Update a key and lookup for a specific root level JSON attribute.

updatekeyandlookup.lua

--EVAL "this script" 2 key lookup jsonvalue attribute

local key, lookup = unpack(KEYS);
local jsonvalue, attribute = unpack(ARGV);
local value = cjson.decode(jsonvalue);

local oldvalue = redis.call('GET', key);
--if this key was set before, remove the old lookup
if type(oldvalue) == 'string' then
    oldvalue = cjson.decode(oldvalue);
    redis.call('HDEL', lookup, oldvalue[attribute]);
end

redis.call('HSET', lookup, value[attribute], key);
return redis.call('SET', key, jsonvalue);