Regression: DataFrame::schema returns incorrect schema for NATURAL JOIN #14058

// Works for datafusion: 41.x and earlier
// Failed for datafusion: 42.x and later (including 44.x)

use datafusion::arrow::util::pretty;
use datafusion::prelude::*;

#[tokio::main]
async fn main() -> datafusion::error::Result<()> {
    let ctx = SessionContext::new();

    // Create table1
    ctx.sql(
        r#"
        CREATE TABLE table1 AS
        SELECT * FROM (
            VALUES
            (1, 'a'),
            (2, 'b'),
            (3, 'c')
        ) AS t(id, value1)
        "#,
    )
    .await?;

    // Create table2
    ctx.sql(
        r#"
        CREATE TABLE table2 AS
        SELECT * FROM (
            VALUES
            (1, 'x'),
            (3, 'y'),
            (4, 'z')
        ) AS t(id, value2)
        "#,
    )
    .await?;

    // Execute NATURAL JOIN query
    let df = ctx.sql("SELECT * FROM table1 NATURAL JOIN table2").await?;

    // Incorrect schema includes all columns from both tables
    let schema = df.schema().as_arrow().clone();
    println!("Schema: {:?}", schema);

    // Output does not include all columns
    let result = df.collect().await?;
    pretty::print_batches(&result)?;

    let result_schema = result.first().unwrap().schema();
    assert_eq!(&schema, &*result_schema, "Schema mismatch");

    Ok(())
}