# DeleteItem
<a name="aws-appsync-resolver-mapping-template-reference-dynamodb-deleteitem"></a>

The `DeleteItem` request mapping document lets you tell the AWS AppSync DynamoDB resolver to make a `DeleteItem` request to DynamoDB, and enables you to specify the following:
+ The key of the item in DynamoDB
+ Conditions for the operation to succeed

The `DeleteItem` mapping document has the following structure:

```
{
    "version" : "2018-05-29",
    "operation" : "DeleteItem",
    "customPartitionKey" : "foo",
    "populateIndexFields" : boolean value,
    "key": {
        "foo" : ... typed value,
        "bar" : ... typed value
    },
    "condition" : {
        ...
    },
    "_version" : 1
}
```

The fields are defined as follows:

## DeleteItem fields
<a name="deleteitem-list"></a>

### DeleteItem fields list
<a name="deleteitem-list-col"></a>

** `version` **  
The template definition version. `2017-02-28` and `2018-05-29` are currently supported. This value is required.

** `operation` **  
The DynamoDB operation to perform. To perform the `DeleteItem` DynamoDB operation, this must be set to `DeleteItem`. This value is required.

** `key` **  
The key of the item in DynamoDB. DynamoDB items may have a single hash key, or a hash key and sort key, depending on the table structure. For more information about specifying a “typed value”, see [Type system (request mapping)](aws-appsync-resolver-mapping-template-reference-dynamodb-typed-values-request.md). This value is required.

** `condition` **  
A condition to determine if the request should succeed or not, based on the state of the object already in DynamoDB. If no condition is specified, the `DeleteItem` request deletes an item regardless of its current state. For more information about conditions, see [Condition expressions](aws-appsync-resolver-mapping-template-reference-dynamodb-condition-expressions.md). This value is optional.

** `_version` **  
A numeric value that represents the latest known version of an item. This value is optional. This field is used for *Conflict Detection* and is only supported on versioned data sources.

**`customPartitionKey`**  
When enabled, this string value modifies the format of the `ds_sk` and `ds_pk` records used by the delta sync table when versioning has been enabled (for more information, see [Conflict detection and sync](https://docs.aws.amazon.com/appsync/latest/devguide/conflict-detection-and-sync.html) in the *AWS AppSync Developer Guide*). When enabled, the processing of the `populateIndexFields` entry is also enabled. This field is optional.

**`populateIndexFields`**  
A boolean value that, when enabled **along with the `customPartitionKey`**, creates new entries for each record in the delta sync table, specifically in the `gsi_ds_pk` and `gsi_ds_sk` columns. For more information, see [Conflict detection and sync](https://docs.aws.amazon.com/appsync/latest/devguide/conflict-detection-and-sync.html) in the *AWS AppSync Developer Guide*. This field is optional. 

The item deleted from DynamoDB is automatically converted into GraphQL and JSON primitive types and is available in the mapping context (`$context.result`).

For more information about DynamoDB type conversion, see [Type system (response mapping)](aws-appsync-resolver-mapping-template-reference-dynamodb-typed-values-responses.md).

For more information about response mapping templates, see [Resolver mapping template overview](resolver-mapping-template-reference-overview.md#aws-appsync-resolver-mapping-template-reference-overview).

## Example 1
<a name="id6"></a>

The following example is a mapping template for a GraphQL mutation `deleteItem(id: ID!)`. If an item exists with this ID, it’s deleted.

```
{
    "version" : "2017-02-28",
    "operation" : "DeleteItem",
    "key" : {
        "id" : $util.dynamodb.toDynamoDBJson($ctx.args.id)
    }
}
```

## Example 2
<a name="id7"></a>

The following example is a mapping template for a GraphQL mutation `deleteItem(id: ID!, expectedVersion: Int!)`. If an item exists with this ID, it’s deleted, but only if its `version` field set to `expectedVersion`:

```
{
    "version" : "2017-02-28",
    "operation" : "DeleteItem",
    "key" : {
        "id" : $util.dynamodb.toDynamoDBJson($ctx.args.id)
    },
    "condition" : {
        "expression"       : "attribute_not_exists(id) OR version = :expectedVersion",
        "expressionValues" : {
            ":expectedVersion" : $util.dynamodb.toDynamoDBJson($expectedVersion)
        }
    }
}
```

For more information about the DynamoDB `DeleteItem` API, see the [DynamoDB API documentation](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_DeleteItem.html).