From 3342fafb4839a27b0be3a6e02149e1accf63cc87 Mon Sep 17 00:00:00 2001
From: Brian Wolff <bawolff+wn@gmail.com>
Date: Fri, 7 Jun 2013 14:29:56 -0300
Subject: [PATCH] Make Special:MIMESearch a non-expensive special page.

This tries to use the index on (img_media_type, img_major_mime, img_minor_mime).
This is not the ideal index for this purpose (due to starting with
img_media_type, and not having an img_name at the end). However it
seems usable due to the low number of values img_media_type can have.
Thus we can just specify all values, and the index will get used
as a range index.

The only potentially problematic thing I see is that it uses
LIMIT X,Y for the offsets (due to being a query page) which can
be expensive on big offsets. If that's an issue, we could limit
the number of results to be at most $wgQueryCacheLimit or something.

Note: There's some discussion on the bug rather negative to this
special page in general. While I agree with much of the criticism,
I still think this special page can be useful, and if it can be
made efficient without needing to modify the indicies, we might
as well.

Bug: 13438
Change-Id: I88826ae7bff0812374157e596f86a19b248220e1
---
 RELEASE-NOTES-1.22                      |  1 +
 includes/QueryPage.php                  |  2 +-
 includes/specials/SpecialMIMEsearch.php | 39 +++++++++++++++++++++----
 3 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/RELEASE-NOTES-1.22 b/RELEASE-NOTES-1.22
index 68e14dc7b1..c1f91bc83b 100644
--- a/RELEASE-NOTES-1.22
+++ b/RELEASE-NOTES-1.22
@@ -217,6 +217,7 @@ production.
   for non-inclusion in ApiQueryQueryPages.
 * (bug 50870) mediawiki.notification: Notification area should remain visible
   when scrolled down.
+* (bug 13438) Special:MIMESearch no longer an expensive special page.
 
 === API changes in 1.22 ===
 * (bug 25553) The JSON output formatter now leaves forward slashes unescaped
diff --git a/includes/QueryPage.php b/includes/QueryPage.php
index 0abeb31e0f..699c843c49 100644
--- a/includes/QueryPage.php
+++ b/includes/QueryPage.php
@@ -588,7 +588,7 @@ abstract class QueryPage extends SpecialPage {
 
 			# $res might contain the whole 1,000 rows, so we read up to
 			# $num [should update this to use a Pager]
-			for ( $i = 0; $i < $num && $row = $dbr->fetchObject( $res ); $i++ ) {
+			for ( $i = 0; $i < $num && $row = $res->fetchObject(); $i++ ) {
 				$line = $this->formatResult( $skin, $row );
 				if ( $line ) {
 					$attr = ( isset( $row->usepatrol ) && $row->usepatrol && $row->patrolled == 0 )
diff --git a/includes/specials/SpecialMIMEsearch.php b/includes/specials/SpecialMIMEsearch.php
index 7ff5d7b550..3eeae310e0 100644
--- a/includes/specials/SpecialMIMEsearch.php
+++ b/includes/specials/SpecialMIMEsearch.php
@@ -35,7 +35,7 @@ class MIMEsearchPage extends QueryPage {
 	}
 
 	function isExpensive() {
-		return true;
+		return false;
 	}
 
 	function isSyndicated() {
@@ -51,12 +51,14 @@ class MIMEsearchPage extends QueryPage {
 	}
 
 	public function getQueryInfo() {
-		return array(
+		$qi = array(
 			'tables' => array( 'image' ),
 			'fields' => array(
 				'namespace' => NS_FILE,
 				'title' => 'img_name',
-				'value' => 'img_major_mime',
+				// Still have a value field just in case,
+				// but it isn't actually used for sorting.
+				'value' => 'img_name',
 				'img_size',
 				'img_width',
 				'img_height',
@@ -65,9 +67,36 @@ class MIMEsearchPage extends QueryPage {
 			),
 			'conds' => array(
 				'img_major_mime' => $this->major,
-				'img_minor_mime' => $this->minor
-			)
+				'img_minor_mime' => $this->minor,
+				// This is in order to trigger using
+				// the img_media_mime index in "range" mode.
+				'img_media_type' => array(
+					MEDIATYPE_BITMAP,
+					MEDIATYPE_DRAWING,
+					MEDIATYPE_AUDIO,
+					MEDIATYPE_VIDEO,
+					MEDIATYPE_MULTIMEDIA,
+					MEDIATYPE_UNKNOWN,
+					MEDIATYPE_OFFICE,
+					MEDIATYPE_TEXT,
+					MEDIATYPE_EXECUTABLE,
+					MEDIATYPE_ARCHIVE,
+				),
+			),
 		);
+		return $qi;
+	}
+
+	/**
+	 * The index is on (img_media_type, img_major_mime, img_minor_mime)
+	 * which unfortunately doesn't have img_name at the end for sorting.
+	 * So tell db to sort it however it wishes (Its not super important
+	 * that this report gives results in a logical order). As an aditional
+	 * note, mysql seems to by default order things by img_name ASC, which
+	 * is what we ideally want, so everything works out fine anyhow.
+	 */
+	function getOrderFields() {
+		return array();
 	}
 
 	function execute( $par ) {
-- 
2.20.1