code: func isIgnorableSpec(tp ast.AlterTableType) bool {
  	// AlterTableLock/AlterTableAlgorithm are ignored.
  	return tp == ast.AlterTableLock || tp == ast.AlterTableAlgorithm
  }
docs: // isIgnorableSpec checks if the spec type is ignorable.
  // Some specs are parsed by ignored. This is for compatibility.