Class: Aws::DynamoDB::Types::AttributeValueUpdate

Inherits:
Struct
  • Object
show all
Includes:
Structure
Defined in:
lib/aws-sdk-dynamodb/types.rb

Overview

For the ‘UpdateItem` operation, represents the attributes to be modified, the action to perform on each, and the new value for each.

<note markdown=“1”> You cannot use ‘UpdateItem` to update any primary key attributes. Instead, you will need to delete the item, and then use `PutItem` to create a new item with new attributes.

</note>

Attribute values cannot be null; string and binary type attributes must have lengths greater than zero; and set type attributes must not be empty. Requests with empty values will be rejected with a ‘ValidationException` exception.

See Also:

Constant Summary collapse

SENSITIVE = 
[]

Instance Attribute Summary collapse

Instance Attribute Details

#action ⇒ String

Specifies how to perform the update. Valid values are ‘PUT` (default), `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 markdown=“1”> 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`.

      </note>

    • 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 a new item with the supplied primary key and number (or set) for the attribute value. The only data types allowed are number, number set, string set or binary set.

Returns:

  • (String) 


279
280
281
282
283
284
 
# File 'lib/aws-sdk-dynamodb/types.rb', line 279

class AttributeValueUpdate < Struct.new(
  :value,
  :action)
  SENSITIVE = []
  include Aws::Structure
end

#value ⇒ Types::AttributeValue

Represents the data for an attribute.

Each attribute value is described as a name-value pair. The name is the data type, and the value is the data itself.

For more information, see [Data Types] in the *Amazon DynamoDB Developer Guide*.

[1]: docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.NamingRulesDataTypes.html#HowItWorks.DataTypes

Returns:



279
280
281
282
283
284
 
# File 'lib/aws-sdk-dynamodb/types.rb', line 279

class AttributeValueUpdate < Struct.new(
  :value,
  :action)
  SENSITIVE = []
  include Aws::Structure
end