Clarify clearing of attribute stats memory.
Clarify clearing of attribute stats memory.

postmind-net/postgres-xl,0x0FFF/gpdb,50wu/gpdb,techdragon/Postgres-XL,randomtask1155/gpdb,atris/gpdb,foyzur/gpdb,cjcjameson/gpdb,rvs/gpdb,techdragon/Postgres-XL,pavanvd/postgres-xl,yuanzhao/gpdb,Chibin/gpdb,0x0FFF/gpdb,atris/gpdb,yazun/postgres-xl,royc1/gpdb,ahachete/gpdb,Postgres-XL/Postgres-XL,atris/gpdb,edespino/gpdb,rvs/gpdb,chrishajas/gpdb,ashwinstar/gpdb,0x0FFF/gpdb,lintzc/gpdb,ashwinstar/gpdb,0x0FFF/gpdb,foyzur/gpdb,oberstet/postgres-xl,CraigHarris/gpdb,yuanzhao/gpdb,Quikling/gpdb,lintzc/gpdb,lintzc/gpdb,zaksoup/gpdb,chrishajas/gpdb,randomtask1155/gpdb,ashwinstar/gpdb,pavanvd/postgres-xl,atris/gpdb,arcivanov/postgres-xl,postmind-net/postgres-xl,edespino/gpdb,greenplum-db/gpdb,zeroae/postgres-xl,oberstet/postgres-xl,CraigHarris/gpdb,50wu/gpdb,atris/gpdb,yuanzhao/gpdb,edespino/gpdb,royc1/gpdb,xinzweb/gpdb,rvs/gpdb,royc1/gpdb,techdragon/Postgres-XL,kaknikhil/gpdb,tangp3/gpdb,yuanzhao/gpdb,rubikloud/gpdb,zeroae/postgres-xl,ovr/postgres-xl,0x0FFF/gpdb,zeroae/postgres-xl,greenplum-db/gpdb,xinzweb/gpdb,lisakowen/gpdb,tangp3/gpdb,postmind-net/postgres-xl,kaknikhil/gpdb,greenplum-db/gpdb,0x0FFF/gpdb,janebeckman/gpdb,jmcatamney/gpdb,janebeckman/gpdb,yuanzhao/gpdb,CraigHarris/gpdb,xuegang/gpdb,adam8157/gpdb,lpetrov-pivotal/gpdb,foyzur/gpdb,rvs/gpdb,foyzur/gpdb,lintzc/gpdb,Chibin/gpdb,Chibin/gpdb,lpetrov-pivotal/gpdb,Quikling/gpdb,adam8157/gpdb,randomtask1155/gpdb,Chibin/gpdb,cjcjameson/gpdb,ovr/postgres-xl,arcivanov/postgres-xl,kaknikhil/gpdb,edespino/gpdb,rvs/gpdb,kaknikhil/gpdb,jmcatamney/gpdb,janebeckman/gpdb,kmjungersen/PostgresXL,edespino/gpdb,tpostgres-projects/tPostgres,pavanvd/postgres-xl,zaksoup/gpdb,lisakowen/gpdb,Quikling/gpdb,yazun/postgres-xl,Chibin/gpdb,cjcjameson/gpdb,50wu/gpdb,zaksoup/gpdb,yuanzhao/gpdb,arcivanov/postgres-xl,Chibin/gpdb,lpetrov-pivotal/gpdb,rubikloud/gpdb,snaga/postgres-xl,50wu/gpdb,ahachete/gpdb,royc1/gpdb,rubikloud/gpdb,atris/gpdb,edespino/gpdb,kmjungersen/PostgresXL,Quikling/gpdb,xinzweb/gpdb,CraigHarris/gpdb,Quikling/gpdb,cjcjameson/gpdb,kaknikhil/gpdb,chrishajas/gpdb,lintzc/gpdb,janebeckman/gpdb,kmjungersen/PostgresXL,yuanzhao/gpdb,foyzur/gpdb,tpostgres-projects/tPostgres,kaknikhil/gpdb,Quikling/gpdb,zaksoup/gpdb,yazun/postgres-xl,CraigHarris/gpdb,CraigHarris/gpdb,rvs/gpdb,tpostgres-projects/tPostgres,arcivanov/postgres-xl,kmjungersen/PostgresXL,janebeckman/gpdb,jmcatamney/gpdb,Chibin/gpdb,tangp3/gpdb,Postgres-XL/Postgres-XL,yuanzhao/gpdb,tangp3/gpdb,xuegang/gpdb,xuegang/gpdb,tangp3/gpdb,techdragon/Postgres-XL,Chibin/gpdb,randomtask1155/gpdb,ashwinstar/gpdb,snaga/postgres-xl,lintzc/gpdb,edespino/gpdb,atris/gpdb,postmind-net/postgres-xl,ashwinstar/gpdb,randomtask1155/gpdb,edespino/gpdb,lpetrov-pivotal/gpdb,Chibin/gpdb,pavanvd/postgres-xl,rvs/gpdb,tangp3/gpdb,cjcjameson/gpdb,cjcjameson/gpdb,Quikling/gpdb,Postgres-XL/Postgres-XL,xinzweb/gpdb,zaksoup/gpdb,lpetrov-pivotal/gpdb,Quikling/gpdb,lpetrov-pivotal/gpdb,50wu/gpdb,cjcjameson/gpdb,cjcjameson/gpdb,yazun/postgres-xl,jmcatamney/gpdb,snaga/postgres-xl,janebeckman/gpdb,kaknikhil/gpdb,yuanzhao/gpdb,50wu/gpdb,ahachete/gpdb,greenplum-db/gpdb,yazun/postgres-xl,lintzc/gpdb,ovr/postgres-xl,tpostgres-projects/tPostgres,xinzweb/gpdb,xinzweb/gpdb,janebeckman/gpdb,chrishajas/gpdb,Chibin/gpdb,greenplum-db/gpdb,xuegang/gpdb,kaknikhil/gpdb,atris/gpdb,zaksoup/gpdb,zaksoup/gpdb,tangp3/gpdb,techdragon/Postgres-XL,lisakowen/gpdb,ahachete/gpdb,chrishajas/gpdb,rubikloud/gpdb,adam8157/gpdb,CraigHarris/gpdb,adam8157/gpdb,kmjungersen/PostgresXL,kaknikhil/gpdb,zaksoup/gpdb,rubikloud/gpdb,adam8157/gpdb,cjcjameson/gpdb,Postgres-XL/Postgres-XL,CraigHarris/gpdb,royc1/gpdb,lisakowen/gpdb,jmcatamney/gpdb,50wu/gpdb,ahachete/gpdb,ashwinstar/gpdb,edespino/gpdb,royc1/gpdb,edespino/gpdb,ahachete/gpdb,greenplum-db/gpdb,zeroae/postgres-xl,jmcatamney/gpdb,xuegang/gpdb,ovr/postgres-xl,lisakowen/gpdb,rubikloud/gpdb,janebeckman/gpdb,greenplum-db/gpdb,kaknikhil/gpdb,lintzc/gpdb,CraigHarris/gpdb,chrishajas/gpdb,jmcatamney/gpdb,postmind-net/postgres-xl,Quikling/gpdb,janebeckman/gpdb,zeroae/postgres-xl,lisakowen/gpdb,0x0FFF/gpdb,randomtask1155/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,adam8157/gpdb,adam8157/gpdb,rubikloud/gpdb,tpostgres-projects/tPostgres,ashwinstar/gpdb,snaga/postgres-xl,lintzc/gpdb,rvs/gpdb,oberstet/postgres-xl,xuegang/gpdb,randomtask1155/gpdb,xuegang/gpdb,chrishajas/gpdb,ahachete/gpdb,lpetrov-pivotal/gpdb,50wu/gpdb,xinzweb/gpdb,snaga/postgres-xl,pavanvd/postgres-xl,lpetrov-pivotal/gpdb,arcivanov/postgres-xl,oberstet/postgres-xl,rvs/gpdb,janebeckman/gpdb,ahachete/gpdb,rvs/gpdb,jmcatamney/gpdb,lisakowen/gpdb,tangp3/gpdb,0x0FFF/gpdb,cjcjameson/gpdb,ashwinstar/gpdb,foyzur/gpdb,royc1/gpdb,Postgres-XL/Postgres-XL,lisakowen/gpdb,rubikloud/gpdb,yuanzhao/gpdb,royc1/gpdb,randomtask1155/gpdb,arcivanov/postgres-xl,ovr/postgres-xl,adam8157/gpdb,foyzur/gpdb,xinzweb/gpdb,xuegang/gpdb,xuegang/gpdb,foyzur/gpdb,chrishajas/gpdb,Quikling/gpdb