Understanding Scan and Scroll in Elasticsearch

Question

Using ES and AngularJS to make a small search app. I'm trying to understand how to implement the scan and scroll feature in ES to use for pagination.

The docs say to make a search request and then to include a 'search_type: scan' and 'scroll' parameters.

Do I just add those parameters to my current search request or do I need to make another search request and specify request as the scan and scroll search request?

zt1983811 · Accepted Answer · 2015-12-10 00:30:31Z

2

As documentation explain you need to make the first call using

GET /old_index/_search?search_type=scan&scroll=1m 
{
    "query": { "match_all": {}},
    "size":  1000
}

The response to this request doesn’t include any hits (means content you search) but scroll id like following

{
    "_scroll_id" : "c2Nhbjs1OzMwNTYzMTkxNjpTSkM2S0cxVFJIeUk1NnZWbGFUV1FnOzMwNTYzMTkxNTpTSkM2S0cxVFJIeUk1NnZWbGFUV1FnOzMwNTYyMjEwNzp4OEkwZE54eVR0cXI4cHAzU2I5UmlBOzMwNTYzNTE0NjpQZEhCSUZXeFJZU3daaDJKZXZCRmh3OzMwNTY0OTg4OTphdEE1OTN2NFFsYVY5ZjJ4SUxuVFpROzE7dG90YWxfaGl0czoyOTIwOw==",
    "took" : 10,
    "timed_out" : false,
    "_shards" : {
        "total" : 5,
        "successful" : 5,
        "failed" : 0
    },
    "hits" : {
        "total" : 2920,
        "max_score" : 0,
        "hits" : []
    }
}

After this you can use normal call with the scroll_id GET /_search/scroll?scroll=1m&_scroll_idc2Nhbjs1OzMwNTYzMTkxNjpTSkM2S0cxVFJIeUk1NnZWbGFUV1FnOzMwNTYzMTkxNTpTSkM2S0cxVFJIeUk1NnZWbGFUV1FnOzMwNTYyMjEwNzp4OEkwZE54eVR0cXI4cHAzU2I5UmlBOzMwNTYzNTE0NjpQZEhCSUZXeFJZU3daaDJKZXZCRmh3OzMwNTY0OTg4OTphdEE1OTN2NFFsYVY5ZjJ4SUxuVFpROzE7dG90YWxfaGl0czoyOTIwOw==

_scroll_id can be in request or body

edited Dec 10, 2015 at 0:30

answered Dec 9, 2015 at 21:18

zt1983811

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3 Comments

user3125823 Over a year ago

so then on the initial request, you basically need to make 2 calls? First to scan&scroll and then another one to /_search/scroll?

user3125823 Over a year ago

Do I have to use scan and scroll or can I just use scroll?

zt1983811 Over a year ago

To answer your first question, yes you need 2 calls, the first one just get scrolling_id. The second question: I think you need both because the costly part of deep pagination is the global sorting of results, but if we disable sorting, then we can return all documents quite cheaply. To do this, we use the scan search type

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