ElasticSearch Rails：如果它存在和将来，则按 date1 排序，否则按 date2 排序

Question

Above are two different records from a Posts model we have stored in elasticsearch. We're trying to put in logic that will put our sticky posts in the feed like regular posts after they've expired.

We want to have it say

"If is_sticky AND stickied_until is in the future sort by stickied_until , else sort by created_at "

I think I have it working in SQL (since we store the bulk of the data there and only the searchable fields in ES), which looks like

ORDER BY
  CASE
  WHEN stickied_until >= '#{DateTime.now.utc}'
  THEN stickied_until
  ELSE created_at
END DESC

but then there's two things controlling the sort, which I'm pretty sure will cause bugs, and also just feels wrong.

Is it possible to do this kind of conditional sorting in ES?

Answer 1

You'll have to use a sort script for this.

{
  "sort": [
    {
      "_script": {
        "type": "number",
        "script": {
          "lang": "painless",
          "source": """
            def is_sticky = doc['is_sticky'].value;
            def created_at = doc['created_at'].value.getMillis();
            if (!is_sticky) {
              return created_at;
            }

            def stickied_until =  doc['stickied_until'].value.getMillis();
            def now = params['now'];

            if (is_sticky && stickied_until > now) {
              return stickied_until;
            }

            return created_at;
          """,
          "params": {
            "now": 1586798403888
          }
        },
        "order": "desc"
      }
    }
  ]
}

Note that I've used query-time constant params['now'] due to reasons explained in the docs .