Experimental - Field map syntax

[nablaone]

This is experimental support for accessing Map columns (String,...).

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": {}
    }
}

Feature is disabled by default, it can be enabled by:

        foo:
            enableFieldMapSyntax: true
            target: [ my-clickhouse-data-source ]

[mieciu]

I would like to have this merged sooner than later, but please remember to add note in docs about this new config option (in a separate PR).

[jakozaur]

@mieciu @nablaone @pdelewski For now, it is an experimental feature. We should design later a proper way to pass extra options.

[pdelewski]

@mieciu @nablaone @pdelewski For now, it is an experimental feature. We should design later a proper way to pass extra options.

Added issue for tracking that #1351