Cores and and ranking (search quality)

[jo...@aol.com]

Hi,

I have data in which I will index and search on.  This data is well define such that I can index into a single core or multiple cores like so: core_1:Jan2015, core_2:Feb2015, core_3:Mar2015, etc.

My question is this: if I put my data in multiple cores and use distributed search will the ranking be different if I had all my data in a single core?  If yes, how will it be different?  Also, will facet and more-like-this quality / result be the same?

Also, reading the distributed search wiki (http://wiki.apache.org/solr/DistributedSearch) it looks like Solr does the search and result merging (all I have to do is issue a search), is this correct?

Thanks!

- MJ

Re: Cores and and ranking (search quality)

[Toke Eskildsen <te...@statsbiblioteket.dk>]

On Thu, 2015-03-05 at 14:34 +0100, johnmunir@aol.com wrote:
> My question is this: if I put my data in multiple cores and use
> distributed search will the ranking be different if I had all my data
> in a single core?

Yes, it will be different. The practical impact depends on how
homogeneous your data are across the shards and how large your shards
are. If you have small and dissimilar shards, your ranking will suffer a
lot.

Work is being done to remedy this:
https://issues.apache.org/jira/browse/SOLR-1632

> Also, will facet and more-like-this quality / result be the same?

It is not formally guaranteed, but for most practical purposes, faceting
on multi-shards will give you the same results as single-shards.

I don't know about more-like-this. My guess is that it will be affected
in the same way that standard searches are.

> Also, reading the distributed search wiki
> (http://wiki.apache.org/solr/DistributedSearch) it looks like Solr does
> the search and result merging (all I have to do is issue a search), is
> this correct?

Yes. From a user-perspective, searches are no different.

- Toke Eskildsen, State and University Library, Denmark