join on table with different charset performance

hi,

I discovered that joining table with different charset (latin1 and utf8) on (varchar to be verified that it is not also on numeric ) result in a very poor performance and erratic behavior.

If using with statement and stays on the UM, the UM process is allocating memory until no more (128G) ,if pushed down to the pm , memory stay stable but the query is very slow, insert select into is not finishing after more than 1hour, whereas when the table are on the same charset, this same operation take 5s.

I verified both way all table in utf8 and all table in latin1, it works even though latin1 seems faster.