A Fast, Sample Postgres Database with Docker

I often find myself needing to spin up a database for testing some code or idea. Here’s a simple approach to getting a local Postgres instance going with a few tables.

First, create an init_db.sql file:

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\c postgres

CREATE TABLE IF NOT EXISTS accounts (
    account_id serial PRIMARY KEY,
    user_id int,
    balance decimal(15,2) NOT NULL
);

CREATE TABLE IF NOT EXISTS users (
    user_id serial PRIMARY KEY,
    name varchar(255) NOT NULL,
    email varchar(255) UNIQUE NOT NULL,
    department_id int
);

CREATE TABLE IF NOT EXISTS departments (
    department_id serial PRIMARY KEY,
    name varchar(255) NOT NULL
);

CREATE TABLE IF NOT EXISTS transactions (
    id serial PRIMARY KEY,
    account_id int,
    amount decimal(15,2) NOT NULL,
    last_updated_at timestamp without time zone NOT NULL
);

DO $$
DECLARE
    counter INT := 1;
    max_rows INT := 100000;
BEGIN
    LOOP
        EXIT WHEN counter > max_rows;
        INSERT INTO accounts (user_id, balance) VALUES (counter, random() * 10000);
        counter := counter + 1;
    END LOOP;

    counter := 1;

    LOOP
        EXIT WHEN counter >max_rows;
        INSERT INTO users (name, email, department_id) VALUES ('User' || counter, 'user' || counter || '@example.com', counter % 3 + 1);
        counter := counter + 1;
    END LOOP;

    counter := 1;

    LOOP
        EXIT WHEN counter >max_rows;
        INSERT INTO departments (name) VALUES ('Department' || counter);
        counter := counter + 1;
    END LOOP;

    counter := 1;

    LOOP
        EXIT WHEN counter >max_rows;
        INSERT INTO transactions (account_id, amount, last_updated_at) VALUES (counter, random() * 200 - 100, CURRENT_DATE - FLOOR(random() * 365)::int);
        counter := counter + 1;
    END LOOP;

    counter := 1;

END $$;
 

This script will create a database called finance with a few tables and some sample data.

Use Docker to spin up an instance. You’ll need a small Dockerfile:

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FROM postgres:15

ENV POSTGRES_DB=postgres
ENV POSTGRES_USER=postgres
ENV POSTGRES_PASSWORD=postgres

COPY init_db.sql /docker-entrypoint-initdb.d/ 

And I like to always use Makefile’s so I don’t have to remember commands. Here’s a simple Makefile:

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@PHONY: build run clean stop connect

clean:
	docker ps -q -f name=my-postgres-db | xargs -r docker stop && docker ps -aq -f name=my-postgres-db | xargs -r docker rm

stop:
	docker ps -q -f name=my-postgres-db | xargs -r docker stop

build:
	docker build -t my-postgres-db .

run: build stop
	docker run --name my-postgres-db  -p 54321:5432 -ti --rm my-postgres-db

connect:
    docker exec -it my-postgres-db psql -U postgres 

Now run make run and you should have a Postgres instance running on port 54321. make clean will stop and remove any running instances.