Watson Discovery按时间片的新闻聚合返回null

Question

I run a query to IBM Watson Discovery service API in a java application:

queryBuilder.filter("blekko.hostrank>20,blekko.chrondate>1492552800,blekko.chrondate<1493157600,blekko.documentType:!\"blog\",blekko.documentType:!\"review\",language:english");
queryBuilder.query("text:" + brand);
queryBuilder.aggregation("[timeslice(blekko.chrondate,1day), term(docSentiment.type)]");
QueryResponse queryResponse = discovery.query(queryBuilder.build()).execute();

I have the following output in the response for the aggregation:

"aggregations": [
    null,
    {
      "results": [
        {
          "key": "positive",
          "matching_results": 245
        },
        {
          "key": "negative",
          "matching_results": 219
        },
        {
          "key": "neutral",
          "matching_results": 11
        }
      ],
      "type": "term",
      "field": "docSentiment.type"
    }
  ]

The timeslice aggregations returns null. Has anybody got experience on that? Thank you.

Answer 1

Looking at the documentation, this issue may be occurring because you are missing the timezone parameter inside of your timeslice:

timeslice: A specialized histogram that uses dates to create interval segments. Valid date interval values are minute, hour, day, week, month, and year. The syntax is timeslice(<field>,<interval>,<time_zone>) . To use timeslice, the time fields in your documents must be of the date data type and in ISO 8601 format. Unless both of these requirements are met, the timeslice parameter does not work correctly...

More information about timeslice and other aggregations can be found in the Query building reference .

I would also recommend using the Watson Discovery API Explorer to make it easier to test your query and see the output:

Watson Discovery API Reference