Redis XDEL in Golang (Detailed Guide w/ Code Examples)

Use Case(s)

The Redis XDEL command is used to delete one or more items from a stream by ID. Common use cases include:

• Cleaning up old data from a stream that's no longer needed.
• Removing erroneous entries in the stream.

Code Examples

Example 1: Deleting a Single Item

package main

import (
    "fmt"
    "github.com/go-redis/redis/v8"
    "context"
)

func main() {
    // Establish a connection to your Redis server
    rdb := redis.NewClient(&redis.Options{
        Addr:     "localhost:6379",
    })

    ctx := context.TODO()

    // Delete a message from the stream 'mystream' with ID '123-0'
    result, err := rdb.XDel(ctx, "mystream", "123-0").Result()
    
    if err != nil {
       fmt.Printf("Error: %v\n", err)
    } else {
       fmt.Printf("Number of Deleted Entries: %v\n", result)
    }
}

This example deletes a single item from the stream 'mystream' with the ID '123-0'. It then prints the number of deleted entries (should be 1 if the specified entry exists).

Example 2: Deleting Multiple Items

package main

import (
    "fmt"
    "github.com/go-redis/redis/v8"
    "context"
)

func main() {
    // Establish a connection to your Redis server
    rdb := redis.NewClient(&redis.Options{
        Addr:     "localhost:6379",
    })

    ctx := context.TODO()

    // Delete multiple messages from the stream 'mystream' with IDs '123-0', '124-0'
    result, err := rdb.XDel(ctx, "mystream", "123-0", "124-0").Result()
    
    if err != nil {
       fmt.Printf("Error: %v\n", err)
    } else {
       fmt.Printf("Number of Deleted Entries: %v\n", result)
    }
}

This example deletes two items from the stream 'mystream' with the IDs '123-0' and '124-0'. It then prints the number of deleted entries (should be 2 if both the specified entries exist).

Best Practices

• Only delete entries when needed to free up memory as it can be an expensive operation.
• Validate the IDs before performing XDEL to avoid runtime errors.

Common Mistakes

• Trying to delete non-existent IDs. This doesn't throw an error but returns 0 indicating that no entries were deleted.
• Not handling the error properly that occurs during the execution of the XDel() function.

FAQs

1. What happens if I try to delete an ID that doesn't exist in the stream? If you try to delete a non-existent ID, Redis doesn't throw an error. Instead, it returns 0 indicating that no entries were deleted.

2. Is there a way to delete all entries from a stream? Yes, you could use the XTRIM command with the MAXLEN set to 0 to delete all entries in a stream. However, be careful when using this command as data once deleted cannot be recovered.