querystring part of cache key

there were discussions recently about the method being part of the cache 
key, since the response for different methods on the same URI could 
presumably be cacheable and different.

What about query string?  If the result to something that has a 
querystring is marked as cachable by the origin server, then is it 
deemed part of the URI for the cache key?  I'd presume yes.

Since URIs can be arbitrarily long, yet database fields aren't good with 
this, I'd presume it's common practise to look up based on some hash 
value.  Is this approach used?  Is there any industry-standard hashing 
method, e.g. MD5 of method+URI(normalised) + querystring ?

TIA

Adrien

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Adrien de Croy - WinGate Proxy Server - http://www.wingate.com