CODEWITHSUNDEEP
elasticsearch
eric
eric

Reputation: 2759

Should I be using a nested object or a normal field?

I've been taking baby steps into using Elasticsearch, and while researching a separate issue I ran into this question. Here, swatkins asked about querying nested objects, and a responder pointed out that nested objects weren't necessary given his model. I've copied the model here, and made some changes to reflect my particular question:

[{
    id:4635,
    description:"This is a test description",
    author:"John",
    author_id:51421,
    meta: {
        title:"This is a test title for a video",
        description:"This is my video description",
        url:"/url_of_video"
        awesomeness-level: "pretty-awesome"
        kung-fu: true
    }
},
{
    id:4636,
    description:"This is a test description 2",
    author:"John",
    author_id:51421,
    meta: {
        title:"This is an example title for a video",
        description:"This is my video description2",
        url:"/url_of_video2"
        kung-fu:false
        monsters:true
        monsters-present: "Dracula, The Mummy"
    }
}]

Our application allows users to define custom metadata, so we're using a nested object to represent that data. At first glance, it looks similar to swatkins' model, so I thought that maybe we shouldn't be using a nested object.

The big difference is each objects meta might be different, note the second video has meta specifically about "monster movies", while the first video references an "awesomeness-level". So, should I be using a nested object, or just mapping metadata as a normal field? If we do the latter, will the first video have empty metadata fields? Does that really even matter? Thanks in advance!

Upvotes: 1

Views: 201

Answers (1)

imotov
imotov

Reputation: 30163

Assuming that your example represents two elasticsearch documents, it doesn't look like you need to make meta a nested object. It makes sense to use nested objects when one parent object has multiple nested objects and your searches involve several fields of the nested objects. For example, if you have a record like this:

{
  "name": "apple",
  "attributes": [
     {
       "color": "yellow",
       "size": "big"
     },
     {
       "color": "red",
       "size": "small"
     }
  ]
}

and you want this record to be found when you search for color:yellow AND shape:big or color:red AND shape:small but don't want it to be returned when you search for color:yellow AND shape:small, it makes sense to make attributes a nested object. It will allow you to index and search each attribute independently and then get parent object of matching attribute.

Upvotes: 1

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