kibana/dev_docs/tutorials/saved_objects.mdx

---
id: kibDevTutorialSavedObject
slug: /kibana-dev-docs/tutorial/saved-objects
title: Register a new saved object type
summary: Learn how to register a new saved object type.
date: 2021-02-05
tags: ['kibana','onboarding', 'dev', 'architecture', 'tutorials']
---

Saved Object type definitions should be defined in their own `my_plugin/server/saved_objects` directory.

The folder should contain a file per type, named after the snake_case name of the type, and an index.ts file exporting all the types.

**src/plugins/my_plugin/server/saved_objects/dashboard_visualization.ts**

```ts
import { SavedObjectsType } from 'src/core/server';

export const dashboardVisualization: SavedObjectsType = {
  name: 'dashboard_visualization', [1]
  hidden: false,
  namespaceType: 'single',
  mappings: {
    dynamic: false,
    properties: {
      description: {
        type: 'text',
      },
      hits: {
        type: 'integer',
      },
    },
  },
  migrations: {
    '1.0.0': migratedashboardVisualizationToV1,
    '2.0.0': migratedashboardVisualizationToV2,
  },
};
```

[1] Since the name of a Saved Object type forms part of the url path for the public Saved Objects HTTP API, 
these should follow our API URL path convention and always be written as snake case.

**src/plugins/my_plugin/server/saved_objects/index.ts**

```ts
export { dashboardVisualization } from './dashboard_visualization';
export { dashboard } from './dashboard';
```

**src/plugins/my_plugin/server/plugin.ts**

```ts
import { dashboard, dashboardVisualization } from './saved_objects';

export class MyPlugin implements Plugin {
  setup({ savedObjects }) {
    savedObjects.registerType(dashboard);
    savedObjects.registerType(dashboardVisualization);
  }
}
```

## Mappings

Each Saved Object type can define its own Elasticsearch field mappings. Because multiple Saved Object
types can share the same index, mappings defined by a type will be nested under a top-level field that matches the type name.

For example, the mappings defined by the dashboard_visualization Saved Object type:

**src/plugins/my_plugin/server/saved_objects/dashboard_visualization.ts**

```ts
import { SavedObjectsType } from 'src/core/server';

export const dashboardVisualization: SavedObjectsType = {
  name: 'dashboard_visualization',
  ...
  mappings: {
    properties: {
      dynamic: false,
      description: {
        type: 'text',
      },
      hits: {
        type: 'integer',
      },
    },
  },
  migrations: { ... },
};
```

Will result in the following mappings being applied to the .kibana index:

```ts
{
  "mappings": {
    "dynamic": "strict",
    "properties": {
      ...
      "dashboard_vizualization": {
        "dynamic": false,
        "properties": {
          "description": {
            "type": "text",
          },
          "hits": {
            "type": "integer",
          },
        },
      }
    }
  }
}
```
Do not use field mappings like you would use data types for the columns of a SQL database. Instead, field mappings are analogous to a 
SQL index. Only specify field mappings for the fields you wish to search on or query. By specifying `dynamic: false`
 in any level of your mappings, Elasticsearch will accept and store any other fields even if they are not specified in your mappings.

Since Elasticsearch has a default limit of 1000 fields per index, plugins should carefully consider the 
fields they add to the mappings. Similarly, Saved Object types should never use `dynamic: true` as this can cause an arbitrary
 amount of fields to be added to the .kibana index.

 ## References

Declare <DocLink id="kibDevDocsSavedObjectsIntro" section="References" text="Saved Object references"/> by adding an id, type and name to the
 `references` array.

```ts
router.get(
  { path: '/some-path', validate: false },
  async (context, req, res) => {
    const object = await context.core.savedObjects.client.create(
      'dashboard',
      {
        title: 'my dashboard',
        panels: [
          { visualization: 'vis1' }, [1]
        ],
        indexPattern: 'indexPattern1'
      },
      { references: [
          { id: '...', type: 'visualization', name: 'vis1' },
          { id: '...', type: 'index_pattern', name: 'indexPattern1' },
        ]
      }
    )
    ...
  }
);
```
[1] Note how `dashboard.panels[0].visualization` stores the name property of the reference (not the id directly) to be able to uniquely 
identify this reference. This guarantees that the id the reference points to always remains up to date. If a
 visualization id was directly stored in `dashboard.panels[0].visualization` there is a risk that this id gets updated without 
 updating the reference in the references array.

## Writing migrations

Saved Objects support schema changes between Kibana versions, which we call migrations. Migrations are
 applied when a Kibana installation is upgraded from one version to the next, when exports are imported via
  the Saved Objects Management UI, or when a new object is created via the HTTP API.

Each Saved Object type may define migrations for its schema. Migrations are specified by the Kibana version number, receive an input document,
 and must return the fully migrated document to be persisted to Elasticsearch.

Let’s say we want to define two migrations: - In version 1.1.0, we want to drop the subtitle field and append it to the title - In version
 1.4.0, we want to add a new id field to every panel with a newly generated UUID.

First, the current mappings should always reflect the latest or "target" schema. Next, we should define a migration function for each step in the schema evolution:

**src/plugins/my_plugin/server/saved_objects/dashboard_visualization.ts**

```ts
import { SavedObjectsType, SavedObjectMigrationFn } from 'src/core/server';
import uuid from 'uuid';

interface DashboardVisualizationPre110 {
  title: string;
  subtitle: string;
  panels: Array<{}>;
}
interface DashboardVisualization110 {
  title: string;
  panels: Array<{}>;
}

interface DashboardVisualization140 {
  title: string;
  panels: Array<{ id: string }>;
}

const migrateDashboardVisualization110: SavedObjectMigrationFn<
  DashboardVisualizationPre110, [1]
  DashboardVisualization110
> = (doc) => {
  const { subtitle, ...attributesWithoutSubtitle } = doc.attributes;
  return {
    ...doc, [2]
    attributes: {
      ...attributesWithoutSubtitle,
      title: `${doc.attributes.title} - ${doc.attributes.subtitle}`,
    },
  };
};

const migrateDashboardVisualization140: SavedObjectMigrationFn<
  DashboardVisualization110,
  DashboardVisualization140
> = (doc) => {
  const outPanels = doc.attributes.panels?.map((panel) => {
    return { ...panel, id: uuid.v4() };
  });
  return {
    ...doc,
    attributes: {
      ...doc.attributes,
      panels: outPanels,
    },
  };
};

export const dashboardVisualization: SavedObjectsType = {
  name: 'dashboard_visualization', [1]
  /** ... */
  migrations: {
    // Takes a pre 1.1.0 doc, and converts it to 1.1.0
    '1.1.0': migrateDashboardVisualization110,

    // Takes a 1.1.0 doc, and converts it to 1.4.0
    '1.4.0': migrateDashboardVisualization140, [3]
  },
};
```
[1] It is useful to define an interface for each version of the schema. This allows TypeScript to ensure that you are properly handling the input and output 
 types correctly as the schema evolves.

[2] Returning a shallow copy is necessary to avoid type errors when using different types for the input and output shape.

[3] Migrations do not have to be defined for every version. The version number of a migration must always be the earliest Kibana version
 in which this migration was released. So if you are creating a migration which will
 be part of the v7.10.0 release, but will also be backported and released as v7.9.3, the migration version should be: 7.9.3.

 Migrations should be written defensively, an exception in a migration function will prevent a Kibana upgrade from succeeding and will cause downtime for our users. 
 Having said that, if a 
 document is encountered that is not in the expected shape, migrations are encouraged to throw an exception to abort the upgrade. In most scenarios, it is better to
  fail an upgrade than to silently ignore a corrupt document which can cause unexpected behaviour at some future point in time.

It is critical that you have extensive tests to ensure that migrations behave as expected with all possible input documents. Given how simple it is to test all the branch 
conditions in a migration function and the high impact of a bug in this code, there’s really no reason not to aim for 100% test code coverage.