Why I keep getting this error " Wrong number of args calling Redis command From Lua script" even I get desired output

Question

I trying to execute this lua script i get proper output too. But i keep getting Wrong number of args calling Redis command From Lua script

def new_get_following(self, start, count, user_id=0):
        script = """
        local envs = redis.call('zrevrange',KEYS[1],ARGV[3],ARGV[4]);
        redis.call('sadd',ARGV[1],unpack(envs));
        local favs = redis.call('sinter',ARGV[2],ARGV[1]);
        local acts= redis.call('mget',unpack(envs));
        redis.call('del',ARGV[1]);
        return {favs,envs,acts}
        """
        count = int(start) + int(count) - 1
        print count
        fav_key = self.fav_key + ":" + str(user_id)
        following_stream_key = self.following_stream_key + ":" + str(user_id)
        tmp_key = int(time.time())
        return self.exectute(script, args=[tmp_key, fav_key, start, count], keys=[following_stream_key])

Use the MONITOR command (from redis-cli) to understand what is exactly sent to Redis by your application. — Didier Spezia
– Didier Spezia, Commented Jun 23, 2015 at 16:40

Uwe Keim · Accepted Answer · 2021-12-08 11:50:44Z

2

Maybe it is just a typo and has already been corrected but:

self.exectute shouldn't it be self.execute?

edited Dec 8, 2021 at 11:50

Uwe Keim

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answered Jun 23, 2015 at 17:07

Ignacio

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Comments

Nae · Accepted Answer · 2022-07-27 09:13:19Z

1

In the code last line is causing error.

local envs = redis.call('zrevrange',KEYS[1],ARGV[3],ARGV[4]);
local acts= redis.call('mget',unpack(envs));

As if envs is empty table then second line:

local acts= redis.call('mget',unpack(envs));

becomes this:

local acts= redis.call('mget',unpack());

so lua keeps throwing error. For avoid this error we can use redis.pacall which gives Response error object which can be checked in output can handle error. So final code should be

def new_get_following(self, start, count, user_id=0):
        script = """
        local envs = redis.call('zrevrange',KEYS[1],ARGV[3],ARGV[4]);
        redis.call('sadd',ARGV[1],unpack(envs));
        local favs = redis.call('sinter',ARGV[2],ARGV[1]);
        local acts= redis.pcall('mget',unpack(envs));
        redis.call('del',ARGV[1]);
        return {favs,envs,acts}
        """
        count = int(start) + int(count) - 1
        print count
        fav_key = self.fav_key + ":" + str(user_id)
        following_stream_key = self.following_stream_key + ":" + str(user_id)
        tmp_key = int(time.time())
        return self.exectute(script, args=[tmp_key, fav_key, start, count], keys=[following_stream_key])

edited Jul 27, 2022 at 9:13

Nae

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answered Jun 25, 2015 at 14:43

jayprakashstar

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1 Comment

Ignacio Over a year ago

That seems wrong. acts would be true or false, whether the pcall succeeded or not. So you are not getting the results from mget anywhere. Why don't you test envs length first with #envs and if > 0 then you do the mget thing ?

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