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From "Fuad Efendi" <>
Subject RE: Lucene FieldCache memory requirements
Date Tue, 03 Nov 2009 01:27:25 GMT
Ok, my "naive" thinking about FieldCache: for each Term we can quickly
retrieve DocSet. What are memory requirements? Theoretically,
[maxdoc]x[4-bytes DocumentID], plus some (small) array to store terms
pointing to (large) arrays of DocumentIDs.

Mike suggested to make this
memory requirement even lower... but please correct me if I am wrong with
formula, and I am unsure how it is currently implemented...


> -----Original Message-----
> From: Fuad Efendi []
> Sent: November-02-09 8:21 PM
> To:
> Subject: RE: Lucene FieldCache memory requirements
> Mark,
> I don't understand this:
> > so with a ton of docs and a few uniques, you get a temp boost in the RAM
> > reqs until it sizes it down.
> Sizes down??? Why is it called Cache indeed? And how SOLR uses it if it is
> not cache?
> And this:
> > A pointer for each doc.
> Why can't we use (int) DocumentID? For me, it is natural; 64-bit pointer
> an object in RAM is not natural (in Lucene world)...
> So, is it [maxdoc]x[4-bytes], or [maxdoc]x[8-bytes]?...
> -Fuad

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