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From Aaron Daubman <>
Subject Re: Tips on creating a custom QueryCache?
Date Wed, 30 May 2012 18:44:25 GMT

: 1) Any recommendations on which best to sub-class? I'm guessing, for this
> : scenario with "rare" batch puts and no evictions, I'd be looking for get
> : performance. This will also be on a box with many CPUs - so I wonder if
> the
> : older LRUCache would be preferable?
> i suspect you are correct ... the entire point of the other caches is
> dealingwith faster replacement, so you really don't care.
> You might even find it worth while to write your own
> "NoReplacementCache" from scratch backed by a HashMap (instead of the
> LinkedHashMap used in LRUCache)

I really like this idea (roll-your-own cache using a simple HashMap).
However, as much searching as I've done, I've come up short on anything
that describes concurrency in Solr. The short question is, for such a
cache, do I need to worry about concurrent access (I'm guessing that the
firstSearcher QuerySenderListener process would be
single-threaded/non-concurrent, and thus writes would never be an issue -
is this correct?) - e.g. for my case, would I back the "NoReplacementCache"
with a HashMap or ? The bigger question is: what are the parallel task
execution paths in Solr and under what conditions are they possible?

Thanks again,

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