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From Jason Rutherglen <jason.rutherg...@gmail.com>
Subject Re: How to leverage the LogMergePolicy "calibrateSizeByDeletes" patch in Solr ?
Date Tue, 22 Sep 2009 18:36:40 GMT
I have a working version of Simple FieldCache Merging LUCENE-1785 that
should go in real soon.

On Tue, Sep 22, 2009 at 11:14 AM, Mark Miller <markrmiller@gmail.com> wrote:
> 1. see IndexWriter and the method/class that Mike pointed out earlier
> for the warming.
>
> 2. See Lucene-831 - I think we will get some form of that in someday.
>
> Tim Smith wrote:
>> This sounds pretty interesting
>>
>> is there a proposed API for doing this warming yet?
>> Is there a ticket tracking this?
>>
>> for my use cases, it would be really nice for applications to be able
>> to associate a custom "IndexCache" object with an index reader, then
>> this pluggable "AutoWarmer" would be in charge of initializing this
>> cache for a segment reader. I have a number of caches outside the
>> realm of regular field caches that i associate with a segment,
>> currently doing this after getting the IndexReader by iterating over
>> its segments, and getting a cache object shared across all instances
>> of the same logical segment. it would be nice if i could just have my
>> "cache" object subclass a lucene IndexCache class and drop it right
>> into this auto warming infrastructure (would greatly simplify things).
>>
>> then, once the index reader has been closed, it would call close on
>> any attached IndexCache objects in order to free up memory/objects.
>> (so i don't have to maintain reference counts anymore)
>>
>> Seems this could also greatly simplify the current field caching
>> mechanisms, as the field caches could be associated with an
>> IndexReader directly using the attached "IndexCache" object, instead
>> of using static weak reference hash maps. (could then add methods like
>> getFieldCache() to the IndexReader)
>>
>>  -- Tim Smith
>>
>> Michael McCandless wrote:
>>> Well described, that's exactly it!  I like the concrete example :)
>>>
>>> Thanks Yonik.
>>>
>>> Mike
>>>
>>> On Tue, Sep 22, 2009 at 1:38 PM, Yonik Seeley
>>> <yonik@lucidimagination.com> wrote:
>>>
>>>> OK Mike, thanks for your patience - I understand now :-)
>>>>
>>>> Here's an example that helped me understand - hopefully it will add to
>>>> others understanding more than it confuses ;-)
>>>>
>>>> IW.getReader() => segments={A, B}
>>>>  // something causes a merge of A,B into AB to start
>>>> addDoc(doc1)
>>>>  // doc1 goes into segment C
>>>> IW.getReader() => segments={A, B, C}
>>>>  // merge isn't done yet, so getReader() still returns A,B instead of
>>>> AB, but doc1 is still searchable!
>>>>
>>>> OK, in this scenario, there's no advantage to warming in the IW vs the app.
>>>> Let's start over with a little different timing:
>>>>
>>>> segments={A,B}
>>>>  // something causes a merge of A,B into AB to start
>>>> addDoc(doc1)
>>>>  // doc1 goes into segment C
>>>>  // merging of A,B into AB finishes
>>>> IW.getReader() => segments={AB, C}
>>>>
>>>> Oh, no... with warming at the app level, we need to warm the huge AB
>>>> segment before doc1 is visible.  We could continue using the old
>>>> reader while the warming is ongoing, so no user requests will
>>>> experience long queries, but doc1 isn't in the old segment.
>>>>
>>>> With warming in the IW (basically warming becomes part of the same
>>>> operation as merging), then getReader() would return segments={A,B,C}
>>>> and doc1 would still be instantly searchable.
>>>>
>>>> The only way to duplicate this functionality at the app layer would be
>>>> to recognize that there is a new segment, try and figure out what old
>>>> segments were merged to create this new segment, and create a reader
>>>> that's a mix of old and new to avoid unwarmed segments - not nice.
>>>>
>>>> -Yonik
>>>> http://www.lucidimagination.com
>>>>
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>>>>
>>>>
>>>>
>>>
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>>>
>>
>
>
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