Repository Guidelines

This repository contains a small teaching Lakehouse stack (Spark + Trino + Iceberg + MinIO) intended for demos and mentoring.

Project Structure & Module Organization

docker-compose.yml: orchestrates Spark, Trino, MinIO, PostgreSQL, and Jupyter.
spark/: Spark image (Dockerfile) and spark-defaults.conf.
jupyter/: Jupyter image (Dockerfile) based on the Spark image.
trino/: catalog config, e.g. trino/catalog/lakehouse.properties.
src/: PySpark and SQL examples split by engine (src/spark/..., src/trino/...).
notebooks/: demo notebooks (mounted into Jupyter at /opt/work).

Keep new examples in src/ or notebooks/, and avoid mixing configuration and code.

Run from the repo root:

docker compose build: build custom Spark and Jupyter images.
docker compose up -d: start the full stack in the background.
docker compose ps: check container status.
docker compose down -v: stop the stack and remove volumes (for a clean slate).

Use docker compose logs -f <service> when debugging (spark-master, trino, minio, etc.).

Python: PEP 8, 4-space indentation, snake_case for functions, lower_snake_case for files (e.g. spark_join_demo.py).
SQL: uppercase keywords, schema.table naming, short English identifiers; comments may be in Russian.
Compose/Docker: service names kebab-case (spark-master), env vars UPPER_SNAKE_CASE.
Prefer small, focused examples; reuse helpers from src/ in notebooks where possible.

There is no formal automated test suite yet. Validate changes by:

building and starting the stack, then
running src/spark/cluster_smoke.py or the SQL in src/spark/iceberg_demo.sql,
opening notebooks/spark-basic-test.ipynb in Jupyter and checking it runs end-to-end.

If you add tests, prefer pytest under tests/ and mark slow, integration-heavy tests clearly.

Commits: short, descriptive subject in Russian or English, present tense (e.g. Спарк запускается, создаётся тестовая таблица, Add Iceberg join demo).
Keep changes small and focused; update README.md when behavior, ports, or images change.
PRs should describe the problem, the solution, and any impact on local setup; include screenshots (Trino UI, MinIO, Jupyter) when UI changes are relevant.

When editing as an automated agent:

Respect this file and avoid large refactors without an explicit request.
Preserve Russian user-facing text unless the change is explicitly about translation.
Prefer minimal changes that keep the demo simple and robust for newcomers.