SQLite

  if( SQLITE_OK==sqlite3VdbeMemGrow(pMem, nByte, 0) ){
    p->apCsr[iCur] = pCx = (VdbeCursor*)pMem->z;
    memset(pCx, 0, sizeof(VdbeCursor));
    pCx->iDb = iDb;
    pCx->nField = nField;
    if( nField ){
      pCx->aType = (u32 *)&pMem->z[ROUND8(sizeof(VdbeCursor))];
      pCx->aOffset = pCx->aType + nField;
    }
    if( isBtreeCursor ){
      pCx->pCursor = (BtCursor*)
          &pMem->z[ROUND8(sizeof(VdbeCursor))+(2*nField+2)*sizeof(u32)];
      sqlite3BtreeCursorZero(pCx->pCursor);
    }
  }

  pDest = &aMem[pOp->p3];
  memAboutToChange(p, pDest);
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( p2<pC->nField );
  aType = pC->aType;
  aOffset = pC->aOffset;
#ifndef SQLITE_OMIT_VIRTUALTABLE
  assert( pC->pVtabCursor==0 ); /* OP_Column never called on virtual table */
#endif
  pCrsr = pC->pCursor;
  assert( pCrsr!=0 || pC->pseudoTableReg>0 ); /* pCrsr NULL on PseudoTables */
  assert( pCrsr!=0 || pC->nullRow );          /* pC->nullRow on PseudoTables */

        pC->aRow = (u8*)pReg->z;
      }else{
        MemSetTypeFlag(pDest, MEM_Null);
        goto op_column_out;
      }
    }else{
      assert( pCrsr );
      if( pC->isIndex ){
        assert( sqlite3BtreeCursorIsValid(pCrsr) );
        VVA_ONLY(rc =) sqlite3BtreeKeySize(pCrsr, &payloadSize64);
        assert( rc==SQLITE_OK ); /* True because of CursorMoveto() call above */
        /* sqlite3BtreeParseCellPtr() uses getVarint32() to extract the
        ** payload size, so it is impossible for payloadSize64 to be
        ** larger than 32 bits. */
        assert( (payloadSize64 & SQLITE_MAX_U32)==(u64)payloadSize64 );

    /* If there is more header available for parsing in the record, try
    ** to extract additional fields up through the p2+1-th field 
    */
    if( pC->iHdrOffset<aOffset[0] ){
      /* Make sure zData points to enough of the record to cover the header. */
      if( pC->aRow==0 ){
        memset(&sMem, 0, sizeof(sMem));
        rc = sqlite3VdbeMemFromBtree(pCrsr, 0, pC->aOffset[0], pC->isIndex,
                                     &sMem);
        if( rc!=SQLITE_OK ){
          goto op_column_error;
        }
        zData = (u8*)sMem.z;
      }else{
        zData = pC->aRow;
      }

      ** will work for everything else.  Content is also irrelevant if
      ** the content length is 0. */
      zData = t<=13 ? (u8*)&payloadSize64 : 0;
      sMem.zMalloc = 0;
    }else{
      memset(&sMem, 0, sizeof(sMem));
      sqlite3VdbeMemMove(&sMem, pDest);
      rc = sqlite3VdbeMemFromBtree(pCrsr, aOffset[p2], len,  pC->isIndex,
                                   &sMem);
      if( rc!=SQLITE_OK ){
        goto op_column_error;
      }
      zData = (u8*)sMem.z;
    }
    sqlite3VdbeSerialGet(zData, t, pDest);

  assert( OPFLAG_BULKCSR==BTREE_BULKLOAD );
  sqlite3BtreeCursorHints(pCur->pCursor, (pOp->p5 & OPFLAG_BULKCSR));

  /* Since it performs no memory allocation or IO, the only value that
  ** sqlite3BtreeCursor() may return is SQLITE_OK. */
  assert( rc==SQLITE_OK );

  /* Set the VdbeCursor.isTable and isIndex variables. Previous versions of
  ** SQLite used to check if the root-page flags were sane at this point
  ** and report database corruption if they were not, but this check has
  ** since moved into the btree layer.  */  
  pCur->isTable = pOp->p4type!=P4_KEYINFO;
  pCur->isIndex = !pCur->isTable;
  break;
}

/* Opcode: OpenEphemeral P1 P2 * P4 P5
** Synopsis: nColumn=P2
**
** Open a new cursor P1 to a transient table.

      pCx->isTable = 0;
    }else{
      rc = sqlite3BtreeCursor(pCx->pBt, MASTER_ROOT, 1, 0, pCx->pCursor);
      pCx->isTable = 1;
    }
  }
  pCx->isOrdered = (pOp->p5!=BTREE_UNORDERED);
  pCx->isIndex = !pCx->isTable;
  break;
}

/* Opcode: SorterOpen P1 * * P4 *
**
** This opcode works like OP_OpenEphemeral except that it opens
** a transient index that is specifically designed to sort large
** tables using an external merge-sort algorithm.
*/
case OP_SorterOpen: {
  VdbeCursor *pCx;

  assert( pOp->p1>=0 );
  assert( pOp->p2>=0 );
  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, 1);
  if( pCx==0 ) goto no_mem;
  pCx->pKeyInfo = pOp->p4.pKeyInfo;
  assert( pCx->pKeyInfo->db==db );
  assert( pCx->pKeyInfo->enc==ENC(db) );
  pCx->isSorter = 1;
  rc = sqlite3VdbeSorterInit(db, pCx);
  break;
}

/* Opcode: OpenPseudo P1 P2 P3 * P5
** Synopsis: content in r[P2@P3]
**

  assert( pOp->p1>=0 );
  assert( pOp->p3>=0 );
  pCx = allocateCursor(p, pOp->p1, pOp->p3, -1, 0);
  if( pCx==0 ) goto no_mem;
  pCx->nullRow = 1;
  pCx->pseudoTableReg = pOp->p2;
  pCx->isTable = 1;
  pCx->isIndex = 0;
  pCx->multiPseudo = pOp->p5;
  break;
}

/* Opcode: Close P1 * * * *
**
** Close a cursor previously opened as P1.  If P1 is not

  rc = sqlite3BtreeMovetoUnpacked(pC->pCursor, pIdxKey, 0, 0, &res);
  if( pOp->p4.i==0 ){
    sqlite3DbFree(db, pFree);
  }
  if( rc!=SQLITE_OK ){
    break;
  }
  pC->seekResult = res;
  alreadyExists = (res==0);
  pC->nullRow = 1-alreadyExists;
  pC->deferredMoveto = 0;
  pC->cacheStatus = CACHE_STALE;
  if( pOp->opcode==OP_Found ){
    if( alreadyExists ) pc = pOp->p2 - 1;
  }else{

  pC->nullRow = 0;
  pC->cacheStatus = CACHE_STALE;
  pC->deferredMoveto = 0;
  if( res!=0 ){
    pc = pOp->p2 - 1;
    assert( pC->rowidIsValid==0 );
  }
  pC->seekResult = res;
  break;
}

/* Opcode: Sequence P1 P2 * * *
** Synopsis: r[P2]=rowid
**
** Find the next available sequence number for cursor P1.

case OP_Insert: 
case OP_InsertInt: {
  Mem *pData;       /* MEM cell holding data for the record to be inserted */
  Mem *pKey;        /* MEM cell holding key  for the record */
  i64 iKey;         /* The integer ROWID or key for the record to be inserted */
  VdbeCursor *pC;   /* Cursor to table into which insert is written */
  int nZero;        /* Number of zero-bytes to append */
  int seekResult;   /* Result of prior seek or 0 if no USESEEKRESULT flag */
  const char *zDb;  /* database name - used by the update hook */
  const char *zTbl; /* Table name - used by the opdate hook */
  int op;           /* Opcode for update hook: SQLITE_UPDATE or SQLITE_INSERT */

  pData = &aMem[pOp->p2];
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  assert( memIsValid(pData) );

** Write into register P2 the current sorter data for sorter cursor P1.
*/
case OP_SorterData: {
  VdbeCursor *pC;

  pOut = &aMem[pOp->p2];
  pC = p->apCsr[pOp->p1];
  assert( pC->isSorter );
  rc = sqlite3VdbeSorterRowkey(pC, pOut);
  break;
}

/* Opcode: RowData P1 P2 * * *
** Synopsis: r[P2]=data
**

  pOut = &aMem[pOp->p2];
  memAboutToChange(p, pOut);

  /* Note that RowKey and RowData are really exactly the same instruction */
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC->isSorter==0 );
  assert( pC->isTable || pOp->opcode!=OP_RowData );
  assert( pC->isIndex || pOp->opcode==OP_RowData );
  assert( pC!=0 );
  assert( pC->nullRow==0 );
  assert( pC->pseudoTableReg==0 );
  assert( pC->pCursor!=0 );
  pCrsr = pC->pCursor;
  assert( sqlite3BtreeCursorIsValid(pCrsr) );

  /* The OP_RowKey and OP_RowData opcodes always follow OP_NotExists or
  ** OP_Rewind/Op_Next with no intervening instructions that might invalidate
  ** the cursor.  Hence the following sqlite3VdbeCursorMoveto() call is always
  ** a no-op and can never fail.  But we leave it in place as a safety.
  */
  assert( pC->deferredMoveto==0 );
  rc = sqlite3VdbeCursorMoveto(pC);
  if( NEVER(rc!=SQLITE_OK) ) goto abort_due_to_error;

  if( pC->isIndex ){
    assert( !pC->isTable );
    VVA_ONLY(rc =) sqlite3BtreeKeySize(pCrsr, &n64);
    assert( rc==SQLITE_OK );    /* True because of CursorMoveto() call above */
    if( n64>db->aLimit[SQLITE_LIMIT_LENGTH] ){
      goto too_big;
    }
    n = (u32)n64;
  }else{
    VVA_ONLY(rc =) sqlite3BtreeDataSize(pCrsr, &n);
    assert( rc==SQLITE_OK );    /* DataSize() cannot fail */
    if( n>(u32)db->aLimit[SQLITE_LIMIT_LENGTH] ){
      goto too_big;
    }
  }
  if( sqlite3VdbeMemGrow(pOut, n, 0) ){
    goto no_mem;
  }
  pOut->n = n;
  MemSetTypeFlag(pOut, MEM_Blob);
  if( pC->isIndex ){
    rc = sqlite3BtreeKey(pCrsr, 0, n, pOut->z);
  }else{
    rc = sqlite3BtreeData(pCrsr, 0, n, pOut->z);
  }
  pOut->enc = SQLITE_UTF8;  /* In case the blob is ever cast to text */
  UPDATE_MAX_BLOBSIZE(pOut);
  REGISTER_TRACE(pOp->p2, pOut);

  VdbeCursor *pC;
  BtCursor *pCrsr;
  int res;

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->isSorter==(pOp->opcode==OP_SorterSort) );
  res = 1;
  if( isSorter(pC) ){
    rc = sqlite3VdbeSorterRewind(db, pC, &res);
  }else{
    pCrsr = pC->pCursor;
    assert( pCrsr );
    rc = sqlite3BtreeFirst(pCrsr, &res);

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  assert( pOp->p5<ArraySize(p->aCounter) );
  pC = p->apCsr[pOp->p1];
  if( pC==0 ){
    break;  /* See ticket #2273 */
  }
  assert( pC->isSorter==(pOp->opcode==OP_SorterNext) );
  if( isSorter(pC) ){
    assert( pOp->opcode==OP_SorterNext );
    rc = sqlite3VdbeSorterNext(db, pC, &res);
  }else{
    /* res = 1; // Always initialized by the xAdvance() call */
    assert( pC->deferredMoveto==0 );
    assert( pC->pCursor );

  BtCursor *pCrsr;
  int nKey;
  const char *zKey;

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->isSorter==(pOp->opcode==OP_SorterInsert) );
  pIn2 = &aMem[pOp->p2];
  assert( pIn2->flags & MEM_Blob );
  pCrsr = pC->pCursor;
  if( pOp->p5 & OPFLAG_NCHANGE ) p->nChange++;
  assert( pCrsr!=0 );
  assert( pC->isTable==0 );
  rc = ExpandBlob(pIn2);

** of the following structure.
*/
typedef struct VdbeOp Op;

/*
** Boolean values
*/
typedef unsigned char Bool;

/* Opaque type used by code in vdbesort.c */
typedef struct VdbeSorter VdbeSorter;

/* Opaque type used by the explainer */
typedef struct Explain Explain;

*/
struct VdbeCursor {
  BtCursor *pCursor;    /* The cursor structure of the backend */
  Btree *pBt;           /* Separate file holding temporary table */
  KeyInfo *pKeyInfo;    /* Info about index keys needed by index cursors */
  int pseudoTableReg;   /* Register holding pseudotable content. */
  i16 nField;           /* Number of fields in the header */

  i8 iDb;               /* Index of cursor database in db->aDb[] (or -1) */


  Bool rowidIsValid;    /* True if lastRowid is valid */
  Bool useRandomRowid;  /* Generate new record numbers semi-randomly */
  Bool nullRow;         /* True if pointing to a row with no data */
  Bool deferredMoveto;  /* A call to sqlite3BtreeMoveto() is needed */
  Bool isTable;         /* True if a table requiring integer keys */
  Bool isIndex;         /* True if an index containing keys only - no data */
  Bool isOrdered;       /* True if the underlying table is BTREE_UNORDERED */
  Bool isSorter;        /* True if a new-style sorter */
  Bool multiPseudo;     /* Multi-register pseudo-cursor */
  sqlite3_vtab_cursor *pVtabCursor;  /* The cursor for a virtual table */
  const sqlite3_module *pModule;     /* Module for cursor pVtabCursor */
  i64 seqCount;         /* Sequence counter */
  i64 movetoTarget;     /* Argument to the deferred sqlite3BtreeMoveto() */
  i64 lastRowid;        /* Rowid being deleted by OP_Delete */
  VdbeSorter *pSorter;  /* Sorter object for OP_SorterOpen cursors */

  /* Result of last sqlite3BtreeMoveto() done by an OP_NotExists */
  int seekResult;

  /* 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
  ** CACHE_STALE and so setting cacheStatus=CACHE_STALE guarantees that
  ** the cache is out of date.
  **
  ** aRow might point to (ephemeral) data for the current row, or it might
  ** be NULL.
  */
  u32 cacheStatus;      /* Cache is valid if this matches Vdbe.cacheCtr */
  u32 payloadSize;      /* Total number of bytes in the record */
  u16 nHdrParsed;       /* Number of header fields parsed so far */
  u16 nFieldPresent;    /* Number of fields in the record */
  u32 szRow;            /* Byte available in aRow */
  u32 iHdrOffset;       /* Offset to next unparsed byte of the header */
  u32 *aType;           /* Type values for all entries in the record */
  u32 *aOffset;         /* Cached offsets to the start of each columns data */
  const u8 *aRow;       /* Data for the current row, if all on one page */
};
typedef struct VdbeCursor VdbeCursor;

/*
** When a sub-program is executed (OP_Program), a structure of this type
** is allocated to store the current value of the program counter, as

  ** triggering asserts related to mutexes.
  */
  assert( v->aVar[0].flags&MEM_Int );
  v->aVar[0].u.i = iRow;

  rc = sqlite3_step(p->pStmt);
  if( rc==SQLITE_ROW ){

    u32 type = v->apCsr[0]->aType[p->iCol];
    if( type<12 ){
      zErr = sqlite3MPrintf(p->db, "cannot open value of type %s",
          type==0?"null": type==7?"real": "integer"
      );
      rc = SQLITE_ERROR;
      sqlite3_finalize(p->pStmt);
      p->pStmt = 0;
    }else{
      p->iOffset = v->apCsr[0]->aOffset[p->iCol];
      p->nByte = sqlite3VdbeSerialTypeLen(type);
      p->pCsr =  v->apCsr[0]->pCursor;
      sqlite3BtreeEnterCursor(p->pCsr);
      sqlite3BtreeCacheOverflow(p->pCsr);
      sqlite3BtreeLeaveCursor(p->pCsr);
    }
  }

  if( rc==SQLITE_ROW ){