Update data.table.R

R/data.table.R

@@ -1336,7 +1336,11 @@ replace_dot_alias = function(e) {
 
     if (is.data.table(jval)) {
       setattr(jval, 'class', class(x)) # fix for #64
-      if (haskey(x) && all(key(x) %chin% names(jval)) && suppressWarnings(is.sorted(jval, by=key(x))))  # TO DO: perhaps this usage of is.sorted should be allowed internally then (tidy up and make efficient)
+      if (haskey(x) && 
+          all(key(x) == names(jval)) && ## order of names should matter for the key; %chin% wouldn't care about order!
+          ((is.null(irows) && jsub %iscall% "list" && all(vapply_1b(as.list(jsub)[-1L], is.name))) || ##fix for #4498
+           suppressWarnings(is.sorted(jval, by=key(x))))
+          )  # TO DO: perhaps this usage of is.sorted should be allowed internally then (tidy up and make efficient)
         setattr(jval, 'sorted', key(x))
       if (any(sapply(jval, is.null))) stop("Internal error: j has created a data.table result containing a NULL column") # nocov
     }