Trait ObjectIndex

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pub trait ObjectIndex: Send + Sync {
    // Required methods
    fn build(entries: &[IndexEntry]) -> Result<Self>
       where Self: Sized;
    fn lookup(&self, oid: &[u8]) -> Option<IndexRow>;
    fn lookup_batch(&self, oids: &[&[u8]]) -> Vec<Option<IndexRow>>;
    fn ordinals_batch(&self, oids: &[&[u8]]) -> Vec<Option<u32>>;
    fn extents_batch(&self, oids: &[&[u8]]) -> Vec<Option<(u64, u64)>>;
    fn sum_uncompressed(&self) -> u64;
    fn count_type(&self, t: ObjType) -> usize;
    fn name(&self) -> &'static str;
    fn len(&self) -> usize;
    fn ipc_bytes(&self) -> usize;
    fn resident_bytes(&self) -> usize;

    // Provided method
    fn is_empty(&self) -> bool { ... }
}

Expand description

A git object index over Apache Arrow IPC.

build is where Self: Sized, so it stays out of the vtable and Box<dyn ObjectIndex> still works — which is how the bench drives both arms through one loop.

Required Methods§

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fn build(entries: &[IndexEntry]) -> Result<Self>
where Self: Sized,

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fn lookup(&self, oid: &[u8]) -> Option<IndexRow>

Resolve one oid. None for an absent oid and for an oid of the wrong width.

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fn lookup_batch(&self, oids: &[&[u8]]) -> Vec<Option<IndexRow>>

The batch path, and the one that matters: have negotiation sends up to 1000 oids at a time, the push connectivity check sends thousands. Positional — out[i] answers oids[i].

This is the full-row access pattern: all five facts of each object.

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fn ordinals_batch(&self, oids: &[&[u8]]) -> Vec<Option<u32>>

oid → ordinal and stop. No payload column is touched at all.

Identical in every implementation, because every implementation shares the same stree. It is here as the floor: whatever this costs is what no payload layout can remove, and lookup_batch minus this is the only part any of these layouts can change. Without it a three-way tie is unreadable — it could mean the layouts are equivalent, or it could mean the harness never read a payload byte.

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fn extents_batch(&self, oids: &[&[u8]]) -> Vec<Option<(u64, u64)>>

The partial-row access pattern: byte extent only, two of the five facts. This is extents(&[oid]), what the wire path actually asks for when it is about to copy bytes out of a pack.

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fn sum_uncompressed(&self) -> u64

Full column scan: total uncompressed bytes over every object. The quota gate. Reads one 8-byte fact per row and nothing else.

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fn count_type(&self, t: ObjType) -> usize

Full column scan with a predicate: how many objects of this type. Reads one byte per row and nothing else — the most column-shaped query there is, and the one a row-packed layout should lose worst.

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