PostgresPersistence

Implements: IReferenceable, IUnreferenceable, IConfigurable, IOpenable, ICleanable

Description

The PostgresPersistence class allows you to create persistence components that store data in PostgreSQL using the official driver.

Important points

• This is the most basic persistence component that is only able to store data items of any type.
• Specific CRUD operations over the data items must be implemented in child classes by accessing self._db or self._collection properties.

Configuration parameters

• table: (optional) PostgreSQL table name
• schema: (optional) PostgreSQL schema name connection(s):
• discovery_key: (optional) key 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

Constructors

Creates a new instance of the persistence component.

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

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

Fields

Instance methods

clear

Clears a component’s state.

clear(context: Optional[IContext])

• context: IContext - (optional) a context to trace execution through a call chain.

_clear_schema

Clears all auto-created objects.

_clear_schema()

close

Closes the component and frees used resources.

close(context: Optional[IContext])

• context: IContext - (optional) a context to trace execution through a call chain.

configure

Configures the component.

configure(config: ConfigParams)

• context: IContext - (optional) a context to trace execution through a call chain.

_convert_from_public

Converts an 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 an 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.

create

Creates a data item.

create(context: Optional[str], item: T): Optional[T]

• context: IContext - (optional) a context to trace execution through a call chain.
• item: T - item to be created.
• returns: Optional[T] - created item

_request

Performs a request to the database.

_request(query: str, params: List[str] = None): dict

• query: str - string with sql query to database
• params: List[str] - optional list of query parameters
• returns: dict - result of the query

_create_schema

Checks if a table exists and if it doesn’t, it creates the necessary database objects.

_create_schema(context: Optional[IContext])

• context: IContext - (optional) a context to trace execution through a call chain.

_define_schema

Defines database schema via auto create objects or convenience methods.

_define_schema()

delete_by_filter

Deletes data items that match to a given filter. This method shall be called by a public delete_by_filter method from child class that receives FilterParams and converts them into a filter function.

delete_by_filter(context: Optional[str], filter: Any)

• context: IContext - (optional) a context to trace execution through a call chain.
• filter: Any - (optional) filter function used to filter items.

_ensure_index

Adds index definition to create it on opening.

_ensure_index(keys: Any, options: Any = None)

• keys: Any - index keys (fields)
• options: Any - index options

_ensure_schema

Adds a statement to schema definition.

_ensure_schema(schema_statement: str)

• schema_statement: str - statement to be added to the schema

_generate_columns

Generates a list of column names to use in SQL statements like: “column1,column2,column3”.

_generate_columns(values: Any): str

• values: Any - array with column values or a key-value map
• returns: str - generated list of column names

_generate_parameters

Generates a list of value parameters to use in SQL statements like: “%s,%s,%s”.

_generate_parameters(values: Any): str

• values: Any - array with values or a key-value map
• returns: str - generated list of value parameters

_generate_set_parameters

Generates a list of column sets to use in UPDATE statements like: column1=%s,column2=%s.

_generate_set_parameters(values: Any): str

• values: Any - key-value map with columns and values
• returns: str - generated list of column sets

_generate_values

Generates a list of column parameters.

_generate_values(values: Any): List[Any]

• values: Any - key-value map with columns and values
• returns: List[Any] - generated list of column values

get_count_by_filter

Gets a number of data items retrieved by a given filter.

This method shall be called by a public get_count_by_filter method from a child class that receives FilterParams and converts them into a filter function.

get_count_by_filter(context: Optional[IContext], filter: Any): int

• context: IContext - (optional) a context to trace execution through a call chain.
• filter: Any - (optional) JSON object filter.
• returns: int - number of filtered items.

get_list_by_filter

Gets a list of data items retrieved by a given filter and sorted according to sort parameters.

This method shall be called by a public get_list_by_filter method from a child class that receives FilterParams and converts them into a filter function.

get_list_by_filter(context: Optional[IContext], filter: Any, sort: Any = None, select: Any = None): List[T]

• context: IContext - (optional) a context to trace execution through a call chain.
• filter: Any - (optional) filter function to filter items
• sort: Any - (optional) sorting parameters
• select: Any - (optional) projection parameters (not used yet)
• returns: List[T] - data list of filtered results.

get_one_random

Gets a random item from items that match to a given filter.

This method shall be called by a public get_one_random method from a child class that receives FilterParams and converts them into a filter function.

get_one_random(context: Optional[IContext], filter: Any): T

• context: IContext - (optional) a context to trace execution through a call chain.
• filter: Any - (optional) a filter function to filter items.
• returns: T - random item.

get_page_by_filter

Gets a page of data items retrieved by a given filter and sorted according to sort parameters.

This method shall be called by a public get_page_by_filter method from a child class that receives FilterParams and converts them into a filter function.

get_page_by_filter(context: Optional[IContext], filter: Any, paging: PagingParams, sort: Any = None, select: Any = None): DataPage

• context: IContext - (optional) a context to trace execution through a call chain.
• filter: Any - (optional) filter for JSON objects
• paging: PagingParams - (optional) paging parameters
• sort: Any - (optional) sorting JSON object
• select: Any - (optional) projection JSON object
• returns: DataPage - data page with filtered result

is_open

Checks if the component is opened.

is_open(): bool

• returns: bool - True if the component has been opened and False otherwise.

open

Opens the component.

open(context: Optional[IContext])

• context: IContext - (optional) a context to trace execution through a call chain.

_quote_identifier

Adds a single quote to each side of the string.

_quote_identifier(value: str): Optional[str]

• value: str - string where quotes need to be added
• returns: Optional[str] - string with added quotes

_quoted_table_name

Joins schema and database name in dot notation

_quoted_table_name(): Optional[str]

• returns: Optional[str] - string with added quotes

set_references

Sets references to dependent components.

set_references(references: IReferences)

• references: IReferences - references to locate the component dependencies.

unset_references

Unsets (clears) previously set references to dependent components.

unset_references()

Examples

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

    def get_by_name(self, context, name):
        criteria = {'name': name}
        return self._model.find_one(criteria)

    def set(self, context, item):
        criteria = {'name': item['name']}
        options = { 'upsert': True, 'new': True }
        return self._model.find_one_and_update(criteria, item, options)

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

persistence.open("123")
persistence.set("123", {'name': "ABC"})

item = persistence.get_by_name("123", "ABC")
print(item) # Result: { 'name': "ABC" }

# ...