Method poll_next

datafusion/physical-plan/src/memory.rs:93–122

(
        mut self: std::pin::Pin<&mut Self>,
        _: &mut Context<'_>,
    )

    type Item = Result<RecordBatch>;

    fn poll_next(
        mut self: std::pin::Pin<&mut Self>,
        _: &mut Context<'_>,
    ) -> Poll<Option<Self::Item>> {
        if self.index >= self.data.len() {
            return Poll::Ready(None);
        }
        self.index += 1;
        let batch = &self.data[self.index - 1];
        // return just the columns requested
        let batch = match self.projection.as_ref() {
            Some(columns) => batch.project(columns)?,
            None => batch.clone(),
        };

        let Some(&fetch) = self.fetch.as_ref() else {
            return Poll::Ready(Some(Ok(batch)));
        };
        if fetch == 0 {
            return Poll::Ready(None);
        }

        let batch = if batch.num_rows() > fetch {
            batch.slice(0, fetch)
        } else {
            batch
        };
        self.fetch = Some(fetch - batch.num_rows());
        Poll::Ready(Some(Ok(batch)))
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        (self.data.len(), Some(self.data.len()))