Redis Bitmaps

Bitmaps are used to support Bit oriented operations. Suppose if you want to maintain attendence of sudents (ids 1 to 100), 100 bits are enough to save today attendence.

SETBIT key offset value Sets or clears the bit at offset in the string value stored at key. Example setbit today 8 1 Above statement sets 8th bit of key “today” to 1. BITCOUNT key start end Count number of bits set in given bitmap key. Example bitcount today 1 100 Above statement returns 7, means 7 students attended for today class.

k@hk-Inspiron-N5010:~$ redis-cli 
127.0.0.1:6379> setbit today 8 1 
(integer) 0 
127.0.0.1:6379> setbit today 10 1 
(integer) 0 
127.0.0.1:6379> setbit today 13 1 
(integer) 0 
127.0.0.1:6379> setbit today 17 1 
(integer) 0 
127.0.0.1:6379> setbit today 23 1 
(integer) 0 
127.0.0.1:6379> setbit today 29 1 
(integer) 0 
127.0.0.1:6379> setbit today 31 1 
(integer) 0 
127.0.0.1:6379> bitcount today 1 100 
(integer) 7 

 

SETBIT key offset value

Sets or clears the bit at offset in the string value stored at key.

Example

setbit today 8 1

Above statement sets 8^th bit of key “today” to 1.

BITCOUNT key start end

Count number of bits set in given bitmap key.

Example

bitcount today 1 100

Above statement returns 7, means 7 students attended for today class.

Prevoius                                                 Next                                                 Home