The read is aborted if the generation associated with the stored key does not match if_equal. This is primarily useful in conjunction with a ReadOptions::byte_range request to ensure consistency.

• The special value of StorageGeneration::Unknown() (the default) disables this condition.

• The special value of StorageGeneration::NoValue() specifies a condition that the value not exist. This condition is valid but of limited use since the only possible read results are “not found” and “aborted”.