From 3a10ab5965b965f7512b652d0df99afffc510e46 Mon Sep 17 00:00:00 2001
From: Brad Jorsch <bjorsch@wikimedia.org>
Date: Fri, 16 Jun 2017 14:57:42 -0400
Subject: [PATCH] Adjust Shortpages query with multiple content namespaces

MariaDB can't effectively use the page_redirect_namespace_len index when
there are multiple namespaces. Instead, let's query each namespace
individually and UNION them together.

Bug: T168010
Change-Id: I632fbc599e06a3c2faabd55f5d87339f968f58bb
---
 includes/specials/SpecialShortpages.php | 51 +++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/includes/specials/SpecialShortpages.php b/includes/specials/SpecialShortpages.php
index 3282a7a1cd..f980e7112c 100644
--- a/includes/specials/SpecialShortpages.php
+++ b/includes/specials/SpecialShortpages.php
@@ -65,6 +65,57 @@ class ShortPagesPage extends QueryPage {
 		];
 	}
 
+	public function reallyDoQuery( $limit, $offset = false ) {
+		$fname = static::class . '::reallyDoQuery';
+		$dbr = $this->getRecacheDB();
+		$query = $this->getQueryInfo();
+		$order = $this->getOrderFields();
+
+		if ( $this->sortDescending() ) {
+			foreach ( $order as &$field ) {
+				$field .= ' DESC';
+			}
+		}
+
+		$tables = isset( $query['tables'] ) ? (array)$query['tables'] : [];
+		$fields = isset( $query['fields'] ) ? (array)$query['fields'] : [];
+		$conds = isset( $query['conds'] ) ? (array)$query['conds'] : [];
+		$options = isset( $query['options'] ) ? (array)$query['options'] : [];
+		$join_conds = isset( $query['join_conds'] ) ? (array)$query['join_conds'] : [];
+
+		if ( $limit !== false ) {
+			$options['LIMIT'] = intval( $limit );
+		}
+
+		if ( $offset !== false ) {
+			$options['OFFSET'] = intval( $offset );
+		}
+
+		$namespaces = $conds['page_namespace'];
+		if ( count( $namespaces ) === 1 ) {
+			$options['ORDER BY'] = $order;
+			$res = $dbr->select( $tables, $fields, $conds, $fname,
+				$options, $join_conds
+			);
+		} else {
+			unset( $conds['page_namespace'] );
+			$options['INNER ORDER BY'] = $order;
+			$options['ORDER BY'] = [ 'value' . ( $this->sortDescending() ? ' DESC' : '' ) ];
+			$sql = $dbr->unionConditionPermutations(
+				$tables,
+				$fields,
+				[ 'page_namespace' => $namespaces ],
+				$conds,
+				$fname,
+				$options,
+				$join_conds
+			);
+			$res = $dbr->query( $sql, $fname );
+		}
+
+		return $res;
+	}
+
 	function getOrderFields() {
 		return [ 'page_len' ];
 	}
-- 
2.20.1