Shulou(Shulou.com)06/01 Report--

Practical applications of Setbit

Scenario: 100 million users, each user logging in/doing any operation, recorded as active today, otherwise recorded as inactive

Weekly ratings: Prize-winning Active users: 7 consecutive days of activity

Monthly reviews, etc...

Idea:

Userid dt active

1 2013-07-27 1

1 2013-0726 1

If it is placed in a table, 1: the table increases sharply, 2: the group sum operation is used, and the calculation is slow.

Bitmap: Bitmap

Log0721: '011001............... 0'

......

log0726 : '011001............... 0'

Log0727 : '0110000............. 1'

1: Record user login:

A bitmap is generated by date every day. After the user logs in, the bit value on the user_id bit is set to 1.

2: Take the bitmap of 1 week and calculate,

A 1 in the upper bit is a continuous login user.

redis 127.0.0.1: 6379> setbit mon 1000000 0 (100 million users on Monday initial state, all 0)

(integer) 0

redis 127.0.0.1: 6379> setbit mon 3 1

(integer) 0

redis 127.0.0.1: 6379> setbit mon 5 1

(integer) 0

redis 127.0.0.1: 6379> setbit mon 7 1 (User 7 logs in once on Monday, counted as 1)

(integer) 0

redis 127.0.0.1:6379> setbit thur 100000000 0

(integer) 0

redis 127.0.0.1:6379> setbit thur 3 1

(integer) 0

redis 127.0.0.1:6379> setbit thur 5 1

(integer) 0

redis 127.0.0.1:6379> setbit thur 8 1

(integer) 0

redis 127.0.0.1:6379> setbit wen 100000000 0

(integer) 0

redis 127.0.0.1:6379> setbit wen 3 1

(integer) 0

redis 127.0.0.1:6379> setbit wen 4 1

(integer) 0

redis 127.0.0.1:6379> setbit wen 6 1

(integer) 0

redis 127.0.0.1:6379> bitop and res mon feb wen

(integer) 12500001

As in the previous example, advantages:

1: Save space, 100 million people log in every day, with 100 million bits, about 1200WByte, about 10M characters can be expressed

2: Easy to calculate

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.