Redis/Jedis - Delete by pattern?

Question

Normally, I get the key set then use a look to delete each key/value pair.

Is it possible to just delete all keys via pattern?

ie:

Del sample_pattern:*

Cotsen

Answer 1

It seems, for Jedis, to "delete by pattern" is basically getting all the keys of a specific pattern then loop through it.

ie

Set<String> keys = jedis.keys(pattern);
for (String key : keys) {
    jedis.del(key);
} 

Cotsen

Scan is better. But you can reduce the number of call to jedis by doing Set<String> keys = jedis.keys(pattern); jedis.del(keys.toArray(new String[keys.size()])); – Markle

A more efficient way to do it without using KEYS can be found below: https://mcmap.net/q/756428/-redis-jedis-delete-by-pattern – Correy

Answer 2

KEYS is not recommended to use due to its inefficiencies when used in production. Please see https://redis.io/commands/keys. Instead, it is better to use SCAN. Additionally, a more efficient call than repeated calls to jedis.del() is to make one single call to jedis to remove the matching keys, passing in an array of keys to delete. A more efficient solution is presented below:

Set<String> matchingKeys = new HashSet<>();
ScanParams params = new ScanParams();
params.match("sample_pattern:*");

try(Jedis jedis = jedisPoolFactory.getPool().getResource()) {
    String nextCursor = "0";

    do {
        ScanResult<String> scanResult = jedis.scan(nextCursor, params);
        List<String> keys = scanResult.getResult();
        nextCursor = scanResult.getStringCursor();

        matchingKeys.addAll(keys);

    } while(!nextCursor.equals("0"));

    if (matchingKeys.size() == 0) {
      return;
    }

    jedis.del(matchingKeys.toArray(new String[matchingKeys.size()]));
}

Laywoman

I wonder twho things - why KEYS is so ineffective, and whether SCANning of non-trivial entries (say, 10kb JSONs) is really more effective than using KEYS. I mean - keys is basically like SCAN, only dropping the content and returning in one bulk. Which wou need to do here anyway. – Mcgrath

Since Redis is generally considered to be single-threaded, the KEYS command could block for seconds if the set is sufficiently large. In many production environments, waiting for even a couple milliseconds could cause major performance problems since Redis is assumed to be fast. – Coniine

Much more efficient than the answer marked as correct. Thank you. However, you must instantiate jedisPool before using it in the try block: JedisPool jedisPool = new JedisPool(); Further, all that needs to be called is jedisPool.getResource(). The factory part is no longer necessary, nor is the .getPool() method called on it. – Correy

I think scanResult.getStringCursor() is deprecated. Replaced with scanResult.getCursor(). – Groos

Answer 3

You should try using eval. I'm no Lua expert, but this code works.

private static final String DELETE_SCRIPT_IN_LUA =
    "local keys = redis.call('keys', '%s')" +
    "  for i,k in ipairs(keys) do" +
    "    local res = redis.call('del', k)" +
    "  end";

public void deleteKeys(String pattern) {
  Jedis jedis = null;

  try {
    jedis = jedisPool.getResource();

    if (jedis == null) {
      throw new Exception("Unable to get jedis resource!");
    }

    jedis.eval(String.format(DELETE_SCRIPT_IN_LUA, pattern));  
  } catch (Exception exc) {
    if (exc instance of JedisConnectionException && jedis != null) {
      jedisPool.returnBrokenResource(jedis);
      jedis = null;
    }

    throw new RuntimeException("Unable to delete that pattern!");
  } finally {
    if (jedis != null) {
      jedisPool.returnResource(jedis);
    }
  }
}

And then call:

deleteKeys("temp:keys:*");

This guarantees a one server-side call, multiple delete operation.

Pilose

Answer 4

You can do it with the Redisson in one line:

redisson.getKeys().deleteByPattern(pattern)

Johanna

this would be useful for me thanks – Strangury

Answer 5

You can do it with bash:

$ redis-cli KEYS "sample_pattern:*" | xargs redis-cli DEL

Librium

sorry, forgot to mention that i want to do this in java code. but this is useful. – Cotsen

@yaojiang I never wrote a line of Java but here's my take, see the updated answer. – Librium

no dice. it looks like the jedis implementation only allows me to do something like jedis.del(key1, key2, key3,...); – Cotsen

@yaojiang Oh, I thought jedis.keys() would return a collection of keys. What does it return btw? – Librium

one or more string args, or byte[]. – Cotsen