PostgreSQL

TL;DR
Functions
Extensions of interest
1. PostGIS
2. postgresql_anonymizer
Make it distributed
Further readings
1. Sources

TL;DR

One can store one's credentials in ~/.pgpass:

# line format => hostname:port:database:username:password`
# can use wildcards
postgres.lan:5643:postgres:postgres:BananaORama
*:*:sales:elaine:modestPassword

The credential file's permissions must be 0600, or it will be ignored.

Database roles represent both users and groups.
Roles are distinct from the OS' users and groups, and are global across the whole installation (there are no DB-specific roles).

Extensions in PostgreSQL are managed per database.

Setup

# Installation.
brew install 'postgresql@16'
sudo dnf install 'postgresql' 'postgresql-server'
sudo zypper install 'postgresql15' 'postgresql15-server'

# Set the password in environment variables.
export PGPASSWORD='securePassword'

# Set up the credentials file.
cat <<EOF > ~/'.pgpass'
postgres.lan:5643:postgres:postgres:BananaORama
*:*:sales:elaine:modestPassword
EOF
chmod '600' ~/'.pgpass'

# Set up the per-user services file.
# do *not* use spaces around the '=' sign.
cat <<EOF > ~/'.pg_service.conf'
[prod]
host=prod.0123456789ab.eu-west-1.rds.amazonaws.com
port=5433
user=master
EOF

Usage

# Connect to servers via CLI client.
# If not given:
# - the hostname defaults to 'localhost';
# - the port defaults to '5432';
# - the username defaults to the current user;
# - the 'sslmode' parameter defaults to 'prefer'.
psql 'my-db'
psql 'my-db' 'user'
psql 'postgres://host'
psql 'postgresql://host:5433/my-db?sslmode=require'
psql -U 'username' -d 'my-db' -h 'hostname' -p 'port' -W
psql --host 'host.fqnd' --port '5432' --username 'postgres' --database 'postgres' --password
psql "service=prod sslmode=disable"

# List available databases.
psql … --list

# Execute commands.
psql 'my-db' … -c 'select * from tableName;' -o 'out.file'
psql 'my-db' … -c 'select * from tableName;' -H
psql 'my-db' … -f 'commands.sql'

# Initialize a test DB.
pgbench -i 'test-db'
pgbench -i 'test-db' -h 'hostname' -p '5555' -U 'user'

# Create full backups of databases.
pg_dump -U 'postgres' -d 'sales' -F 'custom' -f 'sales.bak'
pg_dump --host 'host.fqnd' --port '5432' --username 'postgres' --dbname 'postgres' --password --schema-only
pg_dump … -T 'customers,orders' -t 'salespeople,performances'
pg_dump … -s --format 'custom'

# Dump users and groups to file
pg_dumpall -h 'host.fqnd' -p '5432' -U 'postgres' -l 'postgres' -W --roles-only --file 'roles.sql'
pg_dumpall -h 'host.fqnd' -p '5432' -U 'postgres' -l 'postgres' -Wrf 'roles.sql' --no-role-passwords

# Restore backups.
pg_restore -U 'postgres' -d 'sales' 'sales.bak'

# Execute commands from file
# E.g., restore from dump
psql -h 'host.fqnd' -U 'postgres' -d 'postgres' -W -f 'dump.sql' -e

# Generate scram-sha-256 hashes using only tools from PostgreSQL.
# Requires to actually create and delete users.
createuser 'dummyuser' -e --pwprompt && dropuser 'dummyuser'

# Generate scram-sha-256 hashes.
# Leverage https://github.com/supercaracal/scram-sha-256
scram-sha-256 'mySecretPassword'

-- Load extensions from the underlying operating system
-- They must be already installed on the instance
ALTER SYSTEM SET shared_preload_libraries = 'anon';
ALTER DATABASE postgres SET session_preload_libraries = 'anon';

Also see yugabyte/yugabyte-db for a distributed, PostgreSQL-like DBMS.

Functions

Refer CREATE FUNCTION.

CREATE OR REPLACE FUNCTION just_return_1() RETURNS integer
LANGUAGE SQL
RETURN 1;

SELECT just_return_1();

CREATE OR REPLACE FUNCTION increment(i integer) RETURNS integer
AS $$
  BEGIN
    RETURN i + 1;
  END;
$$
LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION entries_in_column(
  table_name TEXT,
  column_name TEXT
) RETURNS INTEGER
LANGUAGE plpgsql
AS $func$
  DECLARE result INTEGER;
  BEGIN
    EXECUTE format('SELECT count(%s) FROM %s LIMIT 2', column_name, table_name) INTO result;
    RETURN result;
  END;
$func$;
SELECT * FROM entries_in_column('vendors','vendor_id');

Extensions of interest

PostGIS

TODO

`postgresql_anonymizer`

Extension to mask or replace personally identifiable information or other sensitive data in a DB.

Refer postgresql_anonymizer and An In-Depth Guide to Postgres Data Masking with Anonymizer.

Admins declare masking rules using the PostgreSQL Data Definition Language (DDL) and specify the anonymization strategy inside each tables' definition.

Example

docker run --rm -d -e 'POSTGRES_PASSWORD=postgres' -p '6543:5432' 'registry.gitlab.com/dalibo/postgresql_anonymizer'
psql -h 'localhost' -p '6543' -U 'postgres' -d 'postgres' -W

=# SELECT * FROM people LIMIT 1;
 id | firstname | lastname |   phone
----+-----------+----------+------------
 T1 | Sarah     | Conor    | 0609110911

-- 1. Activate the dynamic masking engine
=# CREATE EXTENSION IF NOT EXISTS anon CASCADE;
=# SELECT anon.start_dynamic_masking();

-- 2. Declare a masked user
=# CREATE ROLE skynet LOGIN PASSWORD 'skynet';
=# SECURITY LABEL FOR anon ON ROLE skynet IS 'MASKED';

-- 3. Declare masking rules
=# SECURITY LABEL FOR anon ON COLUMN people.lastname IS 'MASKED WITH FUNCTION anon.fake_last_name()';
=# SECURITY LABEL FOR anon ON COLUMN people.phone IS 'MASKED WITH FUNCTION anon.partial(phone,2,$$******$$,2)';

-- 4. Connect with the masked user and test masking
=# \connect - skynet
=# SELECT * FROM people LIMIT 1;
 id | firstname | lastname |   phone
----+-----------+----------+------------
 T1 | Sarah     | Morris   | 06******11

Make it distributed

Refer How to Scale a Single-Server Database: A Guide to Distributed PostgreSQL.
See also yugabyte/yugabyte-db.

10 KiB Raw Blame History

PostgreSQL

TL;DR

Functions

Extensions of interest

PostGIS

postgresql_anonymizer

Make it distributed

Further readings

Sources

10 KiB

Raw Blame History

`postgresql_anonymizer`