From bf40d6267cca491fd4d575af4ec4b1db455840ff Mon Sep 17 00:00:00 2001
From: =?utf8?q?Gerg=C5=91=20Tisza?= <tgr.huwiki@gmail.com>
Date: Thu, 5 Feb 2015 03:43:22 +0000
Subject: [PATCH] Add File::getDescriptionTouched() method

Fetch page_touched timestamp of file description page via a DB query
(possibly to a foreign DB).

Not sure about the performance implications; could add a memcached
layer on top, but the same DB lookup was already done for local
files.

Bug: T88648
Change-Id: I891c806aab235ff2c0e73c98b06b64fbe78e1517
---
 includes/filerepo/file/File.php      | 11 +++++++++++
 includes/filerepo/file/LocalFile.php | 19 +++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/includes/filerepo/file/File.php b/includes/filerepo/file/File.php
index df85f9c723..6ca61b26b7 100644
--- a/includes/filerepo/file/File.php
+++ b/includes/filerepo/file/File.php
@@ -2046,6 +2046,17 @@ abstract class File {
 		return $this->repo->getFileTimestamp( $this->getPath() );
 	}
 
+	/**
+	 * Returns the timestamp (in TS_MW format) of the last change of the description page.
+	 * Returns false if the file does not have a description page, or retrieving the timestamp
+	 * would be expensive.
+	 * @since 1.25
+	 * @return string|bool
+	 */
+	public function getDescriptionTouched() {
+		return false;
+	}
+
 	/**
 	 * Get the SHA-1 base 36 hash of the file
 	 *
diff --git a/includes/filerepo/file/LocalFile.php b/includes/filerepo/file/LocalFile.php
index b2e5b00fa4..699c9154a2 100644
--- a/includes/filerepo/file/LocalFile.php
+++ b/includes/filerepo/file/LocalFile.php
@@ -109,6 +109,9 @@ class LocalFile extends File {
 	/** @var string Description of current revision of the file */
 	private $description;
 
+	/** @var string TS_MW timestamp of the last change of the file description */
+	private $descriptionTouched;
+
 	/** @var bool Whether the row was upgraded on load */
 	private $upgraded;
 
@@ -1777,6 +1780,22 @@ class LocalFile extends File {
 		return $this->timestamp;
 	}
 
+	/**
+	 * @return bool|string
+	 */
+	public function getDescriptionTouched() {
+		// The DB lookup might return false, e.g. if the file was just deleted, or the shared DB repo
+		// itself gets it from elsewhere. To avoid repeating the DB lookups in such a case, we
+		// need to differentiate between null (uninitialized) and false (failed to load).
+		if ( $this->descriptionTouched === null ) {
+			$cond = array( 'page_namespace' => $this->title->getNamespace(), 'page_title' => $this->title->getDBkey() );
+			$touched = $this->repo->getSlaveDB()->selectField( 'page', 'page_touched', $cond, __METHOD__ );
+			$this->descriptionTouched = $touched ? wfTimestamp( TS_MW, $touched ) : false;
+		}
+
+		return $this->descriptionTouched;
+	}
+
 	/**
 	 * @return string
 	 */
-- 
2.20.1