SQLite

static SQLITE_NOINLINE void sqlite3ExprDeleteNN(sqlite3 *db, Expr *p){
  assert( p!=0 );
  /* Sanity check: Assert that the IntValue is non-negative if it exists */
  assert( !ExprHasProperty(p, EP_IntValue) || p->u.iValue>=0 );
  if( !ExprHasProperty(p, EP_TokenOnly) ){
    /* The Expr.x union is never used at the same time as Expr.pRight */
    assert( p->x.pList==0 || p->pRight==0 );
    if( p->pLeft && p->op!=TK_SELECT_COLUMN ) sqlite3ExprDeleteNN(db, p->pLeft);
    sqlite3ExprDelete(db, p->pRight);
    if( ExprHasProperty(p, EP_MemToken) ) sqlite3DbFree(db, p->u.zToken);
    if( ExprHasProperty(p, EP_xIsSelect) ){
      sqlite3SelectDelete(db, p->x.pSelect);
    }else{
      sqlite3ExprListDelete(db, p->x.pList);
    }

/*
** Get a VDBE for the given parser context.  Create a new one if necessary.
** If an error occurs, return NULL and leave a message in pParse.
*/
static SQLITE_NOINLINE Vdbe *allocVdbe(Parse *pParse){
  Vdbe *v = pParse->pVdbe = sqlite3VdbeCreate(pParse);
  if( v ) sqlite3VdbeAddOp2(v, OP_Init, 0, 1);
  if( pParse->pToplevel==0
   && OptimizationEnabled(pParse->db,SQLITE_FactorOutConst)
  ){
    pParse->okConstFactor = 1;
  }
  return v;
}

*/
case OP_Eq:               /* same as TK_EQ, jump, in1, in3 */
case OP_Ne:               /* same as TK_NE, jump, in1, in3 */
case OP_Lt:               /* same as TK_LT, jump, in1, in3 */
case OP_Le:               /* same as TK_LE, jump, in1, in3 */
case OP_Gt:               /* same as TK_GT, jump, in1, in3 */
case OP_Ge: {             /* same as TK_GE, jump, in1, in3 */
  int res, res2;      /* Result of the comparison of pIn1 against pIn3 */
  char affinity;      /* Affinity to use for comparison */
  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;

      assert( pOp->opcode==OP_Eq || pOp->opcode==OP_Ne );
      assert( (flags1 & MEM_Cleared)==0 );
      assert( (pOp->p5 & SQLITE_JUMPIFNULL)==0 );
      if( (flags1&MEM_Null)!=0
       && (flags3&MEM_Null)!=0
       && (flags3&MEM_Cleared)==0
      ){
        res = 0;  /* Operands are equal */
      }else{
        res = 1;  /* Operands are not equal */
      }
    }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];
        iCompare = 1;    /* Operands are not equal */
        memAboutToChange(p, pOut);
        MemSetTypeFlag(pOut, MEM_Null);
        REGISTER_TRACE(pOp->p2, pOut);
      }else{
        VdbeBranchTaken(2,3);
        if( pOp->p5 & SQLITE_JUMPIFNULL ){
          goto jump_to_p2;

      sqlite3VdbeMemExpandBlob(pIn1);
      flags1 &= ~MEM_Zero;
    }
    if( flags3 & MEM_Zero ){
      sqlite3VdbeMemExpandBlob(pIn3);
      flags3 &= ~MEM_Zero;
    }
    res = sqlite3MemCompare(pIn3, pIn1, pOp->p4.pColl);
  }
  switch( pOp->opcode ){
    case OP_Eq:    res2 = res==0;     break;
    case OP_Ne:    res2 = res;        break;
    case OP_Lt:    res2 = res<0;      break;
    case OP_Le:    res2 = res<=0;     break;
    case OP_Gt:    res2 = res>0;      break;
    default:       res2 = res>=0;     break;
  }

  /* Undo any changes made by applyAffinity() to the input registers. */
  assert( (pIn1->flags & MEM_Dyn) == (flags1 & MEM_Dyn) );
  pIn1->flags = flags1;
  assert( (pIn3->flags & MEM_Dyn) == (flags3 & MEM_Dyn) );
  pIn3->flags = flags3;

  if( pOp->p5 & SQLITE_STOREP2 ){
    pOut = &aMem[pOp->p2];
    iCompare = res;
    res2 = res2!=0;  /* For this path res2 must be exactly 0 or 1 */
    if( (pOp->p5 & SQLITE_KEEPNULL)!=0 && (pOut->flags & MEM_Null)!=0 ){
      /* The KEEPNULL flag prevents OP_Eq from overwriting a NULL with 1
      ** and prevents OP_Ne from overwriting NULL with 0. */
      assert( pOp->opcode==OP_Ne || pOp->opcode==OP_Eq );
      assert( res2==0 || res2==1 );
      if( (pOp->opcode==OP_Eq)==res2 ) break;
    }
    memAboutToChange(p, pOut);
    MemSetTypeFlag(pOut, MEM_Int);
    pOut->u.i = res2;
    REGISTER_TRACE(pOp->p2, pOut);
  }else{
    VdbeBranchTaken(res!=0, (pOp->p5 & SQLITE_NULLEQ)?2:3);
    if( res2 ){
      goto jump_to_p2;
    }
  }
  break;
}

/* Opcode: ElseNotEq * P2 * * *
**
** This opcode must immediately follow an Lt or Gt comparison operator.
** If the operands in that previous comparison had been used with an Eq
** operator and if the result of that Eq would be NULL or false (0), then
** then jump to P2.  If the result of comparing the two previous operands
** using Eq would have been true (1), then fall through.
*/
case OP_ElseNotEq: {       /* same as TK_ESCAPE, jump */
  assert( pOp>aOp );
  assert( pOp[-1].opcode==OP_Lt || pOp[-1].opcode==OP_Gt );
  assert( pOp[-1].p5 & SQLITE_STOREP2 );
  VdbeBranchTaken(iCompare!=0, 2);
  if( iCompare!=0 ) goto jump_to_p2;
  break;
}


/* Opcode: Permutation * * * P4 *

  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 */
#endif /* SQLITE_OMIT_TRACE */
  assert( pOp->p2>0 );
  goto jump_to_p2;

}

#ifdef SQLITE_ENABLE_CURSOR_HINTS
/* Opcode: CursorHint P1 * * P4 *
**
** Provide a hint to cursor P1 that it only needs to return rows that
** satisfy the Expr in P4.  TK_REGISTER terms in the P4 expression refer