How do I use Psycopg2's LoggingConnection?

Question

I'd like to log the queries that psycopg2 is making, but the psycopg2 documentation doesn't really specify how LoggingConnection should be used.

import logging
from psycopg2.extras import LoggingConnection

db_settings = {
    "user": "abcd",
    "password": "efgh",
    "host": "postgres.db",
    "database": "dev",
}

conn = LoggingConnection(**db_settings)

Gives an error

LoggingConnection(**db_settings) TypeError: function takes at most 2 arguments (5 given)

Answer 1

Seems like setting the connection_factory=LoggingConnection works

import logging
import psycopg2
from psycopg2.extras import LoggingConnection

logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger(__name__)

db_settings = {
    "user": "abcd",
    "password": "efgh",
    "host": "postgres.db",
    "database": "dev",
}

conn = psycopg2.connect(connection_factory=LoggingConnection, **db_settings)
conn.initialize(logger)

cur = conn.cursor()
cur.execute("SELECT * FROM table LIMIT 5")

Answer 2

If you want to use LoggingConnection directly, you need to provide the DSN as a libpq connection string to LoggingConnection() - either a key/value connection string or a connection URI works:

from psycopg2.extras import LoggingConnection

DSN = "postgresql://john:secret@localhost/mydb"
#DSN = "host=localhost dbname=mydb user=john password=secret"

logfile = open('db.log', 'a')

conn = LoggingConnection(DSN)
conn.initialize(logfile)

cur = conn.cursor()
cur.execute('SELECT 1')

However, I would probably use a connection factory like @kristi demonstrated.