SETBIT _key_ _offset_ _value_ (Redis >

2.1.8) = Time complexity: O(1)

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 is limited to 2<sup>32-1 (which 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</sup>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 value

Integer reply, specifically: the original bit value stored at offset.