# Nested field in app search

**URL:** <https://discuss.elastic.co/t/nested-field-in-app-search/252233>\
**Category:** Elastic Search\
**Tags:** elastic-app-search\
**Created:** [October 15, 2020, 4:01pm UTC](https://discuss.elastic.co/t/nested-field-in-app-search/252233 "2020-10-15T16:01:10Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![JasonStoltz](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jasonstoltz/32/49893_2.png) [@JasonStoltz](https://discuss.elastic.co/u/JasonStoltz)\
**Post date:** [October 20, 2020, 3:01pm UTC](https://discuss.elastic.co/t/nested-field-in-app-search/252233/2 "2020-10-20T15:01:04Z")

</div>

EDIT: Response updated by JasonStoltz August 25th, 2021, to be a bit more understandable.

Modeling relational data in _any_ object data store can be challenging.

Because App Search does not support nested objects, you'll need to flatten your data.

That's _generally_ the concept, but that could be accomplished a few different way.

Here are some thoughts.

Assuming you have two types of objects, Cars, and Events, where Car can have many Events associated with it.

```auto
Car:
- id
- make
- model
- events: Event[]

Event:
- id
- name
- slug

```

**Solution 1: Nest Event fields into Car as separate arrays**

Instead of:

```auto
[{
  id: 1,
  make: 'kia',
  model: 'sorento',
  events: [
    {id: 100, date: '10-15-2021', slug: 'demo-sale'},
    {id: 200, date: '09-6-2021', slug: 'blowout-sale'}
  ]
}]

```

You could have:

```auto
[{
  id: 1,
  make: 'kia',
  model: 'sorento',
  events.ids: [100, 200],
  events.dates: ['10-15-2021', '09-6-2021'],
  events.slugs: ['demo-sale', 'blowout-sale']
}]

```

That will get your use case working, filtering by `event.slug`.

However, there's a number of difficulties with this:

1. You'll find it difficult if you want to do any filtering by more than 1 sub-field. I.e., you can't do a filter on both `events.slug` and `events.date`.

For instance, if you had the following:

```auto
  events.id: [100, 200, 300],
  events.date: ['10-15-2021', '09-6-2021', '08-12-2021'],
  events.slugs: ['demo-sale', 'blowout-sale', 'another-sale']

```

And you wanted to find cars found at an '08-12-2021' occurrence of 'demo-sale' you'd query like:

```auto
events.date='08-12-2021' and events.slugs='demo-sale'

```

You would get a hit on the Kia Sorrento document based on a date and slug from _different_ events, which is not what we want:

```auto
  events.id: [100, 200, 300],
  events.date: ['10-15-2021', '09-6-2021', **'08-12-2021'**],
  events.slugs: [**'demo-sale'** , 'blowout-sale', 'another-sale']

```

**Solution 2: Duplicate the Car document for each Event**

In document stores like Elasticsearch or App Search, it's not uncommon to duplicate your data. So you could try creating 1 instance of Car for each event.

```auto
[{
  id: 1,
  make: 'kia',
  model: 'sorento',
  event.id: 100,
  event.date: '10-15-2021',
  event.slug: 'demo-sale'
},{
  id: 2,
  make: 'kia',
  model: 'sorento',
  event.id: 100,
  event.date: '10-15-2021',
  event.slug: 'demo-sale'
}]

```

That means you could filter by 'event.slug' and 'event.date', which we couldn't do with the previous example.

Data maintenance gets a bit trickier as you now have to update a bunch of documents every time you update Car details.

It also makes querying by Car details harder, as searching for `model='sorento'` returns duplicate entries. You'd have to use the `grouping` option in your search: [Search API group | Elastic App Search Documentation [7.14] | Elastic](https://www.elastic.co/guide/en/app-search/current/grouping.html).

Additionally, what happens if you have other relationships as well? Like if Cars in addition to Events have Retailers. You couldn't conceivably maintain a record for every Event and Retailer combination.

**Solution 3: Event as the main object with nested Car fields**

```auto
[{
  id: 100,
  date: '10-15-2021',
  slug: 'demo-sale'
  car.id: 1,
  car.make: 'kia',
  car.model: 'sorento',
},{
  id: 100,
  date: '10-15-2021',
  slug: 'demo-sale'
  car.id: 2,
  car.make: 'toyota',
  car.model: 'corolla',
},{
  car.id: 1,
  car.make: 'kia',
  car.model: 'sorento',
  id: 100,
  date: '10-15-2021',
  slug: 'demo-sale'
}]

```

This is comparable to the first previous solution, and suffers from the same challenges.

**Option 4: Separate Engines for Cars and Events**

```auto
// Events
[
  {
    id: 100,
    date: '10-15-2021',
    slug: 'demo-sale',
    cars: [1, 2]
  },
  {
    id: 200,
    date: '09-6-2021',
    slug: 'blowout-sale',
    cars: [1, 2]
   }
]

// Cars
[
  {
    id: 1,
    make: 'kia',
    model: 'sorento'
    event_slugs: ['demo-sale', 'blowout-sale'],
    event_ids: [100, 200]
},{
    id: 2,
    make: 'toyota',
    model: 'corolla',
    event_slugs: ['demo-sale', 'blowout-sale'],
    event_ids: [100, 200]
  }
]

```

You could query for Cars and filter by `event_slugs`.

If you needed to filter by multiple fields, you could accomplish this in 2 queries:  
Query 1: Query Events by `date` and `slug` to get a list of event ids  
Query 2: Query Cars and filter by `event_id`

This seems pretty clean to me. But it make data management a bit more complicated.

There could be a number of variation on this, and it would largely depend on how you're planning to query and / or display data.

**Huge disclaimer:** I personally have not done any of these, so this is all theoretical. I would love to hear from others that may have experience with this. I would also love to hear back from you if any of these solutions work.

---

_[View the full topic](https://discuss.elastic.co/t/nested-field-in-app-search/252233)._