SQLite

** The cell content is not freed or deallocated.  It is assumed that
** the cell content has been copied someplace else.  This routine just
** removes the reference to the cell from pPage.
**
** "sz" must be the number of bytes in the cell.
*/
static void dropCell(MemPage *pPage, int idx, int sz, int *pRC){

  u32 pc;         /* Offset to cell content of cell being deleted */
  u8 *data;       /* pPage->aData */
  u8 *ptr;        /* Used to move bytes around within data[] */
  u8 *endPtr;     /* End of loop */
  int rc;         /* The return code */
  int hdr;        /* Beginning of the header.  0 most pages.  100 page 1 */

  if( *pRC ) return;

  assert( idx>=0 && idx<pPage->nCell );
  assert( sz==cellSize(pPage, idx) );

    return;
  }
  rc = freeSpace(pPage, pc, sz);
  if( rc ){
    *pRC = rc;
    return;
  }
  endPtr = &data[pPage->cellOffset + 2*pPage->nCell - 2];
  while( ptr<endPtr ){
    ptr[0] = ptr[2];
    ptr[1] = ptr[3];
    ptr += 2;
  }
  pPage->nCell--;
  put2byte(&data[hdr+3], pPage->nCell);
  pPage->nFree += 2;
}

/*

  u16 flags1;         /* Copy of initial value of pIn1->flags */
  u16 flags3;         /* Copy of initial value of pIn3->flags */

  pIn1 = &aMem[pOp->p1];
  pIn3 = &aMem[pOp->p3];
  flags1 = pIn1->flags;
  flags3 = pIn3->flags;
  if( (flags1 | flags3)&MEM_Null ){
    /* One or both operands are NULL */
    if( pOp->p5 & SQLITE_NULLEQ ){
      /* If SQLITE_NULLEQ is set (which will only happen if the operator is
      ** OP_Eq or OP_Ne) then take the jump or not depending on whether
      ** or not both operands are null.
      */
      assert( pOp->opcode==OP_Eq || pOp->opcode==OP_Ne );
      res = (flags1 & flags3 & MEM_Null)==0;
    }else{
      /* SQLITE_NULLEQ is clear and at least one operand is NULL,
      ** then the result is always NULL.
      ** The jump is taken if the SQLITE_JUMPIFNULL bit is set.
      */
      if( pOp->p5 & SQLITE_STOREP2 ){
        pOut = &aMem[pOp->p2];

/* Opcode: Trace * * * P4 *
**
** If tracing is enabled (by the sqlite3_trace()) interface, then
** the UTF-8 string contained in P4 is emitted on the trace callback.
*/
case OP_Trace: {
  char *zTrace;
  char *z;

  if( db->xTrace && (zTrace = (pOp->p4.z ? pOp->p4.z : p->zSql))!=0 ){


    z = sqlite3VdbeExpandSql(p, zTrace);
    db->xTrace(db->pTraceArg, z);
    sqlite3DbFree(db, z);
  }
#ifdef SQLITE_DEBUG
  if( (db->flags & SQLITE_SqlTrace)!=0
   && (zTrace = (pOp->p4.z ? pOp->p4.z : p->zSql))!=0
  ){
    sqlite3DebugPrintf("SQL-trace: %s\n", zTrace);
  }
#endif /* SQLITE_DEBUG */

  break;
}
#endif


/* Opcode: Noop * * * * *
**

  u = 0;
  while( idx<szHdr && u<p->nField && d<=nKey ){
    u32 serial_type;

    idx += getVarint32(&aKey[idx], serial_type);
    pMem->enc = pKeyInfo->enc;
    pMem->db = pKeyInfo->db;
    /* pMem->flags = 0; // sqlite3VdbeSerialGet() will set this for us */
    pMem->zMalloc = 0;
    d += sqlite3VdbeSerialGet(&aKey[d], serial_type, pMem);
    pMem++;
    u++;
  }
  assert( u<=pKeyInfo->nField + 1 );
  p->nField = u;
  return (void*)p;
}

/*
** This routine destroys a UnpackedRecord object.
*/
void sqlite3VdbeDeleteUnpackedRecord(UnpackedRecord *p){
#ifdef SQLITE_DEBUG
  int i;
  Mem *pMem;

  assert( p!=0 );
  assert( p->flags & UNPACKED_NEED_DESTROY );
  for(i=0, pMem=p->aMem; i<p->nField; i++, pMem++){
    /* The unpacked record is always constructed by the
    ** sqlite3VdbeUnpackRecord() function above, which makes all
    ** strings and blobs static.  And none of the elements are
    ** ever transformed, so there is never anything to delete.
    */
    if( NEVER(pMem->zMalloc) ) sqlite3VdbeMemRelease(pMem);
  }
#endif
  if( p->flags & UNPACKED_NEED_FREE ){
    sqlite3DbFree(p->pKeyInfo->db, p);
  }
}

/*
** This function compares the two table rows or index records