SQL: group by converted date doesn't work

[astefan]

Test data:

POST localhost:9200/calcs/doc/_bulk

{"index":{}}
{"date2":"1977-04-20","date0":"2004-04-15"}
{"index":{}}
{"date2":"1995-09-03","date0":"1972-07-04"}
{"index":{}}
{"date2":"1997-09-19","date0":"1975-11-12"}
{"index":{}}
{"date2":"1980-07-26","date0":"2004-06-04"}
{"index":{}}
{"date2":"1997-05-30","date0":"2004-06-19"}

Query: SELECT {fn CONVERT(date0, SQL_DOUBLE)} AS x FROM calcs GROUP BY x

Result:

{
    "error": {
        "root_cause": [
            {
                "type": "sql_illegal_argument_exception",
                "reason": "No idea what's the DataType for class org.elasticsearch.script.JodaCompatibleZonedDateTime"
            }
        ],
        "type": "search_phase_execution_exception",
        "reason": "all shards failed",
        "phase": "query",
        "grouped": true,
        "failed_shards": [
            {
                "shard": 0,
                "index": "calcs",
                "node": "Aw7CDFFcQLmM_uCa97TTow",
                "reason": {
                    "type": "script_exception",
                    "reason": "runtime error",
                    "script_stack": [
                        "org.elasticsearch.xpack.sql.type.DataTypes.fromJava(DataTypes.java:79)",
                        "org.elasticsearch.xpack.sql.type.DataTypeConversion.convert(DataTypeConversion.java:372)",
                        "org.elasticsearch.xpack.sql.expression.function.scalar.whitelist.InternalSqlScriptUtils.cast(InternalSqlScriptUtils.java:471)",
                        "InternalSqlScriptUtils.cast(InternalSqlScriptUtils.docValue(doc,params.v0),params.v1)",
                        "                                                                                 ^---- HERE"
                    ],
                    "script": "InternalSqlScriptUtils.cast(InternalSqlScriptUtils.docValue(doc,params.v0),params.v1)",
                    "lang": "painless",
                    "caused_by": {
                        "type": "sql_illegal_argument_exception",
                        "reason": "No idea what's the DataType for class org.elasticsearch.script.JodaCompatibleZonedDateTime"
                    }
                }
            }
        ],
        "caused_by": {
            "type": "sql_illegal_argument_exception",
            "reason": "No idea what's the DataType for class org.elasticsearch.script.JodaCompatibleZonedDateTime"
        }
    },
    "status": 400
}

[elasticmachine]

Pinging @elastic/es-search

[astefan]

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