feat(database/gredis): add Scan method for incremental key retrieval

[phuonganhniie]

Overview

This pull request introduces the Scan method to the GroupGeneric struct in gredis package, providing an efficient and non-blocking approach to iterate over keys that match a given pattern in Redis. This method is designed to handle large datasets more gracefully than the Keys command, offering incremental retrieval without the risk of blocking the Redis server.

Changes

• Scan Method: Implements the Redis SCAN command within the GroupGeneric struct. It accepts a cursor, pattern, and count, returning a slice of keys matching the pattern and the next cursor position for continued scanning.

Why It's Needed

The SCAN command is essential for applications dealing with large data sets in Redis, where using the Keys command might lead to performance bottlenecks or blocking the server. By providing a Scan method, it easier and safer to get keys little by little, improving overall application responsiveness.

Available since Redis version: 2.8.0

Usage Example

Below is a simple example demonstrating how to use the new Scan method:

var cursor uint64 = 0
var allKeys []string
var count int = 100

for {
    keys, nextCursor, err := redis.GroupGeneric().Scan(ctx, cursor, "*pattern*", count)
    if err != nil {
        log.Fatalf("Scan failed: %v", err)
    }
    allKeys = append(allKeys, keys...)
    if nextCursor == 0 {
        break
    }
    cursor = nextCursor
}

fmt.Println("Retrieved keys:", allKeys)

Testing

Includes comprehensive unit tests covering:

• Successful key retrieval with various patterns.
• Proper handling of negative cursor and count values.
• Edge cases, such as empty patterns, pattern with no matches.

I'd love to hear your thoughts and feedback on this! Looking forward to your review.

[phuonganhniie]

@gqcn Hi John, I'm looking forward to your review. If you need any information, pls don't hesitate contact me.