Ingest and query time in RFC3339

Hi,

I'm having a time format in the Kafka Messages as follows:
```sh
"_time": "2021-08-10T07:08:08.873Z",
```

I'm using the following schema for the date:
```json
"dateTimeFieldSpecs": [
{
"name": "_time",
"dataType": "STRING",
"format": "1:MILLISECONDS:SIMPLE_DATE_FORMAT:yyyy-MM-dd'T'HH:mm:ss.SSS'Z'",
"granularity": "1:MINUTES"
}
],
```
(I'm using a Java format here)

How can I check that the ingest in Pinot is working with the specified date time field?

Then in a Presto SQL the DATETIMECONVERT doesn't work as expected and returns an error:
```sql
SELECT DATETIMECONVERT("_time", '1:MILLISECONDS:SIMPLE_DATE_FORMAT:yyyy-mm-ddTHH:MM:SS.%fZ', '1:DAYS:SIMPLE_DATE_FORMAT:yyyyMMdd', '1:DAYS'),
max(value_number) AS max_1
FROM abc.xyz
LIMIT 1000;
```
(Here I'm using a python format? as described in superset)

The returned error is as follows:
```sh
pinot error: must be real number, not dict
```

How can I use the column "_time" with the RFC 3339 format as the date time field in Presto / Superset?

Thanks for your help and cheers!

Start by reproducing the supplied dateTimeFieldSpecs for _time and the DATETIMECONVERT query against the RFC3339 value. Check Pinot's documented date-time format and ingestion behavior, then verify whether the query succeeds and returns the requested day format without the reported error.

Written by the indexing model from the issue text.