WebSocket Set Operations

The DBX WebSocket API provides real-time set operations for Redis. This guide covers all available set methods and their usage patterns.

Installation

npm install @0dbx/redis

Basic Usage

import { DbxWsClient } from "@0dbx/redis";
 
// Create WebSocket client
const wsClient = new DbxWsClient("ws://localhost:3000/redis_ws");
 
// Set operations
await wsClient.set.addMember("tags", "redis");
const members = await wsClient.set.getMembers("tags");

Connection Setup

Before using set operations, establish a WebSocket connection:

import { DBXWebSocketClient } from "@effortlesslabs/dbx";
 
const client = new DBXWebSocketClient({
  url: "ws://localhost:8080/ws",
  token: "your-jwt-token",
});
 
await client.connect();

Set Operations

SADD - Add Members to Set

Add one or more members to a set.

Request:

{
  "id": "req-1",
  "method": "SADD",
  "params": {
    "key": "users:online",
    "members": ["user:123", "user:456", "user:789"]
  }
}

Response:

{
  "id": "req-1",
  "result": {
    "added": 3
  }
}

SREM - Remove Members from Set

Remove one or more members from a set.

Request:

{
  "id": "req-2",
  "method": "SREM",
  "params": {
    "key": "users:online",
    "members": ["user:123", "user:456"]
  }
}

Response:

{
  "id": "req-2",
  "result": {
    "removed": 2
  }
}

SMEMBERS - Get All Set Members

Get all members of a set.

Request:

{
  "id": "req-3",
  "method": "SMEMBERS",
  "params": {
    "key": "users:online"
  }
}

Response:

{
  "id": "req-3",
  "result": {
    "members": ["user:123", "user:456", "user:789"]
  }
}

SISMEMBER - Check Member Exists

Check if a member exists in a set.

Request:

{
  "id": "req-4",
  "method": "SISMEMBER",
  "params": {
    "key": "users:online",
    "member": "user:123"
  }
}

Response:

{
  "id": "req-4",
  "result": {
    "exists": true
  }
}

SCARD - Get Set Cardinality

Get the number of members in a set.

Request:

{
  "id": "req-5",
  "method": "SCARD",
  "params": {
    "key": "users:online"
  }
}

Response:

{
  "id": "req-5",
  "result": {
    "cardinality": 3
  }
}

SPOP - Remove and Return Random Member

Remove and return a random member from a set.

Request:

{
  "id": "req-6",
  "method": "SPOP",
  "params": {
    "key": "users:online",
    "count": 1
  }
}

Response:

{
  "id": "req-6",
  "result": {
    "members": ["user:456"]
  }
}

SRANDMEMBER - Get Random Member

Get one or more random members from a set without removing them.

Request:

{
  "id": "req-7",
  "method": "SRANDMEMBER",
  "params": {
    "key": "users:online",
    "count": 2
  }
}

Response:

{
  "id": "req-7",
  "result": {
    "members": ["user:123", "user:789"]
  }
}

SMOVE - Move Member Between Sets

Move a member from one set to another.

Request:

{
  "id": "req-8",
  "method": "SMOVE",
  "params": {
    "source": "users:online",
    "destination": "users:away",
    "member": "user:123"
  }
}

Response:

{
  "id": "req-8",
  "result": {
    "moved": true
  }
}

SINTER - Set Intersection

Get the intersection of multiple sets.

Request:

{
  "id": "req-9",
  "method": "SINTER",
  "params": {
    "keys": ["users:online", "users:premium", "users:active"]
  }
}

Response:

{
  "id": "req-9",
  "result": {
    "members": ["user:123", "user:789"]
  }
}

SINTERSTORE - Store Set Intersection

Store the intersection of multiple sets in a new set.

Request:

{
  "id": "req-10",
  "method": "SINTERSTORE",
  "params": {
    "destination": "users:online_premium",
    "keys": ["users:online", "users:premium"]
  }
}

Response:

{
  "id": "req-10",
  "result": {
    "cardinality": 2
  }
}

SUNION - Set Union

Get the union of multiple sets.

Request:

{
  "id": "req-11",
  "method": "SUNION",
  "params": {
    "keys": ["users:online", "users:away"]
  }
}

Response:

{
  "id": "req-11",
  "result": {
    "members": ["user:123", "user:456", "user:789", "user:101"]
  }
}

SUNIONSTORE - Store Set Union

Store the union of multiple sets in a new set.

Request:

{
  "id": "req-12",
  "method": "SUNIONSTORE",
  "params": {
    "destination": "users:all",
    "keys": ["users:online", "users:away", "users:offline"]
  }
}

Response:

{
  "id": "req-12",
  "result": {
    "cardinality": 5
  }
}

SDIFF - Set Difference

Get the difference between sets (members in first set but not in others).

Request:

{
  "id": "req-13",
  "method": "SDIFF",
  "params": {
    "keys": ["users:online", "users:premium"]
  }
}

Response:

{
  "id": "req-13",
  "result": {
    "members": ["user:456"]
  }
}

SDIFFSTORE - Store Set Difference

Store the difference between sets in a new set.

Request:

{
  "id": "req-14",
  "method": "SDIFFSTORE",
  "params": {
    "destination": "users:online_non_premium",
    "keys": ["users:online", "users:premium"]
  }
}

Response:

{
  "id": "req-14",
  "result": {
    "cardinality": 1
  }
}

SSCAN - Scan Set Members

Iterate over set members using cursor-based pagination.

Request:

{
  "id": "req-15",
  "method": "SSCAN",
  "params": {
    "key": "users:online",
    "cursor": 0,
    "count": 10,
    "match": "user:*"
  }
}

Response:

{
  "id": "req-15",
  "result": {
    "cursor": 0,
    "members": ["user:123", "user:456", "user:789"]
  }
}

Error Handling

All WebSocket set operations return standardized error responses:

{
  "id": "request-id",
  "error": {
    "code": "ERROR_CODE",
    "message": "Human readable error message"
  }
}

Common error codes:

KEY_NOT_FOUND: The specified set key doesn't exist
TYPE_MISMATCH: The key exists but is not a set type
INVALID_VALUE: The value is not valid for the operation
AUTHENTICATION_FAILED: Invalid or missing authentication token
RATE_LIMITED: Request rate limit exceeded

TypeScript SDK Example

import { DbxWsClient } from "@0dbx/redis";
 
const wsClient = new DbxWsClient("ws://localhost:3000/redis_ws");
 
// Set operations
await wsClient.set.addMember("user:1:tags", "admin");
await wsClient.set.addMember("user:1:tags", "moderator");
const tags = await wsClient.set.getMembers("user:1:tags");
console.log(tags); // ["admin", "moderator"]

Best Practices

Set Naming: Use descriptive set names that clearly indicate their purpose
Member Uniqueness: Remember that sets only store unique members
Batch Operations: Use SADD/SREM with multiple members for efficiency
Memory Usage: Be mindful of set size as all members are loaded into memory
Key Expiration: Set appropriate TTL on set keys for temporary data
Set Operations: Use intersection, union, and difference operations for complex queries

Performance Considerations

Set operations are generally very fast for membership testing
SMEMBERS can be expensive for large sets - consider using SSCAN for iteration
Set operations (SINTER, SUNION, SDIFF) are O(N) where N is the size of the smallest set
SPOP and SRANDMEMBER are O(1) operations
Consider using set partitioning for very large datasets
Set operations are atomic, making them suitable for concurrent access patterns

Common Use Cases

User Sessions

// Track online users
await client.set.sadd("users:online", [userId]);
 
// Check if user is online
const isOnline = await client.set.sismember("users:online", userId);
 
// Get online user count
const onlineCount = await client.set.scard("users:online");

Tags and Categories

// Add tags to a post
await client.set.sadd("post:123:tags", ["javascript", "redis", "tutorial"]);
 
// Get all tags for a post
const tags = await client.set.smembers("post:123:tags");
 
// Find posts with specific tags
const taggedPosts = await client.set.sinter(["tag:javascript:posts", "tag:redis:posts"]);

Unique Collections

// Track unique visitors
await client.set.sadd("site:visitors", [visitorId]);
 
// Get unique visitor count
const uniqueVisitors = await client.set.scard("site:visitors");
 
// Check if visitor has been before
const isReturning = await client.set.sismember("site:visitors", visitorId);