Redis

SETBIT key offset value

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 232 (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 232 -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 232 -1 (512MB allocation) takes ~300ms, setting bit number 230 -1 (128MB allocation) takes ~80ms, setting bit number 228 -1 (32MB allocation) takes ~30ms and setting bit number 226 -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 value

Integer reply: the original bit value stored at offset.

Examples

redis>  SETBIT mykey 7 1
(integer) 0
redis>  SETBIT mykey 7 0
(integer) 1
redis>  GET mykey
"\u0000"
redis> 
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