int iPrev = pMerger->aTree[1];/* Index of iterator to advance */
  int i;                        /* Index of aTree[] to recalculate */

  /* Advance the current iterator */
  rc = vdbeSorterIterNext(&pMerger->aIter[iPrev]);

  /* Update contents of aTree[] */












  for(i=(pMerger->nTree+iPrev)/2; rc==SQLITE_OK && i>0; i=i/2){







    rc = vdbeSorterDoCompare(pThread, pMerger, i);


  }


























  *pbEof = (pMerger->aIter[pMerger->aTree[1]].pFile==0);


  return rc;
}

/*
** The main routine for sorter-thread operations.
*/
static void *vdbeSorterThreadMain(void *pCtx){

  int iPrev = pMerger->aTree[1];/* Index of iterator to advance */
  int i;                        /* Index of aTree[] to recalculate */

  /* Advance the current iterator */
  rc = vdbeSorterIterNext(&pMerger->aIter[iPrev]);

  /* Update contents of aTree[] */
  if( rc==SQLITE_OK ){
    int i;                      /* Index of aTree[] to recalculate */
    VdbeSorterIter *pIter1;     /* First iterator to compare */
    VdbeSorterIter *pIter2;     /* Second iterator to compare */
    u8 *pKey2;                  /* To pIter2->aKey, or 0 if record cached */

    /* Find the first two iterators to compare. The one that was just
    ** advanced (iPrev) and the one next to it in the array.  */
    pIter1 = &pMerger->aIter[(iPrev & 0xFFFE)];
    pIter2 = &pMerger->aIter[(iPrev | 0x0001)];
    pKey2 = pIter2->aKey;

    for(i=(pMerger->nTree+iPrev)/2; i>0; i=i/2){
      /* Compare pIter1 and pIter2. Store the result in variable iRes. */
      int iRes;
      if( pIter1->pFile==0 ){
        iRes = +1;
      }else if( pIter2->pFile==0 ){
        iRes = -1;
      }else{
        vdbeSorterCompare(pThread, 0,
            pIter1->aKey, pIter1->nKey, pKey2, pIter2->nKey, &iRes
        );
      }

      /* If pIter1 contained the smaller value, set aTree[i] to its index.
      ** Then set pIter2 to the next iterator to compare to pIter1. In this
      ** case there is no cache of pIter2 in pThread->pUnpacked, so set
      ** pKey2 to point to the record belonging to pIter2.
      **
      ** Alternatively, if pIter2 contains the smaller of the two values,
      ** set aTree[i] to its index and update pIter1. If vdbeSorterCompare()
      ** was actually called above, then pThread->pUnpacked now contains
      ** a value equivalent to pIter2. So set pKey2 to NULL to prevent
      ** vdbeSorterCompare() from decoding pIter2 again.
      **
      ** If the two values were equal, then the value from the oldest
      ** PMA should be considered smaller. The VdbeSorter.aIter[] array
      ** is sorted from oldest to newest, so pIter1 contains older values
      ** than pIter2 iff (pIter1<pIter2).  */
      if( iRes<0 || (iRes==0 && pIter1<pIter2) ){
        pMerger->aTree[i] = (int)(pIter1 - pMerger->aIter);
        pIter2 = &pMerger->aIter[ pMerger->aTree[i ^ 0x0001] ];
        pKey2 = pIter2->aKey;
      }else{
        if( pIter1->pFile ) pKey2 = 0;
        pMerger->aTree[i] = (int)(pIter2 - pMerger->aIter);
        pIter1 = &pMerger->aIter[ pMerger->aTree[i ^ 0x0001] ];
      }
    }
    *pbEof = (pMerger->aIter[pMerger->aTree[1]].pFile==0);
  }

  return rc;
}

/*
** The main routine for sorter-thread operations.
*/
static void *vdbeSorterThreadMain(void *pCtx){