redis - Redis ZADD:仅在分数较低时更新

Question

我需要为添加到集合中的每个键存储最低的分数，但是当我执行ZADD时，即使分数更高，Redis也会用新值覆盖分数。

ZADD myorderset 1 'one' 2 'two' 3 'three'
(integer) 3

ZRANGE myorderset 0 -1 WITHSCORES
1) "one"
2) "1"
3) "two"
4) "2"
5) "three"
6) "3"

ZADD myorderset 5 'three'
(integer) 0

ZRANGE myorderset 0 -1 WITHSCORES
1) "one"
2) "1"
3) "two"
4) "2"
5) "three"
6) "5"

在示例情况下，我不需要更新键“三”，因为新分数比现有分数(3)高(5)。有没有办法在本地执行此操作，还是需要在Lua中创建脚本？
我一直在研究 ZADD修饰符 (XX, NX, CH)，但是它们都不满足我的需要。
非常感谢你!

Answer 1

针对此CAS用例的Lua脚本将是最简单且惯用的解决方案:

127.0.0.1:6379> ZADD myorderset 1 'one' 2 'two' 3 'three'
(integer) 3
127.0.0.1:6379> EVAL "local s = redis.call('ZSCORE', KEYS[1], ARGV[2]) if not s or s > ARGV[1] then redis.call('ZADD', KEYS[1], ARGV[1], ARGV[2]) end" 1 myorderset 5 'three'
(nil)
127.0.0.1:6379> ZRANGE myorderset 0 -1 WITHSCORES
1) "one"
2) "1"
3) "two"
4) "2"
5) "three"
6) "3"
127.0.0.1:6379> EVAL "local s = redis.call('ZSCORE', KEYS[1], ARGV[2]) if not s or s > ARGV[1] then redis.call('ZADD', KEYS[1], ARGV[1], ARGV[2]) end" 1 myorderset 2 'three'
(nil)
127.0.0.1:6379> ZRANGE myorderset 0 -1 WITHSCORES
1) "one"
2) "1"
3) "three"
4) "2"
5) "two"
6) "2"