In addition to that, I think the only way to solve this is to rely on the
aggregator node to actually re-rank after having aggregated.

Cheer

On Fri, Sep 9, 2016 at 11:48 PM, Alessandro Benedetti <abenede...@apache.org
> wrote:

> Let me explain further,
> let's assume a simple case when we have 2 shards.
> ReRankDocs =10 , rows=10 .
>
> Correct me if I am wrong Joel,
> What we would like :
> 1 page : top 10 re-scored
> 2 page: remaining 10 re-scored
> From page 3 the original scored docs.
> This is what is happening in a single sol instance if we put reRankDocs to
> 20.
>
> Let's see with sharing :
> To get the first page we get top 10 ( re-scored) from shard1 and top 10
> reranked for shard 2.
> Then the merged top 10 ( re-scored) will be calculated, and that is the
> page 1.
>
> But when we require the page 2, which means we additionally ask now :
> 20 docs to shard1, 10 re-scored and 10 not.
> 20 docs to shard2, 10 re-scored and 10 not.
> At this point we have 40 docs to merge and rank..
> The docs with the original score can go at any position ( not necessarily
> the last 20)
> In the page 2 we can find potentially docs with the original score.
> This is even more likely if the scores are on differente scales (e.g. the
> re-scored 0<x<1  and original >100 ) .
>
> Am I right ?
> Did I make any wrong assumption so far ?
>
> Cheers
>
>
> On Fri, Sep 9, 2016 at 7:47 PM, Joel Bernstein <joels...@gmail.com> wrote:
>
>> I'm not understanding where the inconsistency comes into play.
>>
>> The re-ranking occurs on the shards. The aggregator node will be sent some
>> docs that have been re-scored and others that are not. But the sorting
>> should be the same as someone pages through the result set.
>>
>>
>>
>> Joel Bernstein
>> http://joelsolr.blogspot.com/
>>
>> On Fri, Sep 9, 2016 at 9:28 AM, Alessandro Benedetti <
>> abenede...@apache.org>
>> wrote:
>>
>> > Hi guys,
>> > was just experimenting some reranker with really low number of rerank
>> docs
>> > ( 10= pageSize) .
>> > Let's focus on the distributed enviroment and  the manual sharding
>> > approach.
>> >
>> > Currently what happens is that the reranking task is delivered by the
>> > shards, they rescore the docs and then send them back to the aggregator
>> > node.
>> >
>> > If you want to rerank only few docs ( leaving the others with the
>> original
>> > score following), this can be done in a single Solr instance ( the
>> howmany
>> > logic manages that in the reranker) .
>> >
>> > What happens when you move to a distributed environment ?
>> > The aggregator will aggregate both rescored and original scored
>> documents,
>> > making the final ranking inconsistent.
>> > In the other hand if we make the rarankingDocs threshold dynamic ( to
>> adapt
>> > to start+rows) we can incur in the very annoying issue of having a
>> document
>> > sliding through the pages ( visible in the first page , then appearing
>> > again in the third ect ect).
>> >
>> > Any thought ?
>> >
>> > Cheers
>> >
>> > --
>> > --------------------------
>> >
>> > Benedetti Alessandro
>> > Visiting card : http://about.me/alessandro_benedetti
>> >
>> > "Tyger, tyger burning bright
>> > In the forests of the night,
>> > What immortal hand or eye
>> > Could frame thy fearful symmetry?"
>> >
>> > William Blake - Songs of Experience -1794 England
>> >
>>
>
>
>
> --
> --------------------------
>
> Benedetti Alessandro
> Visiting card : http://about.me/alessandro_benedetti
>
> "Tyger, tyger burning bright
> In the forests of the night,
> What immortal hand or eye
> Could frame thy fearful symmetry?"
>
> William Blake - Songs of Experience -1794 England
>



-- 
--------------------------

Benedetti Alessandro
Visiting card : http://about.me/alessandro_benedetti

"Tyger, tyger burning bright
In the forests of the night,
What immortal hand or eye
Could frame thy fearful symmetry?"

William Blake - Songs of Experience -1794 England

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