Overview

CacheDB is an in-memory key-value store designed for high performance and low latency. It supports string keys and values, as well as sorted sets, with a command interface similar to that of Redis. CacheDB allows clients to perform common database operations such as setting and getting values, manipulating sorted sets, and managing key expirations (TTLs).

Features

• In-Memory Storage: Fast data access with data stored directly in memory.
• String and Sorted Set (zset) Support: Manage simple key-value pairs and sorted sets for ordered data retrieval.
• TTL Management: Set expiration times for keys to automatically manage data lifecycle.
• Non-Blocking I/O: Handles multiple client connections efficiently.

Getting Started

1. Clone the repository:

   git clone https://github.com/etbala/CacheDB.git
   cd CacheDB

2. Build the project:

   mkdir build
   cd build
   cmake ..
   make -j$(nproc)

3. Run tests:

   ./all_tests

Commands

GET

Purpose: Retrieves the string value associated with the specified key.

Usage: get <key>

Behavior:

• If the key exists and is of type string, it returns the value.
• If the key doesn't exist or is of a different type, it returns nil or an error.

Complexity: O(1) average time.

SET

Purpose: Stores a string value under the specified key.

Usage: set <key> <value>

Behavior:

• If the key already exists and is of type string, it updates the value.
• If the key exists but is of a different type (e.g., a sorted set), it returns an error.
• If the key doesn't exist, it creates a new entry with the given key and value.

Complexity: O(1) average time.

DEL

Purpose: Deletes the specified key from the database.

Usage: del <key>

Behavior:

• Removes the key and its associated value from the database.
• Returns 1 if the key was removed, 0 if the key didn't exist.

Complexity: O(1) average time.

KEYS

Purpose: Lists all the keys in the database.

Usage: keys

Behavior:

• Returns an array of all keys stored in the database.

Complexity: O(N) time, where N is the number of keys in the database.

ZADD

Purpose: Adds a member with a given score to a sorted set.

Usage: zadd <zset_name> <score> <member>

Behavior:

• If the sorted set doesn't exist, it creates one.
• If the member already exists, it updates its score.

Complexity: O(log M), where M is the number of elements in the sorted set.

ZREM

Purpose: Removes a member from a sorted set.

Usage: zrem <zset_name> <member>

Behavior:

• If the member exists in the sorted set, it removes it and returns 1.
• If the member doesn't exist, it returns 0.

Complexity: O(log M), where M is the number of elements in the sorted set.

ZSCORE

Purpose: Retrieves the score associated with a member in a sorted set.

Usage: zscore <zset_name> <member>

Behavior:

• Returns the score if the member exists.
• Returns nil if the member doesn't exist.

Complexity: O(1) average time.

ZQUERY

Purpose: Queries the sorted set for members starting from a given score and member.

Usage: zquery <zset_name> <score> <member> <offset> <limit>

Behavior:

• Retrieves a list of members starting from the specified score and member.
• The offset and limit parameters control pagination.

Complexity: O(log M + R), where M is the number of elements in the sorted set and R is the number of results returned.

PEXPIRE

Purpose: Sets a time-to-live (TTL) for a key in milliseconds.

Usage: pexpire <key> <milliseconds>

Behavior:

• The key will expire and be automatically deleted after the specified time.
• If the key doesn't exist, it returns 0.
• Returns 1 if the TTL was set successfully.

Complexity: O(log N), where N is the number of keys with a TTL set.

PTTL

Purpose: Retrieves the remaining TTL for a key in milliseconds.

Usage: pttl <key>

Behavior:

• Returns the remaining time in milliseconds before the key expires.
• Returns -1 if the key exists but has no associated TTL.
• Returns -2 if the key does not exist.

Complexity: O(1) average time.