This is follow-on from
IMPALA-7331. We don't currently have targeted perf coverage for CHAR as a result of not having any CHAR-type columns in TPC-H or TPC-DS.
CHAR is not a preferred data type in Impala because of the "interesting" space-padding semantics and limited codegen support but people do use it in production. It would be nice to have a way to measure perf regressions or take credit for perf wins if/when we enabled codegen for it.