Hello,

I was reading through sqlite source code for educational purposes. And encountered something that I didn't quite understood. Maybe code or comment is incorrect. To demonstrate what I think the problem is I created this bitbucket project

https://bitbucket.org/tibonarium/list_move_to_end/src/master/

In the file build.c inside function sqlite3CreateIndex there is a comment "Ensure all REPLACE indexes are at the end of the list". But this implementation will not move all elements with property onError=OE_Replace to the end of the list.

if( pTab ){  /* Ensure all REPLACE indexes are at the end of the list */
  Index **ppFrom = &pTab->pIndex;
  Index *pThis;
  for(ppFrom=&pTab->pIndex; (pThis = *ppFrom)!=0; ppFrom=&pThis->pNext){
    Index *pNext;
    if( pThis->onError!=OE_Replace ) continue;
    while( (pNext = pThis->pNext)!=0 && pNext->onError!=OE_Replace ){
      *ppFrom = pNext;
      pThis->pNext = pNext->pNext;
      pNext->pNext = pThis;
      ppFrom = &pNext->pNext;
    }
    break;
  }
}

We can fix it this way

if( pTab ){  /* Ensure all REPLACE indexes are at the end of the list */
  Index **ppFrom = &pTab->pIndex;
  Index *pThis;
  for(ppFrom=&pTab->pIndex; (pThis = *ppFrom)!=0; ppFrom=&pThis->pNext){
    Index *pNext;
    Index *pTail = pThis;
    if( pThis->onError!=OE_Replace ) continue;
    while( (pNext = pThis->pNext)!=0 ){
      if (pNext->onError!=OE_Replace) {
        *ppFrom = pNext;
        pThis->pNext = pNext->pNext;
        pNext->pNext = pTail;
        ppFrom = &pNext->pNext;
      } else {
        pThis = pNext;
      }
    }
    break;
  }
}