Struct GroupSpec 

pub struct GroupSpec { /* private fields */ }

Groups of rows with equal key values, and aggregates over each group.

use std::sync::Arc;
use arrow_array::{ArrayRef, Decimal128Array, Int64Array, RecordBatch, StringArray};
use densa_data::{Aggregate, GroupSpec, LiveTable};

let trades = |ids: Vec<i64>, desks: Vec<&str>, qty: Vec<i64>| {
    RecordBatch::try_from_iter([
        ("id", Arc::new(Int64Array::from(ids)) as ArrayRef),
        ("desk", Arc::new(StringArray::from(desks)) as ArrayRef),
        ("qty", Arc::new(Int64Array::from(qty)) as ArrayRef),
    ])
};
let mut table = LiveTable::new(trades(vec![], vec![], vec![])?.schema(), "id")?;
let by_desk = table.add_groups(
    GroupSpec::new()
        .group_by("desk")
        .aggregate(Aggregate::count())
        .aggregate(Aggregate::sum("qty")),
)?;
table.upsert(trades(vec![1, 2, 3], vec!["fx", "rates", "fx"], vec![5, 7, 10])?)?;
table.upsert(trades(vec![3], vec!["rates"], vec![10])?)?; // trade 3 moves desk

let totals = table.groups(by_desk).unwrap().to_batch()?; // fx: 1 trade, rates: 2
let qty = totals.column(2).as_any().downcast_ref::<Decimal128Array>().unwrap();
assert_eq!((qty.value(0), qty.value(1)), (5, 17));

Implementations

impl GroupSpec

pub fn new() -> Self

No keys and no aggregates yet. Without keys there is exactly one group, of every counted row, even when there are none.

pub fn group_by(self, column: impl Into<String>) -> Self

Groups by column too, after the key columns given before it. Groups are listed by key in the order views sort: ascending, nulls last. -0.0 and 0.0 are one key, and so are all NaNs.

pub fn aggregate(self, aggregate: Aggregate) -> Self

Adds an aggregate column. Every key and aggregate needs its own name.

pub fn filter(self, filter: Filter) -> Self

Counts only rows for which filter is true.

Trait Implementations

impl Clone for GroupSpec

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for GroupSpec

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

Formats the value using the given formatter.

impl Default for GroupSpec

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for GroupSpec

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for GroupSpec