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From "Erick Erickson" <>
Subject Re: Caching
Date Wed, 14 Feb 2007 14:10:44 GMT
This is really an unanswerable question, since, to steal a phrase, "It
depends" <G>...

Do you have any reason to believe that the current performance is inadequate
for you application? Caching is notoriously difficult to get right, so I
wouldn't go there unless there is a *demonstrated* need. By demonstrated, I
mean that you run some tests against your actual data with simulated queries
and measure. By definition, Lucene's caching is "any good" if your
performance meets your target as is. Only if your application does NOT meet
your targets should you consider an additional caching layer. And even in
this case, I'd spend significant time looking at exactly *where* in my
application things were slow rather than jump to caching as an answer.

I do not believe that Lucene actually caches the results of queries. I
believe that Lucene builds caches of terms, sorting information, etc. that
are then applied to all subsequent queries, and that these are the caches
that are built at the first query. So, say storing the results of a query
somewhere and returning that stored copy for the *next* query that is
identical is not something I'd expect Lucene to do.


On 2/14/07, Kainth, Sachin <> wrote:
> Hi all,
> I have read that Lucene performs caching of search results so that if
> you perform the same search in succession the second result should be
> returned faster.  What I wanted to ask is whether this caching is any
> good or whether it's a good idea to add some sort of caching layer on
> top of Lucene to improve on it.
> Any comments will be appreciated.
> Thanks
> Sachin
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