From 4fc5ba8bf83102b02256ff3173501b9f6b609234 Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Mon, 15 Oct 2018 08:08:24 -0700
Subject: [PATCH] messagecache: check overridable message array in
 getMsgFromNamespace()

Follow up to a3d6c1411dad.

This avoids extra queries for messages that have a software defined value.

Bug: T193271
Change-Id: I25aa0e27200a0b417721cf1fbd34a82095405b89
---
 includes/cache/MessageCache.php               | 29 ++++++++++++++-----
 .../includes/cache/MessageCacheTest.php       | 17 +++++++++++
 2 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/includes/cache/MessageCache.php b/includes/cache/MessageCache.php
index 4e0d0a7580..869f768c44 100644
--- a/includes/cache/MessageCache.php
+++ b/includes/cache/MessageCache.php
@@ -52,6 +52,13 @@ class MessageCache {
 	 */
 	protected $cache;
 
+	/**
+	 * Map of (lowercase message key => index) for all software defined messages
+	 *
+	 * @var array
+	 */
+	protected $overridable;
+
 	/**
 	 * @var bool[] Map of (language code => boolean)
 	 */
@@ -258,6 +265,8 @@ class MessageCache {
 			return true;
 		}
 
+		$this->overridable = array_flip( Language::getMessageKeysFor( $code ) );
+
 		# 8 lines of code just to say (once) that message cache is disabled
 		if ( $this->mDisable ) {
 			static $shownDisabled = false;
@@ -1029,14 +1038,18 @@ class MessageCache {
 				$this->cache->getField( $code, 'HASH' )
 			);
 		} else {
-			// Message page does not exist or does not override a software message.
-			// Load the message page, utilizing the individual message cache.
-			$entry = $this->loadCachedMessagePageEntry(
-				$title,
-				$code,
-				$this->cache->getField( $code, 'HASH' )
-			);
-			if ( substr( $entry, 0, 1 ) !== ' ' ) {
+			// Message page either does not exist or does not override a software message
+			if ( !isset( $this->overridable[$this->contLang->lcfirst( $title )] ) ) {
+				// Message page does not override any software-defined message. A custom
+				// message might be defined to have content or settings specific to the wiki.
+				// Load the message page, utilizing the individual message cache as needed.
+				$entry = $this->loadCachedMessagePageEntry(
+					$title,
+					$code,
+					$this->cache->getField( $code, 'HASH' )
+				);
+			}
+			if ( $entry === null || substr( $entry, 0, 1 ) !== ' ' ) {
 				// Message does not have a MediaWiki page definition; try hook handlers
 				$message = false;
 				Hooks::run( 'MessagesPreLoad', [ $title, &$message, $code ] );
diff --git a/tests/phpunit/includes/cache/MessageCacheTest.php b/tests/phpunit/includes/cache/MessageCacheTest.php
index 661f325149..c340c08e49 100644
--- a/tests/phpunit/includes/cache/MessageCacheTest.php
+++ b/tests/phpunit/includes/cache/MessageCacheTest.php
@@ -196,4 +196,21 @@ class MessageCacheTest extends MediaWikiLangTestCase {
 			[ 'ćaB', 'ćaB' ],
 		];
 	}
+
+	public function testNoDBAccess() {
+		global $wgContLanguageCode;
+
+		$dbr = wfGetDB( DB_REPLICA );
+
+		MessageCache::singleton()->getMsgFromNamespace( 'allpages', $wgContLanguageCode );
+
+		$this->assertEquals( 0, $dbr->trxLevel() );
+		$dbr->setFlag( DBO_TRX, $dbr::REMEMBER_PRIOR ); // make queries trigger TRX
+
+		MessageCache::singleton()->getMsgFromNamespace( 'go', $wgContLanguageCode );
+
+		$dbr->restoreFlags();
+
+		$this->assertEquals( 0, $dbr->trxLevel(), "No DB read queries" );
+	}
 }
-- 
2.20.1