Tasks

•   tableName

  The name of the table containing the item to update.

  Constraints:
  Length: 3 – 255
  Pattern: [a-zA-Z0-9_.–]+
  

  property
•   key

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

  property
•   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.

        If you use ADD to increment or decrement a number value for an item that doesn't exist before the update, Amazon 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, Amazon 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. Amazon 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-Amazon 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-Amazon 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.

  property
•   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 Amazon 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 Amazon DynamoDB to check, along with the following:

  • Value-the attribute value for Amazon DynamoDB to check.

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

    • If Exists is true, Amazon 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, Amazon 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, Amazon DynamoDB assumes the attribute exists: You don’t have to set Exists to true, because it is implied.

    Amazon 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.

  property
•   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–(default) If ReturnValues is not specified, or if its value is NONE, then nothing is returned.

  • 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.

  Constraints:
  Allowed Values: NONE, ALL_OLD, UPDATED_OLD, ALL_NEW, UPDATED_NEW

  property
•   returnConsumedCapacity

  Determines whether to include consumed capacity information in the output. If this is set to TOTAL, then this information is shown in the output; otherwise, the consumed capacity information is not shown.

  Constraints:
  Allowed Values: TOTAL, NONE

  property
•   returnItemCollectionMetrics

  Indicates whether to return statistics about item collections, if any, that were modified during the operation. The default for ReturnItemCollectionMetrics is NONE, meaning that no statistics will be returned. To obtain the statistics, set ReturnItemCollectionMetrics to SIZE.

  Constraints:
  Allowed Values: SIZE, NONE

  property
• – init

  Default constructor for a new UpdateItemRequest object. Callers should use the property methods to initialize this object after creating it.

• – initWithTableName:andKey:andAttributeUpdates:

  Constructs a new UpdateItemRequest object. Callers should use properties to initialize any additional object members.

• – setKeyValue:forKey:

  Set a value in the dictionary key for the specified key. This function will alloc and init key if not already done.

• – setAttributeUpdatesValue:forKey:

  Set a value in the dictionary attributeUpdates for the specified key. This function will alloc and init attributeUpdates if not already done.

• – setExpectedValue:forKey:

  Set a value in the dictionary expected for the specified key. This function will alloc and init expected if not already done.

• – description

  Returns a string representation of this object; useful for testing and debugging.