How to use SCAN with the MATCH option in Predis

Question

I have previously used the KEYS command to search for keys matching a certain pattern in my Redis database. Since Redis 2.8, the SCAN command seems to be preferred over KEYS since it returns an iterator instead of scanning through the whole keyspace at once.

I'm using Predis >= 0.8.5 which is supposed to support PHP iterators for the SCAN command. Predis doesn't have a lot of documentation, so I'm wondering how to translate the following KEYS command to it's SCAN counterpart:

$client->keys($pattern)

I have tried the following:

$client->scan('MATCH', $pattern);

Which kind of works - but it doesn't return a native PHP iterator. It would be really nice to use Predis' built-in iterator support.

score 31 · Accepted Answer · answered Feb 16 '15 at 16:06

I found how to do it in the Predis examples directory.

To use SCAN to search for matching keys in a database, you simply use the Predis\Collection\Iterator\Keyspace class:

use Predis\Collection\Iterator;

$client = ...;
$pattern = 'foo*';

foreach (new Iterator\Keyspace($client, $pattern) as $key) {
    ...
}

Apparently Predis has an iterator class in Predis\Collection\Iterator for each of the commands that return iterators:

Keyspace for SCAN
HashKey for HSCAN
SetKey for SSCAN
SortedSetKey for ZSCAN
ListKey for LRANGE - This doesn't really use Redis iterators, but it's a nice interface to LRANGE anyway.

score 0 · Answer 2 · answered Apr 07 '17 at 16:01

Maybe this is helpful for other Predis beginners and you're coming from a PHP/MySQL background like me you can use this:

foreach (new Iterator\HashKey($client, $pattern) as $index => $value) {
    ...
}

When you previously generated an array dataset with $client->hmset($index, $array).

How to use SCAN with the MATCH option in Predis

2 Answers2

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