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.
dynamodb_update_item(TableName, Key, AttributeUpdates, Expected,
ConditionalOperator, ReturnValues, ReturnConsumedCapacity,
ReturnItemCollectionMetrics, UpdateExpression, ConditionExpression,
ExpressionAttributeNames, ExpressionAttributeValues)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
)
)
)
[required] The name of the table containing the item to update.
[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.
This is a legacy parameter. Use UpdateExpression instead. For more
information, see
AttributeUpdates
in the Amazon DynamoDB Developer Guide.
This is a legacy parameter. Use ConditionExpression instead. For more
information, see
Expected
in the Amazon DynamoDB Developer Guide.
This is a legacy parameter. Use ConditionExpression instead. For more
information, see
ConditionalOperator
in the Amazon DynamoDB Developer Guide.
Use ReturnValues if you want to get the item attributes as they appear
before or after they are updated. For
update_item, the valid values are:
NONE - If ReturnValues is not specified, or if its value is
NONE, then nothing is returned. (This setting is the default for
ReturnValues.)
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.
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 to NONE (the default), no statistics are returned.
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 use SET 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, then if_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 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 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.
Similarly, if you use ADD for an existing item to increment or
decrement an attribute value that doesn't exist before the
update, DynamoDB uses 0 as the initial value. For example,
suppose that the item you want to update doesn't have an
attribute named itemcount, but you decide to ADD the number
3 to this attribute anyway. 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 Value is also a set,
then Value is added to the existing set. For example, if the
attribute value is the set [1,2], and the ADD action
specified [3], then the final attribute value is [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 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 the DELETE 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.
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.
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.
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.
svc$update_item(
TableName = "string",
Key = list(
list(
S = "string",
N = "string",
B = raw,
SS = list(
"string"
),
NS = list(
"string"
),
BS = list(
raw
),
M = list(
list()
),
L = list(
list()
),
NULL = TRUE|FALSE,
BOOL = TRUE|FALSE
)
),
AttributeUpdates = list(
list(
Value = list(
S = "string",
N = "string",
B = raw,
SS = list(
"string"
),
NS = list(
"string"
),
BS = list(
raw
),
M = list(
list()
),
L = list(
list()
),
NULL = TRUE|FALSE,
BOOL = TRUE|FALSE
),
Action = "ADD"|"PUT"|"DELETE"
)
),
Expected = list(
list(
Value = list(
S = "string",
N = "string",
B = raw,
SS = list(
"string"
),
NS = list(
"string"
),
BS = list(
raw
),
M = list(
list()
),
L = list(
list()
),
NULL = TRUE|FALSE,
BOOL = TRUE|FALSE
),
Exists = TRUE|FALSE,
ComparisonOperator = "EQ"|"NE"|"IN"|"LE"|"LT"|"GE"|"GT"|"BETWEEN"|"NOT_NULL"|"NULL"|"CONTAINS"|"NOT_CONTAINS"|"BEGINS_WITH",
AttributeValueList = list(
list(
S = "string",
N = "string",
B = raw,
SS = list(
"string"
),
NS = list(
"string"
),
BS = list(
raw
),
M = list(
list()
),
L = list(
list()
),
NULL = TRUE|FALSE,
BOOL = TRUE|FALSE
)
)
)
),
ConditionalOperator = "AND"|"OR",
ReturnValues = "NONE"|"ALL_OLD"|"UPDATED_OLD"|"ALL_NEW"|"UPDATED_NEW",
ReturnConsumedCapacity = "INDEXES"|"TOTAL"|"NONE",
ReturnItemCollectionMetrics = "SIZE"|"NONE",
UpdateExpression = "string",
ConditionExpression = "string",
ExpressionAttributeNames = list(
"string"
),
ExpressionAttributeValues = list(
list(
S = "string",
N = "string",
B = raw,
SS = list(
"string"
),
NS = list(
"string"
),
BS = list(
raw
),
M = list(
list()
),
L = list(
list()
),
NULL = TRUE|FALSE,
BOOL = TRUE|FALSE
)
)
)
if (FALSE) {
# This example updates an item in the Music table. It adds a new attribute
# (Year) and modifies the AlbumTitle attribute. All of the attributes in
# the item, as they appear after the update, are returned in the response.
svc$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"
)
}
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