lora_executor/pull/
source.rs

1use crate::errors::ExecResult;
2use crate::value::Row;
3
4/// Fallible pull-based row cursor.
5///
6/// Each call to [`RowSource::next_row`] returns the next row,
7/// `Ok(None)` when the cursor is exhausted, or an error if execution
8/// fails. The cursor stays in a valid state after an error — callers
9/// may drop it without observing additional side effects.
10pub trait RowSource {
11    /// Pull the next row.
12    fn next_row(&mut self) -> ExecResult<Option<Row>>;
13}
14
15/// Drain a row source into a `Vec<Row>`, propagating the first error.
16pub fn drain<S: RowSource + ?Sized>(source: &mut S) -> ExecResult<Vec<Row>> {
17    let mut out = Vec::new();
18    while let Some(row) = source.next_row()? {
19        out.push(row);
20    }
21    Ok(out)
22}
23
24/// Buffered cursor backed by a pre-computed `Vec<Row>`. Used both as
25/// a simple "rows already collected" adapter and as the leaf fallback
26/// for operators whose internals still require full materialization.
27pub struct BufferedRowSource {
28    iter: std::vec::IntoIter<Row>,
29}
30
31impl BufferedRowSource {
32    pub fn new(rows: Vec<Row>) -> Self {
33        Self {
34            iter: rows.into_iter(),
35        }
36    }
37}
38
39impl RowSource for BufferedRowSource {
40    fn next_row(&mut self) -> ExecResult<Option<Row>> {
41        Ok(self.iter.next())
42    }
43}
44
45/// Yields a single empty row exactly once. The bottom of every plan
46/// chain that doesn't start with an explicit input.
47pub struct ArgumentSource {
48    yielded: bool,
49}
50
51impl ArgumentSource {
52    pub fn new() -> Self {
53        Self { yielded: false }
54    }
55}
56
57impl Default for ArgumentSource {
58    fn default() -> Self {
59        Self::new()
60    }
61}
62
63impl RowSource for ArgumentSource {
64    fn next_row(&mut self) -> ExecResult<Option<Row>> {
65        if self.yielded {
66            Ok(None)
67        } else {
68            self.yielded = true;
69            Ok(Some(Row::new()))
70        }
71    }
72}
lora_executor/pull/source.rs

lora_executor/pull/
source.rs
