From: Roan Kattouw <catrope@users.mediawiki.org>
Date: Sat, 12 Dec 2009 15:38:03 +0000 (+0000)
Subject: Add maintenance script for running queries in batches. This is especially useful... 
X-Git-Tag: 1.31.0-rc.0~38558
X-Git-Url: https://git.cyclocoop.org/%7B%24admin_url%7Dmembres/fiche.php?a=commitdiff_plain;h=7c47f02b7c043bdd7d14e2dc8fd7939d4bce8ad3;p=lhc%2Fweb%2Fwiklou.git

Add maintenance script for running queries in batches. This is especially useful for executing large write queries (e.g. fixing user renames, clearing huge watchlists) on the WMF cluster; before, everyone wrote their own script for this when they needed it.
---

diff --git a/maintenance/runBatchedQuery.php b/maintenance/runBatchedQuery.php
new file mode 100644
index 0000000000..0a113cc265
--- /dev/null
+++ b/maintenance/runBatchedQuery.php
@@ -0,0 +1,60 @@
+<?php
+/**
+ * Run a database query in batches and wait for slaves. This is used on large
+ * wikis to prevent replication lag from going through the roof when executing
+ * large write queries.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @ingroup Maintenance
+ */
+
+require_once( dirname(__FILE__) . '/Maintenance.php' );
+
+class BatchedQueryRunner extends Maintenance {
+	public function __construct() {
+		parent::__construct();
+		$this->mDescription = "Run a query repeatedly until it affects 0 rows, and wait for slaves in between.\n" .
+				"NOTE: You need to set a LIMIT clause yourself.";
+		$this->addOption( 'wait', "Wait for replication lag to go down to this value. Default: 5", false, true );
+	}
+
+	public function execute() {
+		if ( !$this->hasArg() )
+			$this->error( "No query specified. Specify the query as a command line parameter.", true );
+		
+		$query = $this->getArg();
+		$wait = $this->getOption( 'wait', 5 );
+		$n = 1;
+		$dbw = wfGetDb( DB_MASTER );
+		do {
+			$this->output( "Batch $n: " );
+			$n++;
+			$dbw->query( $query );
+			$affected = $dbw->affectedRows();
+			$this->output( "$affected rows\n" );
+			wfWaitForSlaves( $wait );
+		} while ( $affected > 0 );
+	}
+
+	protected function getDbType() {
+		return Maintenance::DB_ADMIN;
+	}
+}
+
+
+$maintClass = "BatchedQueryRunner";
+require_once( DO_MAINTENANCE );