Node Redis Bulk Get (Detailed Guide w/ Code Examples)

Use Case(s)

In Node.js applications, we often need to get multiple keys from a Redis store at once. This can be accomplished using the mget command, which stands for 'Multi Get'. It allows you to retrieve the values of all specified keys.

Code Examples

1. Basic Usage:

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

client.mget(['key1', 'key2', 'key3'], function(err, reply) {
    console.log(reply); // will print the values of key1, key2 and key3
});

This example shows how you can use mget to fetch the values of multiple keys ('key1', 'key2', 'key3') at once.

2. With Promise:

const { promisify } = require('util');
const redis = require('redis');
const client = redis.createClient();
const getAsync = promisify(client.mget).bind(client);

getAsync(['key1', 'key2', 'key3']).then(console.log).catch(console.error);

In this example, we're wrapping the mget call with Node's built-in promisify utility, allowing us to work with Promises instead of callbacks.

Best Practices

• Always handle potential errors in your callback or promise chain to prevent any unhandled exceptions.
• Be mindful about the size of the data you are requesting, as getting too many keys at once could potentially slow down your application.

Common Mistakes

• Not checking if the keys exist before trying to get them. This will return null values for those keys, which may not be the expected behavior in your application.

FAQs

1. Can I use wildcard characters with mget?
   No. The Redis mget command does not support wildcards. If you need to get all keys matching a pattern, you need to first use the keys command to get the keys and then use mget.
2. What happens if some of the keys do not exist?
   If some of the keys don't exist, Redis will return null for those keys.