pIncr->pTask->file2.iEof -= pIncr->mxSz;
  }
}

#define INCRINIT2_NORMAL 0
#define INCRINIT2_TASK   1
#define INCRINIT2_ROOT   2
static int vdbeIncrInit2(PmaReader *pIter, int eMode);

/*
** Initialize the merger argument passed as the second argument. Once this
** function returns, the first key of merged data may be read from the merger
** object in the usual fashion.
**
** If argument eMode is INCRINIT2_ROOT, then it is assumed that any IncrMerge
................................................................................
** objects attached to the PmaReader objects that the merger reads from have
** already been populated, but that they have not yet populated aFile[0] and
** set the PmaReader objects up to read from it. In this case all that is
** required is to call vdbePmaReaderNext() on each iterator to point it at
** its first key.
**
** Otherwise, if eMode is any value other than INCRINIT2_ROOT, then use 
** vdbeIncrInit2() to initialize each PmaReader that feeds data to pMerger.

**
** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
*/
static int vdbeIncrInitMerger(
  SortSubtask *pTask, 
  MergeEngine *pMerger, 
  int eMode                       /* One of the INCRINIT2_XXX constants */
................................................................................
  int rc = SQLITE_OK;             /* Return code */
  int i;                          /* For iterating through PmaReader objects */

  for(i=0; rc==SQLITE_OK && i<pMerger->nTree; i++){
    if( eMode==INCRINIT2_ROOT ){
      rc = vdbePmaReaderNext(&pMerger->aIter[i]);
    }else{
      rc = vdbeIncrInit2(&pMerger->aIter[i], INCRINIT2_NORMAL);
    }
  }

  for(i=pMerger->nTree-1; rc==SQLITE_OK && i>0; i--){
    rc = vdbeSorterDoCompare(pTask, pMerger, i);
  }

  return rc;
}

static int vdbeIncrInit2(PmaReader *pIter, int eMode){
  int rc = SQLITE_OK;
  IncrMerger *pIncr = pIter->pIncr;
  if( pIncr ){
    SortSubtask *pTask = pIncr->pTask;
    sqlite3 *db = pTask->pSorter->db;

    rc = vdbeIncrInitMerger(pTask, pIncr->pMerger, eMode);
................................................................................
    }
  }
  return rc;
}

#if SQLITE_MAX_WORKER_THREADS>0
/*

** The main routine for vdbeIncrInit2() operations run in background threads.
*/
static void *vdbeIncrInit2Thread(void *pCtx){
  PmaReader *pReader = (PmaReader*)pCtx;
  void *pRet = SQLITE_INT_TO_PTR( vdbeIncrInit2(pReader, INCRINIT2_TASK) );
  pReader->pIncr->pTask->bDone = 1;
  return pRet;
}

/*
** Use a background thread to invoke vdbeIncrInit2(INCRINIT2_TASK) on the
** the PmaReader object passed as the first argument.
**
** This call will initialize the various fields of the pIter->pIncr 
** structure and, if it is a multi-threaded IncrMerger, launch a 
** background thread to populate aFile[1].
*/
static int vdbeIncrBgInit2(PmaReader *pIter){
  void *pCtx = (void*)pIter;
  return vdbeSorterCreateThread(pIter->pIncr->pTask, vdbeIncrInit2Thread, pCtx);
}
#endif

/*
** Allocate a new MergeEngine object to merge the contents of nPMA level-0
** PMAs from pTask->file. If no error occurs, set *ppOut to point to
** the new object and return SQLITE_OK. Or, if an error does occur, set *ppOut
................................................................................
    pMain = 0;
  }
  *ppOut = pMain;
  return rc;
}

/*
** Populate iterator *pIter so that it may be used to iterate through all 
** keys stored in all PMAs created by this sorter.





*/
static int vdbePmaReaderIncrInit(VdbeSorter *pSorter){
  int rc;                         /* Return code */
  SortSubtask *pTask0 = &pSorter->aTask[0];
  MergeEngine *pMain = 0;
  sqlite3 *db = pTask0->pSorter->db;
  int iTask;

  rc = vdbeSorterMergeTreeBuild(pSorter, &pMain);
................................................................................
              assert( pIncr->pTask!=pLast );
            }
          }
          if( pSorter->nTask>1 ){
            for(iTask=0; rc==SQLITE_OK && iTask<pSorter->nTask; iTask++){
              PmaReader *p = &pMain->aIter[iTask];
              assert( p->pIncr==0 || p->pIncr->pTask==&pSorter->aTask[iTask] );
              if( p->pIncr ){ rc = vdbeIncrBgInit2(p); }
            }
          }
        }
        pMain = 0;
      }
      if( rc==SQLITE_OK ){
        int eMode = (pSorter->nTask>1 ? INCRINIT2_ROOT : INCRINIT2_NORMAL);
        rc = vdbeIncrInit2(pIter, eMode);
      }
    }else
#endif
    {
      rc = vdbeIncrInitMerger(pTask0, pMain, INCRINIT2_NORMAL);
      pSorter->pMerger = pMain;
      pMain = 0;
................................................................................

  vdbeSorterRewindDebug(db, "rewind");

  /* Assuming no errors have occurred, set up a merger structure to 
  ** incrementally read and merge all remaining PMAs.  */
  assert( pSorter->pReader==0 );
  if( rc==SQLITE_OK ){
    rc = vdbePmaReaderIncrInit(pSorter);
    *pbEof = 0;
  }

  vdbeSorterRewindDebug(db, "rewinddone");
  return rc;
}

    pIncr->pTask->file2.iEof -= pIncr->mxSz;
  }
}

#define INCRINIT2_NORMAL 0
#define INCRINIT2_TASK   1
#define INCRINIT2_ROOT   2
static int vdbePmaReaderIncrInit(PmaReader *pIter, int eMode);

/*
** Initialize the merger argument passed as the second argument. Once this
** function returns, the first key of merged data may be read from the merger
** object in the usual fashion.
**
** If argument eMode is INCRINIT2_ROOT, then it is assumed that any IncrMerge
................................................................................
** objects attached to the PmaReader objects that the merger reads from have
** already been populated, but that they have not yet populated aFile[0] and
** set the PmaReader objects up to read from it. In this case all that is
** required is to call vdbePmaReaderNext() on each iterator to point it at
** its first key.
**
** Otherwise, if eMode is any value other than INCRINIT2_ROOT, then use 
** vdbePmaReaderIncrInit() to initialize each PmaReader that feeds data 
** to pMerger.
**
** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
*/
static int vdbeIncrInitMerger(
  SortSubtask *pTask, 
  MergeEngine *pMerger, 
  int eMode                       /* One of the INCRINIT2_XXX constants */
................................................................................
  int rc = SQLITE_OK;             /* Return code */
  int i;                          /* For iterating through PmaReader objects */

  for(i=0; rc==SQLITE_OK && i<pMerger->nTree; i++){
    if( eMode==INCRINIT2_ROOT ){
      rc = vdbePmaReaderNext(&pMerger->aIter[i]);
    }else{
      rc = vdbePmaReaderIncrInit(&pMerger->aIter[i], INCRINIT2_NORMAL);
    }
  }

  for(i=pMerger->nTree-1; rc==SQLITE_OK && i>0; i--){
    rc = vdbeSorterDoCompare(pTask, pMerger, i);
  }

  return rc;
}

static int vdbePmaReaderIncrInit(PmaReader *pIter, int eMode){
  int rc = SQLITE_OK;
  IncrMerger *pIncr = pIter->pIncr;
  if( pIncr ){
    SortSubtask *pTask = pIncr->pTask;
    sqlite3 *db = pTask->pSorter->db;

    rc = vdbeIncrInitMerger(pTask, pIncr->pMerger, eMode);
................................................................................
    }
  }
  return rc;
}

#if SQLITE_MAX_WORKER_THREADS>0
/*
** The main routine for vdbePmaReaderIncrInit() operations run in 
** background threads.
*/
static void *vdbePmaReaderBgInit(void *pCtx){
  PmaReader *pReader = (PmaReader*)pCtx;
  void *pRet = SQLITE_INT_TO_PTR(vdbePmaReaderIncrInit(pReader,INCRINIT2_TASK));
  pReader->pIncr->pTask->bDone = 1;
  return pRet;
}

/*
** Use a background thread to invoke vdbePmaReaderIncrInit(INCRINIT2_TASK) 
** on the the PmaReader object passed as the first argument.
**
** This call will initialize the various fields of the pIter->pIncr 
** structure and, if it is a multi-threaded IncrMerger, launch a 
** background thread to populate aFile[1].
*/
static int vdbePmaReaderBgIncrInit(PmaReader *pIter){
  void *pCtx = (void*)pIter;
  return vdbeSorterCreateThread(pIter->pIncr->pTask, vdbePmaReaderBgInit, pCtx);
}
#endif

/*
** Allocate a new MergeEngine object to merge the contents of nPMA level-0
** PMAs from pTask->file. If no error occurs, set *ppOut to point to
** the new object and return SQLITE_OK. Or, if an error does occur, set *ppOut
................................................................................
    pMain = 0;
  }
  *ppOut = pMain;
  return rc;
}

/*
** This function is called as part of an sqlite3VdbeSorterRewind() operation
** on a sorter that has written two or more PMAs to temporary files. It sets
** up either VdbeSorter.pMerger (for single threaded sorters) or pReader
** (for multi-threaded sorters) so that it can be used to iterate through
** all records stored in the sorter.
**
** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
*/
static int vdbeSorterSetupMerge(VdbeSorter *pSorter){
  int rc;                         /* Return code */
  SortSubtask *pTask0 = &pSorter->aTask[0];
  MergeEngine *pMain = 0;
  sqlite3 *db = pTask0->pSorter->db;
  int iTask;

  rc = vdbeSorterMergeTreeBuild(pSorter, &pMain);
................................................................................
              assert( pIncr->pTask!=pLast );
            }
          }
          if( pSorter->nTask>1 ){
            for(iTask=0; rc==SQLITE_OK && iTask<pSorter->nTask; iTask++){
              PmaReader *p = &pMain->aIter[iTask];
              assert( p->pIncr==0 || p->pIncr->pTask==&pSorter->aTask[iTask] );
              if( p->pIncr ){ rc = vdbePmaReaderBgIncrInit(p); }
            }
          }
        }
        pMain = 0;
      }
      if( rc==SQLITE_OK ){
        int eMode = (pSorter->nTask>1 ? INCRINIT2_ROOT : INCRINIT2_NORMAL);
        rc = vdbePmaReaderIncrInit(pIter, eMode);
      }
    }else
#endif
    {
      rc = vdbeIncrInitMerger(pTask0, pMain, INCRINIT2_NORMAL);
      pSorter->pMerger = pMain;
      pMain = 0;
................................................................................

  vdbeSorterRewindDebug(db, "rewind");

  /* Assuming no errors have occurred, set up a merger structure to 
  ** incrementally read and merge all remaining PMAs.  */
  assert( pSorter->pReader==0 );
  if( rc==SQLITE_OK ){
    rc = vdbeSorterSetupMerge(pSorter);
    *pbEof = 0;
  }

  vdbeSorterRewindDebug(db, "rewinddone");
  return rc;
}