static int selectExpander(Walker *pWalker, Select *p){
  Parse *pParse = pWalker->pParse;
  int i, j, k;
  SrcList *pTabList;
  ExprList *pEList;
  struct SrcList_item *pFrom;
  sqlite3 *db = pParse->db;
  Expr *pE, *pRight, *pExpr;
  u16 selFlags = p->selFlags;
  u32 elistFlags = 0;

  p->selFlags |= SF_Expanded;
  if( db->mallocFailed  ){
    return WRC_Abort;
  }
  assert( p->pSrc!=0 );
  if( (selFlags & SF_Expanded)!=0 ){
    return WRC_Prune;
  }
  if( pWalker->eCode ){
    /* Renumber selId because it has been copied from a view */
    p->selId = ++pParse->nSelect;
  }
  pTabList = p->pSrc;
  pEList = p->pEList;
  sqlite3WithPush(pParse, p->pWith, 0);

  /* Make sure cursor numbers have been assigned to all entries in
  ** the FROM clause of the SELECT statement.
  */
  sqlite3SrcListAssignCursors(pParse, pTabList);

  /* Look up every table named in the FROM clause of the select.  If
  ** an entry of the FROM clause is a subquery instead of a table or view,
  ** then create a transient table structure to describe the subquery.
  */
  for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
    Table *pTab;
    assert( pFrom->fg.isRecursive==0 || pFrom->pTab!=0 );
    if( pFrom->fg.isRecursive ) continue;
    assert( pFrom->pTab==0 );
#ifndef SQLITE_OMIT_CTE
    if( withExpand(pWalker, pFrom) ) return WRC_Abort;
    if( pFrom->pTab ) {} else
#endif
    if( pFrom->zName==0 ){
#ifndef SQLITE_OMIT_SUBQUERY
      Select *pSel = pFrom->pSelect;
      /* A sub-query in the FROM clause of a SELECT */
      assert( pSel!=0 );
      assert( pFrom->pTab==0 );
      if( sqlite3WalkSelect(pWalker, pSel) ) return WRC_Abort;
      if( sqlite3ExpandSubquery(pParse, pFrom) ) return WRC_Abort;
#endif
    }else{
      /* An ordinary table or view name in the FROM clause */
      assert( pFrom->pTab==0 );
      pFrom->pTab = pTab = sqlite3LocateTableItem(pParse, 0, pFrom);
      if( pTab==0 ) return WRC_Abort;
      if( pTab->nTabRef>=0xffff ){
        sqlite3ErrorMsg(pParse, "too many references to \"%s\": max 65535",
           pTab->zName);
        pFrom->pTab = 0;
        return WRC_Abort;
      }
      pTab->nTabRef++;
      if( !IsVirtual(pTab) && cannotBeFunction(pParse, pFrom) ){
        return WRC_Abort;
      }
#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
      if( IsVirtual(pTab) || pTab->pSelect ){
        i16 nCol;
        u8 eCodeOrig = pWalker->eCode;
        if( sqlite3ViewGetColumnNames(pParse, pTab) ) return WRC_Abort;
        assert( pFrom->pSelect==0 );
        if( pTab->pSelect && (db->flags & SQLITE_EnableView)==0 ){
          sqlite3ErrorMsg(pParse, "access to view \"%s\" prohibited",
            pTab->zName);
        }
#ifndef SQLITE_OMIT_VIRTUALTABLE
        if( IsVirtual(pTab)
         && pFrom->fg.fromDDL
         && ALWAYS(pTab->pVTable!=0)
         && pTab->pVTable->eVtabRisk > ((db->flags & SQLITE_TrustedSchema)!=0)
        ){
          sqlite3ErrorMsg(pParse, "unsafe use of virtual table \"%s\"",
                                  pTab->zName);
        }
#endif
        pFrom->pSelect = sqlite3SelectDup(db, pTab->pSelect, 0);
        nCol = pTab->nCol;
        pTab->nCol = -1;
        pWalker->eCode = 1;  /* Turn on Select.selId renumbering */
        sqlite3WalkSelect(pWalker, pFrom->pSelect);
        pWalker->eCode = eCodeOrig;
        pTab->nCol = nCol;
      }
#endif
    }

    /* Locate the index named by the INDEXED BY clause, if any. */
    if( sqlite3IndexedByLookup(pParse, pFrom) ){
      return WRC_Abort;
    }
  }

  /* Process NATURAL keywords, and ON and USING clauses of joins.
  */
  if( pParse->nErr || db->mallocFailed || sqliteProcessJoin(pParse, p) ){
    return WRC_Abort;
  }

  /* For every "*" that occurs in the column list, insert the names of
  ** all columns in all tables.  And for every TABLE.* insert the names
  ** of all columns in TABLE.  The parser inserted a special expression
  ** with the TK_ASTERISK operator for each "*" that it found in the column
  ** list.  The following code just has to locate the TK_ASTERISK
  ** expressions and expand each one to the list of all columns in
  ** all tables.
  **
  ** The first loop just checks to see if there are any "*" operators
  ** that need expanding.
  */
  for(k=0; k<pEList->nExpr; k++){
    pE = pEList->a[k].pExpr;
    if( pE->op==TK_ASTERISK ) break;
    assert( pE->op!=TK_DOT || pE->pRight!=0 );
    assert( pE->op!=TK_DOT || (pE->pLeft!=0 && pE->pLeft->op==TK_ID) );
    if( pE->op==TK_DOT && pE->pRight->op==TK_ASTERISK ) break;
    elistFlags |= pE->flags;
  }
  if( k<pEList->nExpr ){
    /*
    ** If we get here it means the result set contains one or more "*"
    ** operators that need to be expanded.  Loop through each expression
    ** in the result set and expand them one by one.
    */
    struct ExprList_item *a = pEList->a;
    ExprList *pNew = 0;
    int flags = pParse->db->flags;
    int longNames = (flags & SQLITE_FullColNames)!=0
                      && (flags & SQLITE_ShortColNames)==0;

    for(k=0; k<pEList->nExpr; k++){
      pE = a[k].pExpr;
      elistFlags |= pE->flags;
      pRight = pE->pRight;
      assert( pE->op!=TK_DOT || pRight!=0 );
      if( pE->op!=TK_ASTERISK
       && (pE->op!=TK_DOT || pRight->op!=TK_ASTERISK)
      ){
        /* This particular expression does not need to be expanded.
        */
        pNew = sqlite3ExprListAppend(pParse, pNew, a[k].pExpr);
        if( pNew ){
          pNew->a[pNew->nExpr-1].zEName = a[k].zEName;
          pNew->a[pNew->nExpr-1].eEName = a[k].eEName;
          a[k].zEName = 0;
        }
        a[k].pExpr = 0;
      }else{
        /* This expression is a "*" or a "TABLE.*" and needs to be
        ** expanded. */
        int tableSeen = 0;      /* Set to 1 when TABLE matches */
        char *zTName = 0;       /* text of name of TABLE */
        if( pE->op==TK_DOT ){
          assert( pE->pLeft!=0 );
          assert( !ExprHasProperty(pE->pLeft, EP_IntValue) );
          zTName = pE->pLeft->u.zToken;
        }
        for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
          Table *pTab = pFrom->pTab;
          Select *pSub = pFrom->pSelect;
          char *zTabName = pFrom->zAlias;
          const char *zSchemaName = 0;
          int iDb;
          if( zTabName==0 ){
            zTabName = pTab->zName;
          }
          if( db->mallocFailed ) break;
          if( pSub==0 || (pSub->selFlags & SF_NestedFrom)==0 ){
            pSub = 0;
            if( zTName && sqlite3StrICmp(zTName, zTabName)!=0 ){
              continue;
            }
            iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
            zSchemaName = iDb>=0 ? db->aDb[iDb].zDbSName : "*";
          }
          for(j=0; j<pTab->nCol; j++){
            char *zName = pTab->aCol[j].zName;
            char *zColname;  /* The computed column name */
            char *zToFree;   /* Malloced string that needs to be freed */
            Token sColname;  /* Computed column name as a token */

            assert( zName );
            if( zTName && pSub
             && sqlite3MatchEName(&pSub->pEList->a[j], 0, zTName, 0)==0
            ){
              continue;
            }

            /* If a column is marked as 'hidden', omit it from the expanded
            ** result-set list unless the SELECT has the SF_IncludeHidden
            ** bit set.
            */
            if( (p->selFlags & SF_IncludeHidden)==0
             && IsHiddenColumn(&pTab->aCol[j]) 
            ){
              continue;
            }
            tableSeen = 1;

            if( i>0 && zTName==0 ){
              if( (pFrom->fg.jointype & JT_NATURAL)!=0
                && tableAndColumnIndex(pTabList, i, zName, 0, 0, 1)
              ){
                /* In a NATURAL join, omit the join columns from the 
                ** table to the right of the join */
                continue;
              }
              if( sqlite3IdListIndex(pFrom->pUsing, zName)>=0 ){
                /* In a join with a USING clause, omit columns in the
                ** using clause from the table on the right. */
                continue;
              }
            }
            pRight = sqlite3Expr(db, TK_ID, zName);
            zColname = zName;
            zToFree = 0;
            if( longNames || pTabList->nSrc>1 ){
              Expr *pLeft;
              pLeft = sqlite3Expr(db, TK_ID, zTabName);
              pExpr = sqlite3PExpr(pParse, TK_DOT, pLeft, pRight);
              if( zSchemaName ){
                pLeft = sqlite3Expr(db, TK_ID, zSchemaName);
                pExpr = sqlite3PExpr(pParse, TK_DOT, pLeft, pExpr);
              }
              if( longNames ){
                zColname = sqlite3MPrintf(db, "%s.%s", zTabName, zName);
                zToFree = zColname;
              }
            }else{
              pExpr = pRight;
            }
            pNew = sqlite3ExprListAppend(pParse, pNew, pExpr);
            sqlite3TokenInit(&sColname, zColname);
            sqlite3ExprListSetName(pParse, pNew, &sColname, 0);
            if( pNew && (p->selFlags & SF_NestedFrom)!=0 ){
              struct ExprList_item *pX = &pNew->a[pNew->nExpr-1];
              sqlite3DbFree(db, pX->zEName);
              if( pSub ){
                pX->zEName = sqlite3DbStrDup(db, pSub->pEList->a[j].zEName);
                testcase( pX->zEName==0 );
              }else{
                pX->zEName = sqlite3MPrintf(db, "%s.%s.%s",
                                           zSchemaName, zTabName, zColname);
                testcase( pX->zEName==0 );
              }
              pX->eEName = ENAME_TAB;
            }
            sqlite3DbFree(db, zToFree);
          }
        }
        if( !tableSeen ){
          if( zTName ){
            sqlite3ErrorMsg(pParse, "no such table: %s", zTName);
          }else{
            sqlite3ErrorMsg(pParse, "no tables specified");
          }
        }
      }
    }
    sqlite3ExprListDelete(db, pEList);
    p->pEList = pNew;
  }
  if( p->pEList ){
    if( p->pEList->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
      sqlite3ErrorMsg(pParse, "too many columns in result set");
      return WRC_Abort;
    }
    if( (elistFlags & (EP_HasFunc|EP_Subquery))!=0 ){
      p->selFlags |= SF_ComplexResult;
    }
  }
  return WRC_Continue;
}