Method: Aws::DynamoDB::Client#get_item

Defined in:: lib/aws-sdk-dynamodb/client.rb

#get_item(params = {}) ⇒ `Types::GetItemOutput`

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.

Examples:

Example: To read an item from a table


# This example retrieves an item from the Music table. The table has a partition key and a sort key (Artist and
# SongTitle), so you must specify both of these attributes.

resp = client.get_item({
  key: {
    "Artist" => "Acme Band", 
    "SongTitle" => "Happy Day", 
  }, 
  table_name: "Music", 
})

resp.to_h outputs the following:
{
  item: {
    "AlbumTitle" => "Songs About Life", 
    "Artist" => "Acme Band", 
    "SongTitle" => "Happy Day", 
  }, 
}

Request syntax with placeholder values


resp = client.get_item({
  table_name: "TableArn", # required
  key: { # required
    "AttributeName" => "value", # value <Hash,Array,String,Numeric,Boolean,IO,Set,nil>
  },
  attributes_to_get: ["AttributeName"],
  consistent_read: false,
  return_consumed_capacity: "INDEXES", # accepts INDEXES, TOTAL, NONE
  projection_expression: "ProjectionExpression",
  expression_attribute_names: {
    "ExpressionAttributeNameVariable" => "AttributeName",
  },
})

Response structure


resp.item #=> Hash
resp.item["AttributeName"] #=> <Hash,Array,String,Numeric,Boolean,IO,Set,nil>
resp.consumed_capacity.table_name #=> String
resp.consumed_capacity.capacity_units #=> Float
resp.consumed_capacity.read_capacity_units #=> Float
resp.consumed_capacity.write_capacity_units #=> Float
resp.consumed_capacity.table.read_capacity_units #=> Float
resp.consumed_capacity.table.write_capacity_units #=> Float
resp.consumed_capacity.table.capacity_units #=> Float
resp.consumed_capacity.local_secondary_indexes #=> Hash
resp.consumed_capacity.local_secondary_indexes["IndexName"].read_capacity_units #=> Float
resp.consumed_capacity.local_secondary_indexes["IndexName"].write_capacity_units #=> Float
resp.consumed_capacity.local_secondary_indexes["IndexName"].capacity_units #=> Float
resp.consumed_capacity.global_secondary_indexes #=> Hash
resp.consumed_capacity.global_secondary_indexes["IndexName"].read_capacity_units #=> Float
resp.consumed_capacity.global_secondary_indexes["IndexName"].write_capacity_units #=> Float
resp.consumed_capacity.global_secondary_indexes["IndexName"].capacity_units #=> Float

Parameters:

params (Hash) (defaults to: {}) —

({})

Options Hash (params):

:table_name (required, String) —

The name of the table containing the requested item. You can also provide the Amazon Resource Name (ARN) of the table in this parameter.
:key (required, Hash<String,Types::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.
:attributes_to_get (Array<String>) —

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

[1]: docs.aws.amazon.com/amazondynamodb/latest/developerguide/LegacyConditionalParameters.AttributesToGet.html
:consistent_read (Boolean) —

Determines the read consistency model: If set to ‘true`, then the operation uses strongly consistent reads; otherwise, the operation uses eventually consistent reads.
:return_consumed_capacity (String) —
Determines the level of detail about either provisioned or on-demand 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.
:projection_expression (String) —

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*.

[1]: docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html
:expression_attribute_names (Hash<String,String>) —
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`
^

<note markdown=“1”> Tokens that begin with the : character are *expression attribute values*, which are placeholders for the actual value at runtime.
```
</note>
```
For more information on expression attribute names, see [Specifying Item Attributes] in the *Amazon DynamoDB Developer Guide*.

[1]: docs.aws.amazon.com/amazondynamodb/latest/developerguide/ReservedWords.html [2]: docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html

Returns:

(Types::GetItemOutput) —
Returns a response object which responds to the following methods:
- #item => Hash<String,Types::AttributeValue>
- #consumed_capacity => Types::ConsumedCapacity