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<title>[30238] trunk/src/wp-includes/taxonomy.php: In `wp_insert_term()`, clean up accidental duplicate terms after insert.</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/30238">30238</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/30238","name":"Review Commit"}}</script></dd>
<dt style="float: left; width: 6em; font-weight: bold">Author</dt> <dd>boonebgorges</dd>
<dt style="float: left; width: 6em; font-weight: bold">Date</dt> <dd>2014-11-05 00:59:51 +0000 (Wed, 05 Nov 2014)</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'>In `wp_insert_term()`, clean up accidental duplicate terms after insert.
In <a href="https://core.trac.wordpress.org/changeset/30056">[30056]</a>, the UNIQUE index was removed from the 'slug' column of `wp_terms`.
While we have numerous checks in place to avoid the creation of unwanted
duplicate term+term_taxonomy pairs, it's possible that in certain edge cases -
such as during the lag caused by database replication, or a race condition
involving near-simultaneous creation of more than one term - we'll end up
unwittingly inserting two identical rows.
The current changeset minimizes this risk by introducing a failsafe mechanism
into `wp_insert_term()`. After a term and term_taxonomy are INSERTed, we check
to see whether the term just created is a duplicate of an existing term; if so,
we delete the new one and keep the old one. This prevents problems caused by
replication lag, because SELECT queries that take place after an INSERT will
hit the master database; it mitigates race conditions by enforcing that the
term that was created first (ie, the one with the lowest `term_id`) is
always the "canonical" one.
Props nacin, markjaquith.
See <a href="https://core.trac.wordpress.org/ticket/22023">#22023</a>, <a href="https://core.trac.wordpress.org/ticket/5809">#5809</a>.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunksrcwpincludestaxonomyphp">trunk/src/wp-includes/taxonomy.php</a></li>
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<h3>Diff</h3>
<a id="trunksrcwpincludestaxonomyphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-includes/taxonomy.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-includes/taxonomy.php 2014-11-04 21:18:22 UTC (rev 30237)
+++ trunk/src/wp-includes/taxonomy.php 2014-11-05 00:59:51 UTC (rev 30238)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -2902,6 +2902,24 @@
</span><span class="cx" style="display: block; padding: 0 10px"> $wpdb->insert( $wpdb->term_taxonomy, compact( 'term_id', 'taxonomy', 'description', 'parent') + array( 'count' => 0 ) );
</span><span class="cx" style="display: block; padding: 0 10px"> $tt_id = (int) $wpdb->insert_id;
</span><span class="cx" style="display: block; padding: 0 10px">
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ /*
+ * Sanity check: if we just created a term with the same parent + taxonomy + slug but a higher term_id than
+ * an existing term, then we have unwittingly created a duplicate term. Delete the dupe, and use the term_id
+ * and term_taxonomy_id of the older term instead. Then return out of the function so that the "create" hooks
+ * are not fired.
+ */
+ $duplicate_term = $wpdb->get_row( $wpdb->prepare( "SELECT t.term_id, tt.term_taxonomy_id FROM $wpdb->terms t INNER JOIN $wpdb->term_taxonomy tt ON ( tt.term_id = t.term_id ) WHERE t.slug = %s AND tt.parent = %d AND tt.taxonomy = %s AND t.term_id < %d AND tt.term_taxonomy_id != %d", $slug, $parent, $taxonomy, $term_id, $tt_id ) );
+ if ( $duplicate_term ) {
+ $wpdb->delete( $wpdb->terms, array( 'term_id' => $term_id ) );
+ $wpdb->delete( $wpdb->term_taxonomy, array( 'term_taxonomy_id' => $tt_id ) );
+
+ $term_id = (int) $duplicate_term->term_id;
+ $tt_id = (int) $duplicate_term->term_taxonomy_id;
+
+ clean_term_cache( $term_id, $taxonomy );
+ return array( 'term_id' => $term_id, 'term_taxonomy_id' => $tt_id );
+ }
+
</ins><span class="cx" style="display: block; padding: 0 10px"> /**
</span><span class="cx" style="display: block; padding: 0 10px"> * Fires immediately after a new term is created, before the term cache is cleaned.
</span><span class="cx" style="display: block; padding: 0 10px"> *
</span></span></pre>
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