CODEWITHSUNDEEP
elasticsearchlucene
soumitra goswami
soumitra goswami

Reputation: 891

How to limit search results from each index in a multi index search query?

I am using Elasticsearch version 6.3 and I want to make queries across multiple indices.Elasticsearch has support for this and I can give multiple indices as comma separated values in the url with one query in request body and also give size parameter to limit the number of search results returned.However this limits the size of the overall search results and might lead to no results from some indexes- so instead I want to fetch first n number of results from each index.

I tried using multi search api (_msearch) but with that it seems I have to give the same query and size for all indexes and that works, but I am not able to get a single aggregation over the entire result , is there any way to address both the issues?

Upvotes: 0

Views: 1308

Answers (1)

Val
Val

Reputation: 217274

Solution 1:

You're on the right path with the _msearch query. What I would do is to issue one query per index (no aggregations!) with the size you want for that index, as well as another query just for the aggregations, like this:

{ "index": "index1" }
{ "size": 5, "query": { ... }}
{ "index": "index2" }
{ "size": 5, "query": { ... }}
{ "index": "index3" }
{ "size": 5, "query": { ... }}
{ "index": "index1,index2,index3" }
{ "size": 0, "query": { ... }, "aggs": { ... } }

So the first three queries will return document hits from each of the three indexes and the last query will return the aggregation computed on all indexes, but no documents.

Solution 2:

Another way to tackle this if you have a small size, is to have a single query in the query part and then aggregate on the index name and retrieve hits from each index using top_hits, like this:

POST index1,index2,index3/_search
{
  "size": 0,
  "query": { ... },
  "aggs": {
    "indexes": {
      "terms": {
        "field": "_index",
        "size": 50
      },
      "aggs": {
        "hits": {
          "top_hits": {
            "size": 5
          }
        }
      }
    }
  }
}

Upvotes: 3

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