Connect psycopg3 to a PostgreSQL-dialect database

This page explains how to connect the PostgreSQL psycopg3 driver to a PostgreSQL-dialect database in Spanner. psycopg3 is a Python driver for PostgreSQL.

  1. Verify that PGAdapter is running on the same machine as the application that is connecting using the PostgreSQL psycopg3 driver.

    export GOOGLE_APPLICATION_CREDENTIALS=/CREDENTIALS_FILE_PATH/credentials.json
docker pull gcr.io/cloud-spanner-pg-adapter/pgadapter
docker run \
  -d -p 5432:5432 \
  -v ${GOOGLE_APPLICATION_CREDENTIALS}:${GOOGLE_APPLICATION_CREDENTIALS}:ro \
  -e GOOGLE_APPLICATION_CREDENTIALS \
  gcr.io/cloud-spanner-pg-adapter/pgadapter \
  -p PROJECT_NAME -i INSTANCE_NAME \
  -x

    For more information, see Start PGAdapter.

  2. Connect to PGAdapter using TCP.

    import psycopg

with psycopg.connect("host=APPLICATION_HOST port=PORT dbname=DATABASE_NAME sslmode=disable") as conn:
  conn.autocommit = True
  with conn.cursor() as cur:
    cur.execute("select 'Hello world!' as hello")
    print("Greeting from Cloud Spanner PostgreSQL:", cur.fetchone()[0])

    Replace the following:

    • APPLICATION_HOST: the hostname or IP address of the machine where PGAdapter is running. If running locally, use localhost.
    • PORT: the port number where PGAdapter is running. Change this in the connection string if PGAdapter is running on a custom port. Otherwise, use the default port, 5432.

Unix domain sockets

This section explains how to use Unix domain sockets to connect to a PostgreSQL-dialect database. Use Unix domain sockets for the lowest possible latency.

To use Unix domain sockets, PGAdapter must be running on the same host as the client application.

Verify the PostgreSQL JDBC driver is loaded.

import psycopg

with psycopg.connect("host=/tmp
                      port=PORT
                      dbname=DATABASE_NAME") as conn:
conn.autocommit = True
with conn.cursor() as cur:
  cur.execute("select 'Hello world!' as hello")
  print("Greetings from Cloud Spanner PostgreSQL:", cur.fetchone()[0])

Replace the following:

  • /tmp: the default domain socket directory for PGAdapter. This can be changed using the -dir command-line argument.
  • PORT: the port number where PGAdapter is running. Change this in the connection string if PGAdapter is running on a custom port. Otherwise, use the default port, 5432.

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