Clear redis cache

Sometimes with WPML there is a need for clearing the redis cache (noticed when restructuring the product categories)

This can be done with this script (when we have multiple prefixes in the DB, otherwise use Redis command “flushall”.

-- Usage: redis-cli --eval <thisfile.lua> , 'the_search_string_*'
-- Example: redis-cli --eval remove_matching_keys.lua , 'someprefix_*'

-- Solution adapted from this: https://stackoverflow.com/a/65427976
-- the "," is to pass an argument and not a key to the lua script

local searchstring=ARGV[1]
local keys_to_delete = redis.call('keys', searchstring)
-- return keys_to_delete
for _,k in ipairs(keys_to_delete) do
  redis.call('del', k)
end