PyCacheDB: In-Memory Database with Custom Query Language

PyCacheDB is a lightweight, in-memory database/cache system with a custom query language, implemented purely in Python. This project aims to provide a Redis-like experience while helping developers understand the underlying data structures and algorithms.

🔑 Key Features

• In-memory key-value store with multiple data type support
• Custom query language for data manipulation
• Cache eviction policies (LRU, LFU)
• Optional persistence mechanisms
• Network interface for client-server architecture

🚀 Current Progress

• ✅ Core data structures
  • ✅ Hash Table implementation
  • ✅ Binary Tree implementation
  • ✅ Doubly Linked List implementation
• ✅ Caching mechanisms
  • ✅ LRU (Least Recently Used) cache strategy
  • ✅ LFU (Least Frequently Used) cache strategy
• ✅ Query language components
  • ✅ Lexer for tokenizing queries
  • ✅ Command pattern architecture
  • ✅ Parser for executing queries
• ✅ Unit tests for data structures and cache implementations

🛠️ Installation

Clone the repository:

git clone https://github.com/sidnair02/pycachedb.git
cd pycachedb

No external dependencies are required as PyCacheDB uses only the Python standard library.

🧪 Running Tests

Run all tests using the included batch script from the root directory:

# On Windows
run_tests.bat

📝 Usage (coming soon)

from pycachedb import PyCacheDB

# Initialize the database with LRU cache
db = PyCacheDB(eviction_policy="LRU")

# Execute queries using the custom query language
db.execute("SET user:1 'John Doe'")
db.execute("SET user:2 'Jane Smith'")

# Get values
user = db.execute("GET user:1")  # Returns: John Doe

# Delete values
db.execute("DEL user:2")

# Work with lists
db.execute("LPUSH my-list 'item1' 'item2' 'item3'")
items = db.execute("LRANGE my-list 0 -1")  # Returns all items

# Work with hashes
db.execute("HSET user:profile name 'John' age '30' city 'New York'")
city = db.execute("HGET user:profile city")  # Returns: New York

# Use transactions
db.execute("MULTI")
db.execute("SET counter 1")
db.execute("INCR counter")
db.execute("GET counter")
results = db.execute("EXEC")  # Returns: ["OK", "2", "2"]

🏗️ Project Structure

pycachedb/
├── pycachedb/
│   ├── __init__.py
│   ├── __main__.py
│   ├── cache/
│   │   ├── __init__.py
│   │   ├── base.py
│   │   ├── lfu_cache.py
│   │   └── lru_cache.py
│   ├── data_structures/
│   │   ├── __init__.py
│   │   ├── binary_tree.py
│   │   ├── hash_table.py
│   │   └── linked_list.py
│   └── query/
│       ├── __init__.py
│       ├── commands.py
│       ├── lexer.py
│       └── parser.py
├── tests/
│   ├── __init__.py
│   ├── test_doubly_linked_list.py
│   ├── test_hash_table.py
│   ├── test_lfu_cache.py
│   └── test_lru_cache.py
├── run_tests.bat
├── PLAN.md
└── README.md

📋 Implementation Plan

Completed

• Core data structures
  • Hash table for key-value storage
  • Binary tree for ordered operations
  • Doubly linked list for caching mechanisms
• Cache eviction policies
  • LRU (Least Recently Used) implementation
  • LFU (Least Frequently Used) implementation
• Query language components
  • Command pattern architecture
  • Lexer for tokenization
  • Parser for command execution

Next Steps

• Data types & operations
  • Complete list operations (LPUSH, RPUSH, etc.)
  • Complete hash operations (HSET, HGET, etc.)
  • Implement sorted sets
• Persistence & recovery
  • Implement snapshot mechanism
  • Create operation log
  • Build recovery system
• Networking & client interface
  • Socket-based server
  • Command-line client
  • Connection pooling

🤝 Contributing

This project is currently not accepting contributions as it's a personal learning exercise.

📄 License

All rights reserved. This project is not currently licensed for public use or distribution as it's a personal learning exercise.