SQLite

      /* Code constant expressions that where factored out of inner loops */
      addr = pParse->cookieGoto;
      if( pParse->pConstExpr ){
        ExprList *pEL = pParse->pConstExpr;
        pParse->cookieGoto = 0;
        for(i=0; i<pEL->nExpr; i++){
          sqlite3ExprCode(pParse, pEL->a[i].pExpr, pEL->a[i].iAlias);
        }
      }

      /* Finally, jump back to the beginning of the executable code. */
      sqlite3VdbeAddOp2(v, OP_Goto, 0, addr);
    }
  }

    Expr *pOldExpr = pOldItem->pExpr;
    pItem->pExpr = sqlite3ExprDup(db, pOldExpr, flags);
    pItem->zName = sqlite3DbStrDup(db, pOldItem->zName);
    pItem->zSpan = sqlite3DbStrDup(db, pOldItem->zSpan);
    pItem->sortOrder = pOldItem->sortOrder;
    pItem->done = 0;
    pItem->bSpanIsTab = pOldItem->bSpanIsTab;
    pItem->iOrderByCol = pOldItem->iOrderByCol;
    pItem->iAlias = pOldItem->iAlias;
  }
  return pNew;
}

/*
** If cursors, triggers, views and subqueries are all omitted from
** the build, then none of the following routines, except for 

      pEList = pExpr->x.pList;
      aListelem = pEList->a;
      nExpr = pEList->nExpr;
      endLabel = sqlite3VdbeMakeLabel(v);
      if( (pX = pExpr->pLeft)!=0 ){
        tempX = *pX;
        testcase( pX->op==TK_COLUMN );
        testcase( pX->op==TK_REGISTER );
        exprToRegister(&tempX, sqlite3ExprCodeTemp(pParse, pX, &regFree1));
        testcase( regFree1==0 );
        opCompare.op = TK_EQ;
        opCompare.pLeft = &tempX;
        pTest = &opCompare;
        /* Ticket b351d95f9cd5ef17e9d9dbae18f5ca8611190001:
        ** The value in regFree1 might get SCopy-ed into the file result.

        }else{
          pTest = aListelem[i].pExpr;
        }
        nextCase = sqlite3VdbeMakeLabel(v);
        testcase( pTest->op==TK_COLUMN );
        sqlite3ExprIfFalse(pParse, pTest, nextCase, SQLITE_JUMPIFNULL);
        testcase( aListelem[i+1].pExpr->op==TK_COLUMN );
        testcase( aListelem[i+1].pExpr->op==TK_REGISTER );
        sqlite3ExprCode(pParse, aListelem[i+1].pExpr, target);
        sqlite3VdbeAddOp2(v, OP_Goto, 0, endLabel);
        sqlite3ExprCachePop(pParse, 1);
        sqlite3VdbeResolveLabel(v, nextCase);
      }
      if( (nExpr&1)!=0 ){
        sqlite3ExprCachePush(pParse);

** code to fill the register in the initialization section of the
** VDBE program, in order to factor it out of the evaluation loop.
*/
int sqlite3ExprCodeTemp(Parse *pParse, Expr *pExpr, int *pReg){
  int r2;
  pExpr = sqlite3ExprSkipCollate(pExpr);
  if( pParse->cookieGoto>0
   && pParse->nMem<32768
   && pExpr->op!=TK_REGISTER
   && sqlite3ExprIsConstantNotJoin(pExpr)
  ){
    ExprList *p = pParse->pConstExpr;
    int i;
    *pReg  = 0;
    if( p ){
      for(i=0; i<p->nExpr; i++){
        if( sqlite3ExprCompare(p->a[i].pExpr, pExpr, -1)==0 ){
          return p->a[i].iAlias;
        }
      }
    }
    p = sqlite3ExprListAppend(pParse, p, sqlite3ExprDup(pParse->db, pExpr, 0));
    pParse->pConstExpr = p;
    r2 = ++pParse->nMem;
    if( p ) p->a[p->nExpr-1].iAlias = r2;
  }else{
    int r1 = sqlite3GetTempReg(pParse);
    r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
    if( r2==r1 ){
      *pReg = r1;
    }else{
      sqlite3ReleaseTempReg(pParse, r1);

** are reused.
*/
int sqlite3ExprCodeAndCache(Parse *pParse, Expr *pExpr, int target){
  Vdbe *v = pParse->pVdbe;
  int inReg;
  inReg = sqlite3ExprCode(pParse, pExpr, target);
  assert( target>0 );
  /* This routine is called for terms to INSERT or UPDATE.  And the only
  ** other place where expressions can be converted into TK_REGISTER is
  ** in WHERE clause processing.  So as currently implemented, there is
  ** no way for a TK_REGISTER to exist here.  But it seems prudent to



  ** keep the ALWAYS() in case the conditions above change with future
  ** modifications or enhancements. */
  if( ALWAYS(pExpr->op!=TK_REGISTER) ){  
    int iMem;
    iMem = ++pParse->nMem;
    sqlite3VdbeAddOp2(v, OP_Copy, inReg, iMem);
    exprToRegister(pExpr, iMem);
  }
  return inReg;

  combinedFlags = pA->flags | pB->flags;
  if( combinedFlags & EP_IntValue ){
    if( (pA->flags&pB->flags&EP_IntValue)!=0 && pA->u.iValue==pB->u.iValue ){
      return 0;
    }
    return 2;
  }
  if( pA->op!=pB->op /*&& (pA->op!=TK_REGISTER || pA->op2!=pB->op)*/ ){
    if( pA->op==TK_COLLATE && sqlite3ExprCompare(pA->pLeft, pB, iTab)<2 ){
      return 1;
    }
    if( pB->op==TK_COLLATE && sqlite3ExprCompare(pA, pB->pLeft, iTab)<2 ){
      return 1;
    }
    return 2;
  }
  if( pA->op!=TK_COLUMN && ALWAYS(pA->op!=TK_AGG_COLUMN) && pA->u.zToken ){
    if( strcmp(pA->u.zToken,pB->u.zToken)!=0 ){
      return pA->op==TK_COLLATE ? 1 : 2;
    }
  }
  if( (pA->flags & EP_Distinct)!=(pB->flags & EP_Distinct) ) return 2;
  testcase( combinedFlags & EP_TokenOnly );
  testcase( combinedFlags & EP_Reduced );
  if( (combinedFlags & EP_TokenOnly)==0 ){
    if( combinedFlags & EP_xIsSelect ) return 2;
    if( sqlite3ExprCompare(pA->pLeft, pB->pLeft, iTab) ) return 2;
    if( sqlite3ExprCompare(pA->pRight, pB->pRight, iTab) ) return 2;
    if( sqlite3ExprListCompare(pA->x.pList, pB->x.pList, iTab) ) return 2;
    if( (combinedFlags & EP_Reduced)==0 ){
      if( pA->iColumn!=pB->iColumn ) return 2;
      if( pA->iTable!=pB->iTable 
       && pA->op!=TK_REGISTER
       && (pA->iTable!=iTab || pB->iTable>=0) ) return 2;
    }
  }
  return 0;
}

/*

  pDup = sqlite3ExprDup(db, pOrig, 0);
  if( pDup==0 ) return;
  if( pOrig->op!=TK_COLUMN && zType[0]!='G' ){
    incrAggFunctionDepth(pDup, nSubquery);
    pDup = sqlite3PExpr(pParse, TK_AS, pDup, 0, 0);
    if( pDup==0 ) return;
    ExprSetProperty(pDup, EP_Skip);
    if( pEList->a[iCol].iAlias==0 ){
      pEList->a[iCol].iAlias = (u16)(++pParse->nAlias);
    }
    pDup->iTable = pEList->a[iCol].iAlias;
  }
  if( pExpr->op==TK_COLLATE ){
    pDup = sqlite3ExprAddCollateString(pParse, pDup, pExpr->u.zToken);
  }

  /* Before calling sqlite3ExprDelete(), set the EP_Static flag. This 
  ** prevents ExprDelete() from deleting the Expr structure itself,

          pItem->pExpr = pNew;
        }else{
          assert( pItem->pExpr->op==TK_COLLATE );
          assert( pItem->pExpr->pLeft==pE );
          pItem->pExpr->pLeft = pNew;
        }
        sqlite3ExprDelete(db, pE);
        pItem->iOrderByCol = (u16)iCol;
        pItem->done = 1;
      }else{
        moreToDo = 1;
      }
    }
    pSelect = pSelect->pNext;
  }
  for(i=0; i<pOrderBy->nExpr; i++){
    if( pOrderBy->a[i].done==0 ){
      sqlite3ErrorMsg(pParse, "%r ORDER BY term does not match any "
            "column in the result set", i+1);
      return 1;
    }
  }
  return 0;
}

/*
** Check every term in the ORDER BY or GROUP BY clause pOrderBy of
** the SELECT statement pSelect.  If any term is reference to a
** result set expression (as determined by the ExprList.a.iOrderByCol field)
** then convert that term into a copy of the corresponding result set
** column.
**
** If any errors are detected, add an error message to pParse and
** return non-zero.  Return zero if no errors are seen.
*/
int sqlite3ResolveOrderGroupBy(
  Parse *pParse,        /* Parsing context.  Leave error messages here */

    sqlite3ErrorMsg(pParse, "too many terms in %s BY clause", zType);
    return 1;
  }
#endif
  pEList = pSelect->pEList;
  assert( pEList!=0 );  /* sqlite3SelectNew() guarantees this */
  for(i=0, pItem=pOrderBy->a; i<pOrderBy->nExpr; i++, pItem++){
    if( pItem->iOrderByCol ){
      if( pItem->iOrderByCol>pEList->nExpr ){
        resolveOutOfRangeError(pParse, zType, i+1, pEList->nExpr);
        return 1;
      }
      resolveAlias(pParse, pEList, pItem->iOrderByCol-1, pItem->pExpr, zType,0);
    }
  }
  return 0;
}

/*
** pOrderBy is an ORDER BY or GROUP BY clause in SELECT statement pSelect.

    if( zType[0]!='G' ){
      iCol = resolveAsName(pParse, pSelect->pEList, pE2);
      if( iCol>0 ){
        /* If an AS-name match is found, mark this ORDER BY column as being
        ** a copy of the iCol-th result-set column.  The subsequent call to
        ** sqlite3ResolveOrderGroupBy() will convert the expression to a
        ** copy of the iCol-th result-set expression. */
        pItem->iOrderByCol = (u16)iCol;
        continue;
      }
    }
    if( sqlite3ExprIsInteger(pE2, &iCol) ){
      /* The ORDER BY term is an integer constant.  Again, set the column
      ** number so that sqlite3ResolveOrderGroupBy() will convert the
      ** order-by term to a copy of the result-set expression */
      if( iCol<1 || iCol>0xffff ){
        resolveOutOfRangeError(pParse, zType, i+1, nResult);
        return 1;
      }
      pItem->iOrderByCol = (u16)iCol;
      continue;
    }

    /* Otherwise, treat the ORDER BY term as an ordinary expression */
    pItem->iOrderByCol = 0;
    if( sqlite3ResolveExprNames(pNC, pE) ){
      return 1;
    }
    for(j=0; j<pSelect->pEList->nExpr; j++){
      if( sqlite3ExprCompare(pE, pSelect->pEList->a[j].pExpr, -1)==0 ){
        pItem->iOrderByCol = j+1;
      }
    }
  }
  return sqlite3ResolveOrderGroupBy(pParse, pSelect, pOrderBy, zType);
}

/*

  ** the ORDER BY clause covers every term of the result set.  Add
  ** terms to the ORDER BY clause as necessary.
  */
  if( op!=TK_ALL ){
    for(i=1; db->mallocFailed==0 && i<=p->pEList->nExpr; i++){
      struct ExprList_item *pItem;
      for(j=0, pItem=pOrderBy->a; j<nOrderBy; j++, pItem++){
        assert( pItem->iOrderByCol>0 );
        if( pItem->iOrderByCol==i ) break;
      }
      if( j==nOrderBy ){
        Expr *pNew = sqlite3Expr(db, TK_INTEGER, 0);
        if( pNew==0 ) return SQLITE_NOMEM;
        pNew->flags |= EP_IntValue;
        pNew->u.iValue = i;
        pOrderBy = sqlite3ExprListAppend(pParse, pOrderBy, pNew);
        if( pOrderBy ) pOrderBy->a[nOrderBy++].iOrderByCol = (u16)i;
      }
    }
  }

  /* Compute the comparison permutation and keyinfo that is used with
  ** the permutation used to determine if the next
  ** row of results comes from selectA or selectB.  Also add explicit
  ** collations to the ORDER BY clause terms so that when the subqueries
  ** to the right and the left are evaluated, they use the correct
  ** collation.
  */
  aPermute = sqlite3DbMallocRaw(db, sizeof(int)*nOrderBy);
  if( aPermute ){
    struct ExprList_item *pItem;
    for(i=0, pItem=pOrderBy->a; i<nOrderBy; i++, pItem++){

      assert( pItem->iOrderByCol>0  && pItem->iOrderByCol<=p->pEList->nExpr );
      aPermute[i] = pItem->iOrderByCol - 1;
    }
    pKeyMerge = sqlite3KeyInfoAlloc(db, nOrderBy, 1);
    if( pKeyMerge ){
      for(i=0; i<nOrderBy; i++){
        CollSeq *pColl;
        Expr *pTerm = pOrderBy->a[i].pExpr;
        if( pTerm->flags & EP_Collate ){

      testcase( pSub1->pSrc->nSrc>1 );
    }

    /* Restriction 18. */
    if( p->pOrderBy ){
      int ii;
      for(ii=0; ii<p->pOrderBy->nExpr; ii++){
        if( p->pOrderBy->a[ii].iOrderByCol==0 ) return 0;
      }
    }
  }

  /***** If we reach this point, flattening is permitted. *****/

  /* Authorize the subquery */

    ** GROUP BY clause.
    */
    if( pGroupBy ){
      int k;                        /* Loop counter */
      struct ExprList_item *pItem;  /* For looping over expression in a list */

      for(k=p->pEList->nExpr, pItem=p->pEList->a; k>0; k--, pItem++){
        pItem->iAlias = 0;
      }
      for(k=pGroupBy->nExpr, pItem=pGroupBy->a; k>0; k--, pItem++){
        pItem->iAlias = 0;
      }
      if( p->nSelectRow>100 ) p->nSelectRow = 100;
    }else{
      p->nSelectRow = 1;
    }

 

  struct ExprList_item { /* For each expression in the list */
    Expr *pExpr;            /* The list of expressions */
    char *zName;            /* Token associated with this expression */
    char *zSpan;            /* Original text of the expression */
    u8 sortOrder;           /* 1 for DESC or 0 for ASC */
    unsigned done :1;       /* A flag to indicate when processing is finished */
    unsigned bSpanIsTab :1; /* zSpan holds DB.TABLE.COLUMN */


    u16 iOrderByCol;        /* For ORDER BY, column number in result set */
    u16 iAlias;             /* Index into Parse.aAlias[] for zName */



  } *a;                  /* Alloc a power of two greater or equal to nExpr */
};

/*
** An instance of this structure is used by the parser to record both
** the parse tree for an expression and the span of input text for an
** expression.

    ** be the name of an indexed column with TEXT affinity. */
    return 0;
  }
  assert( pLeft->iColumn!=(-1) ); /* Because IPK never has AFF_TEXT */

  pRight = pList->a[0].pExpr;
  op = pRight->op;
  if( op==TK_REGISTER ){
    op = pRight->op2;
  }
  if( op==TK_VARIABLE ){
    Vdbe *pReprepare = pParse->pReprepare;
    int iCol = pRight->iColumn;
    pVal = sqlite3VdbeGetBoundValue(pReprepare, iCol, SQLITE_AFF_NONE);
    if( pVal && sqlite3_value_type(pVal)==SQLITE_TEXT ){
      z = (char *)sqlite3_value_text(pVal);
    }