Bringing Sphinx search support up to code: broken out to a plugin, now supports multiple sites on a single server.

Upgrade notes:
* Index names have changed from hardcoded 'Identica_people' and 'Identica_notices' to use the database name and actual table names. Must reindex.

New events:
* GetSearchEngine to override default search engine class selection from plugins

New scripts:
* gen_config.php generates a sphinx.conf from database configuration (with theoretical support for status_network table, but it doesn't seem to be cleanly queriable right now without knowing the db setup info for that. Needs generalized support.)
* Replaced old sphinx-indexer.sh and sphinx-cron.sh with index_update.php

Other fixes:
* sphinx.conf.sample better matches our live config, skipping unused stopword list and using a more realistic indexer memory limit

Further notes:
* Probably doesn't work right with PostgreSQL yet; Sphinx can pull from PG but the extraction queries currently look like they use some MySQL-specific functions.

plugins/SphinxSearch/SphinxSearchPlugin.php

@@ -0,0 +1,100 @@
+<?php
+/**
+ * StatusNet, the distributed open-source microblogging tool
+ *
+ * PHP version 5
+ *
+ * LICENCE: This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @category  Plugin
+ * @package   StatusNet
+ * @author    Brion Vibber <brion@status.net>
+ * @copyright 2009 Control Yourself, Inc.
+ * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link      http://laconi.ca/
+ */
+
+if (!defined('STATUSNET')) {
+    exit(1);
+}
+
+// Set defaults if not already set in the config array...
+global $config;
+$sphinxDefaults =
+    array('enabled' => true,
+          'server' => 'localhost',
+          'port' => 3312);
+foreach($sphinxDefaults as $key => $val) {
+    if (!isset($config['sphinx'][$key])) {
+        $config['sphinx'][$key] = $val;
+    }
+}
+
+
+
+/**
+ * Plugin for Sphinx search backend.
+ *
+ * @category Plugin
+ * @package  StatusNet
+ * @author   Brion Vibber <brion@status.net>
+ * @license  http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link     http://laconi.ca/
+ * @link     http://twitter.com/
+ */
+
+class SphinxSearchPlugin extends Plugin
+{
+    /**
+     * Automatically load any classes used
+     *
+     * @param string $cls the class
+     * @return boolean hook return
+     */
+    function onAutoload($cls)
+    {
+        switch ($cls) {
+        case 'SphinxSearch':
+            include_once INSTALLDIR . '/plugins/SphinxSearch/' .
+              strtolower($cls) . '.php';
+            return false;
+        default:
+            return true;
+        }
+    }
+
+    /**
+     * Create sphinx search engine object for the given table type.
+     *
+     * @param Memcached_DataObject $target
+     * @param string $table
+     * @param out &$search_engine SearchEngine object on output if successful
+     * @ return boolean hook return
+     */
+    function onGetSearchEngine(Memcached_DataObject $target, $table, &$search_engine)
+    {
+        if (common_config('sphinx', 'enabled')) {
+            if (!class_exists('SphinxClient')) {
+                throw new ServerException('Sphinx PHP extension must be installed.');
+            }
+            $engine = new SphinxSearch($target, $table);
+            if ($engine->is_connected()) {
+                $search_engine = $engine;
+                return false;
+            }
+        }
+        // Sphinx disabled or disconnected
+        return true;
+    }
+}