Redis Chunking (avoid unpack() stack issues)

redis.lua

local keys = redis.call('KEYS', ARGV[1]);
if next(keys) == nil then return keys end;
local chunk_size = 4096; -- must be under 8k, see https://github.com/nhibernate/NHibernate-Caches/issues/62
local n = #keys;
local out = {};

for i=1,n,chunk_size do
    local unpack_start = i;
    local unpack_end = math.min(n, i + chunk_size - 1);
    local vals = redis.call('MGET', unpack(keys, unpack_start, unpack_end));
    for j=unpack_start,unpack_end do
        local key_idx = j -- always sequentially increasing, 1..n
        local val_idx = j-unpack_start+1 -- needs to index into vals array, 1..chunk_size
        out[key_idx] = {keys[key_idx], vals[val_idx]};
    end
end

return out;





local keys = redis.call('KEYS', ARGV[1]);
if next(keys) == nil then return keys end;
local out = {};
for i=1,#keys do out[i] = {keys[i], redis.call('GET', keys[i])} end
return out;



local chunk_size = 5
local n = 2
for i=1,n,chunk_size do
    local unpack_start = i;
    local unpack_end = math.min(n, i + chunk_size - 1);
    for j=unpack_start,unpack_end do
        local key_idx = j -- always sequentially increasing, 1..n
        local val_idx = j-unpack_start+1 -- needs to index into vals array, 1..chunk_size
        print(key_idx, val_idx);
    end
end