Scroll

Introduced 0.1.0

You can use the scroll operation to retrieve a large number of results. For example, for machine learning jobs, you can request an unlimited number of results in batches.

To use the scroll operation, add a scroll parameter to the request header with a search context to tell Lucenia how long you need to keep scrolling. This search context needs to be long enough to process a single batch of results.

Because search contexts consume a lot of memory, we suggest you don’t use the scroll operation for frequent user queries. Instead, use the sort parameter with the search_after parameter to scroll responses for user queries.

Example

To set the number of results that you want returned for each batch, use the size parameter:

GET shakespeare/_search?scroll=10m
{
  "size": 10000
}

Lucenia caches the results and returns a scroll ID to access them in batches:

"_scroll_id" : "DXF1ZXJ5QW5kRmV0Y2gBAAAAAAAAAAUWdmpUZDhnRFBUcWFtV21nMmFwUGJEQQ=="

Pass this scroll ID to the scroll operation to get back the next batch of results:

GET _search/scroll
{
  "scroll": "10m",
  "scroll_id": "DXF1ZXJ5QW5kRmV0Y2gBAAAAAAAAAAUWdmpUZDhnRFBUcWFtV21nMmFwUGJEQQ=="
}

Using this scroll ID, you get results in batches of 10,000 as long as the search context is still open. Typically, the scroll ID does not change between requests, but it can change, so make sure to always use the latest scroll ID. If you don’t send the next scroll request within the set search context, the scroll operation does not return any results.

If you expect billions of results, use a sliced scroll. Slicing allows you to perform multiple scroll operations for the same request, but in parallel. Set the ID and the maximum number of slices for the scroll:

GET shakespeare/_search?scroll=10m
{
  "slice": {
    "id": 0,
    "max": 10
  },
  "query": {
    "match_all": {}
  }
}

With a single scroll ID, you get back 10 results. You can have up to 10 IDs.

Close the search context when you’re done scrolling, because the scroll operation continues to consume computing resources until the timeout:

DELETE _search/scroll/DXF1ZXJ5QW5kRmV0Y2gBAAAAAAAAAAcWdmpUZDhnRFBUcWFtV21nMmFwUGJEQQ==

To close all open scroll contexts:

DELETE _search/scroll/_all

The scroll operation corresponds to a specific timestamp. It doesn’t consider documents added after that timestamp as potential results.

Path and HTTP methods

GET _search/scroll
POST _search/scroll

GET _search/scroll/<scroll-id>
POST _search/scroll/<scroll-id>

URL parameters

All scroll parameters are optional.

Response

{
  "succeeded": true,
  "num_freed": 1
}