scalable changelog redesign

This patch provides a rewritten changelog system that is designed to run
efficiently on both small and large wikis. The patch includes a plugin to
convert changelogs from the current format. The conversion is
non-destructive and happens automatically. For more information on the new
changelog format see "http://wiki.splitbrain.org/wiki:changelog".

Structure
In short the changelog is now stored in per-page changelog files, with a
recent changes cache. The recent changes cache is kept in
"/data/meta/_dokuwiki.changes" and trimmed daily. The per-page changelogs
are kept in "/data/meta/<ns>/<page_id>.changes" files. To preserve
revision information for revisions stored in the attic, the "*.changes"
files are not removed when their page is deleted. This allows the full
life-cycle of page creation, deletion, and reversion to be tracked.

Format
The changelog line format now uses a general "line type" field in place of
the special "minor" change syntax. There is also an extra field that can
be used to store arbitrary data associated with special line types. The
reverted line type (R) is a good example. There the extra field holds the
revision date used as the source for reverting the page. See the wiki for
the complete syntax description.

Code Notes
The changelog functions have been rewritten to load the whole file only if
it is small. For larger files, the function loads only the relevant
chunk(s). Parsed changelog lines are cached in memory to speed future
function calls.

getRevisionInfo
A binary search is used to locate the chunk expected to contain the
requested revision. The whole chunk is parsed, and adjacent lines are
optimistically cached to speed consecutive calls.

getRevisions
Reads the changelog file backwards (newest first) in chunks until the
requested number of lines have been read. Parsed changelog lines are
cached for subsequent calls to getRevisionInfo. Because revisions are read
from the changelog they are no longer guaranteed to exist in the attic.

(Note: Even with lines of arbitrary length getRevisionInfo and
getRevisions never split changelog lines while reading. This is done by
sliding the "file pointer" forward to the end of a line after each blind
seek.)

isMinor
Removed. To detect a minor edit check the type as follows:
$parsed_logline['type']

darcs-hash:20060830182753-05dcb-1c5ea17f581197a33732a8d11da223d809c03506.gz

1 files changed, 177 insertions, 0 deletions

diff --git a/lib/plugins/importoldchangelog/action.php b/lib/plugins/importoldchangelog/action.php
new file mode 100644
index 000000000..400ff6a18
--- /dev/null
+++ b/lib/plugins/importoldchangelog/action.php
@@ -0,0 +1,177 @@
+<?php
+// must be run within Dokuwiki
+if(!defined('DOKU_INC')) die();
+
+if(!defined('DOKU_PLUGIN')) define('DOKU_PLUGIN',DOKU_INC.'lib/plugins/');
+require_once(DOKU_PLUGIN.'action.php');
+
+class action_plugin_importoldchangelog extends DokuWiki_Action_Plugin {
+
+	function getInfo(){
+		return array(
+			'author' => 'Ben Coburn',
+			'email'  => 'btcoburn@silicodon.net',
+			'date'   => '2006-08-30',
+			'name'   => 'Import Old Changelog',
+			'desc'   => 'Imports and converts the single file changelog '.
+                        'from the 2006-03-09b release to the new format. '.
+                        'Also reconstructs missing changelog data from  '.
+                        'old revisions kept in the attic.',
+            'url'    => 'http://wiki.splitbrain.org/wiki:changelog'
+			);
+	}
+
+	function register(&$controller) {
+        $controller->register_hook('TEMPORARY_CHANGELOG_UPGRADE_EVENT', 'BEFORE', $this, 'run_import');
+	}
+
+    function importOldLog($line, &$logs) {
+        global $lang;
+        /*
+        // Note: old log line format
+        //$info['date']  = $tmp[0];
+        //$info['ip']    = $tmp[1];
+        //$info['id']    = $tmp[2];
+        //$info['user']  = $tmp[3];
+        //$info['sum']   = $tmp[4];
+        */
+        $oldline = @explode("\t", $line);
+        if ($oldline!==false && count($oldline)>1) {
+            // trim summary
+            $wasMinor = (substr($oldline[4], 0, 1)==='*');
+            $sum = rtrim(substr($oldline[4], 1), "\n");
+            // guess line type
+            $type = 'E';
+            if ($wasMinor) { $type = 'e'; }
+            if ($sum===$lang['created']) { $type = 'C'; }
+            if ($sum===$lang['deleted']) { $type = 'D'; }
+            // build new log line
+            $tmp = array();
+            $tmp['date']  = $oldline[0];
+            $tmp['ip']    = $oldline[1];
+            $tmp['type']  = $type;
+            $tmp['id']    = $oldline[2];
+            $tmp['user']  = $oldline[3];
+            $tmp['sum']   = $sum;
+            $tmp['extra'] = '';
+            // order line by id
+            if (!isset($logs[$tmp['id']])) { $logs[$tmp['id']] = array(); }
+            $logs[$tmp['id']][$tmp['date']] = $tmp;
+        }
+    }
+
+    function importFromAttic(&$logs) {
+        global $conf, $lang;
+        $base = $conf['olddir'];
+        $stack = array('');
+        $context = ''; // namespace
+        while (count($stack)>0){
+            $context = array_pop($stack);
+            $dir = dir($base.'/'.str_replace(':', '/', $context));
+
+            while (($file = $dir->read()) !== false) {
+                if ($file==='.' || $file==='..') { continue; }
+                $matches = array();
+                if (preg_match('/([^.]*)\.([^.]*)\..*/', $file, $matches)===1) {
+                    $id = (($context=='')?'':$context.':').$matches[1];
+                    $date = $matches[2];
+
+                    // check if page & revision are already logged
+                    if (!isset($logs[$id])) { $logs[$id] = array(); }
+                    if (!isset($logs[$id][$date])) {
+                        $tmp = array();
+                        $tmp['date']  = $date;
+                        $tmp['ip']    = '127.0.0.1'; // original ip lost
+                        $tmp['type']  = 'E';
+                        $tmp['id']    = $id;
+                        $tmp['user']  = ''; // original user lost
+                        $tmp['sum']   = '('.$lang['restored'].')'; // original summary lost
+                        $tmp['extra'] = '';
+                        $logs[$id][$date] = $tmp;
+                    }
+
+                } else if (is_dir($dir->path.'/'.$file)) {
+                    array_push($stack, (($context=='')?'':$context.':').$file);
+                }
+
+            }
+
+            $dir->close();
+        }
+
+    }
+
+    function savePerPageChanges($id, &$changes, &$recent, $trim_time) {
+        $out_lines = array();
+        ksort($changes); // ensure correct order of changes from attic
+        foreach ($changes as $tmp) {
+            $line = implode("\t", $tmp)."\n";
+            array_push($out_lines, $line);
+            if ($tmp['date']>$trim_time) {
+                $recent[$tmp['date']] = $line;
+            }
+        }
+        io_saveFile(metaFN($id, '.changes'), implode('', $out_lines));
+    }
+
+    function resetTimer() {
+        // Add 5 minutes to the script execution timer...
+        // This should be much more than needed.
+        set_time_limit(5*60);
+        // Note: Has no effect in safe-mode!
+    }
+
+    function run_import(&$event, $args) {
+        global $conf;
+        register_shutdown_function('importoldchangelog_plugin_shutdown');
+        touch($conf['changelog'].'_importing'); // changelog importing lock
+        io_saveFile($conf['changelog'], ''); // pre-create changelog
+        io_lock($conf['changelog']);  // hold onto the lock
+        // load old changelog
+        $this->resetTimer();
+        $log = array();
+        $oldlog = file($conf['changelog_old']);
+        foreach ($oldlog as $line) {
+            $this->importOldLog($line, $log);
+        }
+        unset($oldlog); // free memory
+        // look in the attic for unlogged revisions
+        $this->resetTimer();
+        $this->importFromAttic($log);
+        // save per-page changelogs
+        $this->resetTimer();
+        $recent = array();
+        $trim_time = time() - $conf['recent_days']*86400;
+        foreach ($log as $id => $page) {
+            $this->savePerPageChanges($id, $page, $recent, $trim_time);
+        }
+        // save recent changes cache
+        $this->resetTimer();
+        ksort($recent); // ensure correct order of recent changes
+        io_unlock($conf['changelog']); // hand off the lock to io_saveFile
+        io_saveFile($conf['changelog'], implode('', $recent));
+        unlink($conf['changelog'].'_importing'); // changelog importing unlock
+    }
+
+}
+
+function importoldchangelog_plugin_shutdown() {
+    global $conf;
+    $path = array();
+    $path['changelog'] = $conf['changelog'];
+    $path['importing'] = $conf['changelog'].'_importing';
+    $path['failed']    = $conf['changelog'].'_failed';
+    $path['import_ok'] = $conf['changelog'].'_import_ok';
+    io_unlock($path['changelog']); // guarantee unlocking
+    if (file_exists($path['importing'])) {
+        // import did not finish
+        rename($path['importing'], $path['failed']) or trigger_error('Importing changelog failed.', E_USER_WARNING);
+        @unlink($path['import_ok']);
+    } else {
+        // import successful
+        touch($path['import_ok']);
+        @unlink($path['failed']);
+    }
+}
+
+