Getting a Redis Key by Value in Node.js (Detailed Guide w/ Code Examples)

Use Case(s)

A common use case for getting a Redis key by its value is when you don't remember the key, but know the value stored. However, Redis does not natively support this feature as it's a key-value store designed for high-speed lookups by key, and not by value. To get a key by a value, you'll need to manually iterate over all keys and their values, which can be performance costly.

Code Examples

Let's consider an example using node_redis, a popular Node.js client for Redis. In this example, we will search keys by value '1234'.

const redis = require('redis');
const client = redis.createClient();

client.on('connect', function() {
    console.log('connected');
});

client.keys('*', function (err, keys) {
  if (err) return console.log(err);

  for(var i = 0, len = keys.length; i < len; i++) {
    client.get(keys[i], function (err, value) {
      if(value === '1234') console.log(keys[i]);
    });
  }
});

In the above example, we first connect to Redis, then use the keys command with wildcard '*' to get all keys, and finally check each key's value. If the value matches '1234', we log that key.

Best Practices

• Since Redis isn’t designed for searching by value, avoid this operation in a large production database as it can cause performance issues.
• Try to design your data in a way that you can use the key to access values as it was intended.
• For a more efficient lookup, consider using 'secondary indexing' by storing the value you want to search for as a key linked to the actual key.

Common Mistakes

• Using this approach on large datasets or in performance-critical paths can lead to slow responses or even timeouts, as it requires scanning through all keys.

FAQs

• Can Redis natively support getting keys by their values? No, Redis is a key-value store designed for quick retrieval by keys. Searching by values requires scanning all keys and should be avoided if possible.