** to zero.  But it turns out that the apPage[] and aiIdx[] arrays
** do not need to be zeroed and they are large, so we can save a lot
** of run-time by skipping the initialization of those elements.
*/
void sqlite3BtreeCursorZero(BtCursor *p){
  memset(p, 0, offsetof(BtCursor, iPage));
}

/*
** Return the Btree object associated with a BtCursor.
*/
Btree *sqlite3BtreeOfCursor(BtCursor *p){
  assert( p!=0 );
  return p->pBtree;
}

/*
** Close a cursor.  The read lock on the database file is released
** when the last cursor is closed.
*/
int sqlite3BtreeCloseCursor(BtCursor *pCur){
  Btree *pBtree = pCur->pBtree;

  int wrFlag,                          /* 1 for writing.  0 for read-only */
  struct KeyInfo*,                     /* First argument to compare function */
  BtCursor *pCursor                    /* Space to write cursor structure */
);
int sqlite3BtreeCursorSize(void);
void sqlite3BtreeCursorZero(BtCursor*);
void sqlite3BtreeCursorHintFlags(BtCursor*, unsigned);
Btree *sqlite3BtreeOfCursor(BtCursor*);
#ifdef SQLITE_ENABLE_CURSOR_HINTS
void sqlite3BtreeCursorHint(BtCursor*, int, ...);
#endif

int sqlite3BtreeCloseCursor(BtCursor*);
int sqlite3BtreeMovetoUnpacked(
  BtCursor*,

** by this opcode will be used for automatically created transient
** indices in joins.
*/
case OP_OpenAutoindex: 
case OP_OpenEphemeral: {
  VdbeCursor *pCx;
  KeyInfo *pKeyInfo;
  Btree *pBt;

  static const int vfsFlags = 
      SQLITE_OPEN_READWRITE |
      SQLITE_OPEN_CREATE |
      SQLITE_OPEN_EXCLUSIVE |
      SQLITE_OPEN_DELETEONCLOSE |
      SQLITE_OPEN_TRANSIENT_DB;
  assert( pOp->p1>=0 );
  assert( pOp->p2>=0 );
  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, CURTYPE_BTREE);
  if( pCx==0 ) goto no_mem;
  pCx->nullRow = 1;

  rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pBt, 
                        BTREE_OMIT_JOURNAL | BTREE_SINGLE | pOp->p5, vfsFlags);
  if( rc==SQLITE_OK ){
    rc = sqlite3BtreeBeginTrans(pBt, 1);

    if( rc==SQLITE_OK ){
      /* If a transient index is required, create it by calling
      ** sqlite3BtreeCreateTable() with the BTREE_BLOBKEY flag before
      ** opening it. If a transient table is required, just use the
      ** automatically created table with root-page 1 (an BLOB_INTKEY table).
      */
      if( (pKeyInfo = pOp->p4.pKeyInfo)!=0 ){
        int pgno;
        assert( pOp->p4type==P4_KEYINFO );
        rc = sqlite3BtreeCreateTable(pBt, &pgno, BTREE_BLOBKEY | pOp->p5); 
        if( rc==SQLITE_OK ){
          assert( pgno==MASTER_ROOT+1 );
          assert( pKeyInfo->db==db );
          assert( pKeyInfo->enc==ENC(db) );
          pCx->pKeyInfo = pKeyInfo;
          rc = sqlite3BtreeCursor(pBt, pgno, BTREE_WRCSR,
                                  pKeyInfo, pCx->uc.pCursor);
        }
        pCx->isTable = 0;
      }else{
        rc = sqlite3BtreeCursor(pBt, MASTER_ROOT, BTREE_WRCSR,
                                0, pCx->uc.pCursor);
        pCx->isTable = 1;
      }
    }
    if( rc==SQLITE_OK ){
      pCx->isEphemeral = 1;
    }else{
      sqlite3BtreeClose(pBt);
    }
  }
  pCx->isOrdered = (pOp->p5!=BTREE_UNORDERED);
  break;
}

/* Opcode: SorterOpen P1 P2 P3 P4 *

** the sequence value.
*/
case OP_SequenceTest: {
  VdbeCursor *pC;
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( isSorter(pC) );
  assert( !pC->movetoUsed );
  if( (pC->ux.seqCount++)==0 ){
    goto jump_to_p2;
  }
  break;
}

/* Opcode: OpenPseudo P1 P2 P3 * *
** Synopsis: P3 columns in r[P2]

        assert( OP_SeekLE==(OP_SeekLT+1) );
        assert( OP_SeekGT==(OP_SeekGE+1) );
        assert( (OP_SeekLT & 0x0001)==(OP_SeekGE & 0x0001) );
        if( (oc & 0x0001)==(OP_SeekLT & 0x0001) ) oc++;
      }
    } 
    rc = sqlite3BtreeMovetoUnpacked(pC->uc.pCursor, 0, (u64)iKey, 0, &res);
    VVA_ONLY( pC->movetoUsed = 1; )
    pC->ux.movetoTarget = iKey;  /* Used by OP_Delete */
    if( rc!=SQLITE_OK ){
      goto abort_due_to_error;
    }
  }else{
    /* For a cursor with the BTREE_SEEK_EQ hint, only the OP_SeekGE and
    ** OP_SeekLE opcodes are allowed, and these must be immediately followed
    ** by an OP_IdxGT or OP_IdxLT opcode, respectively, with the same key.

case OP_Seek: {    /* in2 */
  VdbeCursor *pC;

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->eCurType==CURTYPE_BTREE );
  assert( !pC->isEphemeral );
  assert( pC->uc.pCursor!=0 );
  assert( pC->isTable );
  pC->nullRow = 0;
  pIn2 = &aMem[pOp->p2];
  VVA_ONLY( pC->movetoUsed = 1; )
  pC->ux.movetoTarget = sqlite3VdbeIntValue(pIn2);
  pC->deferredMoveto = 1;
  break;
}
  

/* Opcode: Found P1 P2 P3 P4 *
** Synopsis: key=r[P3@P4]

  assert( pC->eCurType==CURTYPE_BTREE );
  pCrsr = pC->uc.pCursor;
  assert( pCrsr!=0 );
  res = 0;
  iKey = pIn3->u.i;
  rc = sqlite3BtreeMovetoUnpacked(pCrsr, 0, iKey, 0, &res);
  assert( rc==SQLITE_OK || res==0 );
  VVA_ONLY( pC->movetoUsed = 1; )
  pC->ux.movetoTarget = iKey;  /* Used by OP_Delete */
  pC->nullRow = 0;
  pC->cacheStatus = CACHE_STALE;
  pC->deferredMoveto = 0;
  VdbeBranchTaken(res!=0,2);
  pC->seekResult = res;
  if( res!=0 ){
    assert( rc==SQLITE_OK );

** Write the sequence number into register P2.
** The sequence number on the cursor is incremented after this
** instruction.  
*/
case OP_Sequence: {           /* out2 */
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  assert( p->apCsr[pOp->p1]!=0 );
  assert( p->apCsr[pOp->p1]->eCurType==CURTYPE_BTREE );
  assert( p->apCsr[pOp->p1]->isEphemeral );
  assert( !p->apCsr[pOp->p1]->movetoUsed );
  pOut = out2Prerelease(p, pOp);
  pOut->u.i = p->apCsr[pOp->p1]->ux.seqCount++;
  break;
}


/* Opcode: NewRowid P1 P2 P3 * *
** Synopsis: r[P2]=rowid
**

  assert( pC!=0 );
  assert( pC->eCurType==CURTYPE_BTREE );
  assert( pC->uc.pCursor!=0 );
  assert( pC->deferredMoveto==0 );

  hasUpdateCallback = db->xUpdateCallback && pOp->p4.z && pC->isTable;
  if( pOp->p5 && hasUpdateCallback ){
    sqlite3BtreeKeySize(pC->uc.pCursor, &pC->ux.movetoTarget);
  }

#ifdef SQLITE_DEBUG
  /* The seek operation that positioned the cursor prior to OP_Delete will
  ** have also set the pC->ux.movetoTarget field to the rowid of the row that
  ** is being deleted */
  if( pOp->p4.z && pC->isTable && pOp->p5==0 ){
    i64 iKey = 0;
    sqlite3BtreeKeySize(pC->uc.pCursor, &iKey);
    assert( pC->ux.movetoTarget==iKey ); 
  }
#endif
 
  rc = sqlite3BtreeDelete(pC->uc.pCursor, pOp->p5);
  pC->cacheStatus = CACHE_STALE;

  /* Invoke the update-hook if required. */
  if( rc==SQLITE_OK && hasUpdateCallback ){
    db->xUpdateCallback(db->pUpdateArg, SQLITE_DELETE,
                        db->aDb[pC->iDb].zName, pOp->p4.z, pC->ux.movetoTarget);
    assert( pC->iDb>=0 );
  }
  if( pOp->p2 & OPFLAG_NCHANGE ) p->nChange++;
  break;
}
/* Opcode: ResetCount * * * * *
**

  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->eCurType!=CURTYPE_PSEUDO || pC->nullRow );
  if( pC->nullRow ){
    pOut->flags = MEM_Null;
    break;
  }else if( pC->deferredMoveto ){
    v = pC->ux.movetoTarget;
#ifndef SQLITE_OMIT_VIRTUALTABLE
  }else if( pC->eCurType==CURTYPE_VTAB ){
    assert( pC->uc.pVCur!=0 );
    pVtab = pC->uc.pVCur->pVtab;
    pModule = pVtab->pModule;
    assert( pModule->xRowid );
    rc = pModule->xRowid(pC->uc.pVCur, &v);

**      * A sorter
**      * A virtual table
**      * A one-row "pseudotable" stored in a single register
*/
struct VdbeCursor {
  u8 eCurType;          /* One of the CURTYPE_* values above */
  i8 iDb;               /* Index of cursor database in db->aDb[] (or -1) */



#ifdef SQLITE_DEBUG
  u8 seekOp;            /* Most recent seek operation on this cursor */
  Bool movetoUsed:1;    /* True if ux.movetoTarget has been used */
#endif
  Bool nullRow:1;        /* True if pointing to a row with no data */
  Bool deferredMoveto:1; /* A call to sqlite3BtreeMoveto() is needed */
  Bool isTable:1;        /* True for rowid tables.  False for indexes */
  Bool isEphemeral:1;   /* True for an ephemeral table */
  Bool useRandomRowid:1;/* Generate new record numbers semi-randomly */
  Bool isOrdered:1;     /* True if the underlying table is BTREE_UNORDERED */
  Pgno pgnoRoot;        /* Root page of the open btree cursor */
  int seekResult;       /* Result of previous sqlite3BtreeMoveto() */
  i16 nField;           /* Number of fields in the header */
  u16 nHdrParsed;       /* Number of header fields parsed so far */
  union {
    BtCursor *pCursor;          /* CURTYPE_BTREE.  Btree cursor */
    sqlite3_vtab_cursor *pVCur; /* CURTYPE_VTAB.   Vtab cursor */
    int pseudoTableReg;         /* CURTYPE_PSEUDO. Reg holding content. */
    VdbeSorter *pSorter;        /* CURTYPE_SORTER. Sorter object */
  } uc;

  KeyInfo *pKeyInfo;    /* Info about index keys needed by index cursors */

  union {
    i64 seqCount;         /* Sequence counter.  Only valid if movetoUsed==0 */
    i64 movetoTarget;     /* Rowid moved to. */
  } ux;
#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
  u64 maskUsed;         /* Mask of columns used by this cursor */
#endif

  /* Cached information about the header for the data record that the
  ** cursor is currently pointing to.  Only valid if cacheStatus matches
  ** Vdbe.cacheCtr.  Vdbe.cacheCtr will never take on the value of

** Close a VDBE cursor and release all the resources that cursor 
** happens to hold.
*/
void sqlite3VdbeFreeCursor(Vdbe *p, VdbeCursor *pCx){
  if( pCx==0 ){
    return;
  }
  assert( pCx->isEphemeral==0 || pCx->eCurType==CURTYPE_BTREE );
  switch( pCx->eCurType ){
    case CURTYPE_SORTER: {
      sqlite3VdbeSorterClose(p->db, pCx);
      break;
    }
    case CURTYPE_BTREE: {
      assert( pCx->uc.pCursor!=0 );
      if( pCx->isEphemeral ){
        sqlite3BtreeClose(sqlite3BtreeOfCursor(pCx->uc.pCursor));
        /* The pCx->pCursor will be close automatically, if it exists, by
        ** the call above. */
      }else{

        sqlite3BtreeCloseCursor(pCx->uc.pCursor);
      }
      break;
    }
#ifndef SQLITE_OMIT_VIRTUALTABLE
    case CURTYPE_VTAB: {
      sqlite3_vtab_cursor *pVCur = pCx->uc.pVCur;

  int res, rc;
#ifdef SQLITE_TEST
  extern int sqlite3_search_count;
#endif
  assert( p->deferredMoveto );
  assert( p->isTable );
  assert( p->eCurType==CURTYPE_BTREE );
  assert( !p->isEphemeral );
  assert( p->movetoUsed );
  rc = sqlite3BtreeMovetoUnpacked(p->uc.pCursor, 0, p->ux.movetoTarget, 0,&res);
  if( rc ) return rc;
  if( res!=0 ) return SQLITE_CORRUPT_BKPT;
#ifdef SQLITE_TEST
  sqlite3_search_count++;
#endif
  p->deferredMoveto = 0;
  p->cacheStatus = CACHE_STALE;

  ** to exceed the maximum merge count */
#if SQLITE_MAX_WORKER_THREADS>=SORTER_MAX_MERGE_COUNT
  if( nWorker>=SORTER_MAX_MERGE_COUNT ){
    nWorker = SORTER_MAX_MERGE_COUNT-1;
  }
#endif

  assert( pCsr->pKeyInfo && !pCsr->isEphemeral );
  assert( pCsr->eCurType==CURTYPE_SORTER );
  szKeyInfo = sizeof(KeyInfo) + (pCsr->pKeyInfo->nField-1)*sizeof(CollSeq*);
  sz = sizeof(VdbeSorter) + nWorker * sizeof(SortSubtask);

  pSorter = (VdbeSorter*)sqlite3DbMallocZero(db, sz + szKeyInfo);
  pCsr->uc.pSorter = pSorter;
  if( pSorter==0 ){