Faceting is the arrangement of search results into categories based on indexed terms.  Faceted search provides an effective way to allow users to refine search results, continually drilling down until the desired items are found.

Implementing Faceting with Solr:

It’s  simple to get faceting information from Solr, as there are few prerequisites. Solr offers the following types of faceting:

Field faceting – retrieve the counts for all terms, or just the top terms in any given field. The field must be indexed.
Query faceting – return the number of documents in the current search results that also match the given query.

Faceting commands are added to any normal Solr query request, and the faceting counts come back in the same query response.

Example of Field Facet:

Suppose, user entered following query in search bar.The Solr query to retrieve the top “camera” matches would be:

http://localhost:8983/solr/query?q=camera

And now we want to add search on manufacturers also. we will just need to add following:

&facet=true
&facet.field=manu  // “manu” field available in schema

The query response will now contain facet count information for the given fields in addition to the top matches for the query.

“facet_fields” : {
“manu” : [
"Canon USA" , 25,
"Olympus" , 21,
"Sony" , 12,
"Panasonic" , 9,
"Nikon" , 4 ],

}

Example of Query facet:

For query facet , we will simply write facet.query command to our query request.

Here, we want to fetch result whose price lies between $100 or less, $100-$200.

&facet=true
&facet.query=price:[* TO 100]
&facet.query=price:[100 TO 200]

Response would be as shown below:

“facet_queries” : {
“price:[* TO 100]” : 28,
“price:[100 TO 200]” : 54,
}

Now let’s assume that the user wants to drill down on the constraint $400-$500 from the Price facet to get a new set of results that include only cameras in that price range. For this we use the fq (filter query) parameter, which allows one to filter by a query. We’ll also send the relevant faceting commands again since we also want to update the facet counts.

http://localhost:8983/solr/query?q=camera&facet=on&facet.field=manu&facet.field=camera_type&fq=price:[400 to 500]

There are so many facet.* available that you can use in your search query.

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ProsperaSoft offers Solr development solutions. You can email at info@prosperasoft.com to get in touch with ProsperaSoft Solr experts and consultants.