IdentifiableJsonPostgresPersistence

Implements: IdentifiablePostgresPersistence, IIdentifiable

Description

The IdentifiableJsonPostgresPersistence class allows you to create persistence components used to store data in PosgreSQL databases in JSON or JSONB fields and implement a number of CRUD operations over data items with unique ids.

Important points

• The data items must implement the IIdentifiable interface.
• In basic scenarios child classes shall only override the get_page_by_filter, get_list_by_filter or delete_by_filter operations with a specific filter function.
• All other operations can be used out of the box.
• In complex scenarios child classes can implement additional operations by accessing self._collection and self._model properties.

Configuration parameters

• table: (optional) PostgreSQL table name
• schema: (optional) PostgreSQL schema name

connection(s):

• discovery_key: (optional) key used to retrieve the connection from IDiscovery
• host: host name or IP address
• port: port number (default: 27017)
• uri: resource URI or connection string with all parameters in it

credential(s):

• store_key: (optional) key to retrieve the credentials from ICredentialStore
• username: (optional) username
• password: (optional) user’s password

options:

• connect_timeout: (optional) number of milliseconds to wait before timing out when connecting a new client (default: 0)
• idle_timeout: (optional) number of milliseconds a client must sit idle in the pool and not be checked out (default: 10000)
• max_pool_size: (optional) maximum number of clients the pool can contain (default: 10)

References

• *:logger:*:*:1.0 - (optional) ILogger components to pass log messages
• *:discovery:*:*:1.0 - (optional) IDiscovery services
• *:credential-store:*:*:1.0 - (optional) credential stores to resolve credentials (ICredentialStore)

Constructors

Creates a new instance of the persistence component.

IdentifiableJsonPostgresPersistence(table_name: str = None, schema_name: str = None)

• table_name: str - (optional) a table name.
• schema_name: str - (optional) a schema name.

Instance methods

_convert_from_public

Converts object value from public to internal format.

_convert_from_public(value: Any): Any

• value: Any - object in public format to convert.
• returns: Any - converted object in internal format.

_convert_to_public

Converts object value from internal to public format.

_convert_to_public(value: Any): Any

• value: Any - object in internal format to convert.
• returns: Any - converted object in public format.

_ensure_table

Adds DML statement to automatically create a JSON(B) table

_ensure_table(id_type: str = ‘TEXT’, data_type: str = ‘JSONB’)

• id_type: str - type of the id column (default: TEXT)
• data_type: str - type of the data column (default: JSONB)

update_partially

Updates only few selected fields in a data item.

update_partially(correlation_id: Optional[str], id: Any, data: AnyValueMap): Optional[T]

• correlation_id: Optional[str] - (optional) transaction id used to trace execution through the call chain.
• id: Any - id of the data item to be updated.
• data: AnyValueMap - map with fields to be updated.
• return: Optional[T] - updated item

Examples

class MyPostgresPersistence(IdentifiablePostgresJsonPersistence):

    def __init__(self):
        super(MyPostgresPersistence, self).__init__('mydata', MyDataPostgresSchema())

    def __compose_filter(self, filter):
        filter = filter or FilterParams()
        criteria = []
        name = filter.get_as_nullable_string('name')
        if name is not None:
            criteria.append({'name':name})
        return { '$and': criteria } if len(criteria) > 0 else None

    def get_page_by_filter(self, correlation_id, filter, paging):
        return super().get_page_by_filter(correlation_id, self.__compose_filter(filter), paging, None, None)

persistence = MyPostgresPersistence()
persistence.configure(ConfigParams.from_tuples(
    "host", "localhost",
    "port", 27017
))

persistence.open("123")
persistence.create("123", {'id': "1", 'name': "ABC"})

page = persistence.get_page_by_filter('123', FilterParams.from_tuples('name', 'ABC'), None)
print(page.data)  # Result: { id: "1", name: "ABC" }
persistence.delete_by_id("123", "1")
# ...