From 86a0fff73142b0af3717ccb3c82a2fd693ebaf53 Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Fri, 11 Mar 2016 12:32:43 +0000
Subject: [PATCH] [2.5] Before updating with DBDELTA, drop existing indexes so
 they can be 		 re-added without duplicate key errors.

---
 includes/class-wc-install.php | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/includes/class-wc-install.php b/includes/class-wc-install.php
index c2f9e5d7c7e..58f6d70e21b 100644
--- a/includes/class-wc-install.php
+++ b/includes/class-wc-install.php
@@ -338,7 +338,8 @@ class WC_Install {
 		require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
 
 		/**
-		 * Before updating with DBDELTA, remove any primary keys which could be modified due to schema updates.
+		 * Before updating with DBDELTA, remove any primary keys which could be
+		 * modified due to schema updates.
 		 */
 		if ( $wpdb->get_var( "SHOW TABLES LIKE '{$wpdb->prefix}woocommerce_downloadable_product_permissions';" ) ) {
 			if ( ! $wpdb->get_var( "SHOW COLUMNS FROM `{$wpdb->prefix}woocommerce_downloadable_product_permissions` LIKE 'permission_id';" ) ) {
@@ -346,6 +347,33 @@ class WC_Install {
 			}
 		}
 
+		/**
+		 * Before updating with DBDELTA, drop existing indexes so they can be
+		 * re-added without duplicate key errors. Index lengths were added
+		 * in 2.5.3.
+		 */
+		$indexes_to_remove = array(
+			'woocommerce_attribute_taxonomies'             => 'attribute_name',
+			'woocommerce_termmeta'                         => 'meta_key',
+			'woocommerce_downloadable_product_permissions' => 'download_order_key_product',
+			'woocommerce_order_itemmeta'                   => 'meta_key',
+			'woocommerce_tax_rates'                        => 'tax_rate_country',
+			'woocommerce_tax_rates'                        => 'tax_rate_state',
+			'woocommerce_tax_rates'                        => 'tax_rate_class',
+			'woocommerce_tax_rate_locations'               => 'location_type_code',
+			'woocommerce_shipping_zone_locations'          => 'location_type_code',
+		);
+
+		foreach ( $indexes_to_remove as $table => $key ) {
+			$table = esc_sql( $wpdb->prefix . $table );
+			$key   = esc_sql( $key );
+			if ( $wpdb->get_var( "SHOW TABLES LIKE '{$table}';" ) ) {
+				if ( $wpdb->get_var( "SHOW INDEX FROM {$table} WHERE KEY_NAME = '{$key}';" ) ) {
+					$wpdb->query(  "ALTER TABLE {$table} DROP INDEX `{$key}`;" );
+				}
+			}
+		}
+
 		dbDelta( self::get_schema() );
 	}