CODEWITHSUNDEEP
redislua
guneysus
guneysus

Reputation: 6502

How to retrieve value from table value Redis Lua script

I am trying to extract a value from a json encoded string that returned from a sorted set in Redis.

127.0.0.1:6379> eval 'local r= redis.call("ZRANGEBYSCORE", "iprange:locations", 34625535, "+inf", "LIMIT", 0, 1); return type(r);' 0
"table"
127.0.0.1:6379> eval 'local r= redis.call("ZRANGEBYSCORE", "iprange:locations", 34625535, "+inf", "LIMIT", 0, 1); return r;' 0
1) "{\"countryCode\": \"IT\", \"countryName\": \"Italy\"}"

I just want to extract countryValue from the result.

Tried return r.countryCode;, return r["countryCode"]; but all of them returned (nil)

By the way, I alread handle this json encoded string in my app by decoding this json into data. Just trying to delegate this simple task to Redis Lua script engine.

Upvotes: 0

Views: 414

Answers (1)

Kevin Christopher Henry
Kevin Christopher Henry

Reputation: 48902

Use the built-in JSON library:

eval 'local  r = redis.call("ZRANGEBYSCORE", "iprange:locations", 34625535, "+inf", "LIMIT", 0, 1);
      return cjson.decode(r[1])["countryCode"];'

Note that ZRANGEBYSCORE returns an array of results, represented in Lua by a table. Presumably you'll want to loop over the results and extract countryCode for each.

Upvotes: 2

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