Copyright | (c) 2013-2021 Brendan Hay |
---|---|
License | Mozilla Public License, v. 2.0. |
Maintainer | Brendan Hay <brendan.g.hay+amazonka@gmail.com> |
Stability | auto-generated |
Portability | non-portable (GHC extensions) |
Safe Haskell | None |
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 and there will be no Item
element in the response.
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.
Synopsis
- data GetItem = GetItem' {}
- newGetItem :: Text -> GetItem
- getItem_projectionExpression :: Lens' GetItem (Maybe Text)
- getItem_attributesToGet :: Lens' GetItem (Maybe (NonEmpty Text))
- getItem_expressionAttributeNames :: Lens' GetItem (Maybe (HashMap Text Text))
- getItem_consistentRead :: Lens' GetItem (Maybe Bool)
- getItem_returnConsumedCapacity :: Lens' GetItem (Maybe ReturnConsumedCapacity)
- getItem_tableName :: Lens' GetItem Text
- getItem_key :: Lens' GetItem (HashMap Text AttributeValue)
- data GetItemResponse = GetItemResponse' {}
- newGetItemResponse :: Int -> GetItemResponse
- getItemResponse_consumedCapacity :: Lens' GetItemResponse (Maybe ConsumedCapacity)
- getItemResponse_item :: Lens' GetItemResponse (Maybe (HashMap Text AttributeValue))
- getItemResponse_httpStatus :: Lens' GetItemResponse Int
Creating a Request
Represents the input of a GetItem
operation.
See: newGetItem
smart constructor.
GetItem' | |
|
Instances
Create a value of GetItem
with all optional fields omitted.
Use generic-lens or optics to modify other optional fields.
The following record fields are available, with the corresponding lenses provided for backwards compatibility:
$sel:projectionExpression:GetItem'
, getItem_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 are returned. If any of the requested attributes are not found, they do not appear in the result.
For more information, see Specifying Item Attributes in the Amazon DynamoDB Developer Guide.
$sel:attributesToGet:GetItem'
, getItem_attributesToGet
- This is a legacy parameter. Use ProjectionExpression
instead. For more
information, see
AttributesToGet
in the Amazon DynamoDB Developer Guide.
$sel:expressionAttributeNames:GetItem'
, getItem_expressionAttributeNames
- 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 Specifying Item Attributes in the Amazon DynamoDB Developer Guide.
$sel:consistentRead:GetItem'
, getItem_consistentRead
- Determines the read consistency model: If set to true
, then the
operation uses strongly consistent reads; otherwise, the operation uses
eventually consistent reads.
$sel:returnConsumedCapacity:GetItem'
, getItem_returnConsumedCapacity
- Undocumented member.
$sel:tableName:GetItem'
, getItem_tableName
- The name of the table containing the requested item.
$sel:key:GetItem'
, getItem_key
- 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.
Request Lenses
getItem_projectionExpression :: 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 are returned. If any of the requested attributes are not found, they do not appear in the result.
For more information, see Specifying Item Attributes in the Amazon DynamoDB Developer Guide.
getItem_attributesToGet :: Lens' GetItem (Maybe (NonEmpty Text)) Source #
This is a legacy parameter. Use ProjectionExpression
instead. For more
information, see
AttributesToGet
in the Amazon DynamoDB Developer Guide.
getItem_expressionAttributeNames :: Lens' GetItem (Maybe (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
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 Specifying Item Attributes in the Amazon DynamoDB Developer Guide.
getItem_consistentRead :: 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.
getItem_returnConsumedCapacity :: Lens' GetItem (Maybe ReturnConsumedCapacity) Source #
Undocumented member.
getItem_tableName :: Lens' GetItem Text Source #
The name of the table containing the requested item.
getItem_key :: 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
data GetItemResponse Source #
Represents the output of a GetItem
operation.
See: newGetItemResponse
smart constructor.
GetItemResponse' | |
|
Instances
Create a value of GetItemResponse
with all optional fields omitted.
Use generic-lens or optics to modify other optional fields.
The following record fields are available, with the corresponding lenses provided for backwards compatibility:
$sel:consumedCapacity:GetItemResponse'
, getItemResponse_consumedCapacity
- The capacity units consumed by the GetItem
operation. The data
returned includes the total provisioned throughput consumed, along with
statistics for the table and any indexes involved in the operation.
ConsumedCapacity
is only returned if the ReturnConsumedCapacity
parameter was specified. For more information, see
Read/Write Capacity Mode
in the Amazon DynamoDB Developer Guide.
$sel:item:GetItemResponse'
, getItemResponse_item
- A map of attribute names to AttributeValue
objects, as specified by
ProjectionExpression
.
$sel:httpStatus:GetItemResponse'
, getItemResponse_httpStatus
- The response's http status code.
Response Lenses
getItemResponse_consumedCapacity :: Lens' GetItemResponse (Maybe ConsumedCapacity) Source #
The capacity units consumed by the GetItem
operation. The data
returned includes the total provisioned throughput consumed, along with
statistics for the table and any indexes involved in the operation.
ConsumedCapacity
is only returned if the ReturnConsumedCapacity
parameter was specified. For more information, see
Read/Write Capacity Mode
in the Amazon DynamoDB Developer Guide.
getItemResponse_item :: Lens' GetItemResponse (Maybe (HashMap Text AttributeValue)) Source #
A map of attribute names to AttributeValue
objects, as specified by
ProjectionExpression
.
getItemResponse_httpStatus :: Lens' GetItemResponse Int Source #
The response's http status code.