Update Item
dynamodb_update_item | R Documentation |
Edits an existing item's attributes, or adds a new item to the table if it does not already exist¶
Description¶
Edits an existing item's attributes, or adds a new item to the table if it does not already exist. You can put, delete, or add attribute values. You can also perform a conditional update on an existing item (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).
You can also return the item's attribute values in the same
update_item
operation using the ReturnValues
parameter.
Usage¶
dynamodb_update_item(TableName, Key, AttributeUpdates, Expected,
ConditionalOperator, ReturnValues, ReturnConsumedCapacity,
ReturnItemCollectionMetrics, UpdateExpression, ConditionExpression,
ExpressionAttributeNames, ExpressionAttributeValues,
ReturnValuesOnConditionCheckFailure)
Arguments¶
TableName
[required] The name of the table containing the item to update. You can also provide the Amazon Resource Name (ARN) of the table in this parameter.
Key
[required] 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 simple primary key, you only need to provide a value for the partition key. For a composite primary key, you must provide values for both the partition key and the sort key.
AttributeUpdates
This is a legacy parameter. Use
UpdateExpression
instead. For more information, see AttributeUpdates in the Amazon DynamoDB Developer Guide.Expected
This is a legacy parameter. Use
ConditionExpression
instead. For more information, see Expected in the Amazon DynamoDB Developer Guide.ConditionalOperator
This is a legacy parameter. Use
ConditionExpression
instead. For more information, see ConditionalOperator in the Amazon DynamoDB Developer Guide.ReturnValues
Use
ReturnValues
if you want to get the item attributes as they appear before or after they are successfully updated. Forupdate_item
, the valid values are:NONE
- IfReturnValues
is not specified, or if its value isNONE
, then nothing is returned. (This setting is the default forReturnValues
.)ALL_OLD
- Returns all of the attributes of the item, as they appeared before the UpdateItem operation.UPDATED_OLD
- Returns only the updated attributes, as they appeared before the UpdateItem operation.ALL_NEW
- Returns all of the attributes of the item, as they appear after the UpdateItem operation.UPDATED_NEW
- Returns only the updated attributes, as they appear after the UpdateItem operation.
There is no additional cost associated with requesting a return value aside from the small network and processing overhead of receiving a larger response. No read capacity units are consumed.
The values returned are strongly consistent.
ReturnConsumedCapacity
ReturnItemCollectionMetrics
Determines whether item collection metrics are returned. If set to
SIZE
, the response includes statistics about item collections, if any, that were modified during the operation are returned in the response. If set toNONE
(the default), no statistics are returned.UpdateExpression
An expression that defines one or more attributes to be updated, the action to be performed on them, and new values for them.
The following action values are available for
UpdateExpression
.SET
- Adds one or more attributes and values to an item. If any of these attributes already exist, they are replaced by the new values. You can also useSET
to add or subtract from an attribute that is of type Number. For example:SET myNum = myNum + :val
SET
supports the following functions:if_not_exists (path, operand)
- if the item does not contain an attribute at the specified path, thenif_not_exists
evaluates to operand; otherwise, it evaluates to path. You can use this function to avoid overwriting an attribute that may already be present in the item.list_append (operand, operand)
- evaluates to a list with a new element added to it. You can append the new element to the start or the end of the list by reversing the order of the operands.
These function names are case-sensitive.
REMOVE
- Removes one or more attributes from an item.ADD
- Adds the specified value to the item, if the attribute does not already exist. If the attribute does exist, then the behavior ofADD
depends on the data type of the attribute:If the existing attribute is a number, and if
Value
is also a number, thenValue
is mathematically added to the existing attribute. IfValue
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 uses0
as the initial value.Similarly, if you use
ADD
for an existing item to increment or decrement an attribute value that doesn't exist before the update, DynamoDB uses0
as the initial value. For example, suppose that the item you want to update doesn't have an attribute nameditemcount
, but you decide toADD
the number3
to this attribute anyway. DynamoDB will create theitemcount
attribute, set its initial value to0
, and finally add3
to it. The result will be a newitemcount
attribute in the item, with a value of3
.If the existing data type is a set and if
Value
is also a set, thenValue
is added to the existing set. For example, if the attribute value is the set[1,2]
, and theADD
action specified[3]
, then the final attribute value is[1,2,3]
. An error occurs if anADD
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
ADD
action only supports Number and set data types. In addition,ADD
can only be used on top-level attributes, not nested attributes.DELETE
- Deletes an element from a set.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 theDELETE
action specifies[a,c]
, then the final attribute value is[b]
. Specifying an empty set is an error.The
DELETE
action only supports set data types. In addition,DELETE
can only be used on top-level attributes, not nested attributes.
You can have many actions in a single expression, such as the following:
SET a=:value1, b=:value2 DELETE :value3, :value4, :value5
For more information on update expressions, see Modifying Items and Attributes in the Amazon DynamoDB Developer Guide.
ConditionExpression
A condition that must be satisfied in order for a conditional update to succeed.
An expression can contain any of the following:
Functions:
attribute_exists | attribute_not_exists | attribute_type | contains | begins_with | size
These function names are case-sensitive.
Comparison operators:
= | <> | < | > | <= | >= | BETWEEN | IN
Logical operators:
AND | OR | NOT
For more information about condition expressions, see Specifying Conditions in the Amazon DynamoDB Developer Guide.
ExpressionAttributeNames
One or more substitution tokens for attribute names in an expression. The following are some use cases for using
ExpressionAttributeNames
:To access an attribute whose name conflicts with a DynamoDB reserved word.
To create a placeholder for repeating occurrences of an attribute name in an expression.
To prevent special characters in an attribute name from being misinterpreted in an expression.
Use the # character in an expression to dereference an attribute name. For example, consider the following attribute name:
Percentile
The name of this attribute conflicts with a reserved word, so it cannot be used directly in an expression. (For the complete list of reserved words, see Reserved Words in the Amazon DynamoDB Developer Guide.) To work around this, you could specify the following for
ExpressionAttributeNames
:{"#P":"Percentile"}
You could then use this substitution in an expression, as in this example:
#P = :val
Tokens that begin with the : character are expression attribute values, which are placeholders for the actual value at runtime.
For more information about expression attribute names, see Specifying Item Attributes in the Amazon DynamoDB Developer Guide.
ExpressionAttributeValues
One or more values that can be substituted in an expression.
Use the : (colon) character in an expression to dereference an attribute value. For example, suppose that you wanted to check whether the value of the
ProductStatus
attribute was one of the following:Available | Backordered | Discontinued
You would first need to specify
ExpressionAttributeValues
as follows:{ ":avail":{"S":"Available"}, ":back":{"S":"Backordered"}, ":disc":{"S":"Discontinued"} }
You could then use these values in an expression, such as this:
ProductStatus IN (:avail, :back, :disc)
For more information on expression attribute values, see Condition Expressions in the Amazon DynamoDB Developer Guide.
ReturnValuesOnConditionCheckFailure
An optional parameter that returns the item attributes for an
update_item
operation that failed a condition check.There is no additional cost associated with requesting a return value aside from the small network and processing overhead of receiving a larger response. No read capacity units are consumed.
Value¶
A list with the following syntax:
list(
Attributes = list(
list(
S = "string",
N = "string",
B = raw,
SS = list(
"string"
),
NS = list(
"string"
),
BS = list(
raw
),
M = list(
list()
),
L = list(
list()
),
NULL = TRUE|FALSE,
BOOL = TRUE|FALSE
)
),
ConsumedCapacity = list(
TableName = "string",
CapacityUnits = 123.0,
ReadCapacityUnits = 123.0,
WriteCapacityUnits = 123.0,
Table = list(
ReadCapacityUnits = 123.0,
WriteCapacityUnits = 123.0,
CapacityUnits = 123.0
),
LocalSecondaryIndexes = list(
list(
ReadCapacityUnits = 123.0,
WriteCapacityUnits = 123.0,
CapacityUnits = 123.0
)
),
GlobalSecondaryIndexes = list(
list(
ReadCapacityUnits = 123.0,
WriteCapacityUnits = 123.0,
CapacityUnits = 123.0
)
)
),
ItemCollectionMetrics = list(
ItemCollectionKey = list(
list(
S = "string",
N = "string",
B = raw,
SS = list(
"string"
),
NS = list(
"string"
),
BS = list(
raw
),
M = list(
list()
),
L = list(
list()
),
NULL = TRUE|FALSE,
BOOL = TRUE|FALSE
)
),
SizeEstimateRangeGB = list(
123.0
)
)
)
Request syntax¶
svc$update_item(
TableName = "string",
Key = list(
list(
S = "string",
N = "string",
B = raw,
SS = list(
"string"
),
NS = list(
"string"
),
BS = list(
raw
),
M = list(
list()
),
L = list(
list()
),
NULL = TRUE|FALSE,
BOOL = TRUE|FALSE
)
),
AttributeUpdates = list(
list(
Value = list(
S = "string",
N = "string",
B = raw,
SS = list(
"string"
),
NS = list(
"string"
),
BS = list(
raw
),
M = list(
list()
),
L = list(
list()
),
NULL = TRUE|FALSE,
BOOL = TRUE|FALSE
),
Action = "ADD"|"PUT"|"DELETE"
)
),
Expected = list(
list(
Value = list(
S = "string",
N = "string",
B = raw,
SS = list(
"string"
),
NS = list(
"string"
),
BS = list(
raw
),
M = list(
list()
),
L = list(
list()
),
NULL = TRUE|FALSE,
BOOL = TRUE|FALSE
),
Exists = TRUE|FALSE,
ComparisonOperator = "EQ"|"NE"|"IN"|"LE"|"LT"|"GE"|"GT"|"BETWEEN"|"NOT_NULL"|"NULL"|"CONTAINS"|"NOT_CONTAINS"|"BEGINS_WITH",
AttributeValueList = list(
list(
S = "string",
N = "string",
B = raw,
SS = list(
"string"
),
NS = list(
"string"
),
BS = list(
raw
),
M = list(
list()
),
L = list(
list()
),
NULL = TRUE|FALSE,
BOOL = TRUE|FALSE
)
)
)
),
ConditionalOperator = "AND"|"OR",
ReturnValues = "NONE"|"ALL_OLD"|"UPDATED_OLD"|"ALL_NEW"|"UPDATED_NEW",
ReturnConsumedCapacity = "INDEXES"|"TOTAL"|"NONE",
ReturnItemCollectionMetrics = "SIZE"|"NONE",
UpdateExpression = "string",
ConditionExpression = "string",
ExpressionAttributeNames = list(
"string"
),
ExpressionAttributeValues = list(
list(
S = "string",
N = "string",
B = raw,
SS = list(
"string"
),
NS = list(
"string"
),
BS = list(
raw
),
M = list(
list()
),
L = list(
list()
),
NULL = TRUE|FALSE,
BOOL = TRUE|FALSE
)
),
ReturnValuesOnConditionCheckFailure = "ALL_OLD"|"NONE"
)
Examples¶
## Not run:
# This example updates an item in the Music table. It adds a new attribute
# (Year) and modifies the AlbumTitle attribute. All of the attributes in
# the item, as they appear after the update, are returned in the response.
svc$update_item(
ExpressionAttributeNames = list(
`#AT` = "AlbumTitle",
`#Y` = "Year"
),
ExpressionAttributeValues = list(
`:t` = list(
S = "Louder Than Ever"
),
`:y` = list(
N = "2015"
)
),
Key = list(
Artist = list(
S = "Acme Band"
),
SongTitle = list(
S = "Happy Day"
)
),
ReturnValues = "ALL_NEW",
TableName = "Music",
UpdateExpression = "SET #Y = :y, #AT = :t"
)
## End(Not run)