Search a nested field for multiple values on the same field with elasticsearch

Question

I'm trying to query a nested properties with multiple values.

Here is an example that will be clearer.

Create an index with a nested field

    curl -X DELETE "http://localhost:9200/testing_nested_query/"
    curl -X POST "http://localhost:9200/testing_nested_query/" -d '{
        "mappings": {
            "class": {
              properties: {
                title: {"type": "string"},
                "students": {
                  "type": "nested",
                  "properties": {
                    "name": {"type": "string"}
                  }
                }
              }
            }
        }

    }'

Add some values

    curl -XPUT 'http://localhost:9200/testing_nested_query/class/1' -d '{
      "title": "class1",
      "students": [{"name": "john"},{"name": "jack"},{"name": "jim"}]
    }'

    curl -XPUT 'http://localhost:9200/testing_nested_query/class/2' -d '{
      "title": "class2",
      "students": [{"name": "john"},{"name": "chris"},{"name": "alex"}]
    }'

Query for all classes where john is (2 hits as expected)

curl -XGET 'http://localhost:9200/testing_nested_query/class/_search' -d '{
  "query": {
    "nested": {
      "path":"students",
      "query": {
        "bool": {
          "must": [
            {"match": {"students.name": "john"}}
          ]
        }
      }
    }
  }
}'

Query for classes where both john and jack are attending ( 0 results instead of 1)

curl -XGET 'http://localhost:9200/testing_nested_query/class/_search' -d '{
  "query": {
    "nested": {
      "path":"students",
      "query": {
        "bool": {
          "must": [
            {"match": {"students.name": "john"}},
            {"match": {"students.name": "jack"}}
          ]
        }
      }
    }
  }
}'

I've tried with match and filter but I can never get the query to return the expected values.

Answer 1

It just needs a bit change:

{
  "query": {
    "bool": {
        "must": [
           {
               "nested": {
                  "path":"students",
                  "query": {
                    "bool": {
                      "must": [
                        {"match": {"name": "john"}}
                      ]
                    }
                  }
                }
           },
           {
               "nested": {
                  "path":"students",
                  "query": {
                    "bool": {
                      "must": [
                        {"match": {"name": "jack"}}
                      ]
                    }
                  }
                }
           }
        ]
    }
  }
}

Why?

Basically, in a nested query, the query and the filter are collectively executed on a single nested document - in your case one name. So your query would pick up every nested document and try to find every document that has name equal to john and jack at the same time - which is impossible.

My query tries to find an indexed document that has one nested document with name equal to john and another nested document with name equal to jack. So basically one nested query tries to match one nested document completely.

To prove what I am suggesting, try this:

Create the same index with same mapping as you did

** Then index the following documents **

curl -XPUT 'http://localhost:9200/testing_nested_query/class/1' -d '{
      "title": "class1",
      "students": [{"name": "john", "age": 4},{"name": "jack", "age": 1},{"name": "jim", "age": 9}]
    }'

curl -XPUT 'http://localhost:9200/testing_nested_query/class/2' -d '{
      "title": "class1",
      "students": [{"name": "john", "age": 5},{"name": "jack", "age": 4},{"name": "jim", "age": 9}]
    }'

Now execute the following queries:

{
  "query": {
       "nested": {
          "path":"students",
          "query": {
            "bool": {
              "must": [
                {"match": {"name": "john"}},
                {"match": {"age": 4}}
              ]
            }
          }
        }
  }
}

According to your expectations, this should match 2 documents but it actually matches just only one. Because there is only one nested document that has both name equal to john and age equal to 4.

Hope that helps.

Answer 2

You could also do following way. where you do not need to repeat bool again in a nested block , since there is a only one to match within that block , you can just do term match without bool

{
  "query": {
    "bool": {
      "must": [{
        "nested": {
          "path": "students",
          "query": {
            {
              "term": {
                "name": "john"
              }
            }
          }
        }
      }, {
        "nested": {
          "path": "students",
          "query": {
            {
              "term": {
                "name": "jack"
              }
            }
          }
        }
      }]
    }
  }
}