Documentation

CLASS DOCUMENTATION (NOT FINALIZED):

PROPERTIES:

Type	Properties	Default value
float	PROTOCOL_VERSION const	3.0
dictionary	parameter_status reader alone	{}

METHODS:

Type	Method
Error	connect_to_host(url: String, connect_timeout: int = 30)
Array	execute(sql: String)
void	rollback(process_id: int, process_key: int)
void	close(clean_closure: bool = true)
void	set_ssl_connection()

SIGNALS:

Signal
connection_closed(was_clean_close: bool)
connection_error()
connection_established()

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Property Descriptions

• float PROTOCOL_VERSION const

Default value: 3.0

Version number (minor.major) of the PostgreSQL protocol used when connecting to the backend

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• dictionary parameter_status reader alone

Default value: {}

A dictionary that contains various information about the state of the server. For security reasons the dictionary is always empty if the frontend is disconnected from the backend and updates once the connection is established.

Noted that the server is free to return whatever value it wants. Always remember to check the presence of the key before accessing the associated value.

Example of a typical value that a backend might return. Values may differ depending on the backend:

{"DateStyle":"ISO, DMY", "IntervalStyle":"postgres", "TimeZone":"Europe/Paris", "application_name":"", "client_encoding":"UTF8", "integer_datetimes":"on", "is_superuser":"off", "server_encoding":"UTF8", "server_version":"12.7 (Ubuntu 12.7-0ubuntu0.20.04.1)", "session_authorization":"samuel", "standard_conforming_strings":"on"}

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Method Descriptions

• Error connect_to_host(url: String, connect_timeout: int = 30)

Allows you to connect to a Postgresql backend at the specified url.

The url parameter is a PostgreSQL url ideally in the form "postgresql://user:password@host:port/databasename". All other PostgreSQL url syntaxes specified in this page [https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING] are not yet fully supported.

Noted that the default port for PostgreSQL is 5432.

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• Array execute(sql: String)

Allows to send an SQL string to the backend that should run. The sql parameter can contain one or more valid SQL statements. Returns an Array containing the result of the query (can be empty). The return value will be subject to change in the next version of the PostgreSQL client which will return an array of PostgreSQLQueryResult that will contain much more information about the result of the query.

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• void rollback(process_id : int, process_key : int)

Do not use because it is too unstable, will be subject to modification in future versions.

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• void close(clean_closure: bool = true)

Allows you to close the connection with the backend. If clean_closure is true, the frontend will notify the backend that it requests to close the connection. If false, the frontend forcibly closes the connection without notifying the backend (not recommended sof in exceptional cases).

Has no effect if the frontend is not already connected to the backend.

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• void set_ssl_connection()

Not working at the moment, don't use it. will be subject to change in future versions.

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Signal Descriptions

• connection_closed(was_clean_close: bool)

Fires when the connection to the backend closes. was_clean_close is true if the connection was closed correctly otherwise false.

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• connection_error()

Do not listen to this signal, does not work. will be subject to change see removed in future versions.

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• connection_established()

Trigger when the connection between the frontend and the backend is established. This is usually a good time to start making requests to the backend with execute ().