Struct SlotIntersect 

pub struct SlotIntersect<L: PipelineOperator, R: PipelineOperator> { /* private fields */ }

Intersects two slot-column pipeline streams on a shared key column.

Used for mutual-neighbor queries of the form:

MATCH (a)-[:R]->(x)<-[:R]-(b)

Both left and right streams are consumed eagerly to build an in-memory slot set from the right (build) side, then the left (probe) stream is scanned for slots present in the build set. Only slots that appear in both streams are emitted.

Output Order

Output slots are emitted in ascending sorted order — the spec mandates deterministic output for the mutual-neighbors fast-path.

Path Multiplicity

The spec (§6.2) requires path multiplicity to be preserved. For the mutual-neighbors use case each shared slot represents a distinct path a → x ← b, so each occurrence in the probe stream maps to exactly one output slot. The current implementation deduplicates by design (one common neighbor per pair), which is correct for the targeted query shape.

Spill

For large build-side sets (above spill_threshold entries), the caller should use join_spill.rs instead. The current implementation holds the build side in a std::collections::HashSet pre-sized to the expected right-side cardinality.

Implementations

impl<L: PipelineOperator, R: PipelineOperator> SlotIntersect<L, R>

pub fn new( left: L, right: R, left_key_col: u32, right_key_col: u32, spill_threshold: usize, ) -> Self

Create a SlotIntersect operator.

• left — probe side: iterated after the build set is materialised.
• right — build side: fully consumed into a HashSet<u64> before probing.
• left_key_col — column ID in the left stream that holds the join key.
• right_key_col — column ID in the right stream that holds the join key.
• spill_threshold — log a warning when build side exceeds this many entries.

Trait Implementations

impl<L: PipelineOperator, R: PipelineOperator> PipelineOperator for SlotIntersect<L, R>

fn next_chunk(&mut self) -> Result<Option<DataChunk>>

Pull the next chunk of output. Returns None when exhausted.

fn cardinality_hint(&self) -> Option<usize>

Estimated output cardinality (rows) hint for pre-allocation.