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From Erick Erickson <>
Subject Re: multiple small indexes or one big index?
Date Thu, 02 Jun 2011 11:04:13 GMT
At this size, really consider going to a single index. The lack of
administrative headaches alone is probably well worth the effort....

I almost guarantee that the time you spend re-writing things to keep
the searchers open (and finding the bugs!) will be far more than just
putting all the data in a single index.

But that might just be my preferences showing....


On Wed, Jun 1, 2011 at 5:37 PM, Alexander Rosemann
<> wrote:
> Many thanks for the tips, Erick! I do close each searcher after a search...
> I will change that first thing tmrw. and let you know how that went.
> Multi-threaded searching will be next and if that hasn't helped, I will
> switch to one big index.
> All indexes together are rather small, ~200MB and 50.000 documents.
> -Alex
> On 01.06.2011 23:26, Erick Erickson wrote:
>> I'd start by putting them all in one index. There's no penalty
>> in Lucene for having empty fields in a document, unlike an
>> Alternately, if you're opening then closing searchers each
>> time, that's very expensive. Could you open the searchers
>> once and keep them open (all 90 of them)? That alone might
>> do the trick and be less of a change to your program. You
>> could also fire multiple threads at the searches, but check if
>> you're CPU bound first (if you are, multiple threads won't
>> help much/at all).
>> You haven't said how big these indexes are nor how many
>> documents you're talking about here, so this advice is suspect.
>> Do look at putting it all in one index though, let us know if you
>> have some data indicating how big stuff is/would be.
>> Best
>> Erick
>> On Wed, Jun 1, 2011 at 4:35 PM, Alexander Rosemann
>> <>  wrote:
>>> Hi all, I was wondering whether you could give me some advice on how to
>>> improve my search performance.
>>> I have 90 lucene indexes, each having different fields (~5 per Document).
>>> When I search, I always have to go through all indexes to build my result
>>> set. Searching one index takes approx. 100ms, thus searching all indexes
>>> takes 9s in total.
>>> How can I reduce the time it needs to search?
>>> I decided to create this many indexes because putting all data in one
>>> index
>>> would mean that a document would have ~400 fields, with most of them left
>>> empty. Is that ok? Would a single index be faster compared to multiple
>>> small
>>> ones?
>>> Any pointers are much appreciated.
>>> Regards,
>>> Alex
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