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From Webster Homer <webster.ho...@sial.com>
Subject Re: SolrCloud different score for same document on different replicas.
Date Fri, 06 Jan 2017 16:45:02 GMT
I was seeing something like this, and it turned out to be a problem with
our autoCommit and autoSoftCommit settings. We had overly aggressive
settings that eventually started failing with errors around too many
warming searchers etc...

You can test this by doing a commit and seeing if the replicas start
returning consistent results

On Thu, Jan 5, 2017 at 10:31 AM, Charlie Hull <charlie@flax.co.uk> wrote:

> On 05/01/2017 13:30, Morten B√łgeskov wrote:
>
>>
>>
>> Hi.
>>
>> We've got a SolrCloud which is sharded and has a replication factor of
>> 2.
>>
>> The 2 replicas of a shard may look like this:
>>
>> Num Docs:    5401023
>> Max Doc:    6388614
>> Deleted Docs:    987591
>>
>>
>> Num Docs:    5401023
>> Max Doc:    5948122
>> Deleted Docs:    547099
>>
>> We've seen >10% difference in Max Doc at times with same Num Docs.
>> Our use case is few documents that are search and many small that
>> are filtered against (often updated multiple times a day), so the
>> difference in deleted docs aren't surprising.
>>
>> This results in a different score for a document depending on which
>> replica it comes from. As I see it: it has to do with the different
>> maxDoc value when calculating idf.
>>
>> This in turn alters a specific document's position in the search
>> result over reloads. This is quite confusing (duplicates in pagination).
>>
>> What is the trick to get homogeneous score from different replicas.
>> We've tried using ExactStatsCache & ExactSharedStatsCache, but that
>> didn't seem to make any difference.
>>
>> Any hints to this will be greatly appreciated.
>>
>>
> This was one of things we looked at during our recent Lucene London
> Hackday (see item 3) https://github.com/flaxsearch/london-hackday-2016
>
> I'm not sure there is a way to get a homogenous score - this patch tries
> to keep you connected to the same replica during a session so you don't see
> results jumping over pagination.
>
> Cheers
>
> Charlie
>
>
> --
> Charlie Hull
> Flax - Open Source Enterprise Search
>
> tel/fax: +44 (0)8700 118334
> mobile:  +44 (0)7767 825828
> web: www.flax.co.uk
>

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