Function wrap_null_count_check_expr

datafusion/pruning/src/pruning_predicate.rs:2022–2031

Wrap the statistics expression in a check that skips the expression if the column is all nulls. This is important not only as an optimization but also because statistics may not be accurate for columns that are all nulls. For example, for an `int` column `x` with all nulls, the min/max/null_count statistics might be set to 0 and evaluating `x = 0` would incorrectly include the column. For exampl

(
    statistics_expr: Arc<dyn PhysicalExpr>,
    expr_builder: &mut PruningExpressionBuilder,
)

/// `x_null_count = x_row_count` will be true, which will cause the
/// boolean expression to return false. Therefore, prune out the container.
fn wrap_null_count_check_expr(
    statistics_expr: Arc<dyn PhysicalExpr>,
    expr_builder: &mut PruningExpressionBuilder,
) -> Result<Arc<dyn PhysicalExpr>> {
    // (x_null_count != x_row_count) AND (<statistics_expr>)
    Ok(and_expr(
        column_has_non_nulls_expr(expr_builder)?,
        statistics_expr,
    ))
}

#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub(crate) enum StatisticsType {