Gets and sets the property Action.
Specifies how to perform the update. Valid values are
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
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
the DELETE action specified
[a,c], then the final attribute value
[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, 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
3 to this attribute anyway, even though it currently does
not exist. DynamoDB will create the itemcount attribute, set its initial value
0, and finally add
3 to it. The result will be a new
itemcount attribute in the item, with a value of
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
ADD action specified
, then the final attribute value
[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.