Struct Statistics

pub struct Statistics {
    pub num_rows: Precision<usize>,
    pub total_byte_size: Precision<usize>,
    pub column_statistics: Vec<ColumnStatistics>,
}

Statistics for a relation Fields are optional and can be inexact because the sources sometimes provide approximate estimates for performance reasons and the transformations output are not always predictable.

Fields

num_rows: Precision<usize>

The number of table rows.

total_byte_size: Precision<usize>

Total bytes of the table rows.

column_statistics: Vec<ColumnStatistics>

Statistics on a column level. It contains a ColumnStatistics for each field in the schema of the table to which the Statistics refer.

Implementations

impl Statistics

pub fn new_unknown(schema: &Schema) -> Statistics

Returns a Statistics instance for the given schema by assigning unknown statistics to each column in the schema.

pub fn unknown_column(schema: &Schema) -> Vec<ColumnStatistics>

Returns an unbounded ColumnStatistics for each field in the schema.

pub fn to_inexact(self) -> Statistics

If the exactness of a Statistics instance is lost, this function relaxes the exactness of all information by converting them Precision::Inexact.

pub fn project(self, projection: Option<&Vec<usize>>) -> Statistics

Project the statistics to the given column indices.

For example, if we had statistics for columns {"a", "b", "c"}, projecting to vec![2, 1] would return statistics for columns {"c", "b"}.

pub fn with_fetch( self, schema: Arc<Schema>, fetch: Option<usize>, skip: usize, n_partitions: usize, ) -> Result<Statistics, DataFusionError>

Calculates the statistics after fetch and skip operations apply. Here, self denotes per-partition statistics. Use the n_partitions parameter to compute global statistics in a multi-partition setting.

Trait Implementations

impl Clone for Statistics

fn clone(&self) -> Statistics

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Statistics

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

Formats the value using the given formatter.

impl Display for Statistics

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

Formats the value using the given formatter.

impl PartialEq for Statistics

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Statistics

impl StructuralPartialEq for Statistics