[Developers] query for empty properties?

[Kurt Bollacker]

On Thu, Aug 21, 2008 at 12:39:52AM -0400, Christopher R. Maden wrote:
> Jason Douglas wrote:
> > I want to get only the objects that don't have a specific property  
> > filled in (expected type is an object).  Is there a way to do that?
> 
> "property":{"id":null,"optional":"forbidden"}
> 
> should do it.  No?

I take it back. I was oversimplifying the problem.  Consider the
query:

[
  {
    "*" : null,
    "/people/person/parents" : {
      "id" : null,
      "optional" : "forbidden"
    },
    "limit":1,
    "type" : "/people/person"
  }
]

which will return someone whose parents we do not know.  However, I
will point out that this is not reliable because MQL is doing the
query-then-filtering as I mentioned you needed to do manually. For
example, the query:

[
  {
    "*" : null,
    "/type/object/name" : {
      "optional" : "forbidden",
      "value" : null
    },
    "limit":1,
    "type" : "/people/person"
  }
]

is the same shape as the one above, but people without names are very
rare, so this query times out.  So what I should have said is that the
only *reliable* way to find topics without a specific property is to
query (possibly with cursors), and then filter externally to MQL.

								Kurt :-)



 
> ~Chris
> -- 
> Christopher R. Maden
> Data Architect
> Freebase.com: <URL: http://www.freebase.com/ >
> Metaweb Technologes, Inc. <URL: http://www.metaweb.com/ >
> _______________________________________________
> Developers mailing list
> Developers at freebase.com
> http://lists.freebase.com/mailman/listinfo/developers