WARNING: Version 5.5 of Elasticsearch has passed its EOL date.
This documentation is no longer being maintained and may be removed. If you are running this version, we strongly advise you to upgrade. For the latest information, see the current release documentation.
Search After
editSearch After
editPagination of results can be done by using the from
and size
but the cost becomes prohibitive when the deep pagination is reached.
The index.max_result_window
which defaults to 10,000 is a safeguard, search requests take heap memory and time proportional to from + size
.
The Scroll api is recommended for efficient deep scrolling but scroll contexts are costly and it is not
recommended to use it for real time user requests.
The search_after
parameter circumvents this problem by providing a live cursor.
The idea is to use the results from the previous page to help the retrieval of the next page.
Suppose that the query to retrieve the first page looks like this:
GET twitter/tweet/_search { "size": 10, "query": { "match" : { "title" : "elasticsearch" } }, "sort": [ {"date": "asc"}, {"_uid": "desc"} ] }
A field with one unique value per document should be used as the tiebreaker of the sort specification.
Otherwise the sort order for documents that have the same sort values would be undefined. The recommended way is to use
the field _uid
which is certain to contain one unique value for each document.
The result from the above request includes an array of sort values
for each document.
These sort values
can be used in conjunction with the search_after
parameter to start returning results "after" any
document in the result list.
For instance we can use the sort values
of the last document and pass it to search_after
to retrieve the next page of results:
GET twitter/tweet/_search { "size": 10, "query": { "match" : { "title" : "elasticsearch" } }, "search_after": [1463538857, "tweet#654323"], "sort": [ {"date": "asc"}, {"_uid": "desc"} ] }
The parameter from
must be set to 0 (or -1) when search_after
is used.
search_after
is not a solution to jump freely to a random page but rather to scroll many queries in parallel.
It is very similar to the scroll
API but unlike it, the search_after
parameter is stateless, it is always resolved against the latest
version of the searcher. For this reason the sort order may change during a walk depending on the updates and deletes of your index.