SQL INSERT casts to Int64 when handling UInt64 values

[nuno-faria]

Describe the bug

When performing a SQL INSERT to a BIGINT UNSIGNED column, the wrong type is assumed when mixing UInt64 data with values that can be represented in Int64. However, it works when the inserted values must all be represented in UInt64.

To Reproduce

use datafusion::common::Result;
use datafusion::prelude::SessionContext;

#[tokio::main]
async fn main() -> Result<()> {
    let ctx = SessionContext::new();
    // column is declared as bigint unsigned
    ctx.sql("create table t (v bigint unsigned)").await?;
    let value: u64 = 10000000000000000000;

    // works: all values are u64
    ctx.sql(format!("insert into t values ({value}), ({value})").as_str()).await?.collect().await?;
    ctx.sql("select * from t").await?.show().await?;

    // does not work: one of the values forces the type to be Int64, invalidating {value}
    // Error: ArrowError(CastError("Can't cast value 10000000000000000000 to type Int64"), None)
    ctx.sql(format!("insert into t values ({value}), (1)").as_str()).await?.collect().await?;
    ctx.sql("select * from t").await?.show().await?;

    Ok(())
}

Expected behavior

When at least one of the values must be encoded with UInt64, the assumed type must be UInt64.

Additional context

I can take a look at this issue, but wanted to first make sure this is a bug and not expected behavior.

[jonahgao]

This seems to be a bug in binary_numeric_coercion. The common type of UInt64 and Int8/16/32/64 should not be Int64, because u64::MAX can't fit into it. It should be a wider type, for example, Decimal128(20, 0).