Re: No Limits - Memory Engine

[Rick James]

The (threadbuffers*max connections) part tends to be pessimistic.

(max_heap_table_size*total memory tables) is probably wrong, since max_heap_table_size can be set before each CREATE TABLE...MEMORY, thereby giving different limits. (But I am not sure of the details.) That is, SET to different values before each CREATE.

I have investigated several formulas for total memory footprint, each has flaws. This lists the main components:
http://mysql.rjweb.org/doc.php/memory
You are reaching into a rarely used area -- ENGINE=Memory.

For you, I would recommend reserving enough room for your MEMORY table(s), then follow the guidelines in that link with what memory remains.