> ## Documentation Index
> Fetch the complete documentation index at: https://confidence.spotify.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Entities Reference

> Technical reference for entities in Confidence Metrics.

This section provides technical specifications and reference information for entities.

<Tip>
  For conceptual explanations of entities, see [Entities](./concepts#entity) in the Metrics Concepts page.
</Tip>

## Primary Key Types

Available primary key types for entities:

| Type                  | Description            | Use Case                                        |
| :-------------------- | :--------------------- | :---------------------------------------------- |
| `COLUMN_TYPE_STRING`  | String identifiers     | UUIDs, usernames, session IDs                   |
| `COLUMN_TYPE_INTEGER` | Integer identifiers    | Autoincrementing user IDs, numeric keys         |
| `COLUMN_TYPE_BOOLEAN` | Boolean values         | Binary entity identifiers (rarely used)         |
| `COLUMN_TYPE_DOUBLE`  | Floating point numbers | Numeric identifiers with decimals (rarely used) |

## Entity Constraints

* **Unique names**: Entity display names must be unique within a project
* **Immutable key type**: You cannot change the primary key type after creation
* **Referenced entities**: You cannot delete entities used in fact tables, dimension tables, or metrics
* **Case sensitivity**: Entity names are case-sensitive

## Entity Resource Name Format

Reference entities using the resource name format:

```
entities/{entity_id}
```

Example: `entities/user`, `entities/session`