SQLite

      if( (pCur->curFlags & BTCF_AtLast)!=0 ){
        *pRes = -1;
        return SQLITE_OK;
      }
      /* If the requested key is one more than the previous key, then
      ** try to get there using sqlite3BtreeNext() rather than a full
      ** binary search.  This is an optimization only.  The correct answer
      ** is still obtained without this ase, only a little more slowely */
      if( pCur->info.nKey+1==intKey && !pCur->skipNext ){
        *pRes = 0;
        rc = sqlite3BtreeNext(pCur, pRes);
        if( rc ) return rc;
        if( *pRes==0 ){
          getCellInfo(pCur);
          if( pCur->info.nKey==intKey ){
            return SQLITE_OK;
          }




        }
      }
    }
  }

  if( pIdxKey ){
    xRecordCompare = sqlite3VdbeFindCompare(pIdxKey);

  for(n=1, i=0; i<=pCur->iPage; i++){
    n *= pCur->apPage[i]->nCell;
  }
  return n;
}

/*
** Advance the cursor to the next entry in the database.  If


** successful then set *pRes=0.  If the cursor
** was already pointing to the last entry in the database before
** this routine was called, then set *pRes=1.

**
** The main entry point is sqlite3BtreeNext().  That routine is optimized
** for the common case of merely incrementing the cell counter BtCursor.aiIdx
** to the next cell on the current page.  The (slower) btreeNext() helper
** routine is called when it is necessary to move to a different page or
** to restore the cursor.
**
** The calling function will set *pRes to 0 or 1.  The initial *pRes value
** will be 1 if the cursor being stepped corresponds to an SQL index and
** if this routine could have been skipped if that SQL index had been
** a unique index.  Otherwise the caller will have set *pRes to zero.
** Zero is the common case. The btree implementation is free to use the
** initial *pRes value as a hint to improve performance, but the current
** SQLite btree implementation does not. (Note that the comdb2 btree
** implementation does use this hint, however.)
*/
static SQLITE_NOINLINE int btreeNext(BtCursor *pCur, int *pRes){
  int rc;
  int idx;
  MemPage *pPage;

  assert( cursorOwnsBtShared(pCur) );
  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
  assert( *pRes==0 );
  if( pCur->eState!=CURSOR_VALID ){
    assert( (pCur->curFlags & BTCF_ValidOvfl)==0 );
    rc = restoreCursorPosition(pCur);
    if( rc!=SQLITE_OK ){
      return rc;
    }
    if( CURSOR_INVALID==pCur->eState ){
      *pRes = 1;
      return SQLITE_OK;
    }
    if( pCur->skipNext ){
      assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_SKIPNEXT );
      pCur->eState = CURSOR_VALID;
      if( pCur->skipNext>0 ){
        pCur->skipNext = 0;
        return SQLITE_OK;

    if( !pPage->leaf ){
      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
      if( rc ) return rc;
      return moveToLeftmost(pCur);
    }
    do{
      if( pCur->iPage==0 ){
        *pRes = 1;
        pCur->eState = CURSOR_INVALID;
        return SQLITE_OK;
      }
      moveToParent(pCur);
      pPage = pCur->apPage[pCur->iPage];
    }while( pCur->ix>=pPage->nCell );
    if( pPage->intKey ){
      return sqlite3BtreeNext(pCur, pRes);
    }else{
      return SQLITE_OK;
    }
  }
  if( pPage->leaf ){
    return SQLITE_OK;
  }else{
    return moveToLeftmost(pCur);
  }
}
int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
  MemPage *pPage;
  assert( cursorOwnsBtShared(pCur) );
  assert( pRes!=0 );
  assert( *pRes==0 || *pRes==1 );
  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
  pCur->info.nSize = 0;
  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
  *pRes = 0;
  if( pCur->eState!=CURSOR_VALID ) return btreeNext(pCur, pRes);
  pPage = pCur->apPage[pCur->iPage];
  if( (++pCur->ix)>=pPage->nCell ){
    pCur->ix--;
    return btreeNext(pCur, pRes);
  }
  if( pPage->leaf ){
    return SQLITE_OK;
  }else{
    return moveToLeftmost(pCur);
  }
}

/*
** Step the cursor to the back to the previous entry in the database.  If


** successful then set *pRes=0.  If the cursor
** was already pointing to the first entry in the database before
** this routine was called, then set *pRes=1.

**
** The main entry point is sqlite3BtreePrevious().  That routine is optimized
** for the common case of merely decrementing the cell counter BtCursor.aiIdx
** to the previous cell on the current page.  The (slower) btreePrevious()
** helper routine is called when it is necessary to move to a different page
** or to restore the cursor.
**
** The calling function will set *pRes to 0 or 1.  The initial *pRes value
** will be 1 if the cursor being stepped corresponds to an SQL index and
** if this routine could have been skipped if that SQL index had been
** a unique index.  Otherwise the caller will have set *pRes to zero.
** Zero is the common case. The btree implementation is free to use the
** initial *pRes value as a hint to improve performance, but the current
** SQLite btree implementation does not. (Note that the comdb2 btree
** implementation does use this hint, however.)
*/
static SQLITE_NOINLINE int btreePrevious(BtCursor *pCur, int *pRes){
  int rc;
  MemPage *pPage;

  assert( cursorOwnsBtShared(pCur) );
  assert( pRes!=0 );
  assert( *pRes==0 );
  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
  assert( (pCur->curFlags & (BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey))==0 );
  assert( pCur->info.nSize==0 );
  if( pCur->eState!=CURSOR_VALID ){
    rc = restoreCursorPosition(pCur);
    if( rc!=SQLITE_OK ){
      return rc;
    }
    if( CURSOR_INVALID==pCur->eState ){
      *pRes = 1;
      return SQLITE_OK;
    }
    if( pCur->skipNext ){
      assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_SKIPNEXT );
      pCur->eState = CURSOR_VALID;
      if( pCur->skipNext<0 ){
        pCur->skipNext = 0;
        return SQLITE_OK;

    rc = moveToChild(pCur, get4byte(findCell(pPage, idx)));
    if( rc ) return rc;
    rc = moveToRightmost(pCur);
  }else{
    while( pCur->ix==0 ){
      if( pCur->iPage==0 ){
        pCur->eState = CURSOR_INVALID;
        *pRes = 1;
        return SQLITE_OK;
      }
      moveToParent(pCur);
    }
    assert( pCur->info.nSize==0 );
    assert( (pCur->curFlags & (BTCF_ValidOvfl))==0 );

    pCur->ix--;
    pPage = pCur->apPage[pCur->iPage];
    if( pPage->intKey && !pPage->leaf ){
      rc = sqlite3BtreePrevious(pCur, pRes);
    }else{
      rc = SQLITE_OK;
    }
  }
  return rc;
}
int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
  assert( cursorOwnsBtShared(pCur) );
  assert( pRes!=0 );
  assert( *pRes==0 || *pRes==1 );
  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
  *pRes = 0;
  pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey);
  pCur->info.nSize = 0;
  if( pCur->eState!=CURSOR_VALID
   || pCur->ix==0
   || pCur->apPage[pCur->iPage]->leaf==0
  ){
    return btreePrevious(pCur, pRes);
  }
  pCur->ix--;
  return SQLITE_OK;
}

/*
** Allocate a new page from the database file.

  ** the cursor to the largest entry in the tree that is smaller than
  ** the entry being deleted. This cell will replace the cell being deleted
  ** from the internal node. The 'previous' entry is used for this instead
  ** of the 'next' entry, as the previous entry is always a part of the
  ** sub-tree headed by the child page of the cell being deleted. This makes
  ** balancing the tree following the delete operation easier.  */
  if( !pPage->leaf ){
    int notUsed = 0;
    rc = sqlite3BtreePrevious(pCur, &notUsed);

    if( rc ) return rc;
  }

  /* Save the positions of any other cursors open on this table before
  ** making any modifications.  */
  if( pCur->curFlags & BTCF_Multiple ){
    rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);

  int nZero;              /* Extra zero data appended after pData,nData */
};

int sqlite3BtreeInsert(BtCursor*, const BtreePayload *pPayload,
                       int flags, int seekResult);
int sqlite3BtreeFirst(BtCursor*, int *pRes);
int sqlite3BtreeLast(BtCursor*, int *pRes);
int sqlite3BtreeNext(BtCursor*, int *pRes);
int sqlite3BtreeEof(BtCursor*);
int sqlite3BtreePrevious(BtCursor*, int *pRes);
i64 sqlite3BtreeIntegerKey(BtCursor*);
int sqlite3BtreePayload(BtCursor*, u32 offset, u32 amt, void*);
const void *sqlite3BtreePayloadFetch(BtCursor*, u32 *pAmt);
u32 sqlite3BtreePayloadSize(BtCursor*);

char *sqlite3BtreeIntegrityCheck(Btree*, int *aRoot, int nRoot, int, int*);
struct Pager *sqlite3BtreePager(Btree*);

  if( argc!=2 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
       " ID\"", 0);
    return TCL_ERROR;
  }
  pCur = sqlite3TestTextToPtr(argv[1]);
  sqlite3BtreeEnter(pCur->pBtree);
  rc = sqlite3BtreeNext(pCur, &res);




  sqlite3BtreeLeave(pCur->pBtree);
  if( rc ){
    Tcl_AppendResult(interp, sqlite3ErrName(rc), 0);
    return TCL_ERROR;
  }
  sqlite3_snprintf(sizeof(zBuf),zBuf,"%d",res);
  Tcl_AppendResult(interp, zBuf, 0);

  int rc = SQLITE_OK;        /* Value to return */
  sqlite3 *db = p->db;       /* The database */
  u8 resetSchemaOnFault = 0; /* Reset schema after an error if positive */
  u8 encoding = ENC(db);     /* The database encoding */
  int iCompare = 0;          /* Result of last comparison */
  unsigned nVmStep = 0;      /* Number of virtual machine steps */
#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
  unsigned nProgressLimit = 0;/* Invoke xProgress() when nVmStep reaches this */
#endif
  Mem *aMem = p->aMem;       /* Copy of p->aMem */
  Mem *pIn1 = 0;             /* 1st input operand */
  Mem *pIn2 = 0;             /* 2nd input operand */
  Mem *pIn3 = 0;             /* 3rd input operand */
  Mem *pOut = 0;             /* Output operand */
#ifdef VDBE_PROFILE

  if( db->u1.isInterrupted ) goto abort_due_to_interrupt;
  sqlite3VdbeIOTraceSql(p);
#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
  if( db->xProgress ){
    u32 iPrior = p->aCounter[SQLITE_STMTSTATUS_VM_STEP];
    assert( 0 < db->nProgressOps );
    nProgressLimit = db->nProgressOps - (iPrior % db->nProgressOps);


  }
#endif
#ifdef SQLITE_DEBUG
  sqlite3BeginBenignMalloc();
  if( p->pc==0
   && (p->db->flags & (SQLITE_VdbeListing|SQLITE_VdbeEQP|SQLITE_VdbeTrace))!=0
  ){

#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
  /* Call the progress callback if it is configured and the required number
  ** of VDBE ops have been executed (either since this invocation of
  ** sqlite3VdbeExec() or since last time the progress callback was called).
  ** If the progress callback returns non-zero, exit the virtual machine with
  ** a return code SQLITE_ABORT.
  */
  if( db->xProgress!=0 && nVmStep>=nProgressLimit ){
    assert( db->nProgressOps!=0 );
    nProgressLimit = nVmStep + db->nProgressOps - (nVmStep%db->nProgressOps);
    if( db->xProgress(db->pProgressArg) ){
      rc = SQLITE_INTERRUPT;
      goto abort_due_to_error;
    }
  }

  assert( pOp->p1>0 );
  assert( pOp->p1+pOp->p2<=(p->nMem+1 - p->nCursor)+1 );

#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
  /* Run the progress counter just before returning.
  */
  if( db->xProgress!=0
   && nVmStep>=nProgressLimit
   && db->xProgress(db->pProgressArg)!=0
  ){
    rc = SQLITE_INTERRUPT;
    goto abort_due_to_error;
  }
#endif

  pC->cacheStatus = CACHE_STALE;
#ifdef SQLITE_TEST
  sqlite3_search_count++;
#endif
  if( oc>=OP_SeekGE ){  assert( oc==OP_SeekGE || oc==OP_SeekGT );
    if( res<0 || (res==0 && oc==OP_SeekGT) ){
      res = 0;
      rc = sqlite3BtreeNext(pC->uc.pCursor, &res);
      if( rc!=SQLITE_OK ) goto abort_due_to_error;







    }else{
      res = 0;
    }
  }else{
    assert( oc==OP_SeekLT || oc==OP_SeekLE );
    if( res>0 || (res==0 && oc==OP_SeekLT) ){
      res = 0;
      rc = sqlite3BtreePrevious(pC->uc.pCursor, &res);
      if( rc!=SQLITE_OK ) goto abort_due_to_error;







    }else{
      /* res might be negative because the table is empty.  Check to
      ** see if this is the case.
      */
      res = sqlite3BtreeEof(pC->uc.pCursor);
    }
  }

** This opcode works just like OP_Next except that P1 must be a
** sorter object for which the OP_SorterSort opcode has been
** invoked.  This opcode advances the cursor to the next sorted
** record, or jumps to P2 if there are no more sorted records.
*/
case OP_SorterNext: {  /* jump */
  VdbeCursor *pC;
  int res;

  pC = p->apCsr[pOp->p1];
  assert( isSorter(pC) );
  res = 0;
  rc = sqlite3VdbeSorterNext(db, pC, &res);
  goto next_tail;
case OP_PrevIfOpen:    /* jump */
case OP_NextIfOpen:    /* jump */
  if( p->apCsr[pOp->p1]==0 ) break;
  /* Fall through */
case OP_Prev:          /* jump */
case OP_Next:          /* jump */
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  assert( pOp->p5<ArraySize(p->aCounter) );
  pC = p->apCsr[pOp->p1];
  res = pOp->p3;
  assert( pC!=0 );
  assert( pC->deferredMoveto==0 );
  assert( pC->eCurType==CURTYPE_BTREE );
  assert( res==0 || (res==1 && pC->isTable==0) );
  testcase( res==1 );
  assert( pOp->opcode!=OP_Next || pOp->p4.xAdvance==sqlite3BtreeNext );
  assert( pOp->opcode!=OP_Prev || pOp->p4.xAdvance==sqlite3BtreePrevious );
  assert( pOp->opcode!=OP_NextIfOpen || pOp->p4.xAdvance==sqlite3BtreeNext );
  assert( pOp->opcode!=OP_PrevIfOpen || pOp->p4.xAdvance==sqlite3BtreePrevious);

  /* The Next opcode is only used after SeekGT, SeekGE, and Rewind.
  ** The Prev opcode is only used after SeekLT, SeekLE, and Last. */
  assert( pOp->opcode!=OP_Next || pOp->opcode!=OP_NextIfOpen
       || pC->seekOp==OP_SeekGT || pC->seekOp==OP_SeekGE
       || pC->seekOp==OP_Rewind || pC->seekOp==OP_Found);
  assert( pOp->opcode!=OP_Prev || pOp->opcode!=OP_PrevIfOpen
       || pC->seekOp==OP_SeekLT || pC->seekOp==OP_SeekLE
       || pC->seekOp==OP_Last );

  rc = pOp->p4.xAdvance(pC->uc.pCursor, &res);
next_tail:
  pC->cacheStatus = CACHE_STALE;
  VdbeBranchTaken(res==0,2);
  if( rc ) goto abort_due_to_error;
  if( res==0 ){
    pC->nullRow = 0;
    p->aCounter[pOp->p5]++;
#ifdef SQLITE_TEST
    sqlite3_search_count++;
#endif
    goto jump_to_p2_and_check_for_interrupt;
  }else{
    pC->nullRow = 1;
  }



  goto check_for_interrupt;
}

/* Opcode: IdxInsert P1 P2 P3 P4 P5
** Synopsis: key=r[P2]
**
** Register P2 holds an SQL index key made using the

    KeyInfo *pKeyInfo;     /* Used when p4type is P4_KEYINFO */
    int *ai;               /* Used when p4type is P4_INTARRAY */
    SubProgram *pProgram;  /* Used when p4type is P4_SUBPROGRAM */
    Table *pTab;           /* Used when p4type is P4_TABLE */
#ifdef SQLITE_ENABLE_CURSOR_HINTS
    Expr *pExpr;           /* Used when p4type is P4_EXPR */
#endif
    int (*xAdvance)(BtCursor *, int *);
  } p4;
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
  char *zComment;          /* Comment to improve readability */
#endif
#ifdef VDBE_PROFILE
  u32 cnt;                 /* Number of times this instruction was executed */
  u64 cycles;              /* Total time spent executing this instruction */

#endif
int sqlite3VdbeTransferError(Vdbe *p);

int sqlite3VdbeSorterInit(sqlite3 *, int, VdbeCursor *);
void sqlite3VdbeSorterReset(sqlite3 *, VdbeSorter *);
void sqlite3VdbeSorterClose(sqlite3 *, VdbeCursor *);
int sqlite3VdbeSorterRowkey(const VdbeCursor *, Mem *);
int sqlite3VdbeSorterNext(sqlite3 *, const VdbeCursor *, int *);
int sqlite3VdbeSorterRewind(const VdbeCursor *, int *);
int sqlite3VdbeSorterWrite(const VdbeCursor *, Mem *);
int sqlite3VdbeSorterCompare(const VdbeCursor *, Mem *, int, int *);

#if !defined(SQLITE_OMIT_SHARED_CACHE) 
  void sqlite3VdbeEnter(Vdbe*);
#else

  }

  vdbeSorterRewindDebug("rewinddone");
  return rc;
}

/*
** Advance to the next element in the sorter.




*/
int sqlite3VdbeSorterNext(sqlite3 *db, const VdbeCursor *pCsr, int *pbEof){
  VdbeSorter *pSorter;
  int rc;                         /* Return code */

  assert( pCsr->eCurType==CURTYPE_SORTER );
  pSorter = pCsr->uc.pSorter;
  assert( pSorter->bUsePMA || (pSorter->pReader==0 && pSorter->pMerger==0) );
  if( pSorter->bUsePMA ){
    assert( pSorter->pReader==0 || pSorter->pMerger==0 );
    assert( pSorter->bUseThreads==0 || pSorter->pReader );
    assert( pSorter->bUseThreads==1 || pSorter->pMerger );
#if SQLITE_MAX_WORKER_THREADS>0
    if( pSorter->bUseThreads ){
      rc = vdbePmaReaderNext(pSorter->pReader);
      *pbEof = (pSorter->pReader->pFd==0);
    }else
#endif
    /*if( !pSorter->bUseThreads )*/ {

      assert( pSorter->pMerger!=0 );
      assert( pSorter->pMerger->pTask==(&pSorter->aTask[0]) );
      rc = vdbeMergeEngineStep(pSorter->pMerger, pbEof);

    }
  }else{
    SorterRecord *pFree = pSorter->list.pList;
    pSorter->list.pList = pFree->u.pNext;
    pFree->u.pNext = 0;
    if( pSorter->list.aMemory==0 ) vdbeSorterRecordFree(db, pFree);
    *pbEof = !pSorter->list.pList;
    rc = SQLITE_OK;
  }
  return rc;
}

/*
** Return a pointer to a buffer owned by the sorter that contains the 
** current key.