Network.AWS.DynamoDB.DeleteItem

Deletes a single item in a table by primary key. You can perform a conditional delete operation that deletes the item if it exists, or if it has an expected attribute value.

In addition to deleting an item, you can also return the item's attribute values in the same operation, using the ReturnValues parameter.

Unless you specify conditions, the DeleteItem is an idempotent operation; running it multiple times on the same item or attribute does not result in an error response.

Conditional deletes are useful for deleting items only if specific conditions are met. If those conditions are met, DynamoDB performs the delete. Otherwise, the item is not deleted.

http://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_DeleteItem.html

Request

data DeleteItem

Instances

Eq DeleteItem

Read DeleteItem

Show DeleteItem

ToJSON DeleteItem

AWSRequest DeleteItem

ToQuery DeleteItem

ToPath DeleteItem

ToHeaders DeleteItem

type Sv DeleteItem = DynamoDB

type Rs DeleteItem = DeleteItemResponse

Request constructor

deleteItem

Arguments

:: Text

diTableName

-> DeleteItem

DeleteItem constructor.

The fields accessible through corresponding lenses are:

• diConditionExpression :: Maybe Text
• diConditionalOperator :: Maybe ConditionalOperator
• diExpected :: HashMap Text ExpectedAttributeValue
• diExpressionAttributeNames :: HashMap Text Text
• diExpressionAttributeValues :: HashMap Text AttributeValue
• diKey :: HashMap Text AttributeValue
• diReturnConsumedCapacity :: Maybe ReturnConsumedCapacity
• diReturnItemCollectionMetrics :: Maybe ReturnItemCollectionMetrics
• diReturnValues :: Maybe ReturnValue
• diTableName :: Text

Request lenses

diConditionExpression :: Lens' DeleteItem (Maybe Text)

A condition that must be satisfied in order for a conditional DeleteItem to succeed.

An expression can contain any of the following:

Boolean functions: 'attribute_exists | attribute_not_exists | contains |begins_with'

These function names are case-sensitive.

Comparison operators: ' = | <> | | | |= | BETWEEN | IN'

Logical operators: 'AND | OR | NOT'

For more information on condition expressions, go to Specifying Conditions in the Amazon DynamoDB Developer Guide.

diConditionalOperator :: Lens' DeleteItem (Maybe ConditionalOperator)

There is a newer parameter available. Use ConditionExpression instead. Note that if you use ConditionalOperator and ConditionExpression at the same time, DynamoDB will return a ValidationException exception.

This parameter does not support lists or maps.

A logical operator to apply to the conditions in the Expected map:

AND - If all of the conditions evaluate to true, then the entire map evaluates to true.

OR - If at least one of the conditions evaluate to true, then the entire map evaluates to true.

If you omit ConditionalOperator, then AND is the default.

The operation will succeed only if the entire map evaluates to true.

diExpected :: Lens' DeleteItem (HashMap Text ExpectedAttributeValue)

There is a newer parameter available. Use ConditionExpression instead. Note that if you use Expected and ConditionExpression at the same time, DynamoDB will return a ValidationException exception.

This parameter does not support lists or maps.

A map of attributecondition pairs. Expected/ provides a conditional block for the DeleteItem operation.

Each element of Expected consists of an attribute name, a comparison operator, and one or more values. DynamoDB compares the attribute with the value(s) you supplied, using the comparison operator. For each Expected element, the result of the evaluation is either true or false.

If you specify more than one element in the Expected map, then by default all of the conditions must evaluate to true. In other words, the conditions are ANDed together. (You can use the ConditionalOperator parameter to OR the conditions instead. If you do this, then at least one of the conditions must evaluate to true, rather than all of them.)

If the Expected map evaluates to true, then the conditional operation succeeds; otherwise, it fails.

Expected contains the following:

AttributeValueList - One or more values to evaluate against the supplied attribute. The number of values in the list depends on the ComparisonOperator being used.

For type Number, value comparisons are numeric.

String value comparisons for greater than, equals, or less than are based on ASCII character code values. For example, a is greater than A, and a is greater than B. For a list of code values, see http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters.

For type Binary, DynamoDB treats each byte of the binary data as unsigned when it compares binary values, for example when evaluating query expressions.

ComparisonOperator - A comparator for evaluating attributes in the AttributeValueList. When performing the comparison, DynamoDB uses strongly consistent reads.

The following comparison operators are available:

'EQ | NE | LE | LT | GE | GT | NOT_NULL | NULL | CONTAINS | NOT_CONTAINS |BEGINS_WITH | IN | BETWEEN'

The following are descriptions of each comparison operator.

EQ : Equal. EQ is supported for all datatypes, including lists and maps.

AttributeValueList can contain only one AttributeValue element of type String, Number, Binary, String Set, Number Set, or Binary Set. If an item contains an AttributeValue element of a different type than the one specified in the request, the value does not match. For example, '{S:"6"}' does not equal '{N:"6"}'. Also, '{N:"6"}' does not equal '{NS:["6", "2", "1"]}'.

NE : Not equal. NE is supported for all datatypes, including lists and maps.

AttributeValueList can contain only one AttributeValue of type String, Number, Binary, String Set, Number Set, or Binary Set. If an item contains an AttributeValue of a different type than the one specified in the request, the value does not match. For example, '{S:"6"}' does not equal '{N:"6"}'. Also, '{N:"6"}' does not equal '{NS:["6", "2", "1"]}'.

LE : Less than or equal.

AttributeValueList can contain only one AttributeValue element of type String, Number, or Binary (not a set type). If an item contains an AttributeValue element of a different type than the one specified in the request, the value does not match. For example, '{S:"6"}' does not equal '{N:"6"}'. Also, '{N:"6"}' does not compare to '{NS:["6", "2", "1"]}'.

LT : Less than.

AttributeValueList can contain only one AttributeValue of type String, Number, or Binary (not a set type). If an item contains an AttributeValue element of a different type than the one specified in the request, the value does not match. For example, '{S:"6"}' does not equal '{N:"6"}'. Also, '{N:"6"}' does not compare to '{NS:["6", "2", "1"]}'.

GE : Greater than or equal.

AttributeValueList can contain only one AttributeValue element of type String, Number, or Binary (not a set type). If an item contains an AttributeValue element of a different type than the one specified in the request, the value does not match. For example, '{S:"6"}' does not equal '{N:"6"}'. Also, '{N:"6"}' does not compare to '{NS:["6", "2", "1"]}'.

GT : Greater than.

AttributeValueList can contain only one AttributeValue element of type String, Number, or Binary (not a set type). If an item contains an AttributeValue element of a different type than the one specified in the request, the value does not match. For example, '{S:"6"}' does not equal '{N:"6"}'. Also, '{N:"6"}' does not compare to '{NS:["6", "2", "1"]}'.

NOT_NULL : The attribute exists. NOT_NULL is supported for all datatypes, including lists and maps.

This operator tests for the existence of an attribute, not its data type. If the data type of attribute "a" is null, and you evaluate it using NOT_NULL, the result is a Boolean true. This result is because the attribute "a" exists; its data type is not relevant to the NOT_NULL comparison operator.

NULL : The attribute does not exist. NULL is supported for all datatypes, including lists and maps.

This operator tests for the nonexistence of an attribute, not its data type. If the data type of attribute "a" is null, and you evaluate it using NULL, the result is a Boolean false. This is because the attribute "a" exists; its data type is not relevant to the NULL comparison operator.

CONTAINS : Checks for a subsequence, or value in a set.

AttributeValueList can contain only one AttributeValue element of type String, Number, or Binary (not a set type). If the target attribute of the comparison is of type String, then the operator checks for a substring match. If the target attribute of the comparison is of type Binary, then the operator looks for a subsequence of the target that matches the input. If the target attribute of the comparison is a set ("SS", "NS", or "BS"), then the operator evaluates to true if it finds an exact match with any member of the set.

CONTAINS is supported for lists: When evaluating "'a CONTAINS b'", "a" can be a list; however, "b" cannot be a set, a map, or a list.

NOT_CONTAINS : Checks for absence of a subsequence, or absence of a value in a set.

AttributeValueList can contain only one AttributeValue element of type String, Number, or Binary (not a set type). If the target attribute of the comparison is a String, then the operator checks for the absence of a substring match. If the target attribute of the comparison is Binary, then the operator checks for the absence of a subsequence of the target that matches the input. If the target attribute of the comparison is a set ("SS", "NS", or "BS"), then the operator evaluates to true if it does not find an exact match with any member of the set.

NOT_CONTAINS is supported for lists: When evaluating "'a NOT CONTAINS b'", "a" can be a list; however, "b" cannot be a set, a map, or a list.

BEGINS_WITH : Checks for a prefix.

AttributeValueList can contain only one AttributeValue of type String or Binary (not a Number or a set type). The target attribute of the comparison must be of type String or Binary (not a Number or a set type).

IN : Checks for matching elements within two sets.

AttributeValueList can contain one or more AttributeValue elements of type String, Number, or Binary (not a set type). These attributes are compared against an existing set type attribute of an item. If any elements of the input set are present in the item attribute, the expression evaluates to true.

BETWEEN : Greater than or equal to the first value, and less than or equal to the second value.

AttributeValueList must contain two AttributeValue elements of the same type, either String, Number, or Binary (not a set type). A target attribute matches if the target value is greater than, or equal to, the first element and less than, or equal to, the second element. If an item contains an AttributeValue element of a different type than the one specified in the request, the value does not match. For example, '{S:"6"}' does not compare to '{N:"6"}'. Also, '{N:"6"}' does not compare to '{NS:["6", "2", "1"]}'

For usage examples of AttributeValueList and ComparisonOperator, see Legacy Conditional Parameters in the Amazon DynamoDB Developer Guide.

For backward compatibility with previous DynamoDB releases, the following parameters can be used instead of AttributeValueList and ComparisonOperator:

Value - A value for DynamoDB to compare with an attribute.

Exists - A Boolean value that causes DynamoDB to evaluate the value before attempting the conditional operation:

If Exists is true, DynamoDB will check to see if that attribute value already exists in the table. If it is found, then the condition evaluates to true; otherwise the condition evaluate to false.

If Exists is false, 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 condition evaluates to true. If the value is found, despite the assumption that it does not exist, the condition evaluates to false.

Note that the default value for Exists is true.

The Value and Exists parameters are incompatible with AttributeValueList and ComparisonOperator. Note that if you use both sets of parameters at once, DynamoDB will return a ValidationException exception.

diExpressionAttributeNames :: Lens' DeleteItem (HashMap Text Text)

One or more substitution tokens for simplifying complex expressions. The following are some use cases for using ExpressionAttributeNames:

To shorten an attribute name that is very long or unwieldy in an expression.

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 expression:

'order.customerInfo.LastName = Smith OR order.customerInfo.LastName =Jones'

Now suppose that you specified the following for ExpressionAttributeNames:

'{"#name":"order.customerInfo.LastName"}'

The expression can now be simplified as follows:

'name = Jones'

For more information on expression attribute names, go to Accessing ItemAttributes in the Amazon DynamoDB Developer Guide.

diExpressionAttributeValues :: Lens' DeleteItem (HashMap Text AttributeValue)

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, go to SpecifyingConditions in the Amazon DynamoDB Developer Guide.

diKey :: Lens' DeleteItem (HashMap Text AttributeValue)

A map of attribute names to AttributeValue objects, representing the primary key of the item to delete.

For the primary key, you must provide all of the attributes. For example, with a hash type primary key, you only need to specify the hash attribute. For a hash-and-range type primary key, you must specify both the hash attribute and the range attribute.

diReturnConsumedCapacity :: Lens' DeleteItem (Maybe ReturnConsumedCapacity)

diReturnItemCollectionMetrics :: Lens' DeleteItem (Maybe ReturnItemCollectionMetrics)

A value that 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.

diReturnValues :: Lens' DeleteItem (Maybe ReturnValue)

Use ReturnValues if you want to get the item attributes as they appeared before they were deleted. For DeleteItem, 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 - The content of the old item is returned.

diTableName :: Lens' DeleteItem Text

The name of the table from which to delete the item.

Response

data DeleteItemResponse

Instances

Eq DeleteItemResponse

Read DeleteItemResponse

Show DeleteItemResponse

FromJSON DeleteItemResponse

Response constructor

deleteItemResponse :: DeleteItemResponse

DeleteItemResponse constructor.

The fields accessible through corresponding lenses are:

• dirAttributes :: HashMap Text AttributeValue
• dirConsumedCapacity :: Maybe ConsumedCapacity
• dirItemCollectionMetrics :: Maybe ItemCollectionMetrics

Response lenses

dirAttributes :: Lens' DeleteItemResponse (HashMap Text AttributeValue)

A map of attribute names to AttributeValue objects, representing the item as it appeared before the DeleteItem operation. This map appears in the response only if ReturnValues was specified as ALL_OLD in the request.

dirConsumedCapacity :: Lens' DeleteItemResponse (Maybe ConsumedCapacity)

dirItemCollectionMetrics :: Lens' DeleteItemResponse (Maybe ItemCollectionMetrics)

Information about item collections, if any, that were affected by the operation. ItemCollectionMetrics is only returned if the request asked for it. If the table does not have any local secondary indexes, this information is not returned in the response.

Each ItemCollectionMetrics element consists of:

ItemCollectionKey - The hash key value of the item collection. This is the same as the hash key of the item.

SizeEstimateRange - An estimate of item collection size, in gigabytes. This value is a two-element array containing a lower bound and an upper bound for the estimate. The estimate includes the size of all the items in the table, plus the size of all attributes projected into all of the local secondary indexes on that table. Use this estimate to measure whether a local secondary index is approaching its size limit.

The estimate is subject to change over time; therefore, do not rely on the precision or accuracy of the estimate.