Elasticsearch:: Sorting giving weird results

Question

When I am searching the for the first time, its sorting all documents and giving me the first 5 records. However, if same search query is executed by changing the sort direction(ASC -> DESC), then its not sorting all documents again, its giving me last 5 retrieved documents(from previous search query), sorting them in desc order, and giving it back to me. I was expecting that it will sort all available documents in DESC order, and then retrieve first 5 results.

Am I doing something wrong, or missed any concept.

My search query:

{
    "sort": {
        "taskid": {
            "order": "ASC"
        }
    },
    "from": 0,
    "size": 5,
    "query": {
        "filtered": {
            "query": {
                "match_all": []
            }
        }
    }
}

I have data with taskid 1 to 100. Now above query fetched me record from taskid 1 to 5 in first attempt. Now when I changed the sort direction to desc, I was expecting documents with taskid 96-100(100,99,98,97,96 sequence) should be returned, however I was returned documents with taskid 5,4,3,2,1 in that sequence. Which meant, sorting was done on previous returned result only.

Please note that taskid and _id are same in my document. I had added a redundant field in my mapping which will be same as _id

`order` should come in lower case. It should be rather "asc" or "desc" :) — Richa, Aug 31 '16 at 12:08

score 2 · Accepted Answer · answered Aug 31 '16 at 12:10

Just change the case of the value in order key and you are good to go.

{
"sort": {
    "taskid": {
        "order": "asc"   // or "desc"
    }
},
"from": 0,
"size": 5,
"query": {
    "filtered": {
        "query": {
            "match_all": []
        }
    }
  }
}

Hope this helps..

score 2 · Answer 2 · answered Aug 31 '16 at 12:13

2

In elastic search, sort query is applied after the result are extracted from the es. As per the query mentioned in your question, first result is filtered based on search criteria, and then sorting is applied on the filtered result.

answered Aug 31 '16 at 12:13

Tarang Bhalodia

1,185
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score 0 · Answer 3 · answered Apr 30 '18 at 12:54

If it looks like you are only getting results based on an old subset of your data, then it may be that your newer data has not been indexed yet. This can happen easily in an automated test but with manual testing it is less likely.

Segments are rebuilt every second, so adding a delay/sleep of about a second between indexing and searching should fix your test if this is the problem.

Elasticsearch:: Sorting giving weird results

3 Answers3