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API ReferencePython APIMain Database Interface

Module neug.database

The Neug database module.

Database Objects

class Database(object)

The entrance of the Neug database.

This class is used to open a database connection and manage the database. User should use this class to open a database connection, and then use the connect method to get a Connection object to interact with the database.

By passing an empty string as the database path, the database will be opened in memory mode.

The database could be opened with different modes(read-only or read-write) and different planners.

When the database is opened in read-only mode, other databases could also open the same database directory in read-only mode, inside the same process or in different processes. When the database is opened in read-write mode, no other databases could open the same database directory in either read-only or read-write mode, inside the same process or in different processes.

When the database is closed, all the connections to the database will be closed automatically.

 
    >>> from neug import Database
    >>> db = Database("/tmp/test.db", mode="w")
    >>> conn = db.connect()
 
    >>> # Use the connection to interact with the database
    >>> conn.execute('CREATE TABLE person(id INT64, name STRING);')
    >>> conn.execute('CREATE TABLE knows(FROM person TO person, weight DOUBLE);')
 
    >>> # Import data from csv file.
    >>> conn.execute('COPY person FROM "person.csv"')
    >>> conn.execute('COPY knows FROM "knows.csv" (from="person", to="person");')
 
    >>> res = conn.execute('MATCH(n) return n.id;)
    >>> for record in res:
    >>>     print(record)

version

@property
def version()

Get the version of the database.

mode

@property
def mode() -> str

Get the mode of the database.

  • Returns:
    • str The mode of the database, could be ‘r’, ‘read’, ‘w’, ‘rw’, ‘write’, ‘readwrite’.

connect

def connect() -> Connection

Connect to the database.

  • Returns:
    • Connection A Connection object to interact with the database.
  • Raises:
    • RuntimeError If the database is closed or not opened.

serve

def serve(port: int = 10000, host: str = "localhost", blocking: bool = True)

Start the database server for handling remote connections(TP mode). This method is used to start the database server for handling remote connections. When db.serve() is called, the database will switch to the TP mode, and all the connections to the local database will be closed. After that, no new connections to the local database will be allowed. It will start a server that listens on a specific port, and clients can connect to the server to interact with the database. User could use Session to connect to the server. For detail usage, please refer to the documentation of Session.

  • Parameters:

    • port (int) The port to listen on. Default is 10000.
    • host (str) The host to listen on. Default is ‘localhost’.
    • blocking (bool) Whether to block the process after starting the database server.

  • Returns:

  • Raises:

    • RuntimeError If there are open connections to the local database. If the database is already serving.

  • Notes:

    • Make sure to close all connections before starting the server.
    • After starting the server, no new connections to the local database will be allowed.

stop_serving

def stop_serving()

Stop the database server. This method is used to stop the database server that was started by the serve method. After calling this method, the database will switch back to the local mode, and new connections to the local database will be allowed again.

  • Raises:
    • RuntimeError If the database is not serving.

async_connect

def async_connect() -> AsyncConnection

Connect to the database asynchronously.

  • Returns:
    • AsyncConnection An AsyncConnection object to interact with the database asynchronously.
  • Raises:
    • RuntimeError If the database is closed or not opened.

close

def close()

Close the database connection.

load_builtin_dataset

def load_builtin_dataset(dataset_name: str) -> None

Load a builtin dataset into this database. If the database is in read-only mode, this method will raise an error. If the schema of the dataset conflicts with the existing schema of the database, this method will raise an error.

  • Parameters:

    • dataset_name (str) Name of the builtin dataset to load

  • Raises:

    • RuntimeError If the database is closed or in read-only mode
    • ValueError If the dataset doesn’t exist

from_builtin_dataset

@staticmethod
def from_builtin_dataset(dataset_name: str,
                         database_path: str = None,
                         mode: str = "read-write")

Create a Database instance from a builtin dataset.

  • Parameters:

    • dataset_name (str) The name of the builtin dataset to use.
    • database_path (str) The path to the database file. If None, the database will be opened in memory mode.
    • mode (str) The mode to open the database, could be ‘r’, ‘read’, ‘w’, ‘rw’, ‘write’, ‘readwrite’. Default is ‘read-write’.

  • Returns:

    • Database A Database instance with the builtin dataset loaded.
Python API OverviewDatabase Connection