Insert into the same table inside the filtered range of a FindSet loop can cause infinite loops

[christophstuber]

Sorry for the title :)

This might be more of an edge case, but has happened to me personally.

Consider the following example:

The table MyTable has a field Status, which differentiates "New" from "Old" records. For each record, the "Value" is recalculated, saved into a new record and the previous version is set to "Old". The problem is, that depending on the key, the newly inserted records come after the initially found records and are therefore found by the Next(). This causes an infinite loop.

local procedure MyProcedure()
var
  MyTable1, MyTable2: Record MyTable;
begin
  MyTable1.SetRange(Status, Status::New);
  if MyTable1.FindSet(true) then
    repeat
      MyTable2.Init();
      MyTable2.Validate(Status, Status::New);
      MyTable2.Validate(Value, GetNewValue());
      MyTable2.Insert(true);
      MyTable1.Validate(Status, Status::Old);
      MyTable1.Modify(true);
    until MyTable1.Next() = 0;
end;

The easiest solution is to first save the found records to a temporary buffer, because that is not influenced by the inserts.

local procedure MyProcedure()
var
  MyTable1, MyTable2: Record MyTable;
  TempMyTable: Record MyTable temporary;
begin
  MyTable1.SetRange(Status, Status::New);
  if MyTable1.FindSet(true) then
    repeat
      TempMyTable := MyTable;
      TempMyTable.Insert(false);
      MyTable1.Validate(Status, Status::Old);
      MyTable1.Modify(true);
    until MyTable1.Next() = 0;

  if TempMyTable.FindSet() then
    repeat
      MyTable2.Init();
      MyTable2.Validate(Status, Status::New);
      MyTable2.Validate(Value, GetNewValue());
      MyTable2.Insert(true);
    until TempMyTable.Next() = 0;
end;

Therefore there should be a warning, if the Insert method is used inside a FindSet loop, where both the records used for FindSet and Insert are the same table and both of them are not temporary.