Re: [Extra] Discussing SNIPPET

[Bron Gondwana <[e-mail]>]

On Tue, Sep 18, 2018, at 17:47, Josef 'Jeff' Sipek wrote:
> On Mon, Sep 17, 2018 at 17:31:23 -0700, Chris Newman wrote:
>> On 17 Sep 2018, at 4:52, Bron Gondwana wrote:
> ...
>>> b) Cache Invalidation. Ho hum. Is this an immutable property? If so,>>> what happens if the server implementation changes? I'm quite
>>> happy to>>> call it "softly immutable" myself - it might not be exactly the same>>> bytes, but you can use the old version without major problems.
>> 
>> The 'softly immutable' option works for me. However, I'll propose an>> alternative so we can contrast two reasonable options. We could add
>> a way to>> fetch a FUZZY algorithm identifier for a given folder.
>> Something like:>> 
>> C: A043 STATUS blurdybloop (FUZZYALG)
>> S: * STATUS blurdybloop (FUZZYALG ("ocms:8.0"))
>> 
>> A cached PREVIEW=FUZZY (SNIPPET=FUZZY) from that folder is
>> immutable unless>> the FUZZYALG string changes. This has some non-trivial server
>> implications,>> but if clients really need predictable PREVIEW caching behavior,
>> this is a>> protocol model I'd be willing to implement to provide that.
> 
> For what it's worth, in Dovecot we cache the generated
> snippet/preview along> with a version number and take the 'softly immutable' approach.  For
> example, an email with body of "foobar" would turn into
> "1foobar" in the> cache file.  When a client FETCHes it, we strip the version.  We
> haven't had> the need to up the version yet, but at least in theory it should
> provide us> with a way to tweak the snippet algo and know which cached values
> are stale.
We do something similar at FastMail - we have a keyword (currently $X-ME-Annot-
2) which is a version number for the logic which generated the preview
and a couple of other keywords like $HasAttachment by parsing the
message content.
> I'm not fully caught up on the discussions here so maybe I'm missing
> something, but I was under the impression that the algo can be
> selected per> **email** so wouldn't it really have to be a FETCH * FUZZYALG?.  I
> don't quite> understand what the above STATUS accomplishes; I guess it is
> something like> a uidvalidity for snippets in a folder but I'm not convinced
> that it is> worth it.  If you want to have the latest snippet, just FETCH it.

I agree with that!  It's small enough that re-fetching isn't a big deal
if you are worried that it might be old - and the cost in roundtrips to
check the version first plus the added complexity isn't worth it.
Bron.

--
  Bron Gondwana, CEO, FastMail Pty Ltd
  [e-mail]