Fetching wrong columns

[makorne]

[tests/integration.rs:157] &row = MyRowResult {
    no: 500,
    result: 2,
}
[tests/integration.rs:157] &row = MyRowResult {
    no: 0,
    result: 501,
}

The second row must be:

[tests/integration.rs:157] &row = MyRowResult {
    no: 501,
    result: 2,
}

Test:

#[tokio::test]
async fn it_writes_then_reads_count() {
    let client = prepare("it_writes_then_reads_count").await;

    #[derive(Debug, Row, Serialize, Deserialize)]
    struct MyRow {
        no: u32,
        num: u32
    }

    #[derive(Debug, Row, Serialize, Deserialize)]
    struct MyRowResult {
        no: u32,
        result: u32
    }

    // Create a table.
    client
        .query(
            "
            CREATE TABLE some(no UInt32, num UInt32)
            ENGINE = MergeTree
            ORDER BY no
        ",
        )
        .execute()
        .await
        .expect("cannot create a table");

    // Write to the table.
    let mut insert = client.insert("some").expect("cannot insert");
    for i in 0..1000 {
        insert
            .write(&MyRow { no: i, num: i })
            .await
            .expect("cannot write()");
        insert
            .write(&MyRow { no: i, num: i+1 })
            .await
            .expect("cannot write()");
    }

    insert.end().await.expect("cannot end()");

    // Read from the table.
    let mut cursor = client
        .query("SELECT no, count(*) FROM some WHERE no BETWEEN ? AND ? GROUP BY no ORDER BY no")
        .bind(500)
        .bind(504)
        .fetch::<MyRowResult>()
        .expect("cannot fetch");

    let mut i = 500;

    while let Some(row) = cursor.next().await.expect("cannot next()") {
        dbg!(&row);
        assert_eq!(row.no, i);
        assert_eq!(row.result, 2);
        i += 1;
    }
}

The same with : count(*) as result

[loyd]

Thanks for the issue.

The count returns UInt64 in terms of ClickHouse:

the type of the returned value is UInt64

Thus, using u64 (or any type that deserializes from it) for the result's type fixes your problem.

I don't like such silent errors and I'm going to move to RowBinaryWithNamesAndTypes in #10, because that format provides information about types of columns, that can be useful for conversions. However, even in this case, I think u64 -> u32 should be prohibited and lead to deserialization errors. Thus, I'm closing the issue.