Struct Accumulator 

pub struct Accumulator { /* private fields */ }

A running aggregate.

Implementations

impl Accumulator

pub fn new(name: &str, returns: &LogicalType) -> Result<Self>

A fresh accumulator for a named aggregate returning returns.

Errors

If the name is not an aggregate this crate implements.

pub fn update(&mut self, args: &[Value]) -> Result<()>

Folds one row in.

Errors

If the argument count is wrong for the aggregate, if the value is not one the aggregate can accumulate, or if a whole running total overflows.

pub fn update_run(&mut self, args: &[Vector], rows: usize) -> Result<()>

Folds a whole vector in, in one pass over the data and without building a Value per row.

rows is how many rows to fold, which is the row count of the chunk rather than the capacity of the vectors in it. count(*) takes no argument and reads nothing but that number, and every other aggregate here takes exactly one vector.

A shape the one pass form does not cover falls through to Accumulator::update per row and records itself in crate::fallback, so this always reaches the answer the row at a time loop reaches and never a different one. That is not a slogan about floating point: the running total below is carried into the vector loop rather than restarted at zero, precisely so that the additions happen in the same order and round the same way.

Errors

The same errors Accumulator::update raises, for the same reasons.

pub fn finish(&self) -> Result<Value>

The aggregate’s answer.

Errors

If the running total does not fit the declared return type.

Trait Implementations

impl Clone for Accumulator

fn clone(&self) -> Accumulator

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Accumulator

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

Formats the value using the given formatter.