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)

score 38 · Answer 1 · answered Mar 09 '15 at 19:43

38

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")

answered Mar 09 '15 at 19:43

k107

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Hi, thank you for the example. I personally need the console output. For example, at the end of the sql statement the client prints this to STOUT: ``` [2019-07-15 15:59:51] 1 row retrieved starting from 1 in 2 s 318 ms (execution: 2 s 279 ms, fetching: 39 ms) ``` – Jonathan Jul 15 '19 at 23:47

score 6 · Answer 2 · answered Mar 09 '15 at 19:43

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.

How do I use Psycopg2's LoggingConnection?

2 Answers2

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