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From Grant Ingersoll <>
Subject Re: Bet you didn't know Lucene can...
Date Tue, 25 Oct 2011 19:57:27 GMT

On Oct 25, 2011, at 11:26 AM, mark harwood wrote:

>>> using Lucene that don't fit under the core premise of full text search
>  I've had several use cases over the years that use features peculiar to Lucene but here's
a very simple one I came across today that illustrates its raw index lookup capability:
> I needed a fast, scalable and persistent "Set" implementation to maintain a large cold-list
(millions of string-based keys).
> I benchmarked various implementations using a set of ~6 million keys with 10,000 random
key lookups.
> When it comes to RAM use, retrieval times and start-up costs Lucene stands up very well
against equivalent embedded databases for this task:
> * Benchmarks for times to initially open the set when stored on disk:
> * Benchmarks for Avg key lookup time once opened:
> * Stats for RAM use after 10,000 lookups:

Those charts are beautiful.  I have Lucene/Solr down as an excellent key-value store (I've
seen this done many times) and these charts further cement it.

> I don't doubt all of these implementations could be tweaked (e.g. optimizing the Lucene
index, various DB-specific settings) but I tried to use sensible defaults to make the tests
fair e.g. use of prepared statements, indexes, minimal data retrieved.
> Speeds varied with each run of the random lookup test due to OS-level caching effects
so the best times were recorded in each case.
> The HashSet tests are loaded entirely from file (hence the long start-up time) and are
not a scalable solution because of RAM costs.
> MySQL requires an inter-process call as it was not  embedded but even using a remoted
Lucene call I get significantly better performance (avg 0.5ms lookup vs MySQL 10ms)
> Cheers
> Mark
> ----- Original Message -----
> From: Grant Ingersoll <>
> To:
> Cc: 
> Sent: Saturday, 22 October 2011, 10:11
> Subject: Bet you didn't know Lucene can...
> Hi All,
> I'm giving a talk at ApacheCon titled "Bet you didn't know Lucene can..." (
 It's based on my observation, that over the years, a number of us in the community have done
some pretty cool things using Lucene that don't fit under the core premise of full text search.
 I've got a fair number of ideas for the talk (easily enough for 1 hour), but I wanted to
reach out to hear your stories of ways you've (ab)used Lucene and Solr to see if we couldn't
extend the conversation to a bit more than the conference and also see if I can't inject more
ideas beyond the ones I have.  I don't need deep technical details, but just high level use
case and the basic insight that led you to believe Lucene could solve the problem.
> Thanks in advance,
> Grant
> --------------------------------------------
> Grant Ingersoll
> ---------------------------------------------------------------------
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Grant Ingersoll

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