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From Erick Erickson <erickerick...@gmail.com>
Subject Re: Solr relevancy score different on replicated nodes
Date Mon, 07 Jan 2019 17:02:02 GMT
You misunderstand my point. The wall clock times _will_ be
different on leader and follower. It follows that the
documents contained in the individual segments on
the leader and follower will _not_ be identical.

This leads to _deleted_ documents being in different
segments on the leader and follower. Which also means
that the merge decisions will eventually merge different
segments.

Now remember that over time when you update a doc,
the doc is "marked as deleted", but some of the stats
e.g. termfrequency _still_ include the data for the
deleted docs and will until the segment is merged.

So the term frequency for some term on the leader
will be slightly different than on the follower and thus
the scoring will differ depending on which replica
gets the query. Etc.

The fact that you deleted and re-added the follower
supports the above. And your scores will skew as
you continue to update documents over time.

Generally this isn't something that people concern
themselves with, but if it's important to you you can
try enabling exactstatscache helps, see:
https://lucene.apache.org/solr/guide/6_6/distributed-requests.html

Best,
Erick

On Sun, Jan 6, 2019 at 10:25 PM Ashish Bisht <bishtashish77@gmail.com> wrote:
>
> Hi Erick,
>
> Thank you for the details,but doesn't look like a time difference in
> autocommit caused this issue.As I said if I do retrieve all query/keyword
> query on both server,they returned correct number of docs,its just relevancy
> score is taking diff values.
>
> I waited for brief period,still discrepancy was coming(no indexing also).So
> I went ahead deleting the follower node(thinking leader replica should be in
> correct state).After adding the new replica again,the issue is not
> appearing.
>
> We will monitor same if it appears in future.
>
> Regards
> Ashish
>
>
>
> --
> Sent from: http://lucene.472066.n3.nabble.com/Solr-User-f472068.html

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