Error log says "duplicate column name 'meta robots'"

Every day for the past month, my WP error log has this:

WordPress database error Duplicate column name ‘meta_robots’ for query ALTER TABLE wp_posts ADD COLUMN meta_robots varchar(20) made by require, require_once, require_once, require_once, do_action, call_user_func_array, wp_meta_robots_plugin->meta_robots_addcolumn

How can I find out what is causing this? Where can I view and edit my database columns?