Add comment about possible zero value.
Add comment about possible zero value.

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