From 8ca91024e8bc4e7c13519bcd68d6825450653d22 Mon Sep 17 00:00:00 2001
From: Boone Gorges <boonebgorges@gmail.com>
Date: Wed, 21 Jun 2017 04:12:44 +0000
Subject: [PATCH] Improve cache invalidation when splitting shared terms.

This changeset addresses two related issues:

* When splitting shared terms from hierarchical taxonomies, the process of regenerating the taxonomy hierarchy (`_get_taxonomy_hierarchy()`) requires recursive calls to `get_terms()` in order to descend the tree. By waiting until all shared terms in a term group have been invalidated before regenerating their taxonomy hierarchies, we avoid certain race conditions.
* Previously, a coding error prevented single-term caches from being invalidated for children of split terms. This error dates from [31418].

See #37189.
Built from https://develop.svn.wordpress.org/trunk@40920


git-svn-id: http://core.svn.wordpress.org/trunk@40770 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/taxonomy.php | 22 +++++++++++++++-------
 wp-includes/version.php  |  2 +-
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/wp-includes/taxonomy.php b/wp-includes/taxonomy.php
index 484d26ebbc..f703b5a56b 100644
--- a/wp-includes/taxonomy.php
+++ b/wp-includes/taxonomy.php
@@ -3548,19 +3548,27 @@ function _split_shared_term( $term_id, $term_taxonomy_id, $record = true ) {
 				array( 'parent' => $new_term_id ),
 				array( 'term_taxonomy_id' => $child_tt_id )
 			);
-			clean_term_cache( $term_id, $term_taxonomy->taxonomy );
+			clean_term_cache( (int) $child_tt_id, '', false );
 		}
 	} else {
 		// If the term has no children, we must force its taxonomy cache to be rebuilt separately.
-		clean_term_cache( $new_term_id, $term_taxonomy->taxonomy );
+		clean_term_cache( $new_term_id, $term_taxonomy->taxonomy, false );
 	}
 
+	clean_term_cache( $term_id, $term_taxonomy->taxonomy, false );
+
+	/*
+	 * Taxonomy cache clearing is delayed to avoid race conditions that may occur when
+	 * regenerating the taxonomy's hierarchy tree.
+	 */
+	$taxonomies_to_clean = array( $term_taxonomy->taxonomy );
+
 	// Clean the cache for term taxonomies formerly shared with the current term.
-	$shared_term_taxonomies = $wpdb->get_row( $wpdb->prepare( "SELECT taxonomy FROM $wpdb->term_taxonomy WHERE term_id = %d", $term_id ) );
-	if ( $shared_term_taxonomies ) {
-		foreach ( $shared_term_taxonomies as $shared_term_taxonomy ) {
-			clean_term_cache( $term_id, $shared_term_taxonomy );
-		}
+	$shared_term_taxonomies = $wpdb->get_col( $wpdb->prepare( "SELECT taxonomy FROM $wpdb->term_taxonomy WHERE term_id = %d", $term_id ) );
+	$taxonomies_to_clean = array_merge( $taxonomies_to_clean, $shared_term_taxonomies );
+
+	foreach ( $taxonomies_to_clean as $taxonomy_to_clean ) {
+		clean_taxonomy_cache( $taxonomy_to_clean );
 	}
 
 	// Keep a record of term_ids that have been split, keyed by old term_id. See wp_get_split_term().
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 53969d5b73..c3f8190348 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.9-alpha-40919';
+$wp_version = '4.9-alpha-40920';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.