From fcf1696de4ff140fcc154b8305320a6ba676c47b Mon Sep 17 00:00:00 2001
From: Andrew Nacin <nacin@git.wordpress.org>
Date: Tue, 25 Oct 2011 05:29:28 +0000
Subject: [PATCH] Introduce ->mysql to allow drop-ins to declare themselves as
 MySQL and therefore allow minimum version checks to still apply. fixes
 #18176.

git-svn-id: https://develop.svn.wordpress.org/trunk@19060 602fd350-edb4-49c9-b593-d223f7449a82
---
 wp-admin/includes/update-core.php |  5 ++++-
 wp-admin/update-core.php          |  8 ++++++--
 wp-admin/upgrade.php              |  5 ++++-
 wp-includes/wp-db.php             | 17 +++++++++++++++++
 4 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/wp-admin/includes/update-core.php b/wp-admin/includes/update-core.php
index 911e750bb8..41aeb71485 100644
--- a/wp-admin/includes/update-core.php
+++ b/wp-admin/includes/update-core.php
@@ -337,7 +337,10 @@ function update_core($from, $to) {
 	$required_mysql_version = '5.0';
 	$wp_version = '3.3';
 	$php_compat     = version_compare( $php_version, $required_php_version, '>=' );
-	$mysql_compat   = version_compare( $mysql_version, $required_mysql_version, '>=' ) || file_exists( WP_CONTENT_DIR . '/db.php' );
+	if ( file_exists( WP_CONTENT_DIR . '/db.php' ) && empty( $this->is_mysql ) )
+		$mysql_compat = true;
+	else
+		$mysql_compat = version_compare( $mysql_version, $required_mysql_version, '>=' );
 
 	if ( !$mysql_compat || !$php_compat )
 		$wp_filesystem->delete($from, true);
diff --git a/wp-admin/update-core.php b/wp-admin/update-core.php
index 4f5efcc291..cf2c727ef9 100644
--- a/wp-admin/update-core.php
+++ b/wp-admin/update-core.php
@@ -44,8 +44,12 @@ function list_core_update( $update ) {
 			$submit = __('Re-install Now');
 			$form_action = 'update-core.php?action=do-core-reinstall';
 		} else {
-			$php_compat     = version_compare( $php_version, $update->php_version, '>=' );
-			$mysql_compat   = version_compare( $mysql_version, $update->mysql_version, '>=' ) || file_exists( WP_CONTENT_DIR . '/db.php' );
+			$php_compat     = version_compare( $php_version, $update->php_version, '>=' );			
+			if ( file_exists( WP_CONTENT_DIR . '/db.php' ) && empty( $wpdb->is_mysql ) )
+				$mysql_compat = true;
+			else
+				$mysql_compat = version_compare( $mysql_version, $required_mysql_version, '>=' );
+
 			if ( !$mysql_compat && !$php_compat )
 				$message = sprintf( __('You cannot update because <a href="http://codex.wordpress.org/Version_%1$s">WordPress %1$s</a> requires PHP version %2$s or higher and MySQL version %3$s or higher. You are running PHP version %4$s and MySQL version %5$s.'), $update->current, $update->php_version, $update->mysql_version, $php_version, $mysql_version );
 			elseif ( !$php_compat )
diff --git a/wp-admin/upgrade.php b/wp-admin/upgrade.php
index 84e251baec..4a2a0f4258 100644
--- a/wp-admin/upgrade.php
+++ b/wp-admin/upgrade.php
@@ -38,7 +38,10 @@ $step = (int) $step;
 $php_version    = phpversion();
 $mysql_version  = $wpdb->db_version();
 $php_compat     = version_compare( $php_version, $required_php_version, '>=' );
-$mysql_compat   = version_compare( $mysql_version, $required_mysql_version, '>=' ) || file_exists( WP_CONTENT_DIR . '/db.php' );
+if ( file_exists( WP_CONTENT_DIR . '/db.php' ) && empty( $wpdb->is_mysql ) )
+	$mysql_compat = true;
+else
+	$mysql_compat = version_compare( $mysql_version, $required_mysql_version, '>=' );
 
 @header( 'Content-Type: ' . get_option( 'html_type' ) . '; charset=' . get_option( 'blog_charset' ) );
 ?>
diff --git a/wp-includes/wp-db.php b/wp-includes/wp-db.php
index ebf6a64139..12ce58fd4d 100644
--- a/wp-includes/wp-db.php
+++ b/wp-includes/wp-db.php
@@ -460,6 +460,20 @@ class wpdb {
 	 */
 	var $func_call;
 
+	/**
+	 * Whether MySQL is used as the database engine.
+	 *
+	 * Set in WPDB::db_connect() to true, by default. This is used when checking
+	 * against the required MySQL version for WordPress. Normally, a replacement
+	 * database drop-in (db.php) will skip these checks, but setting this to true
+	 * will force the checks to occur.
+	 *
+	 * @since 3.3.0
+	 * @access public
+	 * @var bool
+	 */
+	public $is_mysql = null;
+
 	/**
 	 * Connects to the database server and selects a database
 	 *
@@ -1015,6 +1029,9 @@ class wpdb {
 	 * @since 3.0.0
 	 */
 	function db_connect() {
+
+		$this->is_mysql = true;
+
 		if ( WP_DEBUG ) {
 			$this->dbh = mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, true );
 		} else {