Filter out empty arrays in JSON

[Andries Engelbrecht]

How do you filter out records with an empty array in drill? 
i.e some records have "url":[]  and some will have an array with data in it. 
When trying to read records with data in the array drill fails due to records 
missing any data in the array. Trying a filter with/* where "url":[0] is not 
null */ fails, also fails if applying url is not null.

Note some of the arrays contains maps, using twitter data as an example below. 
Some records have an empty array with “hashtags”:[]  and others will look 
similar to what is listed below.

"entities": {
    "trends": [],
    "symbols": [],
    "urls": [],
    "hashtags": [
      {
        "text": "GoPatriots",
        "indices": [
          83,
          94
        ]
      }
    ],
    "user_mentions": []
  },


Thanks
—Andries