libZSservicesZSamazonka-dynamodbZSamazonka-dynamodb
Copyright(c) 2013-2021 Brendan Hay
LicenseMozilla Public License, v. 2.0.
MaintainerBrendan Hay <brendan.g.hay+amazonka@gmail.com>
Stabilityauto-generated
Portabilitynon-portable (GHC extensions)
Safe HaskellNone

Amazonka.DynamoDB.GetItem

Description

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

Creating a Request

data GetItem Source #

Represents the input of a GetItem operation.

See: newGetItem smart constructor.

Constructors

GetItem' 

Fields

  • projectionExpression :: 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 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.

  • attributesToGet :: Maybe (NonEmpty Text)

    This is a legacy parameter. Use ProjectionExpression instead. For more information, see AttributesToGet in the Amazon DynamoDB Developer Guide.

  • expressionAttributeNames :: Maybe (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 Specifying Item Attributes in the Amazon DynamoDB Developer Guide.

  • consistentRead :: 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.

  • returnConsumedCapacity :: Maybe ReturnConsumedCapacity
     
  • tableName :: Text

    The name of the table containing the requested item.

  • key :: 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 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.

Instances

Instances details
Eq GetItem Source # 
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Methods

(==) :: GetItem -> GetItem -> Bool #

(/=) :: GetItem -> GetItem -> Bool #

Read GetItem Source # 
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Show GetItem Source # 
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Generic GetItem Source # 
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Associated Types

type Rep GetItem :: Type -> Type #

Methods

from :: GetItem -> Rep GetItem x #

to :: Rep GetItem x -> GetItem #

NFData GetItem Source # 
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rnf :: GetItem -> () #

Hashable GetItem Source # 
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hashWithSalt :: Int -> GetItem -> Int #

hash :: GetItem -> Int #

ToJSON GetItem Source # 
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AWSRequest GetItem Source # 
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type AWSResponse GetItem #

ToHeaders GetItem Source # 
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toHeaders :: GetItem -> [Header] #

ToPath GetItem Source # 
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toPath :: GetItem -> ByteString #

ToQuery GetItem Source # 
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type Rep GetItem Source # 
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type Rep GetItem = D1 ('MetaData "GetItem" "Amazonka.DynamoDB.GetItem" "libZSservicesZSamazonka-dynamodbZSamazonka-dynamodb" 'False) (C1 ('MetaCons "GetItem'" 'PrefixI 'True) ((S1 ('MetaSel ('Just "projectionExpression") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedStrict) (Rec0 (Maybe Text)) :*: (S1 ('MetaSel ('Just "attributesToGet") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedStrict) (Rec0 (Maybe (NonEmpty Text))) :*: S1 ('MetaSel ('Just "expressionAttributeNames") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedStrict) (Rec0 (Maybe (HashMap Text Text))))) :*: ((S1 ('MetaSel ('Just "consistentRead") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedStrict) (Rec0 (Maybe Bool)) :*: S1 ('MetaSel ('Just "returnConsumedCapacity") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedStrict) (Rec0 (Maybe ReturnConsumedCapacity))) :*: (S1 ('MetaSel ('Just "tableName") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedStrict) (Rec0 Text) :*: S1 ('MetaSel ('Just "key") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedStrict) (Rec0 (HashMap Text AttributeValue))))))
type AWSResponse GetItem Source # 
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newGetItem Source #

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_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.

Constructors

GetItemResponse' 

Fields

  • consumedCapacity :: Maybe 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.

  • item :: Maybe (HashMap Text AttributeValue)

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

  • httpStatus :: Int

    The response's http status code.

Instances

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Eq GetItemResponse Source # 
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Read GetItemResponse Source # 
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Show GetItemResponse Source # 
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Generic GetItemResponse Source # 
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Associated Types

type Rep GetItemResponse :: Type -> Type #

NFData GetItemResponse Source # 
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Methods

rnf :: GetItemResponse -> () #

type Rep GetItemResponse Source # 
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type Rep GetItemResponse = D1 ('MetaData "GetItemResponse" "Amazonka.DynamoDB.GetItem" "libZSservicesZSamazonka-dynamodbZSamazonka-dynamodb" 'False) (C1 ('MetaCons "GetItemResponse'" 'PrefixI 'True) (S1 ('MetaSel ('Just "consumedCapacity") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedStrict) (Rec0 (Maybe ConsumedCapacity)) :*: (S1 ('MetaSel ('Just "item") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedStrict) (Rec0 (Maybe (HashMap Text AttributeValue))) :*: S1 ('MetaSel ('Just "httpStatus") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedStrict) (Rec0 Int))))

newGetItemResponse Source #

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.