SQLite

    p->apCsr[iCur] = 0;
  }
  if( SQLITE_OK==sqlite3VdbeMemClearAndResize(pMem, nByte) ){
    p->apCsr[iCur] = pCx = (VdbeCursor*)pMem->z;
    memset(pCx, 0, sizeof(VdbeCursor));
    pCx->iDb = iDb;
    pCx->nField = nField;

    if( isBtreeCursor ){
      pCx->pCursor = (BtCursor*)
          &pMem->z[ROUND8(sizeof(VdbeCursor))+2*sizeof(u32)*nField];
      sqlite3BtreeCursorZero(pCx->pCursor);
    }
  }
  return pCx;

  assert( pOp->p3>0 && pOp->p3<=(p->nMem-p->nCursor) );
  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 );
  aOffset = pC->aType + pC->nField;
#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 */

    ** blob, or NULL.  But it needs to be an integer before we can do
    ** the seek, so convert it. */
    pIn3 = &aMem[pOp->p3];
    if( (pIn3->flags & (MEM_Int|MEM_Real|MEM_Str))==MEM_Str ){
      applyNumericAffinity(pIn3, 0);
    }
    iKey = sqlite3VdbeIntValue(pIn3);
    pC->rowidIsValid = 0;

    /* If the P3 value could not be converted into an integer without
    ** loss of information, then special processing is required... */
    if( (pIn3->flags & MEM_Int)==0 ){
      if( (pIn3->flags & MEM_Real)==0 ){
        /* If the P3 value cannot be converted into any kind of a number,
        ** then the seek is not possible, so jump to 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->pCursor, 0, (u64)iKey, 0, &res);

    if( rc!=SQLITE_OK ){
      goto abort_due_to_error;
    }
    if( res==0 ){
      pC->rowidIsValid = 1;
      pC->lastRowid = iKey;
    }
  }else{
    nField = pOp->p4.i;
    assert( pOp->p4type==P4_INT32 );
    assert( nField>0 );
    r.pKeyInfo = pC->pKeyInfo;
    r.nField = (u16)nField;

    { int i; for(i=0; i<r.nField; i++) assert( memIsValid(&r.aMem[i]) ); }
#endif
    ExpandBlob(r.aMem);
    rc = sqlite3BtreeMovetoUnpacked(pC->pCursor, &r, 0, 0, &res);
    if( rc!=SQLITE_OK ){
      goto abort_due_to_error;
    }
    pC->rowidIsValid = 0;
  }
  pC->deferredMoveto = 0;
  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->pCursor, &res);
      if( rc!=SQLITE_OK ) goto abort_due_to_error;
      pC->rowidIsValid = 0;
    }else{
      res = 0;
    }
  }else{
    assert( oc==OP_SeekLT || oc==OP_SeekLE );
    if( res>0 || (res==0 && oc==OP_SeekLT) ){
      res = 0;
      rc = sqlite3BtreePrevious(pC->pCursor, &res);
      if( rc!=SQLITE_OK ) goto abort_due_to_error;
      pC->rowidIsValid = 0;
    }else{
      /* res might be negative because the table is empty.  Check to
      ** see if this is the case.
      */
      res = sqlite3BtreeEof(pC->pCursor);
    }
  }

  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->pCursor!=0 );
  assert( pC->isTable );
  pC->nullRow = 0;
  pIn2 = &aMem[pOp->p2];
  pC->movetoTarget = sqlite3VdbeIntValue(pIn2);
  pC->rowidIsValid = 0;
  pC->deferredMoveto = 1;
  break;
}
  

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

  assert( pC->isTable );
  assert( pC->pseudoTableReg==0 );
  pCrsr = pC->pCursor;
  assert( pCrsr!=0 );
  res = 0;
  iKey = pIn3->u.i;
  rc = sqlite3BtreeMovetoUnpacked(pCrsr, 0, iKey, 0, &res);
  pC->lastRowid = pIn3->u.i;
  pC->rowidIsValid = res==0 ?1:0;
  pC->nullRow = 0;
  pC->cacheStatus = CACHE_STALE;
  pC->deferredMoveto = 0;
  VdbeBranchTaken(res!=0,2);
  if( res!=0 ){
    pc = pOp->p2 - 1;
    assert( pC->rowidIsValid==0 );
  }
  pC->seekResult = res;
  break;
}

/* Opcode: Sequence P1 P2 * * *
** Synopsis: r[P2]=cursor[P1].ctr++

            && (++cnt<100));
      if( rc==SQLITE_OK && res==0 ){
        rc = SQLITE_FULL;   /* IMP: R-38219-53002 */
        goto abort_due_to_error;
      }
      assert( v>0 );  /* EV: R-40812-03570 */
    }
    pC->rowidIsValid = 0;
    pC->deferredMoveto = 0;
    pC->cacheStatus = CACHE_STALE;
  }
  pOut->u.i = v;
  break;
}

  }else{
    nZero = 0;
  }
  rc = sqlite3BtreeInsert(pC->pCursor, 0, iKey,
                          pData->z, pData->n, nZero,
                          (pOp->p5 & OPFLAG_APPEND)!=0, seekResult
  );
  pC->rowidIsValid = 0;
  pC->deferredMoveto = 0;
  pC->cacheStatus = CACHE_STALE;

  /* Invoke the update-hook if required. */
  if( rc==SQLITE_OK && db->xUpdateCallback && pOp->p4.z ){
    zDb = db->aDb[pC->iDb].zName;
    zTbl = pOp->p4.z;

**
** If P4 is not NULL, then it is the name of the table that P1 is
** pointing to.  The update hook will be invoked, if it exists.
** If P4 is not NULL then the P1 cursor must have been positioned
** using OP_NotFound prior to invoking this opcode.
*/
case OP_Delete: {
  i64 iKey;
  VdbeCursor *pC;

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->pCursor!=0 );  /* Only valid for real tables, no pseudotables */
  iKey = pC->lastRowid;      /* Only used for the update hook */

  /* The OP_Delete opcode always follows an OP_NotExists or OP_Last or
  ** OP_Column on the same table without any intervening operations that
  ** might move or invalidate the cursor.  Hence cursor pC is always pointing
  ** to the row to be deleted and the sqlite3VdbeCursorMoveto() operation
  ** below is always a no-op and cannot fail.  We will run it anyhow, though,
  ** to guard against future changes to the code generator.
  **/

  assert( pC->deferredMoveto==0 );
  rc = sqlite3VdbeCursorMoveto(pC);

  if( NEVER(rc!=SQLITE_OK) ) goto abort_due_to_error;

  rc = sqlite3BtreeDelete(pC->pCursor);
  pC->cacheStatus = CACHE_STALE;

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

    rc = pModule->xRowid(pC->pVtabCursor, &v);
    sqlite3VtabImportErrmsg(p, pVtab);
#endif /* SQLITE_OMIT_VIRTUALTABLE */
  }else{
    assert( pC->pCursor!=0 );
    rc = sqlite3VdbeCursorMoveto(pC);
    if( rc ) goto abort_due_to_error;
    if( pC->rowidIsValid ){
      v = pC->lastRowid;
    }else{
      rc = sqlite3BtreeKeySize(pC->pCursor, &v);
      assert( rc==SQLITE_OK );  /* Always so because of CursorMoveto() above */
    }
  }
  pOut->u.i = v;
  break;
}

/* Opcode: NullRow P1 * * * *
**
** Move the cursor P1 to a null row.  Any OP_Column operations
** that occur while the cursor is on the null row will always
** write a NULL.
*/
case OP_NullRow: {
  VdbeCursor *pC;

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  pC->nullRow = 1;
  pC->rowidIsValid = 0;
  pC->cacheStatus = CACHE_STALE;
  if( pC->pCursor ){
    sqlite3BtreeClearCursor(pC->pCursor);
  }
  break;
}

  assert( pC!=0 );
  pCrsr = pC->pCursor;
  res = 0;
  assert( pCrsr!=0 );
  rc = sqlite3BtreeLast(pCrsr, &res);
  pC->nullRow = (u8)res;
  pC->deferredMoveto = 0;
  pC->rowidIsValid = 0;
  pC->cacheStatus = CACHE_STALE;
#ifdef SQLITE_DEBUG
  pC->seekOp = OP_Last;
#endif
  if( pOp->p2>0 ){
    VdbeBranchTaken(res!=0,2);
    if( res ) pc = pOp->p2 - 1;

    rc = sqlite3VdbeSorterRewind(pC, &res);
  }else{
    pCrsr = pC->pCursor;
    assert( pCrsr );
    rc = sqlite3BtreeFirst(pCrsr, &res);
    pC->deferredMoveto = 0;
    pC->cacheStatus = CACHE_STALE;
    pC->rowidIsValid = 0;
  }
  pC->nullRow = (u8)res;
  assert( pOp->p2>0 && pOp->p2<p->nOp );
  VdbeBranchTaken(res!=0,2);
  if( res ){
    pc = pOp->p2 - 1;
  }

    p->aCounter[pOp->p5]++;
#ifdef SQLITE_TEST
    sqlite3_search_count++;
#endif
  }else{
    pC->nullRow = 1;
  }
  pC->rowidIsValid = 0;
  goto check_for_interrupt;
}

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

  i16 nField;           /* Number of fields in the header */
  u16 nHdrParsed;       /* Number of header fields parsed so far */
#ifdef SQLITE_DEBUG
  u8 seekOp;            /* Most recent seek operation on this cursor */
#endif
  i8 iDb;               /* Index of cursor database in db->aDb[] (or -1) */
  u8 nullRow;           /* True if pointing to a row with no data */
  u8 rowidIsValid;      /* True if lastRowid is valid */
  u8 deferredMoveto;    /* A call to sqlite3BtreeMoveto() is needed */
  Bool isEphemeral:1;   /* True for an ephemeral table */
  Bool useRandomRowid:1;/* Generate new record numbers semi-randomly */
  Bool isTable:1;       /* True if a table requiring integer keys */
  Bool isOrdered:1;     /* True if the underlying table is BTREE_UNORDERED */
  Pgno pgnoRoot;        /* Root page of the open btree cursor */
  sqlite3_vtab_cursor *pVtabCursor;  /* The cursor for a virtual table */
  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 */

  /* 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 */
  u32 szRow;            /* Byte available in aRow */
  u32 iHdrOffset;       /* Offset to next unparsed byte of the header */
  const u8 *aRow;       /* Data for the current row, if all on one page */

  u32 aType[1];         /* Type values for all entries in the record */
  /* 2*nField extra array elements allocated for aType[], beyond the one
  ** static element declared in the structure.  nField total array slots for
  ** aType[] and nField+1 array slots for aOffset[] */
};
typedef struct VdbeCursor VdbeCursor;

#ifdef SQLITE_TEST
  extern int sqlite3_search_count;
#endif
  assert( p->deferredMoveto );
  assert( p->isTable );
  rc = sqlite3BtreeMovetoUnpacked(p->pCursor, 0, p->movetoTarget, 0, &res);
  if( rc ) return rc;
  p->lastRowid = p->movetoTarget;
  if( res!=0 ) return SQLITE_CORRUPT_BKPT;
  p->rowidIsValid = 1;
#ifdef SQLITE_TEST
  sqlite3_search_count++;
#endif
  p->deferredMoveto = 0;
  p->cacheStatus = CACHE_STALE;
  return SQLITE_OK;
}