Apply filter based on Druid Lookup data value

Hi Team,

I am working on a use case where I need to filter on data source based on Lookup data value. I was wondering if the below query would be most efficient or there is other way to write this query to apply the filter. To me it looks like I am hitting lookup twice.

Would appreciate your thoughts here.

{

“queryType” : “select”,

“dataSource” : “wikiticker”,

“granularity” : “all”,

“dimensions” : [“timestamp”, “channel”, “page”, “namespace”,

                    {

                    "type" : "extraction",

                    "dimension" : "namespace",

                    "outputName" : "namespace_description",

                    "extractionFn": {

                            "type":"registeredLookup",

                            "lookup": "wiki_lookup",

                            "retainMissingValue":true,

                            "injective":false

                            }

                    }

             ],

“filter”: { “type”: “selector”,

          "dimension": "namespace",

          "value": "Talk Description",

          "extractionFn": {

                "type":"registeredLookup",

                "lookup": "wiki_lookup",

                "retainMissingValue":true

             }

        },

“metrics” : ,

“intervals” : [ “2015-09-12/2015-09-13” ],

“pagingSpec”:{“pagingIdentifiers”: {}, “threshold”:5}

}