[BUG] dedup raise 500 error when object attribute is specified

[ykmr1224]

What is the bug?
dedup command raise 500 error when object attribute is specified.
Sample query:

source=logs-* | head 10 | dedup attributes

where attributes is struct like:

      {
        "cluster": {
          "name": "xyz-cluster1-ci-prod-us-east-1",
          "region": "us-east-1",
          "env": "prod"
        },
        "log": {
          "file": {
            "path": "/var/log/xyz/abc.log"
          }
        },
        "obs_body_length": 146
      },

error:

{
  "error": {
    "reason": "There was internal problem at backend",
    "details": "java.sql.SQLException: exception while executing query: class java.util.LinkedHashMap cannot be cast to class java.lang.Comparable (java.util.LinkedHashMap and java.lang.Comparable are in module java.base of loader 'bootstrap')",
    "type": "RuntimeException"
  },
  "status": 500
}

How can one reproduce the bug?
run ppl query: source=logs-* | head 10 | dedup attributes

What is the expected behavior?
It should return invalid query error with 4xx status code.

What is your host/environment?

• OS: [e.g. iOS]
• Version [e.g. 22] 3.1
• Plugins

Do you have any screenshots?
If applicable, add screenshots to help explain your problem.

Do you have any additional context?
Add any other context about the problem.

[LantaoJin]

checking

[LantaoJin]

That's because the struct type cannot be sorted whatever in pushdown or non-pushdown. (the same behavior in v2)
@ykmr1224 do you have any background about the usage? seen any user requirements?

[LantaoJin]

Try this query in v2 and v3

source = opensearch_dashboards_sample_data_ecommerce | sort geoip

[LantaoJin]

Anyway, this issue (specific dedup an attribute) can be fixed because that dedup with object doesn't pushdown. So I can fix it in Calcite side. But query source = opensearch_dashboards_sample_data_ecommerce | sort geoip still fail since OpenSearch doesn't support sorting on an object field.