Re: [Extra] Discussing SNIPPET

[Josef 'Jeff' Sipek <[e-mail]>]

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.

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.

Jeff.

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