Index: wp-includes/wp-db.php
===================================================================
--- wp-includes/wp-db.php	(revision 20993)
+++ wp-includes/wp-db.php	(working copy)
@@ -1115,10 +1115,12 @@
 			// Return number of rows affected
 			$return_val = $this->rows_affected;
 		} else {
-			$i = 0;
-			while ( $i < @mysql_num_fields( $this->result ) ) {
-				$this->col_info[$i] = @mysql_fetch_field( $this->result );
-				$i++;
+			if (WP_DEBUG) {
+				$i = 0;
+				while ( $i < @mysql_num_fields( $this->result ) ) {
+					$this->col_info[$i] = @mysql_fetch_field( $this->result );
+					$i++;
+				}
 			}
 			$num_rows = 0;
 			while ( $row = @mysql_fetch_object( $this->result ) ) {