1 – Why would someone use Solr to search on a wide-column database (HBase)?
The power of HBase search (scans) is not filters. All is about the rowkey design. If you want to take full advantage of HBase, you must know all your search queries at the moment of deigning your database. This way, you will put all the “search” intelligence in your rowkeys. But what if you don’t know all your search criteria at the beginning? What if you need to add extra search criterias? Would you create a new “view” of data with another rowkey strategy? What would you do if your client needs to search by “proximity” or a did you mean style?
There is no answer for this question than “it depends”.
2 – Why we did not use Ambari for Solr deployment?
It is not integrated offcially, it does not bring any added-value, it adds some more complexity in ambari-agents scripts (must be altered manually for this use case).