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// Copyright (c) 2026 Austin Han <austinhan1024@gmail.com>
//
// This file is part of RocksGraph.
//
// RocksGraph is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 2 of the License, or
// (at your option) any later version.
//
// RocksGraph is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with RocksGraph. If not, see <https://www.gnu.org/licenses/>.
use crate::types::{PIPELINE_PRODUCE_SIZE, SMALL_VECTOR_LENGTH};
use std::rc::Rc;
use smallvec::{smallvec, SmallVec};
use crate::engine::volcano::steps::traits::ExplainNode;
use crate::{
engine::{
context::GraphCtx,
traverser::Traverser,
volcano::steps::traits::{CoreStep, StepRef},
},
types::{
error::StoreError,
keys::{Rank, DEFAULT_RANK},
Direction, EdgeKey, GValue, LabelId, VertexKey, DIRECTION_INLINE,
},
};
/// A physical step that retrieves specific edges by exact key — a point lookup, used whenever
/// the planner already knows the label(s), end vertex/vertices, and (optionally) rank of the
/// edges being traversed, instead of scanning a vertex's adjacency list and filtering.
///
/// Every template key built in `new` always leaves `primary_id` as the runtime placeholder
/// (filled in with the upstream vertex in `produce`) regardless of direction — `EdgeKey::out_e`
/// and `EdgeKey::in_e` both happen to route their "currently unknown" argument into
/// `primary_id`, so a single unconditional assignment is correct for every key in the buffer,
/// including a mix of OUT and IN keys (the `direction: None` / "both" case).
#[derive(Debug)]
pub struct GetEStep {
// ── Upstream link ──
upstream: Option<StepRef>,
// ── Static/Fixed configuration ──
/// Label IDs to look up (kept for explain()).
label_ids: SmallVec<[LabelId; SMALL_VECTOR_LENGTH]>,
/// End-vertex IDs to look up (kept for explain()).
end_vertex_ids: SmallVec<[VertexKey; SMALL_VECTOR_LENGTH]>,
/// Edge rank (kept for explain()). `None` means DEFAULT_RANK was used.
rank: Option<Rank>,
/// Whether to return the matched edges themselves (true) or the adjacent vertices (false).
output_edges: bool,
/// Whether to link the parent chain on emitted traversers (`false` skips the `Rc::clone`
/// when the plan has no `as()`/`select()`/`path()` anywhere in it).
track_path: bool,
// ── Dynamic/Runtime execution state ──
/// Pre-allocated template EdgeKeys populated with 0 as placeholder for the upstream vertex.
/// Mutated in-place during execution to avoid allocations.
keys_buffer: Vec<EdgeKey>,
}
impl GetEStep {
/// Creates a new `GetEStep` to retrieve edges by exact key.
///
/// `direction`: `Some(OUT)`/`Some(IN)` restricts the lookup to that direction (`outE`/`inE`,
/// or their vertex-emitting `out`/`in` counterparts); `None` builds both an OUT and an IN
/// template per `(label, end_vertex)` pair (`bothE`/`both`).
///
/// `rank`: the edge rank to look up. `None` defaults to `DEFAULT_RANK` — correct whenever
/// the label is known to be single-edge, and the same assumption this step already made
/// before rank filters could be folded in.
pub fn new(
label_ids: SmallVec<[LabelId; SMALL_VECTOR_LENGTH]>,
end_vertex_ids: SmallVec<[VertexKey; SMALL_VECTOR_LENGTH]>,
direction: Option<Direction>,
rank: Option<Rank>,
output_edges: bool,
track_path: bool,
) -> Self {
let directions: SmallVec<[Direction; DIRECTION_INLINE]> = match direction {
Some(d) => smallvec![d],
None => smallvec![Direction::OUT, Direction::IN],
};
let rank = rank.unwrap_or(DEFAULT_RANK);
let mut keys_buffer = Vec::with_capacity(label_ids.len() * end_vertex_ids.len() * directions.len());
for label_id in &label_ids {
for dst in &end_vertex_ids {
for dir in &directions {
let edge_key = match dir {
Direction::OUT => EdgeKey::out_e(0, *label_id, *dst, rank),
Direction::IN => EdgeKey::in_e(*dst, *label_id, 0, rank),
};
keys_buffer.push(edge_key);
}
}
}
Self { upstream: None, label_ids, end_vertex_ids, rank: Some(rank), output_edges, track_path, keys_buffer }
}
}
impl CoreStep for GetEStep {
fn add_upper(&mut self, upstream: StepRef) {
// Sets the upstream step for this edge retrieval.
self.upstream = Some(upstream);
}
fn produce(
&mut self,
ctx: &mut dyn GraphCtx,
) -> Result<Option<SmallVec<[Rc<Traverser>; PIPELINE_PRODUCE_SIZE]>>, StoreError> {
// Produces traversers for edges that match the specified criteria.
loop {
let Some(upstream) = self.upstream.as_ref() else { return Ok(None) };
let Some(t) = upstream.next(ctx)? else { return Ok(None) };
let src = match t.value {
GValue::Vertex(src) => src,
_ => return Err(StoreError::UnexpectedDataType("expected Vertex before outE".into())),
};
let mut results: SmallVec<[_; PIPELINE_PRODUCE_SIZE]> = smallvec![];
let output_edges = self.output_edges;
let to_gvalue = move |edge_key: EdgeKey| {
if output_edges {
GValue::Edge(edge_key)
} else {
GValue::Vertex(edge_key.secondary_id)
}
};
if self.keys_buffer.len() == 1 {
let edge_key = &mut self.keys_buffer[0];
edge_key.primary_id = src;
if ctx.get_edge(edge_key)?.is_some() {
results.push(Traverser::new_rc_conditional(to_gvalue(*edge_key), &t, self.track_path));
}
} else {
for edge_key in &mut self.keys_buffer {
edge_key.primary_id = src;
}
let fetched = ctx.get_edges(&self.keys_buffer)?;
for edge_key in fetched {
results.push(Traverser::new_rc_conditional(to_gvalue(edge_key), &t, self.track_path));
}
}
if !results.is_empty() {
return Ok(Some(results));
}
}
}
fn reset(&mut self) {
// Resets the state of this step and its upstream.
if let Some(up) = &self.upstream {
up.reset();
}
}
fn upper(&self) -> Option<StepRef> {
// Returns a clone of the upstream step reference.
self.upstream.clone()
}
fn explain(&self) -> ExplainNode {
ExplainNode::new("GetEStep").with_params(vec![
("labels", format!("{:?}", self.label_ids)),
("end_vertex_ids", format!("{:?}", self.end_vertex_ids)),
("rank", format!("{:?}", self.rank)),
])
}
}