DeleteRequest

A DeleteRequest is used to perform a delete_item transaction with DynamoDB. It is used for deletting a single record by its primary key. The entire primary key must be provided (including the sort key if it is defined on the table)

https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_DeleteItem.html

class cerami.request.DeleteRequest(client, tablename='', request_attributes=None, reconstructor=None)

A class to perform delete_item request

__init__(client, tablename='', request_attributes=None, reconstructor=None)

constructor for base request

Parameters

• client – A boto3.client('dynamodb')

• tablename – the name of the table to perform the request on

• request_attributes –

  a dict of SearchAttribute objects whose keys represent options that can be passed to client upon execution For example, it may include a FilterExpression key whose value is a SearchAttribute that resolves to a string of filters. This is typically None but can be used to manually build requests:

  Parent.scan.filter(Parent.name == 'Mom').project(Parent.name)
  # The search_attributes can be manually specified
  ScanRequest(client=client, tablename='parents', search_attributes={
      'FilterExpression': SearchAttribute('name = Mom'),
      'ProjectionExpression': SearchAttribute('name'),
  })
  

• reconstructor – a Reconstructor object

add_attribute(attr_class, name, value)

add a search attribute to a to the request_attributes dict

All search attributes must be unique keys. When the key already exists, it will update that value by calling add(). Depending on the attr_class, this can overwrite, append, change the value of the existing search attribute.

Parameters

• attr_class – a SearchAttribute class

• name – the name of the attribute

• value – the value that will be added to the SearchAttribute

For example:

Person.scan.limit(10)
# or ...
Person.scan.add_attribute(SearchAttribute, 'Limit', 10)

build()

build the dict used by dynamodb

Returns

a dict whose keys matching the keys of the request_attributes and whose values are string versions of each attribute

For example:

User.scan.filter(User.email == 'test@test.com').build()
{
    "TableName": "Users",
    "FilterExpression": "#__email = :_email_dpxqm",
    "ExpressionAttributeNames": {
        "#__email": "email"
    },
    "ExpressionAttributeValues": {
        ":_email_dpxqm": {
            "S": "test@test.com"
        }
    }
}

execute()

perform the delete_item request

Returns

a DeleteResponse object built from the delete_item response

For example:

Person.delete.key(Person.email == 'test@test.com').execute()

key(*expressions)

return a new Request setup with the Key attribute

Adds the Key to the request_attributes dict

Parameters

*expressions – a list of BaseExpressions

Returns

the caller of the method. This allows for chaning

For example:

Person.get.key(Person.email == 'test@test.com').build()
{
    "TableName": "people",
    "Key": {
        "email": {
            "S": "test@test.com"
        }
    }
}

returns(value)

return the Request setup with ReturnValues attribute

Adds the ReturnValues to the request attributes dict

Parameters

value – NONE | ALL_OLD | UPDATED_OLD | ALL_NEW | UPDATED_NEW

Returns

the caller of the method. This allows for chaining

For example:

from cerami.request.return_values import UPDATED_NEW
Person.update \
    .key(Person.email == 'test@test.com') \
    .set(Person.name, 'new name') \
    .returns(UPDATED_NEW) \
    .build()
{
    "TableName": "people",
    "ReturnValues": "UPDATED_NEW",
    "Key": {
        "email": {
            "S": "test@test.com"
        }
    },
    "UpdateExpression": "SET #__name = :_name_zhvzz",
    "ExpressionAttributeNames": {
        "#__name": "name"
    },
    "ExpressionAttributeValues": {
        ":_name_zhvzz": {
            "S": "new name"
        }
    }
}