kbmmemtable sorton 报错： List index out of bounds

zhqian 2019-03-08 原文

同一数据集，不同的排序条件，有的可以，但某一条件，却能100%重现报错。

procedure TkbmIndex.InternalFastQuickSort(const L,R:Integer);
var
   I,J:integer;
   P:PkbmRecord;
begin
     if ((R-L)>4) then
//     if ((R-L)>0) then
     begin
          I:=(R+L) div 2;
          if CompareRecords(FIndexFieldList,PkbmRecord(FReferences[L]),PkbmRecord(FReferences[I]),true,false)>0 then
           InternalSwap(L,I);
          if CompareRecords(FIndexFieldList,PkbmRecord(FReferences[L]),PkbmRecord(FReferences[R]),true,false)>0 then
           InternalSwap(L,R);
          if CompareRecords(FIndexFieldList,PkbmRecord(FReferences[I]),PkbmRecord(FReferences[R]),true,false)>0 then
           InternalSwap(I,R);

          J:=R-1;
          InternalSwap(I,J);
          I:=L;
          P:=PkbmRecord(FReferences[J]);
          while true do
          begin
               Inc(I);
               Dec(J);
               while CompareRecords(FIndexFieldList,PkbmRecord(FReferences[I]),P,true,false) < 0 do Inc(I);
               while CompareRecords(FIndexFieldList,PkbmRecord(FReferences[J]),P,true,false) > 0 do Dec(J);
               if (J<I) then break;
               InternalSwap(I,J);
          end;
          InternalSwap(I,R-1);
          InternalFastQuickSort(L,J);
          InternalFastQuickSort(I+1,R);
     end;
end;

　反复跟代码，发现在 kbmMemTable.PAS中，当J减至0时，FReferences[J] 下标越界

试改为FIndexFieldList.Count>0前判断条件却未解决，说明并非是递减原因，改为大于J，未报错，是否有问题，待应用中再关注。

procedure TkbmIndex.InternalFastQuickSort(const L,R:Integer);
var
   I,J:integer;
   P:PkbmRecord;
begin
     if ((R-L)>4) then
//     if ((R-L)>0) then
     begin
          I:=(R+L) div 2;
          if CompareRecords(FIndexFieldList,PkbmRecord(FReferences[L]),PkbmRecord(FReferences[I]),true,false)>0 then
           InternalSwap(L,I);
          if CompareRecords(FIndexFieldList,PkbmRecord(FReferences[L]),PkbmRecord(FReferences[R]),true,false)>0 then
           InternalSwap(L,R);
          if CompareRecords(FIndexFieldList,PkbmRecord(FReferences[I]),PkbmRecord(FReferences[R]),true,false)>0 then
           InternalSwap(I,R);

          J:=R-1;
          InternalSwap(I,J);
          I:=L;
          P:=PkbmRecord(FReferences[J]);
          while true do
          begin
               Inc(I);
               Dec(J);
               while CompareRecords(FIndexFieldList,PkbmRecord(FReferences[I]),P,true,false) < 0 do Inc(I);
               while  (FIndexFieldList.Count>J )and (CompareRecords(FIndexFieldList,PkbmRecord(FReferences[J]),P,true,false) > 0) do Dec(J);
               if (J<I) then break;
               InternalSwap(I,J);
          end;
          InternalSwap(I,R-1);
          InternalFastQuickSort(L,J);
          InternalFastQuickSort(I+1,R);
     end;
end;