astrobase.lcdb module

Serves as a lightweight PostgreSQL DB interface for other modules in this project.

class astrobase.lcdb.LCDB(database=None, user=None, password=None, host=None)

Bases: object

This is an object serving as an interface to a PostgreSQL DB.

LCDB’s main purpose is to avoid creating new postgres connections for each query; these are relatively expensive. Instead, we get new cursors when needed, and then pass these around as needed.

database

Name of the database to connect to.

Type:str

user

User name of the database server user.

Type:str

password

Password for the database server user.

Type:str

host

Database hostname or IP address to connect to.

Type:str

connection

The underlying connection to the database.

Type:psycopg2.Connection object

cursors

The keys of this dict are random hash strings, the values of this dict are the actual Cursor objects.

Type:dict of psycopg2.Cursor objects

open(database, user, password, host)

This opens a new database connection.

Parameters:

• database (str) – Name of the database to connect to.
• user (str) – User name of the database server user.
• password (str) – Password for the database server user.
• host (str) – Database hostname or IP address to connect to.

open_default()

This opens the database connection using the default database parameters given in the ~/.astrobase/astrobase.conf file.

autocommit()

This sets the database connection to autocommit. Must be called before any cursors have been instantiated.

cursor(handle, dictcursor=False)

This gets or creates a DB cursor for the current DB connection.

Parameters:

• handle (str) – The name of the cursor to look up in the existing list or if it doesn’t exist, the name to be used for a new cursor to be returned.
• dictcursor (bool) – If True, returns a cursor where each returned row can be addressed as a dictionary by column name.

Returns:

Return type:

psycopg2.Cursor instance

newcursor(dictcursor=False)

This creates a DB cursor for the current DB connection using a randomly generated handle. Returns a tuple with cursor and handle.

Parameters:dictcursor (bool) – If True, returns a cursor where each returned row can be addressed as a dictionary by column name. Returns:The tuple is of the form (handle, psycopg2.Cursor instance). Return type:tuple

commit()

This just calls the connection’s commit method.

rollback()

This just calls the connection’s commit method.

close_cursor(handle)

Closes the cursor specified and removes it from the self.cursors dictionary.

close_connection()

This closes all cursors currently in use, and then closes the DB connection.