Struct View 

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

The rows of a view, in its order. Cheap to get; reading never allocates.

A row is a RowRef: which of LiveTable::batches holds it, and where. Read its values from that batch’s columns:

use std::sync::Arc;
use densa_data::arrow_array::cast::AsArray;
use densa_data::arrow_array::{ArrayRef, Float64Array, RecordBatch, StringArray};
use densa_data::{LiveTable, Order, ViewSpec};

let rows = RecordBatch::try_from_iter([
    ("symbol", Arc::new(StringArray::from(vec!["AAA", "BBB"])) as ArrayRef),
    ("price", Arc::new(Float64Array::from(vec![150.0, 90.0])) as ArrayRef),
])?;
let mut table = LiveTable::new(rows.schema(), "symbol")?;
let cheapest = table.add_view(ViewSpec::new().sort_by("price", Order::Ascending))?;
table.upsert(rows)?;

let view = table.view(cheapest).unwrap();
let symbols: Vec<&str> = (0..view.len())
    .filter_map(|i| view.row(i))
    .map(|at| {
        let batch = &table.batches()[at.batch];
        // The column's Arrow type, as the table's schema has it (Utf8 here).
        batch.column_by_name("symbol").unwrap().as_string::<i32>().value(at.row)
    })
    .collect();
assert_eq!(symbols, ["BBB", "AAA"]);

Implementations

impl View<'_>

pub fn len(&self) -> usize

Rows in the view.

pub fn is_empty(&self) -> bool

Whether the view is empty.

pub fn row(&self, index: usize) -> Option<RowRef>

Where the row at index (0 is first) is. O(log n).

pub fn record(&self, index: usize) -> Option<RecordId>

The record of the row at index. O(log n).

pub fn position(&self, record: RecordId) -> Option<usize>

Where record’s row is in the view, or None if it is not in it (filtered out, or its key deleted). O(log n): binary searches comparing the row’s sort values.

Trait Implementations

impl<'a> Clone for View<'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 View<'a>

impl<'a> Debug for View<'a>

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

Formats the value using the given formatter.