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)>

The statistics required to evaluate this predicate:

• The unqualified column in the input schema
• Statistics type (e.g. Min or Max or Null_Count)
• The field the statistics value should be placed in for pruning predicate evaluation (e.g. min_value or max_value)

Implementations

impl RequiredColumns

fn new() -> Self

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

fn schema(&self) -> Schema

Returns a schema that describes the columns required to evaluate this pruning predicate. The schema contains the fields for each column in self.columns with the appropriate data type for the statistics. Order matters, this same order is used to evaluate the pruning predicate.

pub(crate) fn iter( &self, ) -> impl Iterator<Item = &(Column, StatisticsType, Field)>

Returns an iterator over items in columns (see doc on self.columns for details)

fn find_stat_column( &self, column: &Column, statistics_type: StatisticsType, ) -> Option<usize>

fn stat_column_expr( &mut self, column: &Column, column_expr: &Arc<dyn PhysicalExpr>, field: &Field, stat_type: StatisticsType, ) -> Result<Arc<dyn PhysicalExpr>>

Rewrites column_expr so that all appearances of column are replaced with a reference to either the min or max statistics column, while keeping track that a reference to the statistics column is required

for example, an expression like col("foo") > 5, when called with Max would result in an expression like col("foo_max") > 5 with the appropriate entry noted in self.columns

fn min_column_expr( &mut self, column: &Column, column_expr: &Arc<dyn PhysicalExpr>, field: &Field, ) -> Result<Arc<dyn PhysicalExpr>>

rewrite col –> col_min

fn max_column_expr( &mut self, column: &Column, column_expr: &Arc<dyn PhysicalExpr>, field: &Field, ) -> Result<Arc<dyn PhysicalExpr>>

rewrite col –> col_max

fn null_count_column_expr( &mut self, column: &Column, column_expr: &Arc<dyn PhysicalExpr>, field: &Field, ) -> Result<Arc<dyn PhysicalExpr>>

rewrite col –> col_null_count

fn row_count_column_expr( &mut self, column: &Column, column_expr: &Arc<dyn PhysicalExpr>, field: &Field, ) -> Result<Arc<dyn PhysicalExpr>>

rewrite col –> col_row_count

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

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)>) -> Self

Converts to this type from the input type.