Amazon DynamoDB
API Reference (API Version 2012-08-10)
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UpdateItem

Edits an existing item's attributes, or inserts a new item if it does not already exist. You can put, delete, or add attribute values. You can also perform a conditional update (insert a new attribute name-value pair if it doesn't exist, or replace an existing name-value pair if it has certain expected attribute values).

In addition to updating an item, you can also return the item's attribute values in the same operation, using the ReturnValues parameter.

Request Syntax

{
    "AttributeUpdates": 
        {
            "string" :
                {
                    "Action": "string",
                    "Value": {
                        "B": "blob",
                        "BS": [
                            "blob"
                        ],
                        "N": "string",
                        "NS": [
                            "string"
                        ],
                        "S": "string",
                        "SS": [
                            "string"
                        ]
                    }
                }
        },
    "Expected": 
        {
            "string" :
                {
                    "Exists": "boolean",
                    "Value": {
                        "B": "blob",
                        "BS": [
                            "blob"
                        ],
                        "N": "string",
                        "NS": [
                            "string"
                        ],
                        "S": "string",
                        "SS": [
                            "string"
                        ]
                    }
                }
        },
    "Key": 
        {
            "string" :
                {
                    "B": "blob",
                    "BS": [
                        "blob"
                    ],
                    "N": "string",
                    "NS": [
                        "string"
                    ],
                    "S": "string",
                    "SS": [
                        "string"
                    ]
                }
        },
    "ReturnConsumedCapacity": "string",
    "ReturnItemCollectionMetrics": "string",
    "ReturnValues": "string",
    "TableName": "string"
}
			

Request Parameters

The request accepts the following data in JSON format.

Note

In the following list, the required parameters are described first.

Key

The primary key of the item to be updated. Each element consists of an attribute name and a value for that attribute.

For the primary key, you must provide all of the attributes. For example, with a hash type primary key, you only need to specify the hash attribute. For a hash-and-range type primary key, you must specify both the hash attribute and the range attribute.

Type: String to AttributeValue object map

Required: Yes

TableName

The name of the table containing the item to update.

Type: String

Length constraints: Minimum length of 3. Maximum length of 255.

Required: Yes

AttributeUpdates

The names of attributes to be modified, the action to perform on each, and the new value for each. If you are updating an attribute that is an index key attribute for any indexes on that table, the attribute type must match the index key type defined in the AttributesDefinition of the table description. You can use UpdateItem to update any non-key attributes.

Attribute values cannot be null. String and binary type attributes must have lengths greater than zero. Set type attributes must not be empty. Requests with empty values will be rejected with a ValidationException.

Each AttributeUpdates element consists of an attribute name to modify, along with the following:

  • Value - The new value, if applicable, for this attribute.

  • Action - Specifies how to perform the update. Valid values for Action are PUT, DELETE, and ADD. The behavior depends on whether the specified primary key already exists in the table.

    If an item with the specified Key is found in the table:

    • PUT - Adds the specified attribute to the item. If the attribute already exists, it is replaced by the new value.

    • DELETE - If no value is specified, the attribute and its value are removed from the item. The data type of the specified value must match the existing value's data type.

      If a set of values is specified, then those values are subtracted from the old set. For example, if the attribute value was the set [a,b,c] and the DELETE action specified [a,c], then the final attribute value would be [b]. Specifying an empty set is an error.

    • ADD - If the attribute does not already exist, then the attribute and its values are added to the item. If the attribute does exist, then the behavior of ADD depends on the data type of the attribute:

      • If the existing attribute is a number, and if Value is also a number, then the Value is mathematically added to the existing attribute. If Value is a negative number, then it is subtracted from the existing attribute.

        Note

        If you use ADD to increment or decrement a number value for an item that doesn't exist before the update, DynamoDB uses 0 as the initial value.

        In addition, if you use ADD to update an existing item, and intend to increment or decrement an attribute value which does not yet exist, DynamoDB uses 0 as the initial value. For example, suppose that the item you want to update does not yet have an attribute named itemcount, but you decide to ADD the number 3 to this attribute anyway, even though it currently does not exist. DynamoDB will create the itemcount attribute, set its initial value to 0, and finally add 3 to it. The result will be a new itemcount attribute in the item, with a value of 3.

      • If the existing data type is a set, and if the Value is also a set, then the Value is added to the existing set. (This is a set operation, not mathematical addition.) For example, if the attribute value was the set [1,2], and the ADD action specified [3], then the final attribute value would be [1,2,3]. An error occurs if an Add action is specified for a set attribute and the attribute type specified does not match the existing set type.

        Both sets must have the same primitive data type. For example, if the existing data type is a set of strings, the Value must also be a set of strings. The same holds true for number sets and binary sets.

      This action is only valid for an existing attribute whose data type is number or is a set. Do not use ADD for any other data types.

    If no item with the specified Key is found:

    • PUT - DynamoDB creates a new item with the specified primary key, and then adds the attribute.

    • DELETE - Nothing happens; there is no attribute to delete.

    • ADD - DynamoDB creates an item with the supplied primary key and number (or set of numbers) for the attribute value. The only data types allowed are number and number set; no other data types can be specified.

If you specify any attributes that are part of an index key, then the data types for those attributes must match those of the schema in the table's attribute definition.

Type: String to AttributeValueUpdate object map

Required: No

Expected

A map of attribute/condition pairs. This is the conditional block for the UpdateItem operation. All the conditions must be met for the operation to succeed.

Expected allows you to provide an attribute name, and whether or not DynamoDB should check to see if the attribute value already exists; or if the attribute value exists and has a particular value before changing it.

Each item in Expected represents an attribute name for DynamoDB to check, along with the following:

  • Value - A value for DynamoDB to compare with an attribute. When performing the comparison, strongly consistent reads are used.

  • Exists - Causes DynamoDB to evaluate the value before attempting a conditional operation:

    • If Exists is true, DynamoDB will check to see if that attribute value already exists in the table. If it is found, then the operation succeeds. If it is not found, the operation fails with a ConditionalCheckFailedException.

    • If Exists is false, DynamoDB assumes that the attribute value does not exist in the table. If in fact the value does not exist, then the assumption is valid and the operation succeeds. If the value is found, despite the assumption that it does not exist, the operation fails with a ConditionalCheckFailedException.

    The default setting for Exists is true. If you supply a Value all by itself, DynamoDB assumes the attribute exists: You don't have to set Exists to true, because it is implied.

    DynamoDB returns a ValidationException if:

    • Exists is true but there is no Value to check. (You expect a value to exist, but don't specify what that value is.)

    • Exists is false but you also specify a Value. (You cannot expect an attribute to have a value, while also expecting it not to exist.)

If you specify more than one condition for Exists, then all of the conditions must evaluate to true. (In other words, the conditions are ANDed together.) Otherwise, the conditional operation will fail.

Type: String to ExpectedAttributeValue object map

Required: No

ReturnConsumedCapacity

If set to TOTAL, the response includes ConsumedCapacity data for tables and indexes. If set to INDEXES, the response includes ConsumedCapacity for indexes. If set to NONE (the default), ConsumedCapacity is not included in the response.

Type: String

Valid Values: INDEXES | TOTAL | NONE

Required: No

ReturnItemCollectionMetrics

If set to SIZE, statistics about item collections, if any, that were modified during the operation are returned in the response. If set to NONE (the default), no statistics are returned.

Type: String

Valid Values: SIZE | NONE

Required: No

ReturnValues

Use ReturnValues if you want to get the item attributes as they appeared either before or after they were updated. For UpdateItem, the valid values are:

  • NONE - If ReturnValues is not specified, or if its value is NONE, then nothing is returned. (This is the default for ReturnValues.)

  • ALL_OLD - If UpdateItem overwrote an attribute name-value pair, then the content of the old item is returned.

  • UPDATED_OLD - The old versions of only the updated attributes are returned.

  • ALL_NEW - All of the attributes of the new version of the item are returned.

  • UPDATED_NEW - The new versions of only the updated attributes are returned.

Type: String

Valid Values: NONE | ALL_OLD | UPDATED_OLD | ALL_NEW | UPDATED_NEW

Required: No

Response Syntax

{
    "Attributes": 
        {
            "string" :
                {
                    "B": "blob",
                    "BS": [
                        "blob"
                    ],
                    "N": "string",
                    "NS": [
                        "string"
                    ],
                    "S": "string",
                    "SS": [
                        "string"
                    ]
                }
        },
    "ConsumedCapacity": {
        "CapacityUnits": "number",
        "GlobalSecondaryIndexes": 
            {
                "string" :
                    {
                        "CapacityUnits": "number"
                    }
            },
        "LocalSecondaryIndexes": 
            {
                "string" :
                    {
                        "CapacityUnits": "number"
                    }
            },
        "Table": {
            "CapacityUnits": "number"
        },
        "TableName": "string"
    },
    "ItemCollectionMetrics": {
        "ItemCollectionKey": 
            {
                "string" :
                    {
                        "B": "blob",
                        "BS": [
                            "blob"
                        ],
                        "N": "string",
                        "NS": [
                            "string"
                        ],
                        "S": "string",
                        "SS": [
                            "string"
                        ]
                    }
            },
        "SizeEstimateRangeGB": [
            "number"
        ]
    }
}
			

Response Elements

The following data is returned in JSON format by the service.

Attributes

A map of attribute values as they appeared before the UpdateItem operation, but only if ReturnValues was specified as something other than NONE in the request. Each element represents one attribute.

Type: String to AttributeValue object map

ConsumedCapacity

Represents the capacity units consumed by an operation. The data returned includes the total provisioned throughput consumed, along with statistics for the table and any indexes involved in the operation. ConsumedCapacity is only returned if it was asked for in the request. For more information, see Provisioned Throughput in the Amazon DynamoDB Developer Guide.

Type: ConsumedCapacity object

ItemCollectionMetrics

Information about item collections, if any, that were affected by the operation. ItemCollectionMetrics is only returned if it was asked for in the request. If the table does not have any local secondary indexes, this information is not returned in the response.

Type: ItemCollectionMetrics object

Errors

For information about the errors that are common to all actions, see Common Errors.

ConditionalCheckFailedException

A condition specified in the operation could not be evaluated.

HTTP Status Code: 400

InternalServerError

An error occurred on the server side.

HTTP Status Code: 500

ItemCollectionSizeLimitExceededException

An item collection is too large. This exception is only returned for tables that have one or more local secondary indexes.

HTTP Status Code: 400

ProvisionedThroughputExceededException

The request rate is too high, or the request is too large, for the available throughput to accommodate. The AWS SDKs automatically retry requests that receive this exception; therefore, your request will eventually succeed, unless the request is too large or your retry queue is too large to finish. Reduce the frequency of requests by using the strategies listed in Error Retries and Exponential Backoff in the Amazon DynamoDB Developer Guide.

HTTP Status Code: 400

ResourceNotFoundException

The operation tried to access a nonexistent table or index. The resource may not be specified correctly, or its status may not be ACTIVE.

HTTP Status Code: 400

Examples

Conditional Update

This example updates the Thread table, changing the LastPostedBy attribute-but only if LastPostedBy is currently "fred@example.com". All of the item's attributes, as they appear after the update, are returned in the response.

Sample Request

POST / HTTP/1.1
Host: dynamodb.<region>.<domain>;
X-Amz-Date: <Date>
Authorization: AWS4-HMAC-SHA256 Credential=<Credential>, SignedHeaders=content-length;content-type;host;user-agent;x-amz-content-sha256;x-amz-date;x-amz-target, Signature=<Signature>
User-Agent: <UserAgentString>
x-amz-content-sha256: <PayloadHash>
Content-Type: application/x-amz-json-1.0
Content-Length: <PayloadSizeBytes>     
Connection: Keep-Alive
X-Amz-Target: DynamoDB_20120810.UpdateItem 

{
    "TableName": "Thread",
    "Key": {
        "ForumName": {
            "S": "Amazon DynamoDB"
        },
        "Subject": {
            "S": "Maximum number of items?"
        }
    },
    "AttributeUpdates": {
        "LastPostedBy": {
            "Value": {
                "S": "alice@example.com"
            },
            "Action": "PUT"
        }
    },
    "Expected": {
        "LastPostedBy": {
            "Value": {
                "S": "fred@example.com"
            },
            "Exists": true
        }
    },
    "ReturnValues": "ALL_NEW"
}
        

Sample Response

HTTP/1.1 200 OK
x-amzn-RequestId: <RequestId> 
x-amz-crc32: <Checksum>
Content-Type: application/x-amz-json-1.0
Content-Length: <PayloadSizeBytes>
Date: <Date>

{
    "Attributes": {
        "LastPostedBy": {
            "S": "alice@example.com"
        },
        "ForumName": {
            "S": "Amazon DynamoDB"
        },
        "LastPostDateTime": {
            "S": "20130320010350"
        },
        "Tags": {
            "SS": ["Update","Multiple Items","HelpMe"]
        },
        "Subject": {
            "S": "Maximum number of items?"
        },
        "Views": {
            "N": "5"
        },
        "Message": {
            "S": "I want to put 10 million data items to an Amazon DynamoDB table.  Is there an upper limit?"
        }
    }
}
        

Atomic Counter

This example increments the Replies attribute in the Thread table whenever someone posts a reply. Because ReturnValues is set to NONE, no output appears in the response payload.

Sample Request

POST / HTTP/1.1
Host: dynamodb.<region>.<domain>;
X-Amz-Date: <Date>
Authorization: AWS4-HMAC-SHA256 Credential=<Credential>, SignedHeaders=content-length;content-type;host;user-agent;x-amz-content-sha256;x-amz-date;x-amz-target, Signature=<Signature>
User-Agent: <UserAgentString>
x-amz-content-sha256: <PayloadHash>
Content-Type: application/x-amz-json-1.0
Content-Length: <PayloadSizeBytes>     
Connection: Keep-Alive
X-Amz-Target: DynamoDB_20120810.UpdateItem 

{
    "TableName": "Thread",
    "Key": {
        "ForumName": {
            "S": "Amazon DynamoDB"
        },
        "Subject": {
            "S": "A question about updates"
        }
    },
    "AttributeUpdates": {
        "Replies": {
            "Action": "ADD",
            "Value": {"N": "1"}
        }
    },
    "ReturnValues" : "NONE"
}
        

Sample Response

HTTP/1.1 200 OK
x-amzn-RequestId: <RequestId> 
x-amz-crc32: <Checksum>
Content-Type: application/x-amz-json-1.0
Content-Length: <PayloadSizeBytes>
Date: <Date>

{          
}