func shallowCopyColumn(colDest, colSrc *expression.Column) *expression.Column { colDest.Correlated = colSrc.Correlated colDest.FromID = colSrc.FromID colDest.Position = colSrc.Position colDest.ID = colSrc.ID colDest.IsAggOrSubq = colSrc.IsAggOrSubq colDest.RetType = colSrc.RetType return colDest }