Standardize the separator in name

Is your feature request related to a problem or challenge?

While working on replacing GetFieldAccess with get_field function, I got the name checking error that due to the mismatch of separator in creating name. I found that most of the name built with single comma and space, so I think we should switch others to this format .join(", ").

Error is like

External error: query failed: DataFusion error: Internal error: Input field name SUM(get_field(CASE WHEN get_field(t2.struct(t1.time,t1.load1,t1.load2,t1.host), Utf8("c3")) IS NOT NULL THEN t2.struct(t1.time,t1.load1,t1.load2,t1.host) END,Utf8("c2"))) does not match with the projection expression SUM(get_field(CASE WHEN get_field(t2.struct(t1.time,t1.load1,t1.load2,t1.host),Utf8("c3")) IS NOT NULL THEN t2.struct(t1.time,t1.load1,t1.load2,t1.host) END,Utf8("c2"))).
This was likely caused by a bug in DataFusion's code and we would welcome that you file an bug report in our issue tracker
[SQL] select t2."struct(t1.time,t1.load1,t1.load2,t1.host)"['c3'] as host, sum((case when t2."struct(t1.time,t1.load1,t1.load2,t1.host)"['c3'] is not null then t2."struct(t1.time,t1.load1,t1.load2,t1.host)" end)['c2']) from (select struct(time,load1,load2,host) from t1) t2 where t2."struct(t1.time,t1.load1,t1.load2,t1.host)"['c3'] IS NOT NULL group by t2."struct(t1.time,t1.load1,t1.load2,t1.host)"['c3'] order by host;

I got one with t2.struct(t1.time,t1.load1,t1.load2,t1.host), Utf8("c3") and another t2.struct(t1.time,t1.load1,t1.load2,t1.host),Utf8("c3"). That is why I think we should fix the separator.

Since the change is quite large, I would like to wait for more comment.

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Describe alternatives you've considered

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Additional context

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You can find the error here with cargo test --test sqllogictests -- expr. Although, it is not on the main branch, but I think most of the changes are unrelated to the name checking issue.

apache / datafusion