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From Ian Lea <>
Subject Re: Sharding Techniques
Date Mon, 09 May 2011 15:51:28 GMT
> ...
> 1. I've not tested my application with single index as initially (a few
> years back) we thought smaller the index size (7 indexes for default 80%
> searches) the faster the search time would be ...

Possibly.  Maybe it will be acceptable to make some searches a bit
slower in order to make the slow ones faster.  But my guess would
still be that a single index with filtered searches would be quicker
for most searches.

> 2. For sharing/caching we create index readers once the server starts and
> use these throughout the server's life (1 day). At the time of searches,
> number of indexes to be read are decided by analyzing the search parameters.
> IndexSearchers are created on persistent IndexReaders and finally a
> ParallelMultiSearcher is created from these IndexSearchers (I hope this is
> not a problem, or is it???)

Sounds fine, except that in latest versions of lucene,
ParallelMultiSearcher is deprecated.

> 3. I had gone through the link you provided and some of the things are
> already implemented (e.g. readOnly=true, NIOFSDirectory, optmizing, etc.).
> We are using filters for some of the fields and caching those filters in the
> memory, through hashtable.

Sounds good.

> Will reducing number of tokens in a particular field in index reduce the
> search time (or CPU, memory etc)?

Yes, in theory, but unless the numbers are really high I doubt you'll notice it.

> E.g. I have 11 documents and tokens in field (fld1) are
> 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 and 2.0.
> The query is - fld1:[ 1.0 TO 2.0 ]
> Would it make any difference if the tokens in documents (in the same field)
> would be
> 1,1,1,1,1,1,1,1,1,2
> ??

Unlikely.  But if those are all always numbers it would be worth
looking at NumericField and NumericRangeQuery.


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