From: Aaron Schulz <aschulz@wikimedia.org>
Date: Wed, 18 Apr 2018 23:09:55 +0000 (-0700)
Subject: Avoid locking aggregated SELECT in Category::refresh
X-Git-Tag: 1.34.0-rc.0~5635^2
X-Git-Url: http://git.cyclocoop.org/%22%20.%20generer_url_ecrire%28%22articles%22%2C%22id_article=%24id_article%22%29%20.%20%22?a=commitdiff_plain;h=3fc98b9c6ba6a8298eec77f4f2b8f9bad0890196;p=lhc%2Fweb%2Fwiklou.git

Avoid locking aggregated SELECT in Category::refresh

LOCK IN SHARE MODE is not allowed with aggregation on postgres/oracle.
Split out the locking and aggregation into two separate queries.

Change-Id: I7f8d113fb678b368437dad84bdb93e81db314cd5
---

diff --git a/includes/Category.php b/includes/Category.php
index 9241730a04..ac5cc42e35 100644
--- a/includes/Category.php
+++ b/includes/Category.php
@@ -335,18 +335,28 @@ class Category {
 
 		$dbw->startAtomic( __METHOD__ );
 
-		$cond1 = $dbw->conditional( [ 'page_namespace' => NS_CATEGORY ], 1, 'NULL' );
-		$cond2 = $dbw->conditional( [ 'page_namespace' => NS_FILE ], 1, 'NULL' );
-		$result = $dbw->selectRow(
+		// Lock all the `categorylinks` records and gaps for this category;
+		// this is a separate query due to postgres/oracle limitations
+		$dbw->selectRowCount(
 			[ 'categorylinks', 'page' ],
-			[ 'pages' => 'COUNT(*)',
-				'subcats' => "COUNT($cond1)",
-				'files' => "COUNT($cond2)"
-			],
+			'*',
 			[ 'cl_to' => $this->mName, 'page_id = cl_from' ],
 			__METHOD__,
 			[ 'LOCK IN SHARE MODE' ]
 		);
+		// Get the aggregate `categorylinks` row counts for this category
+		$catCond = $dbw->conditional( [ 'page_namespace' => NS_CATEGORY ], 1, 'NULL' );
+		$fileCond = $dbw->conditional( [ 'page_namespace' => NS_FILE ], 1, 'NULL' );
+		$result = $dbw->selectRow(
+			[ 'categorylinks', 'page' ],
+			[
+				'pages' => 'COUNT(*)',
+				'subcats' => "COUNT($catCond)",
+				'files' => "COUNT($fileCond)"
+			],
+			[ 'cl_to' => $this->mName, 'page_id = cl_from' ],
+			__METHOD__
+		);
 
 		$shouldExist = $result->pages > 0 || $this->getTitle()->exists();