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Overview
Comment:Detect when a VdbeCursor is still pointing at a valid row but that row has moved, and invalidated the return from prior sqlite3BtreeDataFetch() or sqlite3BtreeKeyFetch() calls.
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SHA1: e6798871ce94961135762669af418cd78540c121
User & Date: drh 2014-03-25 11:00:21
Context
2014-03-25
14:54
Add an ORDER BY test case to speedtest1.c check-in: 58812264 user: drh tags: trunk
13:17
Merge all fixes and enhancements from trunk. check-in: b415dfb6 user: drh tags: threads
11:00
Detect when a VdbeCursor is still pointing at a valid row but that row has moved, and invalidated the return from prior sqlite3BtreeDataFetch() or sqlite3BtreeKeyFetch() calls. check-in: e6798871 user: drh tags: trunk
2014-03-24
16:30
Remove unused variables Parse.nColCache and Parse.iColCache. check-in: 4d7551ce user: dan tags: trunk
Changes
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Changes to src/btree.c.

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/*
** Determine whether or not a cursor has moved from the position it
** was last placed at.  Cursors can move when the row they are pointing
** at is deleted out from under them.
**
** This routine returns an error code if something goes wrong.  The
** integer *pHasMoved is set to one if the cursor has moved and 0 if not.








*/
int sqlite3BtreeCursorHasMoved(BtCursor *pCur, int *pHasMoved){
  int rc;





  rc = restoreCursorPosition(pCur);
  if( rc ){
    *pHasMoved = 1;
    return rc;
  }
  if( pCur->eState!=CURSOR_VALID || NEVER(pCur->skipNext!=0) ){
    *pHasMoved = 1;
  }else{
    *pHasMoved = 0;
  }
  return SQLITE_OK;
}

#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Given a page number of a regular database page, return the page
................................................................................
  u32 *pAmt            /* Write the number of available bytes here */
){
  assert( pCur!=0 && pCur->iPage>=0 && pCur->apPage[pCur->iPage]);
  assert( pCur->eState==CURSOR_VALID );
  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );


  if( pCur->info.nSize==0 ){
    btreeParseCell(pCur->apPage[pCur->iPage], pCur->aiIdx[pCur->iPage],
                   &pCur->info);
  }

  *pAmt = pCur->info.nLocal;
  return (void*)(pCur->info.pCell + pCur->info.nHeader);
}


/*
** For the entry that cursor pCur is point to, return as







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/*
** Determine whether or not a cursor has moved from the position it
** was last placed at.  Cursors can move when the row they are pointing
** at is deleted out from under them.
**
** This routine returns an error code if something goes wrong.  The
** integer *pHasMoved is set as follows:
**
**    0:   The cursor is unchanged
**    1:   The cursor is still pointing at the same row, but the pointers
**         returned by sqlite3BtreeKeyFetch() or sqlite3BtreeDataFetch()
**         might now be invalid because of a balance() or other change to the
**         b-tree.
**    2:   The cursor is no longer pointing to the row.  The row might have
**         been deleted out from under the cursor.
*/
int sqlite3BtreeCursorHasMoved(BtCursor *pCur, int *pHasMoved){
  int rc;

  if( pCur->eState==CURSOR_VALID ){
    *pHasMoved = 0;
    return SQLITE_OK;
  }
  rc = restoreCursorPosition(pCur);
  if( rc ){
    *pHasMoved = 2;
    return rc;
  }
  if( pCur->eState!=CURSOR_VALID || NEVER(pCur->skipNext!=0) ){
    *pHasMoved = 2;
  }else{
    *pHasMoved = 1;
  }
  return SQLITE_OK;
}

#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Given a page number of a regular database page, return the page
................................................................................
  u32 *pAmt            /* Write the number of available bytes here */
){
  assert( pCur!=0 && pCur->iPage>=0 && pCur->apPage[pCur->iPage]);
  assert( pCur->eState==CURSOR_VALID );
  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
  assert( pCur->info.nSize>0 );
#if 0
  if( pCur->info.nSize==0 ){
    btreeParseCell(pCur->apPage[pCur->iPage], pCur->aiIdx[pCur->iPage],
                   &pCur->info);
  }
#endif
  *pAmt = pCur->info.nLocal;
  return (void*)(pCur->info.pCell + pCur->info.nHeader);
}


/*
** For the entry that cursor pCur is point to, return as

Changes to src/vdbeaux.c.

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    p->cacheStatus = CACHE_STALE;
  }else if( p->pCursor ){
    int hasMoved;
    int rc = sqlite3BtreeCursorHasMoved(p->pCursor, &hasMoved);
    if( rc ) return rc;
    if( hasMoved ){
      p->cacheStatus = CACHE_STALE;
      p->nullRow = 1;
    }
  }
  return SQLITE_OK;
}

/*
** The following functions:







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    p->cacheStatus = CACHE_STALE;
  }else if( p->pCursor ){
    int hasMoved;
    int rc = sqlite3BtreeCursorHasMoved(p->pCursor, &hasMoved);
    if( rc ) return rc;
    if( hasMoved ){
      p->cacheStatus = CACHE_STALE;
      if( hasMoved==2 ) p->nullRow = 1;
    }
  }
  return SQLITE_OK;
}

/*
** The following functions: