The reason we use Solr for this specific task is because PostgreSQL cannot efficiently and quickly merge two index queries (time & space). It can do this to a limited degree, but both of these dimensions potentially match 10s of millions of documents, and PG falls over at this.
So you make the r-tree 3 dimensions (lat,lng,time). PostgreSQL supports this.
I dunno I can't envision Solr being more efficient than a properly designed RDBMS for these situations. If you were integrating a full-text search I'd absolutely believe that to be the case but...
We need independent time & geo searches as well. The indexes are vastly smaller in Solr. We use PostgreSQL extensively and prefer it, so it's not a matter of simply wanting to use something different.
That's very interesting. Could you share your story with the mailing list pgsql-hackers a little bit? The guys who work on indexing are quite active on those lists.
Also, there's some new thing I don't understand super well, sp-gist, do you have any thoughts on that?
