Sort Order when relevance is equal

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Sort Order when relevance is equal

Erich Lin
Ignoring the bouncing results problem with multiple shards , is the order of results deterministic when sorting by relevance score or any other field.  

What I mean by this is if two documents have the same score, 

1) will they always be in the same order if we set the preference parameter to an arbitrary string like the user’s session ID. 
2) If so, is there a way to predict this deterministic order? Is it done by ID of the documents as a tiebreaker etc? 
3) If not, could we specify that or do we have to do a secondary sort on ID if we wanted to do that?


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Re: Sort Order when relevance is equal

Mateusz Kaczynski-2
Seconding question.

Also, is it possible that the default order for an equal relevance score changed between 1.0 and 1.2 ? We've noticed seemingly random ordering in our regression when updating.  

On Wednesday, 14 May 2014 00:49:55 UTC, Erich Lin wrote:
Ignoring the bouncing results problem with multiple shards , is the order of results deterministic when sorting by relevance score or any other field.  

What I mean by this is if two documents have the same score, 

1) will they always be in the same order if we set the preference parameter to an arbitrary string like the user’s session ID. 
2) If so, is there a way to predict this deterministic order? Is it done by ID of the documents as a tiebreaker etc? 
3) If not, could we specify that or do we have to do a secondary sort on ID if we wanted to do that?


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Re: Sort Order when relevance is equal

Mateusz Kaczynski-2
In reply to this post by Erich Lin
Seconding question.

Also, is it possible that it changed between versions 1.0 and 1.2? We're trying to upgrade and noticed a seemingly random order of documents with equal relevance in regression testing.

On Wednesday, 14 May 2014 00:49:55 UTC, Erich Lin wrote:
Ignoring the bouncing results problem with multiple shards , is the order of results deterministic when sorting by relevance score or any other field.  

What I mean by this is if two documents have the same score, 

1) will they always be in the same order if we set the preference parameter to an arbitrary string like the user’s session ID. 
2) If so, is there a way to predict this deterministic order? Is it done by ID of the documents as a tiebreaker etc? 
3) If not, could we specify that or do we have to do a secondary sort on ID if we wanted to do that?


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Re: Sort Order when relevance is equal

Clinton Gormley-2
In reply to this post by Erich Lin
Hi Erich

On 14 May 2014 02:49, Erich Lin <[hidden email]> wrote:
1) will they always be in the same order if we set the preference parameter to an arbitrary string like the user’s session ID. 

They will be, until a merge happens (eg from indexing, updating, deleting, or just because...)
 
2) If so, is there a way to predict this deterministic order? Is it done by ID of the documents as a tiebreaker etc? 

It's the order of docs in the Lucene segment
 
3) If not, could we specify that or do we have to do a secondary sort on ID if we wanted to do that?

Yes, you could provide a secondary sort on _uid (not _id) 

Also, is it possible that the default order for an equal relevance score changed between 1.0 and 1.2 ? We've noticed seemingly random ordering in our regression when updating.  

It shouldn't have - if you can reproduce this, please open an issue.

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