strstr($query_result['versiondata'], ":")) {
            $query_result['versiondata'] =
                base64_decode($query_result['versiondata']);
        }
        $data = $this->_unserialize($query_result['versiondata']);
      
        $data['mtime'] = $query_result['mtime'];
        $data['is_minor_edit'] = !empty($query_result['minor_edit']);
      
        if (isset($query_result['content']))
            $data['%content'] = $query_result['content'];
        elseif ($query_result['have_content'])
            $data['%content'] = true;
        else
            $data['%content'] = '';

        // FIXME: this is ugly.
        if (isset($query_result['pagedata'])) {
            // Query also includes page data.
            // We might as well send that back too...
            unset($query_result['versiondata']);
            $data['%pagedata'] = $this->_extract_page_data($query_result);
        }

        return $data;
    }


    /**
     * Create a new revision of a page.
     */
    function set_versiondata($pagename, $version, $data) {
        $dbh = &$this->_dbh;
        $version_tbl = $this->_table_names['version_tbl'];
      
        $minor_edit = (int) !empty($data['is_minor_edit']);
        unset($data['is_minor_edit']);
      
        $mtime = (int)$data['mtime'];
        unset($data['mtime']);
        assert(!empty($mtime));

        @$content = (string) $data['%content'];
        unset($data['%content']);

        unset($data['%pagedata']);
      
        $this->lock();
        $id = $this->_get_pageid($pagename, true);

        $dbh->query(sprintf("DELETE FROM $version_tbl"
                            . " WHERE id=%d AND version=%d",
                            $id, $version));
        // generic slow PearDB bind eh quoting.
        $dbh->query("INSERT INTO $version_tbl"
                    . " (id,version,mtime,minor_edit,content,versiondata)"
                    . " VALUES(?, ?, ?, ?, ?, ?)",
                    array($id, $version, $mtime, $minor_edit, $content,
                    $this->_serialize($data)));

        $this->_update_recent_table($id);
        $this->_update_nonempty_table($id);
      
        $this->unlock();
    }
  
    /**
     * Delete an old revision of a page.
     */
    function delete_versiondata($pagename, $version) {
        $dbh = &$this->_dbh;
        extract($this->_table_names);

        $this->lock();
        if ( ($id = $this->_get_pageid($pagename)) ) {
            $dbh->query("DELETE FROM $version_tbl"
                        . " WHERE id=$id AND version=$version");

            $this->_update_recent_table($id);
            // This shouldn't be needed (as long as the latestversion
            // never gets deleted.)  But, let's be safe.
            $this->_update_nonempty_table($id);
        }
        $this->unlock();
    }

    /**
     * Delete page from the database with backup possibility.
     * i.e save_page('') and DELETE nonempty id
     * Can be undone and is seen in RecentChanges.
     */
    /* // see parent backend.php
    function delete_page($pagename) {
        $mtime = time();
        $user =& $GLOBALS['request']->_user;
        $vdata = array('author' => $user->getId(),
                       'author_id' => $user->getAuthenticatedId(),
                       'mtime' => $mtime);

        $this->lock();
        $version = $this->get_latest_version($pagename);
        $this->set_versiondata($pagename, $version+1, $vdata);
        $this->set_links($pagename, false);
        $pagedata = get_pagedata($pagename);
        $this->update_pagedata($pagename, array('hits' => $pagedata['hits']));
        $this->unlock();
    }
    */

    /**
     * Delete page completely from the database.
     * I'm not sure if this is what we want. Maybe just delete the revisions
     */
    function purge_page($pagename) {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
      
        $this->lock();
        if ( ($id = $this->_get_pageid($pagename, false)) ) {
            $dbh->query("DELETE FROM $nonempty_tbl WHERE id=$id");
            $dbh->query("DELETE FROM $recent_tbl   WHERE id=$id");
            $dbh->query("DELETE FROM $version_tbl  WHERE id=$id");
            $dbh->query("DELETE FROM $link_tbl     WHERE linkfrom=$id");
            $nlinks = $dbh->getOne("SELECT COUNT(*) FROM $link_tbl WHERE linkto=$id");
            if ($nlinks) {
                // We're still in the link table (dangling link) so we can't delete this
                // altogether.
                $dbh->query("UPDATE $page_tbl SET hits=0, pagedata='' WHERE id=$id");
                $result = 0;
            }
            else {
                $dbh->query("DELETE FROM $page_tbl WHERE id=$id");
                $result = 1;
            }
            $this->_update_recent_table();
            $this->_update_nonempty_table();
        } else {
            $result = -1; // already purged or not existing
        }
        $this->unlock();
        return $result;
    }

    // The only thing we might be interested in updating which we can
    // do fast in the flags (minor_edit).   I think the default
    // update_versiondata will work fine...
    //function update_versiondata($pagename, $version, $data) {
    //}

    function set_links($pagename, $links) {
        // Update link table.
        // FIXME: optimize: mysql can do this all in one big INSERT.

        $dbh = &$this->_dbh;
        extract($this->_table_names);

        $this->lock();
        $pageid = $this->_get_pageid($pagename, true);

        $dbh->query("DELETE FROM $link_tbl WHERE linkfrom=$pageid");
	if ($links) {
	    $linkseen = array();
            foreach ($links as $link) {
                $linkto = $link['linkto'];
                if ($linkto === "") { // ignore attributes
                    continue;
                }
                if (isset($link['relation']))
                    $relation = $this->_get_pageid($link['relation'], true);
                else
                    $relation = 0;
                // avoid duplicates
                if (isset($linkseen[$linkto]) and !$relation)
                    continue;
                if (!$relation)
                    $linkseen[$linkto] = true;
                $linkid = $this->_get_pageid($linkto, true);
              	if (!$linkid) {
               	    echo("No link for $linkto on page $pagename");
               	    //printSimpleTrace(debug_backtrace());
               	    trigger_error("No link for $linkto on page $pagename");
                }
                assert($linkid);
                $dbh->query("INSERT INTO $link_tbl (linkfrom, linkto, relation)"
                            . " VALUES ($pageid, $linkid, $relation)");
            }
	    unset($linkseen);
	}
        $this->unlock();
    }
  
    /**
     * Find pages which link to or are linked from a page.
     *
     * TESTME relations: get_links is responsible to add the relation to the pagehash
     * as 'linkrelation' key as pagename. See WikiDB_PageIterator::next
     *   if (isset($next['linkrelation']))
     */
    function get_links($pagename, $reversed=true, $include_empty=false,
                       $sortby='', $limit='', $exclude='',
                       $want_relations = false)
    {
        $dbh = &$this->_dbh;
        extract($this->_table_names);

        if ($reversed)
            list($have,$want) = array('linkee', 'linker');
        else
            list($have,$want) = array('linker', 'linkee');
        $orderby = $this->sortby($sortby, 'db', array('pagename'));
        if ($orderby) $orderby = " ORDER BY $want." . $orderby;
        if ($exclude) // array of pagenames
            $exclude = " AND $want.pagename NOT IN ".$this->_sql_set($exclude);
        else
            $exclude='';

        $qpagename = $dbh->escapeSimple($pagename);
        $sql = "SELECT $want.id AS id, $want.pagename AS pagename, "
            . ($want_relations ? " related.pagename as linkrelation" : " $want.hits AS hits")
            . " FROM "
            . (!$include_empty ? "$nonempty_tbl, " : '')
            . " $page_tbl linkee, $page_tbl linker, $link_tbl "
            . ($want_relations ? " JOIN $page_tbl related ON ($link_tbl.relation=related.id)" : '')
            . " WHERE linkfrom=linker.id AND linkto=linkee.id"
            . " AND $have.pagename='$qpagename'"
            . (!$include_empty ? " AND $nonempty_tbl.id=$want.id" : "")
            //. " GROUP BY $want.id"
            . $exclude
            . $orderby;
        if ($limit) {
            // extract from,count from limit
            list($from,$count) = $this->limit($limit);
            $result = $dbh->limitQuery($sql, $from, $count);
        } else {
            $result = $dbh->query($sql);
        }
      
        return new WikiDB_backend_PearDB_iter($this, $result);
    }

    /**
     * Find if a page links to another page
     */
    function exists_link($pagename, $link, $reversed=false) {
        $dbh = &$this->_dbh;
        extract($this->_table_names);

        if ($reversed)
            list($have, $want) = array('linkee', 'linker');
        else
            list($have, $want) = array('linker', 'linkee');
        $qpagename = $dbh->escapeSimple($pagename);
        $qlink = $dbh->escapeSimple($link);
        $row = $dbh->GetRow("SELECT CASE WHEN $want.pagename='$qlink' THEN 1 ELSE 0 END as result"
                            . " FROM $link_tbl, $page_tbl linker, $page_tbl linkee, $nonempty_tbl"
                            . " WHERE linkfrom=linker.id AND linkto=linkee.id"
                            . " AND $have.pagename='$qpagename'"
                            . " AND $want.pagename='$qlink'");
        return $row['result'];
    }

    function get_all_pages($include_empty=false, $sortby='', $limit='', $exclude='') {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
        $orderby = $this->sortby($sortby, 'db');
        if ($orderby) $orderby = ' ORDER BY ' . $orderby;
        if ($exclude) // array of pagenames
            $exclude = " AND $page_tbl.pagename NOT IN ".$this->_sql_set($exclude);
        else
            $exclude='';

        if (strstr($orderby, 'mtime ')) { // multiple columns possible
            if ($include_empty) {
                $sql = "SELECT "
                    . $this->page_tbl_fields
                    . " FROM $page_tbl, $recent_tbl, $version_tbl"
                    . " WHERE $page_tbl.id=$recent_tbl.id"
                    . " AND $page_tbl.id=$version_tbl.id AND latestversion=version"
                    . $exclude
                    . $orderby;
            }
            else {
                $sql = "SELECT "
                    . $this->page_tbl_fields
                    . " FROM $nonempty_tbl, $page_tbl, $recent_tbl, $version_tbl"
                    . " WHERE $nonempty_tbl.id=$page_tbl.id"
                    . " AND $page_tbl.id=$recent_tbl.id"
                    . " AND $page_tbl.id=$version_tbl.id AND latestversion=version"
                    . $exclude
                    . $orderby;
            }
        } else {
            if ($include_empty) {
                $sql = "SELECT "
                    . $this->page_tbl_fields
                    ." FROM $page_tbl"
                    . ($exclude ? " WHERE $exclude" : '')
                    . $orderby;
            }
            else {
                $sql = "SELECT "
                    . $this->page_tbl_fields
                    . " FROM $nonempty_tbl, $page_tbl"
                    . " WHERE $nonempty_tbl.id=$page_tbl.id"
                    . $exclude
                    . $orderby;
            }
        }
        if ($limit && $orderby) {
            // extract from,count from limit
            list($from,$count) = $this->limit($limit);
            $result = $dbh->limitQuery($sql, $from, $count);
            $options = array('limit_by_db' => 1);
        } else {
            $result = $dbh->query($sql);
            $options = array('limit_by_db' => 0);
        }
        return new WikiDB_backend_PearDB_iter($this, $result, $options);
    }
      
    /**
     * Title search.
     * Todo: exclude
     */
    function text_search($search, $fulltext=false, $sortby='', $limit='',
                         $exclude='')
    {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
        $orderby = $this->sortby($sortby, 'db');
        if ($orderby) $orderby = ' ORDER BY ' . $orderby;
        //else " ORDER BY rank($field, to_tsquery('$searchon')) DESC";

        $searchclass = get_class($this)."_search";
        // no need to define it everywhere and then fallback. memory!
        if (!class_exists($searchclass))
            $searchclass = "WikiDB_backend_PearDB_search";
        $searchobj = new $searchclass($search, $dbh);
      
        $table = "$nonempty_tbl, $page_tbl";
        $join_clause = "$nonempty_tbl.id=$page_tbl.id";
        $fields = $this->page_tbl_fields;

        if ($fulltext) {
            $table .= ", $recent_tbl";
            $join_clause .= " AND $page_tbl.id=$recent_tbl.id";

            $table .= ", $version_tbl";
            $join_clause .= " AND $page_tbl.id=$version_tbl.id AND latestversion=version";

            $fields .= ", $page_tbl.pagedata as pagedata, " . $this->version_tbl_fields;
            $callback = new WikiMethodCb($searchobj, "_fulltext_match_clause");
        } else {
            $callback = new WikiMethodCb($searchobj, "_pagename_match_clause");
        }
        $search_clause = $search->makeSqlClauseObj($callback);
      
        $sql = "SELECT $fields FROM $table"
            . " WHERE $join_clause"
            . "  AND ($search_clause)"
            . $orderby;
         if ($limit) {
             list($from, $count) = $this->limit($limit);
             $result = $dbh->limitQuery($sql, $from, $count);
         } else {
             $result = $dbh->query($sql);
         }
      
        $iter = new WikiDB_backend_PearDB_iter($this, $result);
        $iter->stoplisted = @$searchobj->stoplisted;
        return $iter;
    }

    //Todo: check if the better Mysql MATCH operator is supported,
    // (ranked search) and also google like expressions.
    function _sql_match_clause($word) {
        $word = preg_replace('/(?=[%_\\\\])/', "\\", $word);
        $word = $this->_dbh->escapeSimple($word);
        //$page_tbl = $this->_table_names['page_tbl'];
        //Note: Mysql 4.1.0 has a bug which fails with binary fields.
        //      e.g. if word is lowercased.
        // http://bugs.mysql.com/bug.php?id=1491
        return "LOWER(pagename) LIKE '%$word%'";
    }
    function _sql_casematch_clause($word) {
        $word = preg_replace('/(?=[%_\\\\])/', "\\", $word);
        $word = $this->_dbh->escapeSimple($word);
        return "pagename LIKE '%$word%'";
    }
    function _fullsearch_sql_match_clause($word) {
        $word = preg_replace('/(?=[%_\\\\])/', "\\", $word);
        $word = $this->_dbh->escapeSimple($word);
        //$page_tbl = $this->_table_names['page_tbl'];
        //Mysql 4.1.1 has a bug which fails here if word is lowercased.
        return "LOWER(pagename) LIKE '%$word%' OR content LIKE '%$word%'";
    }
    function _fullsearch_sql_casematch_clause($word) {
        $word = preg_replace('/(?=[%_\\\\])/', "\\", $word);
        $word = $this->_dbh->escapeSimple($word);
        return "pagename LIKE '%$word%' OR content LIKE '%$word%'";
    }

    /**
     * Find highest or lowest hit counts.
     */
    function most_popular($limit=20, $sortby='-hits') {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
        if ($limit < 0){
            $order = "hits ASC";
            $limit = -$limit;
            $where = "";
        } else {
            $order = "hits DESC";
            $where = " AND hits > 0";
        }
        $orderby = '';
        if ($sortby != '-hits') {
            if ($order = $this->sortby($sortby, 'db'))
                $orderby = " ORDER BY " . $order;
        } else {
            $orderby = " ORDER BY $order";
        }
        //$limitclause = $limit ? " LIMIT $limit" : '';
        $sql = "SELECT "
            . $this->page_tbl_fields
            . " FROM $nonempty_tbl, $page_tbl"
            . " WHERE $nonempty_tbl.id=$page_tbl.id"
            . $where
            . $orderby;
         if ($limit) {
             list($from, $count) = $this->limit($limit);
             $result = $dbh->limitQuery($sql, $from, $count);
         } else {
             $result = $dbh->query($sql);
         }

        return new WikiDB_backend_PearDB_iter($this, $result);
    }

    /**
     * Find recent changes.
     */
    function most_recent($params) {
        $limit = 0;
        $since = 0;
        $include_minor_revisions = false;
        $exclude_major_revisions = false;
        $include_all_revisions = false;
        extract($params);

        $dbh = &$this->_dbh;
        extract($this->_table_names);

        $pick = array();
        if ($since)
            $pick[] = "mtime >= $since";
	
      
        if ($include_all_revisions) {
            // Include all revisions of each page.
            $table = "$page_tbl, $version_tbl";
            $join_clause = "$page_tbl.id=$version_tbl.id";

            if ($exclude_major_revisions) {
		// Include only minor revisions
                $pick[] = "minor_edit <> 0";
            }
            elseif (!$include_minor_revisions) {
		// Include only major revisions
                $pick[] = "minor_edit = 0";
            }
        }
        else {
            $table = "$page_tbl, $recent_tbl";
            $join_clause = "$page_tbl.id=$recent_tbl.id";
            $table .= ", $version_tbl";
            $join_clause .= " AND $version_tbl.id=$page_tbl.id";
          
            if ($exclude_major_revisions) {
                // Include only most recent minor revision
                $pick[] = 'version=latestminor';
            }
            elseif (!$include_minor_revisions) {
                // Include only most recent major revision
                $pick[] = 'version=latestmajor';
            }
            else {
                // Include only the latest revision (whether major or minor).
                $pick[] ='version=latestversion';
            }
        }
        $order = "DESC";
        if($limit < 0){
            $order = "ASC";
            $limit = -$limit;
        }
        // $limitclause = $limit ? " LIMIT $limit" : '';
        $where_clause = $join_clause;
        if ($pick)
            $where_clause .= " AND " . join(" AND ", $pick);

        // FIXME: use SQL_BUFFER_RESULT for mysql?
        $sql = "SELECT "
               . $this->page_tbl_fields . ", " . $this->version_tbl_fields
               . " FROM $table"
               . " WHERE $where_clause"
               . " ORDER BY mtime $order";
        if ($limit) {
             list($from, $count) = $this->limit($limit);
             $result = $dbh->limitQuery($sql, $from, $count);
        } else {
            $result = $dbh->query($sql);
        }
        return new WikiDB_backend_PearDB_iter($this, $result);
    }

    /**
     * Find referenced empty pages.
     */
    function wanted_pages($exclude_from='', $exclude='', $sortby='', $limit='') {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
        if ($orderby = $this->sortby($sortby, 'db', array('pagename','wantedfrom')))
            $orderby = 'ORDER BY ' . $orderby;

        if ($exclude_from) // array of pagenames
            $exclude_from = " AND pp.pagename NOT IN ".$this->_sql_set($exclude_from);
        if ($exclude) // array of pagenames
            $exclude = " AND p.pagename NOT IN ".$this->_sql_set($exclude);
        $sql = "SELECT p.pagename, pp.pagename AS wantedfrom"
            . " FROM $page_tbl p, $link_tbl linked"
            .   " LEFT JOIN $page_tbl pp ON linked.linkto = pp.id"
            .   " LEFT JOIN $nonempty_tbl ne ON linked.linkto = ne.id"
            . " WHERE ne.id IS NULL"
            .       " AND p.id = linked.linkfrom"
            . $exclude_from
            . $exclude
            . $orderby;
        if ($limit) {
            // oci8 error: WHERE NULL = NULL appended
            list($from, $count) = $this->limit($limit);
            $result = $dbh->limitQuery($sql, $from, $count * 3);
        } else {
            $result = $dbh->query($sql);
        }
        return new WikiDB_backend_PearDB_generic_iter($this, $result);
    }

    function _sql_set(&$pagenames) {
        $s = '(';
        foreach ($pagenames as $p) {
            $s .= ("'".$this->_dbh->escapeSimple($p)."',");
        }
        return substr($s,0,-1).")";
    }

    /**
     * Rename page in the database.
     */
    function rename_page ($pagename, $to) {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
      
        $this->lock();
        if (($id = $this->_get_pageid($pagename, false)) ) {
            if ($new = $this->_get_pageid($to, false)) {
                // Cludge Alert!
                // This page does not exist (already verified before), but exists in the page table.
                // So we delete this page.
                $dbh->query("DELETE FROM $nonempty_tbl WHERE id=$new");
                $dbh->query("DELETE FROM $recent_tbl WHERE id=$new");
                $dbh->query("DELETE FROM $version_tbl WHERE id=$new");
                // We have to fix all referring tables to the old id
                $dbh->query("UPDATE $link_tbl SET linkfrom=$id WHERE linkfrom=$new");
                $dbh->query("UPDATE $link_tbl SET linkto=$id WHERE linkto=$new");
                $dbh->query("DELETE FROM $page_tbl WHERE id=$new");
            }
            $dbh->query(sprintf("UPDATE $page_tbl SET pagename='%s' WHERE id=$id",
                                $dbh->escapeSimple($to)));
        }
        $this->unlock();
        return $id;
    }

    function _update_recent_table($pageid = false) {
        $dbh = &$this->_dbh;
        extract($this->_table_names);
        extract($this->_expressions);

        $pageid = (int)$pageid;

        $this->lock();
        $dbh->query("DELETE FROM $recent_tbl"
                    . ( $pageid ? " WHERE id=$pageid" : ""));
        $dbh->query( "INSERT INTO $recent_tbl"
                     . " (id, latestversion, latestmajor, latestminor)"
                     . " SELECT id, $maxversion, $maxmajor, $maxminor"
                     . " FROM $version_tbl"
                     . ( $pageid ? " WHERE id=$pageid" : "")
                     . " GROUP BY id" );
        $this->unlock();
    }

    function _update_nonempty_table($pageid = false) {
        $dbh = &$this->_dbh;
        extract($this->_table_names);

        $pageid = (int)$pageid;

        extract($this->_expressions);
        $this->lock();
        $dbh->query("DELETE FROM $nonempty_tbl"
                    . ( $pageid ? " WHERE id=$pageid" : ""));
        $dbh->query("INSERT INTO $nonempty_tbl (id)"
                    . " SELECT $recent_tbl.id"
                    . " FROM $recent_tbl, $version_tbl"
                    . " WHERE $recent_tbl.id=$version_tbl.id"
                    . "       AND version=latestversion"
                    // We have some specifics here (Oracle)
                    //. "  AND content<>''"
                    . "  AND content $notempty"
                    . ( $pageid ? " AND $recent_tbl.id=$pageid" : ""));
      
        $this->unlock();
    }


    /**
     * Grab a write lock on the tables in the SQL database.
     *
     * Calls can be nested.  The tables won't be unlocked until
     * _unlock_database() is called as many times as _lock_database().
     *
     * @access protected
     */
    function lock($tables = false, $write_lock = true) {
        if ($this->_lock_count++ == 0)
            $this->_lock_tables($write_lock);
    }

    /**
     * Actually lock the required tables.
     */
    function _lock_tables($write_lock) {
        trigger_error("virtual", E_USER_ERROR);
    }
  
    /**
     * Release a write lock on the tables in the SQL database.
     *
     * @access protected
     *
     * @param $force boolean Unlock even if not every call to lock() has been matched
     * by a call to unlock().
     *
     * @see _lock_database
     */
    function unlock($tables = false, $force = false) {
        if ($this->_lock_count == 0)
            return;
        if (--$this->_lock_count <= 0 || $force) {
            $this->_unlock_tables();
            $this->_lock_count = 0;
        }
    }

    /**
     * Actually unlock the required tables.
     */
    function _unlock_tables($write_lock) {
        trigger_error("virtual", E_USER_ERROR);
    }


    /**
     * Serialize data
     */
    function _serialize($data) {
        if (empty($data))
            return '';
        assert(is_array($data));
        return serialize($data);
    }

    /**
     * Unserialize data
     */
    function _unserialize($data) {
        return empty($data) ? array() : unserialize($data);
    }
  
    /**
     * Callback for PEAR (DB) errors.
     *
     * @access protected
     *
     * @param A PEAR_error object.
     */
    function _pear_error_callback($error) {
        if ($this->_is_false_error($error))
            return;
      
        $this->_dbh->setErrorHandling(PEAR_ERROR_PRINT);	// prevent recursive loops.
        $this->close();
        trigger_error($this->_pear_error_message($error), E_USER_ERROR);
    }

    /**
     * Detect false errors messages from PEAR DB.
     *
     * The version of PEAR DB which ships with PHP 4.0.6 has a bug in that
     * it doesn't recognize "LOCK" and "UNLOCK" as SQL commands which don't
     * return any data.  (So when a "LOCK" command doesn't return any data,
     * DB reports it as an error, when in fact, it's not.)
     *
     * @access private
     * @return bool True iff error is not really an error.
     */
    function _is_false_error($error) {
        if ($error->getCode() != DB_ERROR)
            return false;

        $query = $this->_dbh->last_query;

        if (! preg_match('/^\s*"?(INSERT|UPDATE|DELETE|REPLACE|CREATE'
                         . '|DROP|ALTER|GRANT|REVOKE|LOCK|UNLOCK)\s/', $query)) {
            // Last query was not of the sort which doesn't return any data.
            //" <--kludge for brain-dead syntax coloring
            return false;
        }
      
        if (! in_array('ismanip', get_class_methods('DB'))) {
            // Pear shipped with PHP 4.0.4pl1 (and before, presumably)
            // does not have the DB::isManip method.
            return true;
        }
      
        if (DB::isManip($query)) {
            // If Pear thinks it's an isManip then it wouldn't have thrown
            // the error we're testing for....
            return false;
        }

        return true;
    }

    function _pear_error_message($error) {
        $class = get_class($this);
        $message = "$class: fatal database error\n"
             . "\t" . $error->getMessage() . "\n"
             . "\t(" . $error->getDebugInfo() . ")\n";

        // Prevent password from being exposed during a connection error
        $safe_dsn = preg_replace('| ( :// .*? ) : .* (?=@) |xs',
                                 '\\1:XXXXXXXX', $this->_dsn);
        return str_replace($this->_dsn, $safe_dsn, $message);
    }

    /**
     * Filter PHP errors notices from PEAR DB code.
     *
     * The PEAR DB code which ships with PHP 4.0.6 produces spurious
     * errors and notices.  This is an error callback (for use with
     * ErrorManager which will filter out those spurious messages.)
     * @see _is_false_error, ErrorManager
     * @access private
     */
    function _pear_notice_filter($err) {
        return ( $err->isNotice()
                 && preg_match('|DB[/\\\\]common.php$|', $err->errfile)
                 && $err->errline == 126
                 && preg_match('/Undefined offset: +0\b/', $err->errstr) );
    }

    /* some variables and functions for DB backend abstraction (action=upgrade) */
    function database () {
        return $this->_dbh->dsn['database'];
    }
    function backendType() {
        return $this->_dbh->phptype;
    }
    function connection() {
        return $this->_dbh->connection;
    }
    function getRow($query) {
        return $this->_dbh->getRow($query);
    }

    function listOfTables() {
        return $this->_dbh->getListOf('tables');
    }
    function listOfFields($database,$table) {
        if ($this->backendType() == 'mysql') {
            $fields = array();
            assert(!empty($database));
            assert(!empty($table));
  	    $result = mysql_list_fields($database, $table, $this->_dbh->connection) or
  	        trigger_error(__FILE__.':'.__LINE__.' '.mysql_error(), E_USER_WARNING);
  	    if (!$result) return array();
              $columns = mysql_num_fields($result);
            for ($i = 0; $i < $columns; $i++) {
                $fields[] = mysql_field_name($result, $i);
            }
            mysql_free_result($result);
            return $fields;
        } else {
            // TODO: try ADODB version?
            trigger_error("Unsupported dbtype and backend. Either switch to ADODB or check it manually.");
            return false;
        }
    }
};

/**
 * This class is a generic iterator.
 *
 * WikiDB_backend_PearDB_iter only iterates over things that have
 * 'pagename', 'pagedata', etc. etc.
 *
 * Probably WikiDB_backend_PearDB_iter and this class should be merged
 * (most of the code is cut-and-paste :-( ), but I am trying to make
 * changes that could be merged easily.
 *
 * @author: Dan Frankowski
 */
class WikiDB_backend_PearDB_generic_iter
extends WikiDB_backend_iterator
{
    function WikiDB_backend_PearDB_generic_iter($backend, $query_result, $field_list = NULL) {
        if (DB::isError($query_result)) {
            // This shouldn't happen, I thought.
            $backend->_pear_error_callback($query_result);
        }
      
        $this->_backend = &$backend;
        $this->_result = $query_result;
        $this->_options = $field_list;
    }

    function count() {
        if (!$this->_result)
            return false;
        return $this->_result->numRows();
    }
  
    function next() {
        if (!$this->_result)
            return false;

        $record = $this->_result->fetchRow(DB_FETCHMODE_ASSOC);
        if (!$record) {
            $this->free();
            return false;
        }
      
        return $record;
    }

    function reset () {
        if ($this->_result) {
            $this->_result->MoveFirst();
        }
    }

    function free () {
        if ($this->_result) {
            $this->_result->free();
            $this->_result = false;
        }
    }

    function asArray () {
    	$result = array();
    	while ($page = $this->next())
    	    $result[] = $page;
        return $result;
    }
}

class WikiDB_backend_PearDB_iter
extends WikiDB_backend_PearDB_generic_iter
{

    function next() {
        $backend = &$this->_backend;
        if (!$this->_result)
            return false;

        $record = $this->_result->fetchRow(DB_FETCHMODE_ASSOC);
        if (!$record) {
            $this->free();
            return false;
        }
      
        $pagedata = $backend->_extract_page_data($record);
        $rec = array('pagename' => $record['pagename'],
                     'pagedata' => $pagedata);

        if (!empty($record['version'])) {
            $rec['versiondata'] = $backend->_extract_version_data($record);
            $rec['version'] = $record['version'];
        }
      
        return $rec;
    }
}

class WikiDB_backend_PearDB_search extends WikiDB_backend_search_sql
{
    // no surrounding quotes because we know it's a string
    // function _quote($word) { return $this->_dbh->addq($word); }
}

// Local Variables:
// mode: php
// tab-width: 8
// c-basic-offset: 4
// c-hanging-comment-ender-p: nil
// indent-tabs-mode: nil
// End: 
?>
