Method max_rows

datafusion/expr/src/logical_plan/plan.rs:1310–1396

Returns the maximum number of rows that this plan can output, if known. If `None`, the plan can return any number of rows. If `Some(n)` then the plan can return at most `n` rows but may return fewer.

(self: &LogicalPlan)

    /// If `None`, the plan can return any number of rows.
    /// If `Some(n)` then the plan can return at most `n` rows but may return fewer.
    pub fn max_rows(self: &LogicalPlan) -> Option<usize> {
        match self {
            LogicalPlan::Projection(Projection { input, .. }) => input.max_rows(),
            LogicalPlan::Filter(filter) => {
                if filter.is_scalar() {
                    Some(1)
                } else {
                    filter.input.max_rows()
                }
            }
            LogicalPlan::Window(Window { input, .. }) => input.max_rows(),
            LogicalPlan::Aggregate(Aggregate {
                input, group_expr, ..
            }) => {
                // Empty group_expr will return Some(1)
                if group_expr
                    .iter()
                    .all(|expr| matches!(expr, Expr::Literal(_, _)))
                {
                    Some(1)
                } else {
                    input.max_rows()
                }
            }
            LogicalPlan::Sort(Sort { input, fetch, .. }) => {
                match (fetch, input.max_rows()) {
                    (Some(fetch_limit), Some(input_max)) => {
                        Some(input_max.min(*fetch_limit))
                    }
                    (Some(fetch_limit), None) => Some(*fetch_limit),
                    (None, Some(input_max)) => Some(input_max),
                    (None, None) => None,
                }
            }
            LogicalPlan::Join(Join {
                left,
                right,
                join_type,
                ..
            }) => match join_type {
                JoinType::Inner => Some(left.max_rows()? * right.max_rows()?),
                JoinType::Left | JoinType::Right | JoinType::Full => {
                    match (left.max_rows()?, right.max_rows()?, join_type) {
                        (0, 0, _) => Some(0),
                        (max_rows, 0, JoinType::Left | JoinType::Full) => Some(max_rows),
                        (0, max_rows, JoinType::Right | JoinType::Full) => Some(max_rows),
                        (left_max, right_max, _) => Some(left_max * right_max),
                    }
                }
                JoinType::LeftSemi | JoinType::LeftAnti | JoinType::LeftMark => {
                    left.max_rows()
                }
                JoinType::RightSemi | JoinType::RightAnti | JoinType::RightMark => {
                    right.max_rows()
                }
            },
            LogicalPlan::Repartition(Repartition { input, .. }) => input.max_rows(),
            LogicalPlan::Union(Union { inputs, .. }) => {