This commit changes the default for the `track_total_hits` option of the search request
to `10,000`. This means that by default search requests will accurately track the total hit count
up to `10,000` documents, requests that match more than this value will set the `"total.relation"`
to `"gte"` (e.g. greater than or equals) and the `"total.value"` to `10,000` in the search response.
Scroll queries are not impacted, they will continue to count the total hits accurately.
The default is set back to `true` (accurate hit count) if `rest_total_hits_as_int` is set in the search request.
I choose `10,000` as the default because that's also the number we use to limit pagination. This means that users will be able to know how far they can jump (up to 10,000) even if the total number of hits is not accurate.
Closes#33028
In Lucene 8 searches can skip non-competitive hits if the total hit count is not requested.
It is also possible to track the number of hits up to a certain threshold. This is a trade off to speed up searches while still being able to know a lower bound of the total hit count. This change adds the ability to set this threshold directly in the track_total_hits search option. A boolean value (true, false) indicates whether the total hit count should be tracked in the response. When set as an integer this option allows to compute a lower bound of the total hits while preserving the ability to skip non-competitive hits when enough matches have been collected.
Relates #33028
Clinton Gormley
Jim Ferenczi