Redis 的 Lua 脚本，它对键的值求和 [英] Lua script for Redis which sums the values of keys

问题描述

我正在构建我的第一个 Redis 服务器端脚本(用于调试)，但由于缺乏 Lua 经验而陷入困境.

I am building out my first Redis server side script (for debugging) and my lack of Lua experience has me quite stuck.

本质上有一个 K/V 对(包含约 1000 个值)的数据集，我想从中列出与模式匹配的所有键.例如在 redis-cli 中:

Essentially have a dataset of K/V pairs (containing ~1000 values) from which I want to list all the KEYS that match a pattern. For example in redis-cli:

> KEYS "carlos:*"
1) "carlos:1"
2) "carlos:2"
3) "carlos:3"
4) "carlos:4"

基于上述输出，我想通过执行 Lua 脚本来返回这些键的总和.目前我的 sum.lua

Based on the above output I want to return the sum of those keys by executing a Lua script. Currently I have the following on my sum.lua

local sum = 0
local matches = redis.call('KEYS', 'carlos:*')

for unpack(matches)
   sum = sum + redis.call('GET', matches)
end

return sum

虽然上述脚本可能不正确，但即使尝试 redis.call('KEYS', 'carlos:*') 本身也会产生以下错误

While the above script is likely incorrect, trying even redis.call('KEYS', 'carlos:*') by itself produces the following error

root@carlos:~# redis-cli EVAL "$(cat sum.lua)"

root@carlos:~# redis-cli EVAL "$(cat sum.lua)"

(错误)ERR 'eval' 命令的参数数量错误

(error) ERR wrong number of arguments for 'eval' command

我尝试了多次语法迭代都无济于事.有什么想法吗?

I have tried a number of iterations of my syntax to no avail. Any ideas?

谢谢

推荐答案

1. EVAL 至少需要两个参数；脚本和您传递给脚本的键数.在这种情况下，您传递的是零键，这意味着可以按如下方式调用脚本:

1. EVAL requires a minimum of two arguments; the script and the number of keys you are passing to the script. In this case, you are passing zero keys, meaning the script can be invoked as follows:

redis-cli EVAL "$(cat sum.lua)" 0

或:

redis-cli --eval sum.lua

您用于迭代从 KEYS 返回的值的循环结构不正确；我已经为你修好了.

Your loop structure for iterating over the values returned from KEYS was incorrect; I have fixed it for you.

您需要使用 Lua 的 tonumber 函数将 GET 返回的值从字符串转换为数字.

You need to convert the value returned from GET from a string to a number using Lua's tonumber function.

进行上述更改后，以下脚本应该适合您:

With the above changes made, the following script should work for you:

local sum = 0
local matches = redis.call('KEYS', 'carlos:*')

for _,key in ipairs(matches) do
    local val = redis.call('GET', key)
    sum = sum + tonumber(val)
end

return sum

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