diff --git a/wp-includes/classes.php b/wp-includes/classes.php
index 7290b11317..27fb326204 100644
--- a/wp-includes/classes.php
+++ b/wp-includes/classes.php
@@ -535,7 +535,17 @@ class WP {
 class WP_Object_Query {
 
 	/**
-	 * Metadata query
+	 * List of metadata queries
+	 *
+	 * A query is an associative array:
+	 * - 'key' string The meta key
+	 * - 'value' string|array The meta value
+	 * - 'compare' (optional) string How to compare the key to the value. 
+	 *		Possible values: '=', '!=', '>', '>=', '<', '<=', 'LIKE', 'IN', 'BETWEEN'. 
+	 *		Default: '='
+	 * - 'type' string (optional) The type of the value.
+	 *		Possible values: 'NUMERIC', 'BINARY', 'CHAR', 'DATE', 'DATETIME', 'DECIMAL', 'SIGNED', 'TIME', 'UNSIGNED'. 
+	 *		Default: 'CHAR'
 	 *
 	 * @since 3.1.0
 	 * @access public
@@ -543,6 +553,27 @@ class WP_Object_Query {
 	 */
 	var $meta_query = array();
 
+	/*
+	 * List of taxonomy queries
+	 *
+	 * A query is an associative array:
+	 * - 'taxonomy' string|array The taxonomy being queried
+	 * - 'terms' string|array The list of terms
+	 * - 'field' string (optional) Which term field is being used.
+	 *		Possible values: 'term_id', 'slug' or 'name'
+	 *		Default: 'slug'
+	 * - 'operator' string (optional)
+	 *		Possible values: 'IN' and 'NOT IN'. 
+	 *		Default: 'IN'
+	 * - 'include_children' bool (optional) Wether to include child terms. 
+	 *		Default: true
+	 *
+	 * @since 3.1.0
+	 * @access public
+	 * @var array
+	 */
+	var $tax_query = array();
+
 	/*
 	 * Populates the $meta_query property
 	 *
@@ -573,6 +604,8 @@ class WP_Object_Query {
 	 * @access protected
 	 * @since 3.1.0
 	 *
+	 * @uses $this->meta_query
+	 *
 	 * @param string $primary_table
 	 * @param string $primary_id_column
 	 * @param string $meta_table
@@ -645,6 +678,44 @@ class WP_Object_Query {
 		return array( $join, $where );
 	}
 
+	/*
+	 * Used internally to generate an SQL string for searching across multiple taxonomies
+	 *
+	 * @access protected
+	 * @since 3.1.0
+	 *
+	 * @uses $this->tax_query
+	 *
+	 * @param string $object_id_column
+	 * @return string
+	 */
+	function get_tax_sql( $object_id_column ) {
+		global $wpdb;
+
+		$sql = array();
+		foreach ( $this->tax_query as $query ) {
+			if ( !isset( $query['include_children'] ) )
+				$query['include_children'] = true;
+			$query['do_query'] = false;
+			$sql[] = get_objects_in_term( $query['terms'], $query['taxonomy'], $query );
+		}
+
+		if ( 1 == count( $sql ) ) {
+			$ids = $wpdb->get_col( $sql[0] );
+		} else {
+			$r = "SELECT object_id FROM $wpdb->term_relationships WHERE 1=1";
+			foreach ( $sql as $query )
+				$r .= " AND object_id IN ($query)";
+
+			$ids = $wpdb->get_col( $r );
+		}
+
+		if ( !empty( $ids ) )
+			return " AND $object_id_column IN(" . implode( ', ', $ids ) . ")";
+		else
+			return ' AND 0 = 1';
+	}
+
 	/*
 	 * Used internally to generate an SQL string for searching across multiple columns
 	 *
diff --git a/wp-includes/query.php b/wp-includes/query.php
index a4547254d6..a78316bc9f 100644
--- a/wp-includes/query.php
+++ b/wp-includes/query.php
@@ -661,15 +661,6 @@ class WP_Query extends WP_Object_Query {
 	 */
 	var $query_vars = array();
 
-	/**
-	 * Taxonomy query, after parsing
-	 *
-	 * @since 3.1.0
-	 * @access public
-	 * @var array
-	 */
-	var $tax_query = array();
-
 	/**
 	 * Holds the data for a single object that is queried.
 	 *
@@ -1382,6 +1373,8 @@ class WP_Query extends WP_Object_Query {
 				$this->is_tax = true;
 			}
 
+			$this->parse_tax_query( $qv );
+
 			$this->parse_meta_query( $qv );
 
 			if ( empty($qv['author']) || ($qv['author'] == '0') ) {
@@ -1490,6 +1483,119 @@ class WP_Query extends WP_Object_Query {
 			do_action_ref_array('parse_query', array(&$this));
 	}
 
+	function parse_tax_query( $q ) {
+		$tax_query = array();
+
+		if ( $this->is_tax ) {
+			foreach ( $GLOBALS['wp_taxonomies'] as $taxonomy => $t ) {
+				if ( $t->query_var && !empty( $q[$t->query_var] ) ) {
+					$tax_query_defaults = array(
+						'taxonomy' => $taxonomy,
+						'field' => 'slug',
+						'operator' => 'IN'
+					);
+
+					$term = str_replace( ' ', '+', $q[$t->query_var] );
+
+					if ( strpos($term, '+') !== false ) {
+						$terms = preg_split( '/[+\s]+/', $term );
+						foreach ( $terms as $term ) {
+							$tax_query[] = array_merge( $tax_query_defaults, array(
+								'terms' => array( $term )
+							) );
+						}
+					} else {
+						$tax_query[] = array_merge( $tax_query_defaults, array(
+							'terms' => preg_split('/[,\s]+/', $term)
+						) );
+					}
+				}
+			}
+		}
+
+		// Category stuff
+		if ( !empty($q['cat']) && '0' != $q['cat'] && !$this->is_singular ) {
+			$q['cat'] = ''.urldecode($q['cat']).'';
+			$q['cat'] = addslashes_gpc($q['cat']);
+			$cat_array = preg_split('/[,\s]+/', $q['cat']);
+			$q['cat'] = '';
+			$req_cats = array();
+			foreach ( (array) $cat_array as $cat ) {
+				$cat = intval($cat);
+				$req_cats[] = $cat;
+				$in = ($cat > 0);
+				$cat = abs($cat);
+				if ( $in ) {
+					$q['category__in'][] = $cat;
+				} else {
+					$q['category__not_in'][] = $cat;
+				}
+			}
+			$q['cat'] = implode(',', $req_cats);
+		}
+
+		if ( !empty($q['category__in']) ) {
+			$tax_query[] = array(
+				'taxonomy' => 'category',
+				'terms' => $q['category__in'],
+				'operator' => 'IN',
+				'field' => 'term_id'
+			);
+		}
+
+		if ( !empty($q['category__not_in']) ) {
+			$tax_query[] = array(
+				'taxonomy' => 'category',
+				'terms' => $q['category__not_in'],
+				'operator' => 'NOT IN',
+				'field' => 'term_id'
+			);
+		}
+
+		// Category stuff for nice URLs
+		if ( '' != $q['category_name'] && !$this->is_singular ) {
+			$q['category_name'] = str_replace( '%2F', '/', urlencode(urldecode($q['category_name'])) );
+			$q['category_name'] = '/' . trim( $q['category_name'], '/' );
+
+			$tax_query[] = array(
+				'taxonomy' => 'category',
+				'terms' => array( basename( $q['category_name'] ) ),
+				'operator' => 'IN',
+				'field' => 'slug'
+			);
+		}
+
+		// Tag stuff
+		if ( !empty($qv['tag_id']) ) {
+			$tax_query[] = array(
+				'taxonomy' => 'post_tag',
+				'terms' => $qv['tag_id'],
+				'operator' => 'IN',
+				'field' => 'term_id'
+			);
+		}
+
+		if ( !empty($q['tag__in']) ) {
+			$tax_query[] = array(
+				'taxonomy' => 'post_tag',
+				'terms' => $q['tag__in'],
+				'operator' => 'IN',
+				'field' => 'term_id'
+			);
+		}
+
+		if ( !empty($q['tag__not_in']) ) {
+			$tax_query[] = array(
+				'taxonomy' => 'post_tag',
+				'terms' => $q['tag__not_in'],
+				'operator' => 'NOT IN',
+				'field' => 'term_id'
+			);
+		}
+
+		$this->tax_query = $tax_query;
+	}
+
 	/**
 	 * Sets the 404 property and saves whether query is feed.
 	 *
@@ -1815,118 +1921,7 @@ class WP_Query extends WP_Object_Query {
 		$search = apply_filters_ref_array('posts_search', array( $search, &$this ) );
 
 		// Taxonomies
-		$tax_query = array();
-
-		if ( $this->is_tax ) {
-			foreach ( $GLOBALS['wp_taxonomies'] as $taxonomy => $t ) {
-				if ( $t->query_var && !empty( $q[$t->query_var] ) ) {
-					$tax_query_defaults = array(
-						'taxonomy' => $taxonomy,
-						'field' => 'slug',
-						'operator' => 'IN'
-					);
-
-					$term = str_replace( ' ', '+', $q[$t->query_var] );
-
-					if ( strpos($term, '+') !== false ) {
-						$terms = preg_split( '/[+\s]+/', $term );
-						foreach ( $terms as $term ) {
-							$tax_query[] = array_merge( $tax_query_defaults, array(
-								'terms' => array( $term )
-							) );
-						}
-					} else {
-						$tax_query[] = array_merge( $tax_query_defaults, array(
-							'terms' => preg_split('/[,\s]+/', $term)
-						) );
-					}
-				}
-			}
-		}
-
-		// Category stuff
-		if ( !empty($q['cat']) && '0' != $q['cat'] && !$this->is_singular ) {
-			$q['cat'] = ''.urldecode($q['cat']).'';
-			$q['cat'] = addslashes_gpc($q['cat']);
-			$cat_array = preg_split('/[,\s]+/', $q['cat']);
-			$q['cat'] = '';
-			$req_cats = array();
-			foreach ( (array) $cat_array as $cat ) {
-				$cat = intval($cat);
-				$req_cats[] = $cat;
-				$in = ($cat > 0);
-				$cat = abs($cat);
-				if ( $in ) {
-					$q['category__in'][] = $cat;
-				} else {
-					$q['category__not_in'][] = $cat;
-				}
-			}
-			$q['cat'] = implode(',', $req_cats);
-		}
-
-		if ( !empty($q['category__in']) ) {
-			$tax_query[] = array(
-				'taxonomy' => 'category',
-				'terms' => $q['category__in'],
-				'operator' => 'IN',
-				'field' => 'term_id'
-			);
-		}
-
-		if ( !empty($q['category__not_in']) ) {
-			$tax_query[] = array(
-				'taxonomy' => 'category',
-				'terms' => $q['category__not_in'],
-				'operator' => 'NOT IN',
-				'field' => 'term_id'
-			);
-		}
-
-		// Category stuff for nice URLs
-		if ( '' != $q['category_name'] && !$this->is_singular ) {
-			$q['category_name'] = str_replace( '%2F', '/', urlencode(urldecode($q['category_name'])) );
-			$q['category_name'] = '/' . trim( $q['category_name'], '/' );
-
-			$tax_query[] = array(
-				'taxonomy' => 'category',
-				'terms' => array( basename( $q['category_name'] ) ),
-				'operator' => 'IN',
-				'field' => 'slug'
-			);
-		}
-
-		// Tag stuff
-		if ( !empty($qv['tag_id']) ) {
-			$tax_query[] = array(
-				'taxonomy' => 'post_tag',
-				'terms' => $qv['tag_id'],
-				'operator' => 'IN',
-				'field' => 'term_id'
-			);
-		}
-
-		if ( !empty($q['tag__in']) ) {
-			$tax_query[] = array(
-				'taxonomy' => 'post_tag',
-				'terms' => $q['tag__in'],
-				'operator' => 'IN',
-				'field' => 'term_id'
-			);
-		}
-
-		if ( !empty($q['tag__not_in']) ) {
-			$tax_query[] = array(
-				'taxonomy' => 'post_tag',
-				'terms' => $q['tag__not_in'],
-				'operator' => 'NOT IN',
-				'field' => 'term_id'
-			);
-		}
-
-		if ( !empty( $tax_query ) ) {
-			$this->tax_query = $tax_query;
-
+		if ( !empty( $this->tax_query ) ) {
 			if ( empty($post_type) ) {
 				$post_type = 'any';
 				$post_status_join = true;
@@ -1934,15 +1929,11 @@ class WP_Query extends WP_Object_Query {
 				$post_status_join = true;
 			}
 
-			$ids = wp_tax_query( $tax_query );
-			if ( !empty($ids) )
-				$where .= " AND $wpdb->posts.ID IN(" . implode( ', ', $ids ) . ")";
-			else
-				$where .= ' AND 0 = 1';
+			$where .= $this->get_tax_sql( "$wpdb->posts.ID" );
 
 			// Back-compat
 			if ( !empty( $ids ) ) {
-				$cat_query = wp_list_filter( $tax_query, array( 'taxonomy' => 'category' ) );
+				$cat_query = wp_list_filter( $this->tax_query, array( 'taxonomy' => 'category' ) );
 				if ( !empty( $cat_query ) ) {
 					$cat_query = reset( $cat_query );
 					$cat = get_term_by( $cat_query['field'], $cat_query['terms'][0], 'category' );
diff --git a/wp-includes/taxonomy.php b/wp-includes/taxonomy.php
index 9b1487172c..9e455c27b6 100644
--- a/wp-includes/taxonomy.php
+++ b/wp-includes/taxonomy.php
@@ -532,40 +532,6 @@ function get_objects_in_term( $terms, $taxonomies, $args = array() ) {
 	return $wpdb->get_col( $sql );	
 }
 
-/*
- * Retrieve object_ids matching one or more taxonomy queries
- *
- * @since 3.1.0
- *
- * @param array $queries A list of taxonomy queries. A query is an associative array:
- *   'taxonomy' string|array The taxonomy being queried
- *   'terms' string|array The list of terms
- *   'field' string Which term field is being used. Can be 'term_id', 'slug' or 'name'
- *   'operator' string Can be 'IN' and 'NOT IN'
- *
- * @return array|WP_Error List of matching object_ids; WP_Error on failure.
- */
-function wp_tax_query( $queries ) {
-	global $wpdb;
-
-	$sql = array();
-	foreach ( $queries as $query ) {
-		if ( !isset( $query['include_children'] ) )
-			$query['include_children'] = true;
-		$query['do_query'] = false;
-		$sql[] = get_objects_in_term( $query['terms'], $query['taxonomy'], $query );
-	}
-
-	if ( 1 == count( $sql ) )
-		return $wpdb->get_col( $sql[0] );
-
-	$r = "SELECT object_id FROM $wpdb->term_relationships WHERE 1=1";
-	foreach ( $sql as $query )
-		$r .= " AND object_id IN ($query)";
-
-	return $wpdb->get_col( $r );
-}
-
 /**
  * Get all Term data from database by Term ID.
  *