From db3917d491a44c76866750889e0f52bc57989ecc Mon Sep 17 00:00:00 2001
From: Gary Pendergast <gary@pento.net>
Date: Mon, 23 May 2016 06:32:29 +0000
Subject: [PATCH] Database: Use the `utf8mb4_unicode_520_ci` collation, when
 available.

The `utf8mb4_unicode_520_ci` (Unicode Collation Algorithm 5.2.0, October 2010) collation is an improvement over `utf8mb4_unicode_ci` (UCA 4.0.0, November 2003).

There is no word on when MySQL will support later UCAs.

Fixes #32105.


Built from https://develop.svn.wordpress.org/trunk@37523


git-svn-id: http://core.svn.wordpress.org/trunk@37491 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/version.php | 2 +-
 wp-includes/wp-db.php   | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/wp-includes/version.php b/wp-includes/version.php
index 0cb7c7f536..2c9097133b 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.6-alpha-37522';
+$wp_version = '4.6-alpha-37523';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.
diff --git a/wp-includes/wp-db.php b/wp-includes/wp-db.php
index 8d9f84c63e..49b6a9ddb8 100644
--- a/wp-includes/wp-db.php
+++ b/wp-includes/wp-db.php
@@ -765,6 +765,11 @@ class wpdb {
 				$this->collate = str_replace( 'utf8_', 'utf8mb4_', $this->collate );
 			}
 		}
+
+		// _unicode_520_ is a better collation, we should use that when it's available.
+		if ( $this->has_cap( 'utf8mb4_520' ) && 'utf8mb4_unicode_ci' === $this->collate ) {
+			$this->collate = 'utf8mb4_unicode_520_ci';
+		}
 	}
 
 	/**
@@ -3193,6 +3198,7 @@ class wpdb {
 	 *
 	 * @since 2.7.0
 	 * @since 4.1.0 Support was added for the 'utf8mb4' feature.
+	 * @since 4.6.0 Support was added for the 'utf8mb4_520' feature.
 	 *
 	 * @see wpdb::db_version()
 	 *
@@ -3231,6 +3237,8 @@ class wpdb {
 				} else {
 					return version_compare( $client_version, '5.5.3', '>=' );
 				}
+			case 'utf8mb4_520' :  // @since 4.6.0
+				return version_compare( $version, '5.6', '>=' );
 		}
 
 		return false;