Enum StatisticsRequest 

pub enum StatisticsRequest {
    Min(Arc<Column>),
    Max(Arc<Column>),
    NullCount(Arc<Column>),
    DistinctCount(Arc<Column>),
    Sum(Arc<Column>),
    ByteSize(Arc<Column>),
    RowCount,
    TotalByteSize,
}

A statistic a caller would like a provider to supply, if it can do so cheaply.

A small, query-aware extension to the existing Statistics model: instead of “give me everything you have for every column”, a caller can ask for a specific list of stats by name. StatisticsRequest is just that vocabulary — DataFusion itself does not populate or consume it. It exists so a request can be threaded from a TableScan (see TableScan::statistics_requests) through ScanArgs::statistics_requests to a TableProvider, which is enough for a query-aware statistics feature to be implemented outside of DataFusion.

Each variant maps onto a field of datafusion_common::Statistics / datafusion_common::ColumnStatistics, so a provider that already populates one can answer the request trivially.

The per-column variants hold an Arc<Column> rather than an owned Column (which carries owned strings) so cloning a request — and the BTreeSet<StatisticsRequest> stored on TableScan, which is cloned with the plan during optimization — stays cheap.

Variants

Min(Arc<Column>)

Smallest non-null value of column.

Max(Arc<Column>)

Largest non-null value of column.

NullCount(Arc<Column>)

Number of NULLs in column.

DistinctCount(Arc<Column>)

Number of distinct values in column (exact or estimated).

Sum(Arc<Column>)

Sum of values in column (numerics, widened per ColumnStatistics::sum_value).

ByteSize(Arc<Column>)

Encoded/output byte size of column.

RowCount

Number of rows in the container (table / file).

TotalByteSize

Total byte size of the container’s output.

Trait Implementations

impl Clone for StatisticsRequest

fn clone(&self) -> StatisticsRequest

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for StatisticsRequest

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for StatisticsRequest

impl Ord for StatisticsRequest

fn cmp(&self, other: &StatisticsRequest) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for StatisticsRequest

fn eq(&self, other: &StatisticsRequest) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl PartialOrd for StatisticsRequest

fn partial_cmp(&self, other: &StatisticsRequest) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl StructuralPartialEq for StatisticsRequest