static int vdbeMergeEngineInit(
  SortSubtask *pTask,             /* Thread that will run pMerger */
  MergeEngine *pMerger,           /* MergeEngine to initialize */
  int eMode                       /* One of the INCRINIT_XXX constants */
){
  int rc = SQLITE_OK;             /* Return code */
  int i;                          /* For looping over PmaReader objects */
  int nTree = pMerger->nTree;





  /* eMode is always INCRINIT_NORMAL in single-threaded mode */
  assert( SQLITE_MAX_WORKER_THREADS>0 || eMode==INCRINIT_NORMAL );

  /* Verify that the MergeEngine is assigned to a single thread */
  assert( pMerger->pTask==0 );
  pMerger->pTask = pTask;


  for(i=0; i<nTree; i++){
    if( SQLITE_MAX_WORKER_THREADS>0 && eMode==INCRINIT_ROOT ){
      /* PmaReaders should be normally initialized in order, as if they are
      ** reading from the same temp file this makes for more linear file IO.
      ** However, in the INCRINIT_ROOT case, if PmaReader aReadr[nTask-1] is
      ** in use it will block the vdbePmaReaderNext() call while it uses
      ** the main thread to fill its buffer. So calling PmaReaderNext()

static int vdbeMergeEngineInit(
  SortSubtask *pTask,             /* Thread that will run pMerger */
  MergeEngine *pMerger,           /* MergeEngine to initialize */
  int eMode                       /* One of the INCRINIT_XXX constants */
){
  int rc = SQLITE_OK;             /* Return code */
  int i;                          /* For looping over PmaReader objects */
  int nTree;                      /* Number of subtrees to merge */

  /* Failure to allocate the merge would have been detected prior to
  ** invoking this routine */
  assert( pMerger!=0 );

  /* eMode is always INCRINIT_NORMAL in single-threaded mode */
  assert( SQLITE_MAX_WORKER_THREADS>0 || eMode==INCRINIT_NORMAL );

  /* Verify that the MergeEngine is assigned to a single thread */
  assert( pMerger->pTask==0 );
  pMerger->pTask = pTask;

  nTree = pMerger->nTree;
  for(i=0; i<nTree; i++){
    if( SQLITE_MAX_WORKER_THREADS>0 && eMode==INCRINIT_ROOT ){
      /* PmaReaders should be normally initialized in order, as if they are
      ** reading from the same temp file this makes for more linear file IO.
      ** However, in the INCRINIT_ROOT case, if PmaReader aReadr[nTask-1] is
      ** in use it will block the vdbePmaReaderNext() call while it uses
      ** the main thread to fill its buffer. So calling PmaReaderNext()