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Subject: Re: [jira] [Commented] (CAY-1595) EHCache implementation of
 Provider<QueryCache>
From: Andrus Adamchik <andrus@objectstyle.org>
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Date: Wed, 27 Jul 2011 23:53:02 +0300
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On Jul 27, 2011, at 11:16 PM, Andrus Adamchik wrote:

> I think we can start with an implementation that quietly ignores =
groups and uses a single cache (and hence a single expiration policy) =
for all query entries. It is rather crippled, as it would preclude =
targeted invalidation, but it will be a start. And then who knows, maybe =
EHC-240 is committed.

So here is an attempt of cache group design over EHCache...=20

First, a few assumptions:

1. if a query has multiple cache groups, we ignore all but the first =
one. This is quite reasonable IMO. It will suffice for most scenarios.

2. We store keys for each cache group in a separate EHCache instance =
within the same CacheManager.=20

3. For entries with no cache groups, we allocate a separate EHCache =
instance.

I think this will allow us to implement all methods of QueryCache =
interface. However we may end up with duplicate cache entries if the =
same query was run with different cache groups, which may potentially =
increase memory use and introduce a new type of cache consistency =
problems. So it is not as flexible as OSCache, but is much better than =
no cache group support at all. As long as users are aware of it, we =
should be fine.
=20
Andrus