Top Hits - ParadeDB

The top hits aggregation is meant to be used in conjunction with the terms aggregation. It returns the top documents for each bucket of a terms aggregation. For example, the following query answers “what are top 3 results sorted by created_at for each rating category?”

SELECT pdb.agg('{"top_hits": {"size": 3, "sort": [{"created_at": "desc"}], "docvalue_fields": ["id", "created_at"]}}')
FROM mock_items
WHERE id @@@ pdb.all()
GROUP BY rating;

Expected Response

      agg
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 {"hits": [{"sort": [10907000251854775808], "docvalue_fields": {"id": [25], "created_at": ["2023-05-09T10:30:15Z"]}}, {"sort": [10906844884854775808], "docvalue_fields": {"id": [26], "created_at": ["2023-05-07T15:20:48Z"]}}, {"sort": [10906666358854775808], "docvalue_fields": {"id": [13], "created_at": ["2023-05-05T13:45:22Z"]}}]}
 {"hits": [{"sort": [10906756363854775808], "docvalue_fields": {"id": [24], "created_at": ["2023-05-06T14:45:27Z"]}}, {"sort": [10906385295854775808], "docvalue_fields": {"id": [28], "created_at": ["2023-05-02T07:40:59Z"]}}, {"sort": [10906236353854775808], "docvalue_fields": {"id": [29], "created_at": ["2023-04-30T14:18:37Z"]}}]}
 {"hits": [{"sort": [10906480573854775808], "docvalue_fields": {"id": [17], "created_at": ["2023-05-03T10:08:57Z"]}}, {"sort": [10906315942854775808], "docvalue_fields": {"id": [20], "created_at": ["2023-05-01T12:25:06Z"]}}, {"sort": [10906218361854775808], "docvalue_fields": {"id": [8], "created_at": ["2023-04-30T09:18:45Z"]}}]}
 {"hits": [{"sort": [10906573359854775808], "docvalue_fields": {"id": [27], "created_at": ["2023-05-04T11:55:23Z"]}}, {"sort": [10905961160854775808], "docvalue_fields": {"id": [15], "created_at": ["2023-04-27T09:52:04Z"]}}, {"sort": [10905202003854775808], "docvalue_fields": {"id": [7], "created_at": ["2023-04-18T14:59:27Z"]}}]}
 {"hits": [{"sort": [10906586188854775808], "docvalue_fields": {"id": [10], "created_at": ["2023-05-04T15:29:12Z"]}}]}
(5 rows)

The sort value returned by the aggregation is Tantivy’s internal sort ID and should be ignored. To get the actual fields, pass a list of fields to docvalue_fields. If a text or JSON field is passed to docvalue_fields, it must be indexed with the literal tokenizer. To specify an offset, use from:

SELECT pdb.agg('{"top_hits": {"size": 3, "from": 1, "sort": [{"created_at": "desc"}], "docvalue_fields": ["id", "created_at"]}}')
FROM mock_items
WHERE id @@@ pdb.all()
GROUP BY rating;

If multiple fields are passed into sort, the additional fields are used as tiebreakers:

SELECT pdb.agg('{"top_hits": {"size": 3, "sort": [{"created_at": "desc"}, {"id": "asc"}], "docvalue_fields": ["id", "created_at"]}}')
FROM mock_items
WHERE id @@@ pdb.all()
GROUP BY rating;

See the Tantivy documentation for all available options.