ddl: better comment

Signed-off-by: xhe <xw897002528@gmail.com>
pingcap · May 18, 2021 · 3354e2e · 3354e2e
1 parent 79fb48c
commit 3354e2e
Showing 1 changed file with 5 additions and 2 deletions.
diff --git a/ddl/placement/bundle.go b/ddl/placement/bundle.go
@@ -143,7 +143,10 @@ func (b *Bundle) Tidy() error {
  if err != nil {
  return err
  }
- // added -engine=tiflash, and it is the only constraint
+ // Constraints.Add() will automatically avoid duplication
+ // if -engine=tiflash is added and there is only one constraint
+ // then it must be -engine=tiflash
+ // it is seen as an empty constraint, so merge it
  if len(rule.Constraints) == 1 {
  extraCnt[rule.Role] += rule.Count
  continue
@@ -152,7 +155,7 @@ func (b *Bundle) Tidy() error {
  newRules = append(newRules, rule)
  }
  for role, cnt := range extraCnt {
- // refer to tidb#22065.
+ // add -engine=tiflash, refer to tidb#22065.
  newRules = append(newRules, &Rule{
  ID: string(role),
  Role: role,