remove more clones#8

appletreeisyellow merged 2 commits intoappletreeisyellow:chunchun/stop-copy-in-SingleDistinctToGroupByappletreeisyellow/datafusion:chunchun/stop-copy-in-SingleDistinctToGroupByfrom

erratic-pattern:chunchun/stop-copy-in-SingleDistinctToGroupByerratic-pattern/arrow-datafusion:chunchun/stop-copy-in-SingleDistinctToGroupByCopy head branch name to clipboard