Vertical format should pretty-print JSON

[alexey-milovidov]

Company or project name

ClickHouse

Describe the improvement

Vertical format should pretty-print JSON. Currently, it is printed on a single line.

Which ClickHouse versions are affected?

master

How to reproduce

.

Error message and/or stacktrace

No response

Additional context

No response

[LokanshRai]

Hello,

I would like to take this as my first PR!

[alexey-milovidov]

@LokanshRai, thanks, this will be very appreciated!

[FRosner]

@alexey-milovidov just for my understanding, is this what you'd expect?

CREATE TABLE test_vertical_json
(
    id UInt32,
    data JSON
)
ENGINE = Memory;

INSERT INTO test_vertical_json VALUES (1, '{"name": "Alice", "age": 30, "address": {"city": "New York", "zip": "10001"}, "hobbies": ["reading", "cycling"]}');
INSERT INTO test_vertical_json VALUES (2, '{"name": "Bob", "age": 25, "address": {"city": "Los Angeles", "zip": "90001"}, "hobbies": ["gaming", "cooking", "traveling"]}');

Row 1:
──────
id:   1
data: {
    "address": {
        "city": "New York",
        "zip": "10001"
    },
    "age": 30,
    "hobbies": [
        "reading",
        "cycling"
    ],
    "name": "Alice"
}

Row 2:
──────
id:   2
data: {
    "address": {
        "city": "Los Angeles",
        "zip": "90001"
    },
    "age": 25,
    "hobbies": [
        "gaming",
        "cooking",
        "traveling"
    ],
    "name": "Bob"
}

[FRosner]

I wrote a draft PR: #88524. I still gotta figure out running the tests locally before I can submit it, but early feedback is very welcome! I'm new to C++ and the codebase, so please pardon any noob questions I might have.

[alexey-milovidov]

Yes, this is how I wanted it!

[FRosner]

@alexey-milovidov I added test cases for nullable JSON columns and realized that those were not working as expected. I fixed that, too, although I'm not sure if it's the best way. Anyway, whenever you have time (or someone else with context around the output formats), here's the PR, waiting for a review. #88524