Today I upgraded my system to macOS Catalina 10.15 and found that the disk would heat up and the fan would start spinning loudly after using it for a while. Even if all applications were closed, this issue still occurred, and I suspected that the system was doing something in the background. I directly opened the system’s built-in Activity Monitor monitoring tool and found that a process called “photoanalysisd” was running in the background, causing the CPU usage to soar to 40% to 50%.