[BUG] Schema returned by SQL plugin are missing date_nanos fields

[mengweieric]

What is the bug?
Schema data returned SQL plugin are missing date_nanos fields.

How can one reproduce the bug?
Try to run query to get schema through PPL query and DSL query in dev tool and do a comparison, you will see date_nanos type startTime and endTime both are missing in schema returned by PPL query. Notice SQL query also has this issue. This issue is seen started from 2.7 to all later versions.

POST _plugins/_ppl
{
  "query": """source = otel-v1-apm-span-000001 """
}

GET /otel-v1-apm-span-000001/_mapping

What is the expected behavior?
date_nano fields should be showing up in schema

What is your host/environment?

• OpenSearch 2.7 and above