Python Question

Setting schema for all queries of a connection in psycopg2: Getting race condition when setting search_path

Our system is running on Ubuntu, python 3.4, postgres 9.4.x and psycopg2.

We (will in the furture) split between

environments using schemas. I've create a convenience method for creating connections to our database. It uses json connection configuration files in order create the connection string. I want to configure the connection to use a particular schema for all following queries using the returned connection. I don't want my queries to have hardcoded schemas, because we should be able to easily switch between them depending on if we are in development, testing or production phase/environment.

Currently the convenience method looks like the following:

def connect(conn_config_file = 'Commons/config/conn_commons.json'):
with open(conn_config_file) as config_file:
conn_config = json.load(config_file)

conn = psycopg2.connect(
"dbname='" + conn_config['dbname'] + "' " +
"user='" + conn_config['user'] + "' " +
"host='" + conn_config['host'] + "' " +
"password='" + conn_config['password'] + "' " +
"port=" + conn_config['port'] + " "
cur = conn.cursor()
cur.execute("SET search_path TO " + conn_config['schema'])

return conn

It works fine as long as you give it time to execute the set
query. Unfortunately, if I'm too fast with executing a following query a race condition happens where the
isn't set. I've tried to force the execution with doing a
before the
return conn
, however, this resets the
to the default schema
so that it doesn't use, say,
. Suggestions at the database or application layer is preferable, however, I know we probably could solve this at the OS level too, any suggestions in that direction are also welcomed.

An example json configuration file looks like the following:

"dbname": "thedatabase",
"user": "theuser",
"host": "localhost",
"password": "theusers_secret_password",
"port": "6432",
"schema": "prod"

Any suggestion is very appreciated.

Answer Source

Maybe wait a little time before returning?

import time; time.sleep(0.1)
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