code: func MutRowFromTypes(types []*types.FieldType) MutRow {
  	c := &Chunk{columns: make([]*column, 0, len(types))}
  	for _, tp := range types {
  		col := makeMutRowColumn(zeroValForType(tp))
  		c.columns = append(c.columns, col)
  	}
  	return MutRow{c: c, idx: 0}
  }
docs: // MutRowFromTypes creates a MutRow from a FieldType slice, each column is initialized to zero value.