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From Michael McCandless <luc...@mikemccandless.com>
Subject Re: Memory consumption in trunk for sorting and faceting
Date Sun, 12 Jun 2011 14:06:42 GMT
Right, not using objects is a huge win, especially on 64 bit JRE.

Cutting over to UTF8 bytes is also a big drop in certain cases, since
it's UTF8 vs UTF16 for 3.x.

Ie, simple ascii fields take half the storage vs 3.x.

Similarly, the terms index in 3.x uses multiple objects per indexed
Term, and no objects in trunk (since it's just a single byte[] holding
the FST), and also uses UTF8 to hold the term data, instead of UTF16.

FST has been backported to 3.x but it's not used yet I think;
back-porting the terms index improvements would be a biggish change...

Mike McCandless

http://blog.mikemccandless.com

On Sun, Jun 12, 2011 at 9:51 AM, Dawid Weiss
<dawid.weiss@cs.put.poznan.pl> wrote:
>> Is it fair to say that the two big innovations that have reduced the
>> memory footprint are:
>> 1> going to byte arrays for string storage
>> 2> the FST work?
>>
>> Final question. It looks like the FST work is back-ported to the
>> current 3_x code branch, is that true? Anything else back-ported
>> there? I'll check that branch out and give it a whirl for kicks.
>
> I'm guessing it's going from Strings to ByteRefs (objects have
> considerable overhead, really). This used to be my favorite showcase
> for students -- manipulate a large array of Integer[] vs. manipulate
> the same size array of int[]. A similar think applies to String
> instances vs. ByteRefs (utf16 vs. utf8 encoding, object header
> overhead, etc).
>
> Dawid
>
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