# Entity

[`Entities`]({{< ref "profiles/concepts/entities.md" >}}) are defined in the [`pb_project.yaml`]({{< ref "profiles/dev-docs/pb-project-yaml/" >}}) file. They are used throughout a Profiles project and consist of names for the entities and the types of [`ids`]({{< ref "profiles/dev-docs/pb-project-yaml/id-types.md" >}}) associated with each for ID stitching and feature creation.

You can also assign a custom ID stitcher and/or a feature view with specific `id_types` as the view's primary key.

```yaml
entities:
   - name: entity_name
     id_column_name: column_name
     id_stitcher: models/custom_ID_stitcher_path   # Optional
     id_types:
         <id_types-config>
     feature_views:     # Optional
         using_ids:
            - id: id_type
              name: view_name
```

| Key | Description |
| :-------------- | :-------- |
| `name` <br/> <span style="color: #4D4DFF;font-size:12px;">Required</span> | `Entity` name. |
| `id_column_name` | Name of the main ID column for an entity. If not provided explicitly, its value is set to `<entity_name>_main_id`. | 
| `id_stitcher` | Model path to the ID stitcher for this entity. When you define a custom `id_stitcher` model in [`profiles.yaml`]({{< ref "profiles/dev-docs/profiles-yaml/" >}}), set this key so the entity uses that model. If left blank, the default ID stitcher is used. |
| [`id_types`]({{< ref "profiles/dev-docs/pb-project-yaml/id-types.md" >}}) <br/> <span style="color: #4D4DFF;font-size:12px;">Required</span> | List of the identifier types associated with the `entity`. |
| [`feature_views`]({{< ref "profiles/concepts/feature-views.md" >}}) | List of `name` and `id_type` (primary key) for each view. |

{{< warning >}}
**Always set `id_stitcher` on each entity that has a custom ID stitcher model defined in `profiles.yaml`.**

If you have an `id_stitcher` model in `profiles.yaml` (for example, `user_id_stitcher` for the user entity) but do not set `id_stitcher` on the entity, the intended ID stitcher is not used and you may see get unintended results.

Set `id_stitcher` to the model path (for example, `id_stitcher: models/user_id_stitcher`).
{{< /warning >}}

## Example

```yaml
# Case 1: Minimal example
entities:
    - name: user
      id_column_name: user_rud_id
      id_types:
         - email
         - user_id

# Case 2: With a custom ID stitcher
entities:
    - name: user
      id_stitcher: models/custom_id_stitcher
      id_types:
         - email
         - user_id

# Case 3: With a feature view
entities:
    - name: user
      id_types:
         - email
         - user_id
      feature_views:
         using_ids:
            - id: email
              name: customer_profile_by_email
```

Note that for the first case in the above example, the `id_column_name` is explicitly set to `user_rud_id`. 

In the other cases, `id_column_name` is not explicitly specified, so this field is set to `user_main_id` by default.

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