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<title>[38229] trunk/src/wp-admin/network/upgrade.php: Multisite: Improve performance of the upgrade page on large networks.</title>
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<dt style="float: left; width: 6em; font-weight: bold">Revision</dt> <dd><a style="font-weight: bold" href="https://core.trac.wordpress.org/changeset/38229">38229</a><script type="application/ld+json">{"@context":"http://schema.org","@type":"EmailMessage","description":"Review this Commit","action":{"@type":"ViewAction","url":"https://core.trac.wordpress.org/changeset/38229","name":"Review Commit"}}</script></dd>
<dt style="float: left; width: 6em; font-weight: bold">Author</dt> <dd>pento</dd>
<dt style="float: left; width: 6em; font-weight: bold">Date</dt> <dd>2016-08-09 11:38:41 +0000 (Tue, 09 Aug 2016)</dd>
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<pre style='padding-left: 1em; margin: 2em 0; border-left: 2px solid #ccc; line-height: 1.25; font-size: 105%; font-family: sans-serif'>Multisite: Improve performance of the upgrade page on large networks.
The query to select the next 5 blogs to upgrade was ordered by `registered`, which isn't indexed. This causes the query to table scan, which will be slow on networks with many blogs.
The query only needs to be ordered by something that won't change, so ordering by `blog_id` is a good replacement. `blog_id` is indexed, and it's the only column being returned, so MySQL is able to optimize for a fast index read.
Props fliespl.
Fixes <a href="https://core.trac.wordpress.org/ticket/37612">#37612</a>.</pre>
<h3>Modified Paths</h3>
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<li><a href="#trunksrcwpadminnetworkupgradephp">trunk/src/wp-admin/network/upgrade.php</a></li>
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<a id="trunksrcwpadminnetworkupgradephp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-admin/network/upgrade.php</h4>
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<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-admin/network/upgrade.php 2016-08-09 10:40:06 UTC (rev 38228)
+++ trunk/src/wp-admin/network/upgrade.php 2016-08-09 11:38:41 UTC (rev 38229)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -55,7 +55,7 @@
</span><span class="cx" style="display: block; padding: 0 10px"> update_site_option( 'wpmu_upgrade_site', $wp_db_version );
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px">
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- $blogs = $wpdb->get_results( "SELECT blog_id FROM {$wpdb->blogs} WHERE site_id = '{$wpdb->siteid}' AND spam = '0' AND deleted = '0' AND archived = '0' ORDER BY registered DESC LIMIT {$n}, 5", ARRAY_A );
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ $blogs = $wpdb->get_results( "SELECT blog_id FROM {$wpdb->blogs} WHERE site_id = '{$wpdb->siteid}' AND spam = '0' AND deleted = '0' AND archived = '0' ORDER BY blog_id DESC LIMIT {$n}, 5", ARRAY_A );
</ins><span class="cx" style="display: block; padding: 0 10px"> if ( empty( $blogs ) ) {
</span><span class="cx" style="display: block; padding: 0 10px"> echo '<p>' . __( 'All done!' ) . '</p>';
</span><span class="cx" style="display: block; padding: 0 10px"> break;
</span></span></pre>
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