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

Use Case(s)

HINCRBY is a Redis command used to increment the integer value of a hash field by a given number. It's commonly used when you need to perform atomic operations. This can be handy in situations like updating real-time data, for instance, maintaining counters or scores in a game.

Code Examples

Let's consider an example where we are creating a leaderboard for a game and updating scores using Redis and Ruby:

require 'redis' # Create a new redis object redis = "localhost", port: 6379) # Set initial score for player1 redis.hset("leaderboard", "player1", 0) # Increment score for player1 by 15 redis.hincrby("leaderboard", "player1", 15)

In this script, we first create a Redis object. Then, we set the initial score for player1 in the leaderboard hash to 0 using hset. Finally, we increment the score of player1 by 15 using hincrby.

Best Practices

  • Always check if the field that you want to increment exists and is of integer type. If it doesn't exist, Redis assumes it's 0 and applies the operation, but if it exists and is not an integer, you'll get an error.
  • Use descriptive names for your keys to make them easily identifiable.

Common Mistakes

  • A common mistake is not handling exceptions when the field value isn't an integer. If you attempt to increment a field storing non-integer values, Redis will throw an error.
  • Another mistake is treating Redis as a persistent storage. It's an in-memory database primarily used for caching, and data can be lost if the server crashes or restarts.


Q: What happens if the field doesn't exist in the hash?

A: Redis treats non-existent fields as having a value of 0, so if you increment a non-existent field, it will hold the increment value after the operation.

Q: What if the current field value isn’t an integer?

A: If the current field value isn't an integer, a runtime error will be raised.

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