Hi,
I found some errors was made by ewww in error log.
Here is some example
2015/03/02 16:48:00 [error] 1206#0: *14678 FastCGI sent in stderr: "PHP message: WordPress database error： BIGINT UNSIGNED value is out of range in '(enterpr1se_info.wp_ewwwio_images.orig_size - enterpr1se_info.wp_ewwwio_images.image_size)' from SELECT orig_size-image_size FROM wp_ewwwio_images LIMIT 72000, 1000，error from do_action('wp_ajax_ewww_savings_loop'), call_user_func_array, ewww_image_optimizer_savings_loop, W3_Db->query, W3_DbCache->query, W3_DbCallUnderlying->query, W3_Db->query, W3_DbProcessor->query, W3_Db->default_query" while reading response header from upstream, client: 218.188.34.9, server: http://www.enterpr1se.info, request: "POST /wp-admin/admin-ajax.php HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "www.enterpr1se.info", referrer: "https://www.enterpr1se.info/wp-admin/options-general.php?page=ewww-image-optimizer%2Fewww-image-optimizer.php&settings-updated=true"
How to fix this error? Thanks