Map keys support

[nablaone]

This is PR add support for querying map columns.

For example:

CREATE TABLE IF NOT EXISTS "foo"
(
    "@timestamp" DateTime64 DEFAULT now64(),
    `bar` Map(String, Nullable(String))
)
ENGINE = MergeTree
ORDER BY ("@timestamp");        

insert into foo values ('2020-01-01 00:00:00', {'a': 'b'});
insert into foo values ('2020-01-01 00:00:00', {'c': 'd', 'e': 'f'});
insert into foo values ('2020-01-01 00:00:00', {'g': 'h', 'i': 'j', 'k': 'l'});

We can access the value of the map by using fieldname.key syntax

{
    "query": {
        "bool": {
            "must": [
                {
                    "match": {
                        "bar.a": "b"
                    }
                }
            ]
        },
        "match_all": {}
    }
}

[nablaone]

/run-integration-tests