Improve MVCC discussion.
Improve MVCC discussion.

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