From 13cf1a5c78aa2a2631a03b1e903f9d902d18ea09 Mon Sep 17 00:00:00 2001
From: Ryan Boren <ryan@git.wordpress.org>
Date: Tue, 26 Aug 2008 19:18:58 +0000
Subject: [PATCH] Use a subquery in category__not_in query if the DB version
 supports it.  Props pedrop. fixes #7599

git-svn-id: https://develop.svn.wordpress.org/trunk@8738 602fd350-edb4-49c9-b593-d223f7449a82
---
 wp-includes/query.php | 17 +++++++++++------
 wp-includes/wp-db.php | 11 +++++++++++
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/wp-includes/query.php b/wp-includes/query.php
index b9c4d29635..e7b89ffc49 100644
--- a/wp-includes/query.php
+++ b/wp-includes/query.php
@@ -1046,12 +1046,17 @@ class WP_Query {
 		}
 
 		if ( !empty($q['category__not_in']) ) {
-			$ids = get_objects_in_term($q['category__not_in'], 'category');
-			if ( is_wp_error( $ids ) )
-				return $ids;
-			if ( is_array($ids) && count($ids > 0) ) {
-				$out_posts = "'" . implode("', '", $ids) . "'";
-				$whichcat .= " AND $wpdb->posts.ID NOT IN ($out_posts)";
+			if ( $wpdb->supports_subqueries() ) {
+				$cat_string = "'" . implode("', '", $q['category__not_in']) . "'";
+				$whichcat .= " AND $wpdb->posts.ID NOT IN (SELECT $wpdb->term_relationships.object_id FROM $wpdb->term_relationships WHERE $wpdb->term_relationships.term_taxonomy_id IN ($cat_string) )";
+			} else {
+				$ids = get_objects_in_term($q['category__not_in'], 'category');
+				if ( is_wp_error( $ids ) )
+					return $ids;
+				if ( is_array($ids) && count($ids > 0) ) {
+					$out_posts = "'" . implode("', '", $ids) . "'";
+					$whichcat .= " AND $wpdb->posts.ID NOT IN ($out_posts)";
+				}
 			}
 		}
 
diff --git a/wp-includes/wp-db.php b/wp-includes/wp-db.php
index b0b37e4960..7b6c6f090f 100644
--- a/wp-includes/wp-db.php
+++ b/wp-includes/wp-db.php
@@ -923,6 +923,17 @@ class wpdb {
 		return ( version_compare(mysql_get_server_info($this->dbh), '4.1.0', '>=') );
 	}
 
+	/**
+	 * Whether of not the database version supports sub-queries.
+	 *
+	 * @since 2.7
+	 *
+	 * @return bool True if sub-queries are supported, false if version does not
+	 */
+	function supports_subqueries() {
+		return ( version_compare(mysql_get_server_info($this->dbh), '4.1.0', '>=') );
+	}
+
 	/**
 	 * Retrieve the name of the function that called wpdb.
 	 *