How to delete multiple redis keys with the same pattern in PHP using phpredis?

Question

By using phpredis, I have saved some data in pagination like this:

   review/itemA/1
   review/itemA/2 

where 1 and 2 are page numbers. I read in the document that you can use wildcards to retrieve multiple keys.

$allKeys = $redis->keys('*');   // all keys will match this.
$keyWithUserPrefix = $redis->keys('user*');

But can I delete all the old keys using wildcards as well when someone has posted a new review? Can I do something like:

$redis->delete('review/itemA/*'); // or  $redis->delete('review/itemA*')

It didn't work however.

Naara

Never use keys command on production environment as it will block the whole DB until the searched key is found. Instead you can use Scan to search specific key for production env. – Berga

Answer 1

When using phpredis, you can get the prefix (which phpredis automatically prepends everywhere) and delete a pattern of keys that way :

<?php
...

$prefix = $redisClient->getOption(Redis::OPT_PREFIX);
$redisClient->delete(array_map(
    function ($key) use ($prefix) {
        return str_replace($prefix, '', $key);
    }, $redisClient->keys('*'))
);

Darlenadarlene

A little improvement to ensure removing the string (prefix) starting to the left: preg_replace( "/^${prefix}/", '', $key ); in favor of str_replace. – Immediacy

Answer 2

No - Redis' DELlete does not accept wildcards, you have to name the keys explicitly. See here for possible directions: https://mcmap.net/q/53904/-how-to-atomically-delete-keys-matching-a-pattern-using-redis

Strapper

Thanks. I ended up using $allKeys = $redis->keys('itemA*'); and looped over the results to delete them one by one. Not sure if that is the best way of doing it. – Naara

Definitely one of the worst ways ;) KEYS is an evil command that you should, as a rule, refrain from using (unless thou be brave, fool or both) – Strapper

Answer 3

With Predis, I do it like this:

    public function delete($key) {
        $keys = $this->client->keys($key);
        foreach ($keys as $key) {
            $this->client->del($key);
        }
    }

Mainland

Answer 4

Predis (->del) allows to pass a keys array too.
It works here and is faster than the del inside the foreach.

$prefix = $this->client->getOptions($this->OPT_PREFIX);
$keys = $this->client->keys("$key*");
if ($keys) $this->client->del($keys);

Springe

A good answer has a better explanation How do I write a good answer? – Dispirited

What's $prefix = $this->client->getOptions($this->OPT_PREFIX); here in this code snippet? – Japha

This is a much better solution than iterating over each key. Upvoted. – Hayne

Answer 5

$bash = 'redis-cli --scan --pattern "' . $path . '*" | xargs -L 1000 redis-cli DEL';

$res = @shell_exec($bash);

Valladares

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Answer 6

I just use

$redis->delete($redis->keys('*'));

It's works fine for me.

Airport

Doesn't this just delete everything since you're matching every key? – Leenaleeper

this is a dangerous answer – Scandinavian

Yeah, but you can use mask like some-namespace/* – Airport

Redis::delete is deprecated now. It possible use Redis::del ? – Studious

Answer 7

There is no wildcard for delete function. workaround as follows,

// returns total number of keys deleted
function delete($key) {
    if (empty($key)) {  // empty key can delete all
      return false;
    }
    $keys = $redis->keys("$key*");  // keys() function returns array of key strings. `*` wild card pattern can be changed as per need
    if(!$keys) {
        return 0;
    }
    $prefix = $redis->getOption(\Redis::OPT_PREFIX); // keys already have prefix, so we clear until delete finish.
    $redis->setOption(\Redis::OPT_PREFIX, '');
    $count = $redis->del($keys);  // del() function delete array of keys and returns number of keys deleted.
    $redis->setOption(\Redis::OPT_PREFIX, $prefix);

    return $count;
}

Note: As @Akash Gangrade commented, keys() not advised to use due to performance. you can consider Tags based cache invalidation like https://symfony.com/doc/current/components/cache/cache_invalidation.html#tag-aware-adapters

Sightly

Answer 8

Using scan and unlink is best practise as they are non blocking commands unlike keys and delete

# The keys set in redis
/*
1) "review/itemA/5"
2) "review/itemA/2"
3) "review/itemA/3"
4) "review/itemA/1"
5) "review/itemA/4"
*/

/**
 * vars used for scan
 */
$i = null;
$result = [];

/**
 * scan redis using desired pattern
 */
while ($result != 0) {
    $result = $redis->scan($i, 'review/itemA/*');
    if (!empty($result)) {
        $all_keys[] = $result;
    }
}

# Use call_user_func_array to flatten multidimensional array into indexed array
## Scan may return duplicate keys, so use array_unique
$unlink_keys = array_unique(call_user_func_array('array_merge', $all_keys));

# As of Redis 4.0 use unlink instead of del to stop blocking
$redis->unlink($unlink_keys);

Chiang

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