How to tag a key in REDIS so later I can remove all keys that match this tag?

Question

Today we save data like that:

redisClient->set($uniquePageID, $data);

and output the data like that:

redisClient->get($uniquePageID)

But now we need to remove the data base on a userID. So we need something like that:

redisClient->set($uniquePageID, $data)->tag($userID);

So we can remove all the keys that related to this userID only, for example:

redisClient->tagDel($userID);

Does REDIS can solve something like that?

Thanks

Answer 1

There's no built-in way to do that. Instead, you need to tag these pages by yourself:

• When setting a page-data pair, also put the page id into a SET of the corresponding user.
• When you want to remove all pages of a given user, scan the SET of the user to get the page ids of this user, and delete these pages.

When scanning the SET, you can use either SMEMBERS or SSCAN command, depends on the size of the SET. If it's a big SET, prefer SSCAN to avoid block Redis for a long time.

Answer 2

I used HSET and HDEL to store and delete items like this:

$this->client = new Predis\Client(array...);
$this->client->hset($key, $tag, $value);
$this->client->hdel($key, $tags)

and if you want to delete every item KEY no matter tag or value you can use del key, it works with any data type including hset

$this->client->del($key);