AWSDynamoDBBatchGetItemInput Class Reference

Inherits from AWSRequest : AWSModel : AWSMTLModel
Declared in AWSDynamoDBModel.h
AWSDynamoDBModel.m

Overview

Represents the input of a BatchGetItem operation.

Required parameters: [RequestItems]

  requestItems

A map of one or more table names and, for each table, a map that describes one or more items to retrieve from that table. Each table name can be used only once per BatchGetItem request.

Each element in the map of items to retrieve consists of the following:

  • ConsistentRead - If true, a strongly consistent read is used; if false (the default), an eventually consistent read is used.

  • ExpressionAttributeNames - One or more substitution tokens for attribute names in the ProjectionExpression parameter. 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 on expression attribute names, see Accessing Item Attributes in the Amazon DynamoDB Developer Guide.

  • Keys - An array of primary key attribute values that define specific items in the table. For each primary key, you must provide all of the key attributes. For example, with a simple primary key, you only need to provide the partition key value. For a composite key, you must provide both the partition key value and the sort key value.

  • ProjectionExpression - A string that identifies one or more attributes to retrieve from the table. These attributes can include scalars, sets, or elements of a JSON document. The attributes in the expression must be separated by commas.

    If no attribute names are specified, then all attributes will be returned. If any of the requested attributes are not found, they will not appear in the result.

    For more information, see Accessing Item Attributes in the Amazon DynamoDB Developer Guide.

  • AttributesToGet -

    This is a legacy parameter, for backward compatibility. New applications should use ProjectionExpression instead. Do not combine legacy parameters and expression parameters in a single API call; otherwise, DynamoDB will return a ValidationException exception.

    This parameter allows you to retrieve attributes of type List or Map; however, it cannot retrieve individual elements within a List or a Map.

    The names of one or more attributes to retrieve. If no attribute names are provided, then all attributes will be returned. If any of the requested attributes are not found, they will not appear in the result.

    Note that AttributesToGet has no effect on provisioned throughput consumption. DynamoDB determines capacity units consumed based on item size, not on the amount of data that is returned to an application.

@property (nonatomic, strong) NSDictionary<NSString*AWSDynamoDBKeysAndAttributes*> *requestItems

Declared In

AWSDynamoDBModel.h

  returnConsumedCapacity

Determines the level of detail about provisioned throughput consumption that is returned in the response:

  • INDEXES - The response includes the aggregate ConsumedCapacity for the operation, together with ConsumedCapacity for each table and secondary index that was accessed.

    Note that some operations, such as GetItem and BatchGetItem, do not access any indexes at all. In these cases, specifying INDEXES will only return ConsumedCapacity information for table(s).

  • TOTAL - The response includes only the aggregate ConsumedCapacity for the operation.

  • NONE - No ConsumedCapacity details are included in the response.

@property (nonatomic, assign) AWSDynamoDBReturnConsumedCapacity returnConsumedCapacity

Declared In

AWSDynamoDBModel.h