Node Redis: Get All Keys Matching Pattern (Detailed Guide w/ Code Examples)

Use Case(s)

One common use case of getting all keys matching a particular pattern in Redis is when you want to fetch all keys that start, end or contain a certain substring. This can be very useful in scenarios where keys are named following a certain convention and you need to retrieve all keys belonging to a specific group.

Code Examples

Using the KEYS command is one way to get all keys matching a pattern:

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

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

  for(var i = 0, len = keys.length; i < len; i++) {
    console.log(keys[i]);
  }
});

In this code snippet, you connect to the Redis server using redis.createClient(). Then, you use the keys('*pattern*') function to get all keys that match the specified pattern.

Remember that KEYS command can be resource-intensive on large databases. It's recommended to use SCAN for such cases, which can be done as follows:

const redis = require('redis');
const client = redis.createClient();
let cursor = '0';

function scan() {
  client.scan(cursor, 'MATCH', '*pattern*', 'COUNT', '100', function(err, reply) {
    if(err) throw err;

    cursor = reply[0];
    reply[1].forEach(function(key, i) {
      console.log(key);
    });

    if(cursor === '0') {
      return console.log('Scan complete');
    } else {
      return scan();
    }
  });
}

scan();

Here we're using the SCAN command with a cursor to iteratively fetch keys matching the pattern.

Best Practices

Avoid using the KEYS command in a production environment as it can potentially block the server while executing. Instead, prefer the SCAN command, which provides an iterator that allows you to retrieve keys in a more controlled manner.

Common Mistakes

One common mistake is not handling the case when the KEYS or SCAN commands return an error. Always ensure to handle potential errors in your callbacks.

FAQs

• Q: Can I use regular expressions with the KEYS or SCAN commands?
  A: No, Redis does not support full regex patterns in KEYS or SCAN commands. It supports only glob-style patterns like *, ? and [chars].