Network.AWS.DynamoDB.GetItem

The GetItem operation returns a set of attributes for the item with the given primary key. If there is no matching item, GetItem does not return any data.

GetItem provides an eventually consistent read by default. If your application requires a strongly consistent read, set ConsistentRead to true. Although a strongly consistent read might take more time than an eventually consistent read, it always returns the last updated value.

See: AWS API Reference for GetItem.

Creating a Request

getItem

Arguments

:: Text

giTableName

-> GetItem

Creates a value of GetItem with the minimum fields required to make a request.

Use one of the following lenses to modify other fields as desired:

• giProjectionExpression
• giAttributesToGet
• giExpressionAttributeNames
• giConsistentRead
• giReturnConsumedCapacity
• giTableName
• giKey

data GetItem

Represents the input of a GetItem operation.

See: getItem smart constructor.

Instances

Eq GetItem

Data GetItem

Read GetItem

Show GetItem

Generic GetItem

ToJSON GetItem

AWSRequest GetItem

ToPath GetItem

ToHeaders GetItem

ToQuery GetItem

Typeable * GetItem

type Rep GetItem

type Rs GetItem = GetItemResponse

Request Lenses

giProjectionExpression :: Lens' GetItem (Maybe Text)

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.

ProjectionExpression replaces the legacy AttributesToGet parameter.

giAttributesToGet :: Lens' GetItem (Maybe (NonEmpty Text))

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.

giExpressionAttributeNames :: Lens' GetItem (HashMap Text Text)

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 on expression attribute names, see Accessing Item Attributes in the Amazon DynamoDB Developer Guide.

giConsistentRead :: Lens' GetItem (Maybe Bool)

Determines the read consistency model: If set to true, then the operation uses strongly consistent reads; otherwise, the operation uses eventually consistent reads.

giReturnConsumedCapacity :: Lens' GetItem (Maybe ReturnConsumedCapacity)

Undocumented member.

giTableName :: Lens' GetItem Text

The name of the table containing the requested item.

giKey :: Lens' GetItem (HashMap Text AttributeValue)

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

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

Destructuring the Response

getItemResponse

Arguments

:: Int

girsResponseStatus

-> GetItemResponse

Creates a value of GetItemResponse with the minimum fields required to make a request.

Use one of the following lenses to modify other fields as desired:

• girsConsumedCapacity
• girsItem
• girsResponseStatus

data GetItemResponse

Represents the output of a GetItem operation.

See: getItemResponse smart constructor.

Instances

Eq GetItemResponse

Data GetItemResponse

Read GetItemResponse

Show GetItemResponse

Generic GetItemResponse

Typeable * GetItemResponse

type Rep GetItemResponse

Response Lenses

girsConsumedCapacity :: Lens' GetItemResponse (Maybe ConsumedCapacity)

Undocumented member.

girsItem :: Lens' GetItemResponse (HashMap Text AttributeValue)

A map of attribute names to AttributeValue objects, as specified by AttributesToGet.

girsResponseStatus :: Lens' GetItemResponse Int

The response status code.