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From Jason Rutherglen <jason.rutherg...@gmail.com>
Subject Re: 2.9 NRT w.r.t. sorting and field cache
Date Tue, 22 Sep 2009 15:36:25 GMT
> When heaving indexing introduces or modifies segments, would
it cause reloading of FieldCache at query time and thus would
impact search performance?

How is this different than previous versions of Lucene? In 2.9
the field caches are only loaded for new segments incrementally,
instead of over the Multi*Reader. It sounds like you're confused
about the key used for the field cache which is now the
freqStream (see IR.getFieldCacheKey) rather than IR so that a
different field cache isn't loaded each time a new instance of
IR is instantiated for an already loaded segment.

Feel free to contribute to the wiki about your experiences, I
think others will have similar questions.

On Mon, Sep 21, 2009 at 10:27 PM, John Wang <john.wang@gmail.com> wrote:
> Hi Yonik:
>
>      Actually that is what I am looking for. Can you please point me to
> where/how sorting is done per-segment?
>
>      When heaving indexing introduces or modifies segments, would it cause
> reloading of FieldCache at query time and thus would impact search
> performance?
>
> thanks
>
> -John
>
> On Tue, Sep 22, 2009 at 1:05 PM, Yonik Seeley <yonik@lucidimagination.com>
> wrote:
>>
>> On Tue, Sep 22, 2009 at 12:56 AM, John Wang <john.wang@gmail.com> wrote:
>> > Looking at the code, seems there is a disconnect between how/when field
>> > cache is loaded when IndexWriter.getReader() is called.
>>
>> I'm not sure what you mean by "disconnect"
>>
>> > Is FieldCache updated?
>>
>> FieldCache entries are populated on demand, as they always have been.
>>
>> > Otherwise, are we reloading FieldCache for each
>> > reader instance?
>>
>> Searching/sorting is now per-segment, and so is the use of the
>> FieldCache.  Segments that don't change shouldn't have to reload their
>> FieldCache entries.
>>
>> -Yonik
>> http://www.lucidimagination.com
>>
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>
>

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