Function is_restrict_null_predicate

datafusion/optimizer/src/utils.rs:114–140

Determine whether a predicate can restrict NULLs. e.g. `c0 > 8` return true; `c0 IS NULL` return false.

(
    predicate: Expr,
    join_cols_of_predicate: impl IntoIterator<Item = &'a Column>,
)

/// `c0 > 8` return true;
/// `c0 IS NULL` return false.
pub fn is_restrict_null_predicate<'a>(
    predicate: Expr,
    join_cols_of_predicate: impl IntoIterator<Item = &'a Column>,
) -> Result<bool> {
    if matches!(predicate, Expr::Column(_)) {
        return Ok(true);
    }

    // If result is single `true`, return false;
    // If result is single `NULL` or `false`, return true;
    Ok(
        match evaluate_expr_with_null_column(predicate, join_cols_of_predicate)? {
            ColumnarValue::Array(array) => {
                if array.len() == 1 {
                    let boolean_array = as_boolean_array(&array)?;
                    boolean_array.is_null(0) || !boolean_array.value(0)
                } else {
                    false
                }
            }
            ColumnarValue::Scalar(scalar) => matches!(
                scalar,
                ScalarValue::Boolean(None) | ScalarValue::Boolean(Some(false))
            ),
        },
    )
}

/// Determines if an expression will always evaluate to null.
/// `c0 + 8` return true