Redis通过lua脚本查Set交集

一 背景

• redis的set结构，不支持批量查询集合是否在set中
• 循环查询会增加网络开销，速度不快，所以通过lua脚本方式批量查询。

二 lua脚本

lua/intersect.lua

local key = KEYS[1]  
local skeys = cjson.decode(ARGV[1])  
local size = #skeys  
local result = {}  
  
for i = 1, size do  
    local isMember = redis.call('sismember', key, skeys[i]);  
    if (tonumber(isMember) > 0) then  
        table.insert(result, skeys[i])  
    end  
end  
local resultSize = #result  
if (resultSize == 0) then  
    return '[]'  
else  
    return cjson.encode(result);  
end

三 java相关代码

...
    private static final Jackson2JsonRedisSerializer<String[]> JACKSON2JSONREDISSERIALIZER = new Jackson2JsonRedisSerializer<>(String[].class);

    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    private DefaultRedisScript<String[]> intersectScript;

    @PostConstruct
    void init() {
        intersectScript = new DefaultRedisScript<>();
        intersectScript.setLocation(new ClassPathResource("lua/intersect.lua"));
        intersectScript.setResultType(String[].class);
    }
	
    /**
     * 取set交集
     * @param key
     * @param skeys
     * @return
     */
    private Set<String> intersect(String key, Set<String> skeys) {
        String[] intersectResults = stringRedisTemplate.execute(intersectScript,
            JACKSON2JSONREDISSERIALIZER,
            JACKSON2JSONREDISSERIALIZER,
            Collections.singletonList(key),
            skeys);
        if (intersectResults == null) {
            return Collections.emptySet();
        }
        return Arrays.stream(intersectResults).collect(Collectors.toSet());
    }
...