[reverted]planner: support set tidb_allow_mpp to `2` or `ENFORCE` to enforce use mpp mode.#24516

Merged

ti-chi-bot merged 14 commits intopingcap:masterfrom LittleFall:enforce-mpp

May 12, 2021

+157-14

Commits on May 8, 2021

expand var tidb_allow_mpp values from {true, false} to {0,1,2}
LittleFall
committed
use typeEnum instead of typeInt to keep compatible with old versions.
LittleFall
committed