Changed the behaviour of default constructor of index scan descriptor
Changed the behaviour of default constructor of index scan descriptor

phisiart/peloton-p3,AllisonWang/peloton,ShuxinLin/peloton,PauloAmora/peloton,PauloAmora/peloton,seojungmin/peloton,cmu-db/peloton,vittvolt/15721-peloton,haojin2/peloton,AllisonWang/peloton,apavlo/peloton,seojungmin/peloton,eric-haibin-lin/peloton-1,eric-haibin-lin/peloton-1,vittvolt/15721-peloton,ShuxinLin/peloton,wangziqi2016/peloton,wangziqi2016/peloton,jessesleeping/iso_peloton,jessesleeping/iso_peloton,PauloAmora/peloton,eric-haibin-lin/peloton-1,vittvolt/15721-peloton,phisiart/peloton-p3,prashasthip/peloton,eric-haibin-lin/peloton-1,malin1993ml/peloton,haojin2/peloton,vittvolt/peloton,cmu-db/peloton,vittvolt/peloton,yingjunwu/peloton,cmu-db/peloton,AngLi-Leon/peloton,apavlo/peloton,ShuxinLin/peloton,AngLi-Leon/peloton,cmu-db/peloton,vittvolt/15721-peloton,seojungmin/peloton,vittvolt/peloton,PauloAmora/peloton,phisiart/peloton-p3,vittvolt/15721-peloton,vittvolt/peloton,malin1993ml/peloton,malin1993ml/peloton,vittvolt/peloton,AngLi-Leon/peloton,yingjunwu/peloton,yingjunwu/peloton,seojungmin/peloton,apavlo/peloton,prashasthip/peloton,cmu-db/peloton,haojin2/peloton,seojungmin/peloton,AllisonWang/peloton,jessesleeping/iso_peloton,ShuxinLin/peloton,haojin2/peloton,eric-haibin-lin/peloton-1,AngLi-Leon/peloton,prashasthip/peloton,AngLi-Leon/peloton,wangziqi2016/peloton,vittvolt/15721-peloton,yingjunwu/peloton,eric-haibin-lin/peloton-1,malin1993ml/peloton,apavlo/peloton,PauloAmora/peloton,AllisonWang/peloton,PauloAmora/peloton,malin1993ml/peloton,haojin2/peloton,vittvolt/peloton,yingjunwu/peloton,ShuxinLin/peloton,phisiart/peloton-p3,apavlo/peloton,AllisonWang/peloton,jessesleeping/iso_peloton,yingjunwu/peloton,prashasthip/peloton,ShuxinLin/peloton,prashasthip/peloton,jessesleeping/iso_peloton,haojin2/peloton,jessesleeping/iso_peloton,wangziqi2016/peloton,jessesleeping/iso_peloton,wangziqi2016/peloton,phisiart/peloton-p3,malin1993ml/peloton,phisiart/peloton-p3,prashasthip/peloton,cmu-db/peloton,seojungmin/peloton,AngLi-Leon/peloton,AllisonWang/peloton,apavlo/peloton,wangziqi2016/peloton