Copyright | (c) 2013-2016 Brendan Hay |
---|---|
License | Mozilla Public License, v. 2.0. |
Maintainer | Brendan Hay <brendan.g.hay@gmail.com> |
Stability | auto-generated |
Portability | non-portable (GHC extensions) |
Safe Haskell | None |
Language | Haskell2010 |
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.
- getItem :: Text -> GetItem
- data GetItem
- giProjectionExpression :: Lens' GetItem (Maybe Text)
- giAttributesToGet :: Lens' GetItem (Maybe (NonEmpty Text))
- giExpressionAttributeNames :: Lens' GetItem (HashMap Text Text)
- giConsistentRead :: Lens' GetItem (Maybe Bool)
- giReturnConsumedCapacity :: Lens' GetItem (Maybe ReturnConsumedCapacity)
- giTableName :: Lens' GetItem Text
- giKey :: Lens' GetItem (HashMap Text AttributeValue)
- getItemResponse :: Int -> GetItemResponse
- data GetItemResponse
- girsConsumedCapacity :: Lens' GetItemResponse (Maybe ConsumedCapacity)
- girsItem :: Lens' GetItemResponse (HashMap Text AttributeValue)
- girsResponseStatus :: Lens' GetItemResponse Int
Creating a Request
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
- 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 .giAttributesToGet
- Important: 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
- 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
For more information on expression attribute names, see Accessing Item Attributes in the Amazon DynamoDB Developer Guide .giConsistentRead
- Determines the read consistency model: If set totrue
, then the operation uses strongly consistent reads; otherwise, the operation uses eventually consistent reads.giReturnConsumedCapacity
- Undocumented member.giTableName
- The name of the table containing the requested item.giKey
- 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 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.
Represents the input of a GetItem operation.
See: getItem
smart constructor.
Request Lenses
giProjectionExpression :: Lens' GetItem (Maybe Text) Source #
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 .
giAttributesToGet :: Lens' GetItem (Maybe (NonEmpty Text)) Source #
Important: 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) Source #
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
For more information on expression attribute names, see Accessing Item Attributes in the Amazon DynamoDB Developer Guide .
giConsistentRead :: Lens' GetItem (Maybe Bool) Source #
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) Source #
Undocumented member.
giKey :: Lens' GetItem (HashMap Text AttributeValue) Source #
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 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.
Destructuring the Response
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
- Undocumented member.girsItem
- A map of attribute names to AttributeValue objects, as specified by AttributesToGet .girsResponseStatus
- -- | The response status code.
data GetItemResponse Source #
Represents the output of a GetItem operation.
See: getItemResponse
smart constructor.
Response Lenses
girsConsumedCapacity :: Lens' GetItemResponse (Maybe ConsumedCapacity) Source #
Undocumented member.
girsItem :: Lens' GetItemResponse (HashMap Text AttributeValue) Source #
A map of attribute names to AttributeValue objects, as specified by AttributesToGet .
girsResponseStatus :: Lens' GetItemResponse Int Source #
- - | The response status code.