support value-wise query result

[xxchan]

https://duckdb.org/dev/sqllogictest/result_verification#row-wise-vs-value-wise-result-ordering

# row-wise
query II
SELECT 42, 84 UNION ALL SELECT 10, 20;
----
42	84
10	20

# value-wise
query II
SELECT 42, 84 UNION ALL SELECT 10, 20;
----
42
84
10
20

[xxchan]

sqlite only supports value-wise.

cockroach only supports row-wise, but will use value-wise when option -bigtest is used (i.e., when testing against sqlite's test cases).

[tv42]

I can work around this with tester.with_validator(sql_result_validator) and something like this. I ripped out the whitespace trimming to keep the code simple, the sqlite tests I was playing with don't have any whitespace ambiquity:

fn sql_result_validator(actual: &[Vec<String>], expected: &[String]) -> bool {
    let expected = expected
        .iter()
        .map(|s| s.split_ascii_whitespace().collect::<Vec<_>>())
        .collect::<Vec<_>>();
    if let Some(first_actual) = actual.first() {
        if expected.iter().all(|v| v.len() == 1) {
            // SQLite "value-wise" compatibility.
            // Flatten and re-chunk based on column width in `actual`.
            let expected = expected.into_iter().flatten().collect::<Vec<_>>();
            let expected = expected.chunks(first_actual.len()).collect::<Vec<_>>();
            return expected == actual;
        }
    }
    actual == expected
}

[xxchan]

FYI, #123 contains support for value sort. I forget whether it's finished though.