Sets or clears the bit at offset in the string value stored at key.
The bit is either set or cleared depending on value, which can be either 0 or 1. When key does not exist, a new string value is created. The string is grown to make sure it can hold a bit at offset. The offset argument is required to be greater than or equal to 0, and smaller than 2^32 (this limits bitmaps to 512MB). When the string at key is grown, added bits are set to 0.
Warning: When setting the last possible bit (offset equal to 2^32 -1) and
the string value stored at key does not yet hold a string value, or holds a
small string value, Redis needs to allocate all intermediate memory which can
block the server for some time.
On a 2010 MacBook Pro, setting bit number 2^32 -1 (512MB allocation) takes
~300ms, setting bit number 2^30 -1 (128MB allocation) takes ~80ms, setting bit
number 2^28 -1 (32MB allocation) takes ~30ms and setting bit number 2^26 -1 (8MB
allocation) takes ~8ms.
Note that once this first allocation is done, subsequent calls to SETBIT for
the same key will not have the allocation overhead.
@return
@integer-reply: the original bit value stored at offset.
@examples
SETBIT mykey 7 1
SETBIT mykey 7 0
GET mykey