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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 20:43:00 GMT
Yeah it's all package private, I think it should be protected.

One would use OneMerge.info to then obtain the newly merged SR
via IW.getReader(). There's no reason not to include the newly
merged SR in OneMerge, there wasn't a need when 1516 was written.

On Tue, Sep 22, 2009 at 12:00 PM, Tim Smith <tsmith@attivio.com> wrote:
> Jason Rutherglen wrote:
>
> For that you can subclass IW.mergeSuccess.
>
>
>
> looks like thats package private :(
> also doesn't look like it has the merged output SegmentReader which could be
> used for cache loading/cache key (since it may not have been opened yet, but
> with NRT it should be available?)
> OneMerge looks heavily package private as well
>
>  -- Tim
>
> On Tue, Sep 22, 2009 at 11:43 AM, Tim Smith <tsmith@attivio.com> wrote:
>
>
> Jason Rutherglen wrote:
>
> I have a working version of Simple FieldCache Merging LUCENE-1785 that
> should go in real soon.
>
>
>
> Will this contain a callback mechanism i can register with to know what
> segments are being merged?
> that way i can merge my own caches as well at the application layer, perhaps
> exposed through something like IndexReaderWarmer.warmMerge(IndexReader[]
> input, IndexReader output)
>
> 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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