From 4c73c8a67647c1daaa3bdfa798a32c13ae466e6f Mon Sep 17 00:00:00 2001
From: Piotr Miazga <piotr@polishdeveloper.pl>
Date: Thu, 8 Nov 2018 18:45:47 -0500
Subject: [PATCH] Provide a script to reset the page_random column

Bug: T208909
Change-Id: I914ff44d1212c565e08ff17effbd682dfe7f70fb
---
 autoload.php                    |   1 +
 maintenance/resetPageRandom.php | 126 ++++++++++++++++++++++++++++++++
 2 files changed, 127 insertions(+)
 create mode 100644 maintenance/resetPageRandom.php

diff --git a/autoload.php b/autoload.php
index 3daeee1939..8e764ae7ef 100644
--- a/autoload.php
+++ b/autoload.php
@@ -1207,6 +1207,7 @@ $wgAutoloadLocalClasses = [
 	'RepoGroup' => __DIR__ . '/includes/filerepo/RepoGroup.php',
 	'RequestContext' => __DIR__ . '/includes/context/RequestContext.php',
 	'ResetAuthenticationThrottle' => __DIR__ . '/maintenance/resetAuthenticationThrottle.php',
+	'ResetPageRandom' => __DIR__ . '/maintenance/resetPageRandom.php',
 	'ResetUserEmail' => __DIR__ . '/maintenance/resetUserEmail.php',
 	'ResetUserTokens' => __DIR__ . '/maintenance/resetUserTokens.php',
 	'ResourceFileCache' => __DIR__ . '/includes/cache/ResourceFileCache.php',
diff --git a/maintenance/resetPageRandom.php b/maintenance/resetPageRandom.php
new file mode 100644
index 0000000000..61102218e2
--- /dev/null
+++ b/maintenance/resetPageRandom.php
@@ -0,0 +1,126 @@
+<?php
+/**
+ * Resets the page_random field for articles in the provided time range.
+ *
+ * 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
+ *
+ * @file
+ * @ingroup Maintenance
+ */
+
+require_once __DIR__ . '/Maintenance.php';
+
+/**
+ * Maintenance script that resets page_random over a time range.
+ *
+ * @ingroup Maintenance
+ */
+class ResetPageRandom extends Maintenance {
+	public function __construct() {
+		parent::__construct();
+		$this->addDescription( 'Reset the page_random for articles within given date range' );
+		$this->addOption( 'from',
+			'From date range selector to select articles to update, ex: 20041011000000' );
+		$this->addOption( 'to',
+			'To date range selector to select articles to update, ex: 20050708000000' );
+		$this->addOption( 'dry', 'Do not update column' );
+		$this->addOption( 'batch-start',
+			'Optional: Use when you need to restart the reset process from a given page ID offset'
+			. ' in case a previous reset failed or was stopped'
+		);
+		// Initialize batch size to a good default value and enable the batch size option.
+		$this->setBatchSize( 200 );
+	}
+
+	public function execute() {
+		$batchSize = $this->getBatchSize();
+		$dbw = $this->getDB( DB_MASTER );
+		$lbFactory = \MediaWiki\MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
+		$dbr = $this->getDB( DB_REPLICA );
+		$from = wfTimestampOrNull( TS_MW, $this->getOption( 'from' ) );
+		$to = wfTimestampOrNull( TS_MW, $this->getOption( 'to' ) );
+
+		if ( $from === null || $to === null ) {
+			$this->output( "--from and --to have to be provided" . PHP_EOL );
+			return false;
+		}
+		if ( $from >= $to ) {
+			$this->output( "--from has to be smaller than --to" . PHP_EOL );
+			return false;
+		}
+		$batchStart = (int)$this->getOption( 'batch-start', 0 );
+		$changed = 0;
+		$dry = (bool)$this->getOption( 'dry' );
+
+		$message = "Resetting page_random column within date range from $from to $to";
+		if ( $batchStart > 0 ) {
+			$message .= " starting from page ID $batchStart";
+		}
+		$message .= $dry ? ". dry run" : '.';
+
+		$this->output( $message . PHP_EOL );
+		do {
+			$this->output( "  ...doing chunk of $batchSize from $batchStart " . PHP_EOL );
+
+			// Find the oldest page revision associated with each page_id. Iff it falls in the given
+			// time range AND it's greater than $batchStart, yield the page ID. If it falls outside the
+			// time range, it was created before or after the occurrence of T208909 and its page_random
+			// is considered valid. The replica is used for this read since page_id and the rev_timestamp
+			// will not change between queries.
+			$res = $dbr->select(
+				'page',
+				'page_id',
+				[
+					'(' . $dbr->selectSQLText( 'revision', 'MIN(rev_timestamp)', 'rev_page=page_id' ) . ') ' .
+						'BETWEEN ' . $dbr->addQuotes( $dbr->timestamp( $from ) ) .
+						' AND ' . $dbr->addQuotes( $dbr->timestamp( $to ) ),
+					'page_id > ' . $dbr->addQuotes( $batchStart )
+				],
+				__METHOD__,
+				[ 'LIMIT' => $batchSize, 'ORDER BY' => 'page_id' ]
+			);
+
+			foreach ( $res as $row ) {
+				if ( !$dry ) {
+					# Update the row...
+					$dbw->update( 'page',
+						[ 'page_random' => wfRandom() ],
+						[ 'page_id' => $row->page_id ],
+						__METHOD__ );
+					$changed += $dbw->affectedRows();
+				} else {
+					$changed++;
+				}
+			}
+			if ( $row ) {
+				$batchStart = $row->page_id;
+			} else {
+				// We don't need to set the $batchStart as $res is empty,
+				// and we don't need to do another loop
+				// the while() condition will evaluate to false and
+				// we will leave the do{}while() block.
+			}
+
+			$lbFactory->waitForReplication();
+		} while ( $res->numRows() === $batchSize );
+		$this->output( "page_random reset complete ... changed $changed rows" . PHP_EOL );
+
+		return true;
+	}
+}
+
+$maintClass = ResetPageRandom::class;
+require_once RUN_MAINTENANCE_IF_MAIN;
-- 
2.20.1