Redis Lua script - how to pass array as argument to a Lua script in nodejs?

Question

I am calling a Lua script from nodejs. I want to pass an array as argument. I am facing problem to parse that array in Lua.

Below is an example:

var script = 'local actorlist = ARGV[1] 
if #actorlist > 0 then
for i, k in ipairs(actorlist) do
   redis.call("ZADD","key", 1, k)
end
end';

client.eval(
     script, //lua source
     0,
     ['keyv1','keyv2']
     function(err, result) {
         console.log(err+'------------'+result);
     }
    );

It gives me this error:

"ERR Error running script (call to f_b263a24560e4252cf018189a4c46c40ce7d1b21a): @user_script:1: user_script:1: bad argument #1 to 'ipairs' (table expected, got string)

What is the value of ARGV[1] suppose to be? How does it get its value? eg. is it a string containing comma separated list of actors? — greatwolf
– greatwolf, Commented Jan 9, 2017 at 13:59
According to redis.io/commands/eval, you should be using ARGV or KEYS called with client.eval(script, 2, ... — greatwolf
– greatwolf, Commented Jan 9, 2017 at 14:07
@greatwolf, ARGV[1] would be array of values like ['keyv1','keyv2'] — Suyog Kale
– Suyog Kale, Commented Jan 10, 2017 at 10:32
Not according to the error message. It sees a string, not an array. — greatwolf
– greatwolf, Commented Jan 10, 2017 at 11:40
Judging from this issue, looks like js arrays turn into strings when passed into eval. Is there a reason for not unpacking the array first and passing them in as separate arguments? — greatwolf
– greatwolf, Commented Jan 10, 2017 at 12:02

Petofi · Accepted Answer · 2017-07-14 15:35:47Z

3

You can do it just by using ARGV:

local actorlist = ARGV

for i, k in ipairs(actorlist) do

and pass arguments in console like this:

eval "_script_" 0 arg1 arg2 argN

answered Jul 14, 2017 at 15:35

Petofi

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Comtaler · Accepted Answer · 2018-07-12 21:15:59Z

-1

You can only pass in strings into Redis lua script.

If you need an array of values to be pass into Redis lua script, you can do this:

let script = `
if #ARVG > 0 then
    for i, k in ipairs(ARGV) do
       redis.call("ZADD","key", 1, k)
    end
end`;

client.eval(
     script, //lua source
     0,
     ...['keyv1','keyv2'],
     function(err, result) {
         console.log(err+'------------'+result);
     }
);

The key here is to pass keyv1 and keyv2 as a separate params when calling eval. (I am using es6 syntax here)

answered Jul 12, 2018 at 21:15

Comtaler

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