Although how range_optimizer_max_mem_size operates is explained in the official doc, it’s not a well-known variable and surely not a variable you need to modify under most circumstances. But from time to time we get some performance tickets related to this. What problem does this variable cause if it is not properly sized? Let’s find out [&]

https://www.percona.com/blog/2021/01/21/low-value-in-range_optimizer_max_mem_size-might-cause-full-table-scan/