Redis XREVRANGE in Ruby (Detailed Guide w/ Code Examples)

Use Case(s)

The Redis XREVRANGE command is used to fetch data from a stream in a reverse order, starting from the maximum ID and moving towards the minimum. In Ruby, this functionality can be particularly useful when you want to get the most recent entries in a stream first. This could be helpful in scenarios such as:

  1. Fetching latest comments or posts feed in a social media application.
  2. Retrieving the newest logs or events in system monitoring applications.

Code Examples

Let's consider an example where we have a stream named 'mystream' and we want to fetch its entries in reverse order.

require 'redis' redis = # Add some data to the stream redis.xadd('mystream', '*', 'field1', 'value1', 'field2', 'value2') # Get all entries in reverse order using XREVRANGE entries = redis.xrevrange('mystream', '+', '-') entries.each do |entry| puts "ID: #{entry[0]}, Fields: #{entry[1]}" end

In the above code, '+' represents the highest possible stream ID and '-' represents the lowest possible stream ID. When you run this script, it lists out all entries of 'mystream' in reverse order.

Best Practices

  1. Pagination: If your stream contains a large number of entries, fetching all at once may not be memory-efficient. It's better to fetch data in chunks using pagination. You can use COUNT option for this purpose along with the last fetched ID as the new end range.

  2. Error Handling: Always handle potential exceptions that may occur during Redis operations to prevent your application from crashing unexpectedly.

Common Mistakes

  1. Wrong Order of IDs: The first argument to XREVRANGE is the higher ID and the second one is the lower ID. A common mistake is to provide these in the wrong order which results in an empty result set.

  2. Ignoring Large Data Set: If you're dealing with very large data sets, using XREVRANGE without pagination can cause memory issues or slow performance due to the amount of data being fetched at once.


Q: Can I use XREVRANGE with a specific range of IDs? A: Yes, instead of '+' and '-', you can provide specific stream IDs as start and end range.

Q: What if the stream doesn't exist? A: If the provided stream does not exist, XREVRANGE will simply return an empty list.

Was this content helpful?

Start building today

Dragonfly is fully compatible with the Redis ecosystem and requires no code changes to implement.