From mboxrd@z Thu Jan  1 00:00:00 1970
From: grant@antiflux.org (Grant Hollingworth)
Date: Wed, 28 May 2008 22:49:32 -0400
Subject: [sup-talk] [PATCH] maildir speedups
In-Reply-To: <1211682829-sup-9284@south>
References: <f96e0240804301150w5e07823cuf3b16fc7dffa759e@mail.gmail.com>
	<1211254100-sup-9575@south>
	<f96e0240805200924u1c991392oe36de853e208bab8@mail.gmail.com>
	<f96e0240805201808k4bcf9947j45779b751a9abb66@mail.gmail.com>
	<1211682829-sup-9284@south>
Message-ID: <1212028646-sup-7356@spooky.local>

* William Morgan [2008-05-24 22:34 -0400]:
> Published on 'maildir-speedups' and merged into next. Thanks!

Sup had my CPU working overtime after I updated. I ran ruby-prof and found
that the line

    @ids_to_fns.delete_if { |k, v| !@ids.include?(k) }

in Maildir#scan_mailbox was the culprit.

Those id lists are pretty long and include? means comparing each id (a Bignum)
in @ids_to_fns with every id in @ids.

A faster method is

    @ids_to_fns = @ids.inject({}) do |hash, i|
      hash[i] = @ids_to_fns[i]
      hash
    end

Or (less pretty but faster and probably clearer)

    new_ids_to_fns = {}
    @ids.each {|i| new_ids_to_fns[i] = @ids_to_fns[i] }
    @ids_to_fns = new_ids_to_fns

But I guess the real question is whether the line is even needed. There
probably won't be a big difference between @ids_to_fns.keys and @ids, so why
not leave some extra values in the hash?