DuckDB Elixir Port - Project Summary

View Source

Overview

This project is a 100% exact port of the DuckDB Python client to Elixir. All documentation has been created to enable a development agent to implement this port using Test-Driven Development.

What Has Been Created

1. Complete Technical Documentation

All technical design documents are located in the docs/ directory:

docs/TECHNICAL_DESIGN.md

  • Complete architecture overview
  • Module structure and hierarchy
  • API surface documentation (Connection, Relation, Type system, etc.)
  • Data type mapping between DuckDB and Elixir
  • NIF layer design using Rustler
  • Integration points (Arrow, Explorer, Nx)
  • Performance considerations
  • Security considerations

docs/IMPLEMENTATION_ROADMAP.md

  • 12-phase implementation plan
  • Detailed task breakdown per phase
  • Test-driven development workflow
  • Dependencies between phases
  • Success criteria for each phase
  • Timeline estimation (~5 months full-time)
  • Risk management strategy

docs/PYTHON_API_REFERENCE.md

  • Complete catalog of Python API to port
  • Module-level API functions
  • DuckDBPyConnection class reference
  • DuckDBPyRelation class reference
  • Type system documentation
  • Expression API
  • Value types
  • Enums and exceptions
  • Key test files to reference

2. Implementation Guide

AGENT_PROMPT.md

This is the PRIMARY document for the implementation agent. It contains:

  • Mission statement and critical rules
  • Required reading checklist
  • Mandatory TDD workflow (7 steps)
  • Docker environment setup instructions
  • Complete project structure to create
  • Dependencies to add (Elixir and Rust)
  • Phase 0 implementation instructions (infrastructure setup)
  • Phase 1 starter implementation (basic connection)
  • Testing guidelines and examples
  • Error handling patterns
  • Documentation requirements
  • Common pitfalls to avoid
  • Success criteria checklists

3. Updated README

README.md

  • Project overview and status
  • Quick start examples
  • Development setup instructions
  • Project structure
  • Documentation index
  • Implementation progress tracking
  • Contributing guidelines

Reference Implementation

The duckdb-python/ directory contains the complete Python client source code. This is the authoritative reference for all implementation decisions:

  • Source Code: duckdb-python/src/duckdb_py/ (C++ implementation)
  • Python API: duckdb-python/duckdb/ (Python wrapper)
  • Tests: duckdb-python/tests/ (comprehensive test suite)
  • Documentation: duckdb-python/README.md and docstrings

Implementation Approach

Test-Driven Development (TDD)

The project MUST be implemented using strict TDD:

  1. Port Python tests from duckdb-python/tests/
  2. Tests fail initially (no implementation yet)
  3. Implement Rust NIF layer
  4. Implement Elixir wrapper
  5. Tests pass
  6. Verify against Python behavior
  7. Document and move to next feature

Technology Stack

  • Elixir: 1.18+ (host language)
  • Rustler: 0.35 (NIF framework)
  • Rust: Latest stable (NIF implementation)
  • DuckDB Rust bindings: 1.1+ (database access)
  • Docker: Development environment
  • ExUnit: Testing
  • Mox: Mocking for tests

Architecture

User Code (Elixir)
    ↓
DuckdbEx Module (Elixir wrapper with idiomatic API)
    ↓
DuckdbEx.Native (Elixir NIF interface)
    ↓
Rust NIF Layer (type conversions, resource management)
    ↓
DuckDB Rust Bindings
    ↓
DuckDB C++ Engine

File Organization

duckdb_ex/
├── AGENT_PROMPT.md              ← START HERE for implementation
├── PROJECT_SUMMARY.md           ← This file
├── README.md                    ← Project overview
├── docs/
│   ├── TECHNICAL_DESIGN.md      ← Architecture & design
│   ├── IMPLEMENTATION_ROADMAP.md ← Phased plan
│   └── PYTHON_API_REFERENCE.md  ← Python API catalog
├── duckdb-python/               ← Python reference (CRITICAL)
│   ├── src/                     ← C++ implementation
│   ├── duckdb/                  ← Python wrapper
│   └── tests/                   ← Test suite to port
├── lib/duckdb_ex/               ← Elixir modules (TO BE CREATED)
├── native/duckdb_nif/           ← Rust NIF (TO BE CREATED)
├── test/                        ← Ported tests (TO BE CREATED)
├── Dockerfile                   ← TO BE CREATED
└── docker-compose.yml           ← TO BE CREATED

Next Steps for Implementation Agent

Immediate Actions (Phase 0)

  1. Read Documentation

    • [ ] Read AGENT_PROMPT.md completely
    • [ ] Read docs/TECHNICAL_DESIGN.md
    • [ ] Read docs/IMPLEMENTATION_ROADMAP.md
    • [ ] Read docs/PYTHON_API_REFERENCE.md

  2. Set Up Environment

    • [ ] Create Dockerfile (template in AGENT_PROMPT.md)
    • [ ] Create docker-compose.yml (template in AGENT_PROMPT.md)
    • [ ] Build: docker-compose build
    • [ ] Verify: docker-compose run dev

  3. Initialize Rustler

    • [ ] Run: mix rustler.new duckdb_nif
    • [ ] Update mix.exs with dependencies
    • [ ] Create basic NIF skeleton
    • [ ] Verify NIF loads: DuckdbEx.Native.test_nif()

  4. Create Infrastructure

    • [ ] Create all exception modules
    • [ ] Create module stubs (Connection, Relation, Result, Type)
    • [ ] Set up test infrastructure
    • [ ] Verify tests run (even if empty)

  5. Checkpoint: Docker builds, tests run, NIF loads

After Phase 0

Follow the implementation sequence in docs/IMPLEMENTATION_ROADMAP.md:

  • Phase 1: Basic Connection
  • Phase 2: Type System
  • Phase 3: Relation API
  • Phase 4: Data Source Integration
  • ... (see roadmap for complete sequence)

Key Principles

1. This is a Port, Not a Redesign

  • Copy Python behavior exactly
  • Only deviate when Elixir language requires it
  • Document all deviations
  • When in doubt, check Python source

2. Reference First, Implement Second

  • Never guess Python behavior
  • Always check duckdb-python/ source code
  • Run Python version to verify behavior
  • Port the exact semantics to Elixir

3. Test-Driven Development is Mandatory

  • Port tests before implementing
  • Tests must fail initially
  • Implementation makes tests pass
  • No feature without tests

4. Check Python for Every Question

Questions you should answer by checking Python source:

  • "What should this function return?" → Check Python
  • "How should errors be handled?" → Check Python
  • "What parameters does this take?" → Check Python
  • "What's the exact behavior?" → Check Python and run it
  • "Are there edge cases?" → Check Python tests

Success Criteria

Per Phase

  • [ ] All Python tests ported
  • [ ] All ported tests passing
  • [ ] No memory leaks
  • [ ] Full documentation
  • [ ] Code reviewed
  • [ ] Behavior verified against Python

Overall Project

  • [ ] 100% API parity with Python
  • [ ] All Python tests ported and passing
  • [ ] Performance within 20% of Python
  • [ ] Complete documentation
  • [ ] Published on Hex.pm

Important Notes

Docker is Required

All development MUST happen in Docker to ensure:

  • Consistent build environment
  • Proper DuckDB library installation
  • Rust toolchain availability
  • Reproducible builds

Reference the Python Source Constantly

The duckdb-python/ directory is your bible. For ANY implementation question:

  1. Find the corresponding Python file
  2. Read the implementation
  3. Check the tests
  4. Port the exact behavior

Don't Skip the Tests

Testing is not optional. The TDD approach ensures:

  • Correctness (matches Python exactly)
  • Completeness (all features implemented)
  • Regression prevention
  • Documentation through tests

Resources

In This Repository

  • duckdb-python/ - Complete Python source code
  • AGENT_PROMPT.md - Implementation guide
  • docs/ - All technical documentation

External Resources

Contact and Support

For the implementation agent:

  • Primary Reference: duckdb-python/ directory
  • Implementation Guide: AGENT_PROMPT.md
  • Technical Questions: Check Python source first
  • Behavior Questions: Run Python code to verify

Version History

  • 2025-01-XX: Initial documentation created
    • Complete technical design
    • Implementation roadmap
    • Python API reference
    • Agent implementation guide

License

MIT License - This is a port of the MIT-licensed DuckDB Python client.

Remember: This is a 100% exact port. When implementing any feature, the first question should always be: "What does the Python client do?" Then port that exact behavior to Elixir.

Good luck! 🦆