[Plugin: WP Super Cache] Nav menu update clears all blog cache

Thanks, I have commented out that line on our production systems.

I am guessing what you really wanted to do was either
wp-cache.php::wp_cache_clean_cache()
wp-cache-phase2.php::wp_cache_phase2_clean_cache()

I do not think it is working properly. This is what I did:

1) I downloaded and installed the wp-super-cache dev version on our test WP system. I manually removed the original plugin/wp-super-cache and copied the new dev version there. I verified that the code was changed:

add_action( 'wp_update_nav_menu', 'wp_cache_clear_cache_on_menu' );

function wp_cache_clear_cache_on_menu() {
        global $wpdb;
        wp_cache_clear_cache( $wpdb->blogid );
}

2) I manually copied our production cache to the WP dev system <wp base>/wp-content/cache
3) I went into one of our sites and updated a menu. It took about 1 minute to complete.

Observation before nav menu update –
Before updating the menu I noticed there were 3 subdirectories in the cache:
<wp base>/wp-content/cache/blogs
<wp base>/wp-content/cache/meta
<wp base>/wp-content/cache/supercache

Both /blogs and /supercache contained dozens of subdirectories named after our blog sites. For the site (test.usc.edu) I was about to update the nav menu I verified that it had existing cache (/blogs/test.usc.edu/*html and /supercache/test.usc.edu/*html)

Observation after nav menu update –
/blogs was completely empty (this included all the other site’s cache)
/supercache/test.usc.edu/ was empty (but the other sites’s caches were untouched)

I am not familiar with (super cache) caching so I do not know what the difference is between /blogs and /supercache. It appears to me that a nav menu update is incorrectly clearing all the content from /blogs, but is now correctly only clearing the blog’s cache in /supercache.