# DeltaEvent

<!-- DO NOT EDIT: this page is autogenerated from the type comments -->

```ts
type DeltaEvent<TRow, TKey> = 
  | {
  key: TKey;
  metadata?: Record<string, unknown>;
  type: "enter";
  value: TRow;
}
  | {
  key: TKey;
  metadata?: Record<string, unknown>;
  type: "exit";
  value: TRow;
}
  | {
  key: TKey;
  metadata?: Record<string, unknown>;
  previousValue: TRow;
  type: "update";
  value: TRow;
};
```

Defined in: [packages/db/src/query/effect.ts:59](https://github.com/TanStack/db/blob/main/packages/db/src/query/effect.ts#L59)

Delta event emitted when a row enters, exits, or updates within a query result

## Type Parameters

### TRow

`TRow` *extends* `object` = `Record`\<`string`, `unknown`\>

### TKey

`TKey` *extends* `string` \| `number` = `string` \| `number`

## Union Members

### Type Literal

```ts
{
  key: TKey;
  metadata?: Record<string, unknown>;
  type: "enter";
  value: TRow;
}
```

#### key

```ts
key: TKey;
```

#### metadata?

```ts
optional metadata?: Record<string, unknown>;
```

#### type

```ts
type: "enter";
```

#### value

```ts
value: TRow;
```

Current value for the entering row

***

### Type Literal

```ts
{
  key: TKey;
  metadata?: Record<string, unknown>;
  type: "exit";
  value: TRow;
}
```

#### key

```ts
key: TKey;
```

#### metadata?

```ts
optional metadata?: Record<string, unknown>;
```

#### type

```ts
type: "exit";
```

#### value

```ts
value: TRow;
```

Current value for the exiting row

***

### Type Literal

```ts
{
  key: TKey;
  metadata?: Record<string, unknown>;
  previousValue: TRow;
  type: "update";
  value: TRow;
}
```

#### key

```ts
key: TKey;
```

#### metadata?

```ts
optional metadata?: Record<string, unknown>;
```

#### previousValue

```ts
previousValue: TRow;
```

Previous value before the batch

#### type

```ts
type: "update";
```

#### value

```ts
value: TRow;
```

Current value after the update