node-redis/examples/scan.js

'use strict';

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

var cursor = '0';

function scan () {
    client.scan(
        cursor,
        'MATCH', 'q:job:*',
        'COUNT', '10',
        function (err, res) {
            if (err) throw err;

            // Update the cursor position for the next scan
            cursor = res[0];
            // get the SCAN result for this iteration
            var keys = res[1];

            // Remember: more or less than COUNT or no keys may be returned
            // See http://redis.io/commands/scan#the-count-option
            // Also, SCAN may return the same key multiple times
            // See http://redis.io/commands/scan#scan-guarantees
            // Additionally, you should always have the code that uses the keys
            // before the code checking the cursor.
            if (keys.length > 0) {
                console.log('Array of matching keys', keys);
            }

            // It's important to note that the cursor and returned keys
            // vary independently. The scan is never complete until redis
            // returns a non-zero cursor. However, with MATCH and large
            // collections, most iterations will return an empty keys array.

            // Still, a cursor of zero DOES NOT mean that there are no keys.
            // A zero cursor just means that the SCAN is complete, but there
            // might be one last batch of results to process.

            // From <http://redis.io/commands/scan>:
            // 'An iteration starts when the cursor is set to 0,
            // and terminates when the cursor returned by the server is 0.'
            if (cursor === '0') {
                return console.log('Iteration complete');
            }

            return scan();
        }
    );
}
scan();