Apache SOLR search by category

I am using apache-solr-1.4.1 and jdk1.6.0_14.

I have the following scenario. I have 3 categories of data indexed in SOLR i.e. CITIES, STATES, COUNTRIES. When I query data from SOLR I need the search result from SOLR based on the following criteria:

In a single query to SOLR I need data fetched from SOLR grouped by each category with a predefined results count for each cate开发者_C百科gory.

How can I specify this condition in SOLR?

I have tried to use SOLR Field Collapsing feature, but I am not able to get the desired output from SOLR.

Please suggest.

My solution is not exactly what you have asked but is my take on what SOLR does best, which is full text search. Instead of grouping the results by "category", I'd suggest you order the results by relevance score but also provide a facet count for the category values. In my experience users expect a "search" to behave like Google, with the best matches at the top. Deviating form this norm confuses the user in most cases.

If you want exactly as you have asked (actual results grouped by category) then you could use a relational database and do a group_by or write a custom function query with SOLR (I cannot advise on this as I've never done it).

More info: index the data with the appropriate fields, e.g. name, population, etc. But also add a field called "category", which would have a value of either CITIES, STATES or COUNTRIES. Then perform a standard SOLR search, which will return results in order of relevance - i.e. best matches at the top. As part of the request, you can specify a facet.field=category, which will return counts for the search results for each of the given categories (in the "facet" results section). In the UI you can then create links for each category facet which performs the original search plus &fq=category:CITIES, etc., thus restricting results to just that category. See the facetting overview on the SOLR wiki for more info.