How to do match multiple nested object in one document with inner hits in elasticsearch

Question

How do I write a query with two search terms which matches nested objects with inner hits highlighted.

Below is the sample usecase:

I have a mapping:

"mappings": {
      "properties": {
        "grocery_name": {
          "type": "text"
        },
        "items": {
          "type": "nested",
          "properties": {
            "name": {
              "type": "text"
            },
            "stock": {
              "type": "integer"
            },
            "category": {
              "type": "text"
            }
          }
        }
      }
    }

and the data looks like below

{
  "grocery_name": "Elastic Eats",
  "items": [
    {
      "name": "Red banana",
      "stock": "12",
      "category": "fruit"
    },
    {
      "name": "Cavendish banana",
      "stock": "10",
      "category": "fruit"
    },
    {
      "name": "peach",
      "stock": "10",
      "category": "fruit"
    },
    {
      "name": "carrot",
      "stock": "9",
      "category": "vegetable"
    },
    {
      "name": "broccoli",
      "stock": "5",
      "category": "vegetable"
    }
  ]
}

here if i want a document which has peach and carrot both in nested docs i can do search with multiple nested queries like below

{
  "query": {
    "bool": {
      "must": [
        {
          "nested": {
            "path": "items",
            "query": {
              "match_phrase": {
                "items.name": {
                  "query": "carrot"
                }
              }
            }
          }
        },
        {
          "nested": {
            "path": "items",
            "query": {
              "match_phrase": {
                "items.name": {
                  "query": "peach"
                }
              }
            }
          }
        }
      ]
    }
  }
}

the above query works perfectly, but if i add inner hits i can't add for both nested queries , if i do i get following error



[inner_hits] already contains an entry for key[items]

i want to get each matched nested object highlighted, as _source highlighting is not supported in elasticsearch is there any way i can do highlighting for each nested object?

Answer 1

You certainly can have multiple inner_hits but they need to be appropriately named:

{
  "query": {
    "bool": {
      "must": [
        {
          "nested": {
            "inner_hits": {
              "name": "carrot"     <--
            }, 
            "path": "items",
            "query": {
              "match_phrase": {
                "items.name": {
                  "query": "carrot"
                }
              }
            }
          }
        },
        {
          "nested": {
            "inner_hits": {     
              "name": "peach"      <--
            },
            "path": "items",
            "query": {
              "match_phrase": {
                "items.name": {
                  "query": "peach"
                }
              }
            }
          }
        }
      ]
    }
  }
}

You were getting the error b/c if no name is provided, the system will default to the nested path which is items in both of your subqueries.