Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
1.7k views
in Technique[技术] by (71.8m points)

aggregate - How to get an Elasticsearch aggregation with multiple fields

I'm attempting to find related tags to the one currently being viewed. Every document in our index is tagged. Each tag is formed of two parts - an ID and text name:

{
    ...
    meta: {
        ...
        tags: [
            {
                id: 123,
                name: 'Biscuits'
            },
            {
                id: 456,
                name: 'Cakes'
            },
            {
                id: 789,
                name: 'Breads'
            }
        ]
    }
}

To fetch the related tags I am simply querying the documents and getting an aggregate of their tags:

{
    "query": {
        "bool": {
            "must": [
                {
                    "match": {
                        "item.meta.tags.id": "123"
                    }
                },
                {
                    ...
                }
            ]
        }
    },
    "aggs": {
        "baked_goods": {
            "terms": {
                "field": "item.meta.tags.id",
                "min_doc_count": 2
            }
        }
    }
}

This works perfectly, I am getting the results I want. However, I require both the tag ID and name to do anything useful. I have explored how to accomplish this, the solutions seem to be:

  1. Combine the fields when indexing
  2. A script to munge together the fields
  3. A nested aggregation

Option one and two are are not available to me so I have been going with 3 but it's not responding in an expected manner. Given the following query (still searching for documents also tagged with 'Biscuits'):

{
    ...
    "aggs": {
        "baked_goods": {
            "terms": {
                "field": "item.meta.tags.id",
                "min_doc_count": 2
            },
            "aggs": {
                "name": {
                    "terms": {
                        "field": "item.meta.tags.name"
                    }
                }
            }
        }
    }
}

I will get this result:

{
    ...
    "aggregations": {
        "baked_goods": {
            "buckets": [
                {
                    "key": "456",
                    "doc_count": 11,
                    "name": {
                        "buckets": [
                            {
                                "key": "Biscuits",
                                "doc_count": 11
                            },
                            {
                                "key": "Cakes",
                                "doc_count": 11
                            }
                        ]
                    }
                }
            ]
        }
    }
}

The nested aggregation includes both the search term and the tag I'm after (returned in alphabetical order).

I have tried to mitigate this by adding an exclude to the nested aggregation but this slowed the query down far too much (around 100 times for 500000 docs). So far the fastest solution is to de-dupe the result manually.

What is the best way to get an aggregation of tags with both the tag ID and tag name in the response?

Thanks for making it this far!

question from:https://stackoverflow.com/questions/30728583/how-to-get-an-elasticsearch-aggregation-with-multiple-fields

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

By the looks of it, your tags is not nested. For this aggregation to work, you need it nested so that there is an association between an id and a name. Without nested the list of ids is just an array and the list of names is another array:

    "item": {
      "properties": {
        "meta": {
          "properties": {
            "tags": {
              "type": "nested",           <-- nested field
              "include_in_parent": true,  <-- to, also, keep the flat array-like structure
              "properties": {
                "id": {
                  "type": "integer"
                },
                "name": {
                  "type": "string"
                }
              }
            }
          }
        }
      }
    }

Also, note that I've added to the mapping this line "include_in_parent": true which means that your nested tags will, also, behave like a "flat" array-like structure.

So, everything you had so far in your queries will still work without any changes to the queries.

But, for this particular query of yours, the aggregation needs to change to something like this:

{
  "aggs": {
    "baked_goods": {
      "nested": {
        "path": "item.meta.tags"
      },
      "aggs": {
        "name": {
          "terms": {
            "field": "item.meta.tags.id"
          },
          "aggs": {
            "name": {
              "terms": {
                "field": "item.meta.tags.name"
              }
            }
          }
        }
      }
    }
  }
}

And the result is like this:

   "aggregations": {
      "baked_goods": {
         "doc_count": 9,
         "name": {
            "doc_count_error_upper_bound": 0,
            "sum_other_doc_count": 0,
            "buckets": [
               {
                  "key": 123,
                  "doc_count": 3,
                  "name": {
                     "doc_count_error_upper_bound": 0,
                     "sum_other_doc_count": 0,
                     "buckets": [
                        {
                           "key": "biscuits",
                           "doc_count": 3
                        }
                     ]
                  }
               },
               {
                  "key": 456,
                  "doc_count": 2,
                  "name": {
                     "doc_count_error_upper_bound": 0,
                     "sum_other_doc_count": 0,
                     "buckets": [
                        {
                           "key": "cakes",
                           "doc_count": 2
                        }
                     ]
                  }
               },
               .....

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...