Connect to PostgreSQL from Domino

This topic describes how to connect to PostgreSQL from Domino. PostgreSQL is an open-source relational database that can run on a wide variety of local systems and clouds.

Warning

Connect to Postgres

For Python and psycopg2, Domino recommends the psycopg2 library to interact with PostgreSQL databases from Python.
Use the following Dockerfile instruction to install psycopg2 in your environment. You must already have pip installed.
```
USER root
RUN pip install psycopg2
USER ubuntu
```
Set the following as Domino environment variables to store secure information about your PostgreSQL connection.
- POSTGRES_HOST
  
  Hostname where your DB is running. Make sure your PostgreSQL DB and network firewall are configured to accept connections from Domino.
- POSTGRES_USER
  
  The PostgreSQL user you want to authenticate as.
- POSTGRES_PASSWORD
  
  The password for the user chosen previously.
  
  See Environment variables for secure credential storage to learn more about Domino environment variables.

See the psycopg2 documentation for detailed information about how to use the package. The following is an example to connect to PostgreSQL with psycopg2 where:

You have set up environment variables with the hostname, username, and password.
Your user has access to a database named db1 in the target PostgreSQL instance.

The database contains a table named metrics.

import psycopg2
import os

# fetch values from environment variables and set the target database
hostname = os.environ['POSTGRES_HOST']
username = os.environ['POSTGRES_USER']
password = os.environ['POSTGRES_PASSWORD']
dbname = 'db1'

# set up a connection object with parameters for your database
conn = psycopg2.connect(
  host=hostname,
  port=5432,
  user=username,
  password=password,
  database=dbname, )

# create a cursor in your connection
cur = conn.cursor()

# execute a query on the metrics table and store the response
cur.execute("SELECT * FROM metrics;")
results = cur.fetchall()

# display the contents of the response
print(results)

The results object created in the previous example is a Python array of entries from the queried table.

Connect to R and RPostgreSQL

To connect to R and RPostgreSQL, Domino recommends the RPostgreSQL library to interact with PostgreSQL databases from R.
Use the following Dockerfile instruction to add RPostgreSQL to your environment.
```
USER root
RUN R -e 'install.packages("RPostgreSQL")'
USER ubuntu
```
Set up the Domino environment variables to store secure information about your PostgreSQL connection.
- POSTGRES_HOST
  
  Hostname where your DB is running. Make sure your PostgreSQL DB and network firewall are configured to accept connections from Domino.
- POSTGRES_USER
  
  The PostgreSQL user you want to authenticate as.
- POSTGRES_PASSWORD
  
  The password for the user chosen previously.
  
  See Environment variables for secure credential storage to learn more about Domino environment variables.

See the RPostgreSQL documentation for information about how to use the package. The following is an example for connecting to PostgreSQL with RPostgreSQL where:

You have set up environment variables with the hostname, username, and password.
Your user has access to a database named db1 in the target PostgreSQL instance.

The database contains a table named metrics`.

# load the library
library(RPostgreSQL)

# fetch values from environment variables and set the target database
hostname <- Sys.getenv['POSTGRES_HOST']
username <-  Sys.getenv['POSTGRES_USER']
password <- Sys.getenv['POSTGRES_PASSWORD']
database <- 'db1'

# set up a driver and use it to create a connection to your database
drv <- dbDriver("PostgreSQL")
conn <- dbConnect(
  drv,
  host=hostname,
  port=5432,
  user=username,
  password=password,
  dbname=database )

# run a query and load the response into a dataframe
df_postgres <- dbGetQuery(conn, "SELECT * from metrics;")

# close your connection when finished
dbDisconnect(conn)