Question 121658 in Redis Question posted in
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Redis index scan for not equals operator

I’m trying to use Redis sorted set as my secondary index while the actual data is stored on AWS S3.

Let’s say if I want to support a condition like Name!= 'uma' is there anyway to achieve that using the inbuilt pattern matching?

For example, Let’s i have below as my sorted set key

ZADD mykey 0 uma:7000
ZADD mykey 0 umesh:7001
ZADD mykey 0 mahes:7002

Can I do something like ZSCAN mykey 0 match !uma?

I don’t want to get all data in-memory and apply != in the application layer.

Thanks in advance

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2

Answers


  1. 0

    You could create a temporary set containing the members you don’t want and then use ZDIFF:

    > ZADD mykey 3 uma:7000
(integer) 1
> ZADD mykey 4 umesh:7001
(integer) 1
> ZADD mykey 5 mahes:7002
(integer) 1

    Add some temp values:

    > ZADD tempkey 0 uma:7000
(integer) 1

    And get the difference:

    > ZDIFF 2 mykey tempkey WITHSCORES
1) "umesh:7001"
2) "4"
3) "mahes:7002"
4) "5"

    Oh. And be sure to clean up the temp set:

    > UNLINK tempkey
(integer) 1
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  2. 0

    You can use Lua Script + ZSCAN to do the job. The following is a one-liner that achieves the goal.

    redis-cli eval 'local res = redis.call("zscan", KEYS[1], ARGV[1]); local matches = {}; local kv = res[2]; for i=0,(#kv/2-1) do local k = kv[i * 2 + 1]; local v = kv[i * 2 + 2]; if k ~= ARGV[2] then matches[#matches + 1] = k; matches[#matches + 1] = v; end end res[2] = matches; return res' 1 mykey cursor-starting-from-0 uma

    There’s a similar question for SCAN. I tried to modify the one-liner in that answer, and made a comment. However, the return value for SCAN is quite different from ZSCAN, so I wrote a dedicated answer for it.

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