CODEWITHSUNDEEP
node.jsredis
Manish Sapkal
Manish Sapkal

Reputation: 6241

redis hash - get top 5 keys order by date

I have stored my data in redis hash like this : 

client> hmset date:20150513 user 21 m 20 f  1
client> hmset date:20150514 user 17 m 10 f  7
client> hmset date:20150515 user 13 m  3 f 10
client> hmset date:20150516 user 15 m 10 f  5
client> hmset date:20150517 user 15 m 10 f  5
client> hmset date:20150518 user  7 m  3 f  4
client> hmset date:20150519 user 10 m  7 f  3

This is datewise user summary (including male, female bifurcation). Now I want to fetch top 5 keys order by date in descending order. In the above case, I want

date:20150519, date:20150518, date:20150517, date:20150516 and date:20150515.

How do I write script (luascript) or command to retrive data?

Upvotes: 3

Views: 2031

Answers (1)

Itamar Haber
Itamar Haber

Reputation: 50052

The best way to go about this is to store your dates in a Sorted Set whose score is the date. Your example's data would require something like:

client> ZADD dates 20150515 20150515 20150516 20150516 20150517 20150517 20150518 20150518 20150519 20150519

Now you can easily get the top 5 entries with:

client> ZREVRANGEBYSCORE dates +inf -inf LIMIT 0 5

and follow with an HMGET for each reply. You could also use SORT to actually fetch the data, all in one command, i.e.

client> SORT dates GET date:*->user GET date:*->m GET date:*->f LIMIT 0 5 DESC

Lastly, this is of course very doable with Lua, but unless there are additional requirements that you need to address, a script is probably an overkill here.

Upvotes: 3

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