How to delete Redis keys using pattern

Posted on May 9, 2019  •  1 minutes  • 141 words

So Googling this question show a common approach using KEYS command and then pipe them to DEL command, which looks something like this in Lua script

local keys = redis.call('keys', ARGV[1])
for i=1,#keys,5000 do
    redis.call('del', unpack(keys, i, math.min(i+4999, #keys)))
end
return keys

Doing things like this would be fine for development where the keyspace is small and frequent of use is low.

However, if you were to do this at a larger keyspace and a lot more frequent, the KEYS command will block Redis instance and making other commands to fail.

The alternative is to use SCAN and loop until the cursor is 0. A naive implementation is like below.

redis.replicate_commands()
local matches = redis.call('scan', '0', 'match', ARGV[1], 'count', '10000')

while matches[1] ~= "0" do
    for i=1,#matches[2],5000 do
        redis.call('del', unpack(matches[2], i, math.min(i+4999, #matches[2])))
    end

    matches = redis.call('scan', matches[1])
end
return matches[2]