Struct Groups 

pub struct Groups<'a> { /* private fields */ }

The groups of a GroupSpec, ordered by key. Cheap to get.

Implementations

impl Groups<'_>

pub fn len(&self) -> usize

Number of groups: the rows of to_batch. A spec without keys always has one.

pub fn is_empty(&self) -> bool

Whether there are no groups: the spec has keys and no row is counted.

pub fn revision(&self) -> u64

Increases whenever a group changes (and sometimes when a bulk change recounts the same groups): rebuild a display of to_batch only when it moved.

pub fn to_batch(&self) -> Result<RecordBatch, DataError>

The groups as one record batch, one row per group in key order: the key columns, then each aggregate. Keys, min and max have the column’s type, except that dictionary columns come out decoded (as their value type) and floats canonical (0.0 for -0.0, one NaN). Counts are UInt64, never null. Sums of integers are Decimal128(38, 0), which holds any sum a table can produce; sums of decimals Decimal128(38, scale), null if the exact sum needs more than 38 digits; sums of floats Float64. Means are Float64. Any other aggregate over no values is null. Allocates.

Errors

DataError::Arrow if Arrow cannot assemble a column (over 2 GiB of strings).

Trait Implementations

impl<'a> Clone for Groups<'a>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<'a> Copy for Groups<'a>

impl<'a> Debug for Groups<'a>

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

Formats the value using the given formatter.