Struct RequiredColumns 

pub struct RequiredColumns {
    columns: Vec<(Column, StatisticsType, Field)>,
}

Describes which columns statistics are necessary to evaluate a PruningPredicate.

This structure permits reading and creating the minimum number statistics, which is important since statistics may be non trivial to read (e.g. large strings or when there are 1000s of columns).

Handles creating references to the min/max statistics for columns as well as recording which statistics are needed

Fields

columns: Vec<(Column, StatisticsType, Field)>

Implementations

impl RequiredColumns

pub fn single_column(&self) -> Option<&Column>

Returns Some(column) if this is a single column predicate.

Returns None if this is a multi-column predicate.

Examples:

• a > 5 OR a < 10 returns Some(a)
• a > 5 OR b < 10 returns None
• true returns None

Trait Implementations

impl Clone for RequiredColumns

fn clone(&self) -> RequiredColumns

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for RequiredColumns

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

Formats the value using the given formatter.

impl Default for RequiredColumns

fn default() -> RequiredColumns

Returns the “default value” for a type.

impl From<Vec<(Column, StatisticsType, Field)>> for RequiredColumns

fn from(columns: Vec<(Column, StatisticsType, Field)>) -> RequiredColumns

Converts to this type from the input type.