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From "Haroldo Nascimento" <>
Subject Re: Index: mixing the structure of persistence
Date Mon, 26 Nov 2007 14:27:37 GMT

  I have a very great volume of data (6.000.000 of documents) and I
need to have a very fast search. I am thinking about using Terracotta
(with Lucene) for clustering the solution.

  One of the advantages of the Terracotta is that part of the index is
stored in memory and part is persisted em disk. If not to find in
memory the application searchs in disk. This is transparent for the
user. The problem would be in the process of updat of index.

  Another solution would be to persist the index using only Lucene,
but I believe that the reply time very using disk either bigger that
the solution in memory.

  You know some document comparative about the solution em memory
(RAMDirectory) and solution em disk using Lucene?

  Tip: In another application I am using the solution index in memory
(RAMDirectory), to initiate the process of load of the indice I
serialized the RAMDirectory object. For it I need  insert "implements
Serializable" in some classrooms of Lucene.

On Nov 25, 2007 5:55 PM, Erick Erickson <> wrote:
> As I understand, Lucene does a fair amount of caching of terms in
> memory without you having to specify anything.
> But it's hard to see how your question relates. Remember that Lucene is
> finding *all* matching docs. So searching in a RAMdirectory and then
> searching in the file doesn't really seem possible since Lucene has to
> search
> the entire index every time to score the docs. It doesn't stop after
> the first hit, since the next hit may score higher.
> But I'm sure Lucene *does* cache portions of the index in RAM when
> possible, but I've never had occasion to dig into the details.
> Which leads me to ask "Why do you care?". Is there a specific
> situation you're trying to get better performance from or is this more
> of a background question? If you have a specific situation, please describe
> it in some detail so better minds than mine can give you a better
> response <G>....
> Best
> Erick
> On Nov 24, 2007 10:26 AM, Haroldo Nascimento <>
> wrote:
> > Hi,
> >
> >  I have a question ?
> >
> >  Lucene offers a mixing structure of storage of index, that is, first
> > do search in memoria (ARMDirectory) and in case of not found do search
> > in index file automatically ? For example: Load part of index in
> > memory for do the search fastest.
> >
> >  Thnaks
> >
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