jetro-experimental

Structural-index substrate for fast JSON queries. Standalone stage-1 scanner + Mison-style key-bitmap layer. Built to slot under jetro for $..find(k == lit) shapes without materialising the value tree.

What it does

Given a JSON byte buffer, build:

1. Stage-1 columns from simd-json byte offset, kind, depth for every structural character ({, }, [, ], ", :, ,, scalar starts). AVX2 fast path; scalar/memchr fallback elsewhere.
2. Sidecar — parent[], close_of[] for tree navigation.
3. Mison key bitmaps interned key dictionary with a Roaring bitmap per key over token positions. Compound predicates via bitmap-AND.

Built once, reusable. Queries like $..find(x == "test") use the bitmap to skip every JSON object that doesn't contain key x, and a SIMD byte compare to validate the value. No Val tree allocation.

Why

Mison (Li et al., VLDB 2017) — speculative key-bitmap indices outperform tree walks on selective queries by 10-100×. jetro-experimental is a self-contained Mison-style substrate that builds the structural columns and key bitmaps directly from raw JSON in a single pass.

Architecture

                   ┌──────────────────────────────┐
                   │ JSON bytes (&[u8])           │
                   └──────────────┬───────────────┘
                                  │
                                  ▼
              ┌──────────────────────────────────────────┐
              │ stage-1 SIMD/scalar scan                 │
              │  • emit offset/kind/depth columns        │
              └──────────────────────────────────────────┘
                                  │
                                  ▼
              ┌──────────────────────────────────────┐
              │ index build (one fused walk)         │
              │  • parent / close_of                 │
              │  • role classification               │
              │  • key interner + Roaring bitmaps    │
              └──────────────────────────────────────┘
                                  │
                                  ▼
                    StructuralIndex  +  KeyBitmaps
                                  │
                                  ▼
              ┌─────────┬────────┬──────────┬─────────┐
              │ find_eq │ count  │ ancestors│ slice() │
              │  (Mison)│   (1)  │ (parents)│  raw    │
              └─────────┴────────┴──────────┴─────────┘

Quick start

use jetro_experimental::{from_bytes, find_eq, count_key};

let bytes = br#"{"a":{"x":"test"},"b":{"x":"nope"},"c":{"x":"test"}}"#;
let idx = from_bytes(bytes).unwrap();

// Mison-style: every object whose `x` key equals "test".
for obj_tok in find_eq(&idx, bytes, "x", b"test") {
    let span = idx.byte_span(obj_tok);
    let raw = &bytes[span.start as usize..span.end as usize];
    println!("{}", std::str::from_utf8(raw).unwrap());
}
// → {"x":"test"}
// → {"x":"test"}

// Popcount only — no value walk.
let n = count_key(&idx, "x");
assert_eq!(n, 3);

Public API

Entry points

fn from_bytes(buf: &[u8]) -> Result<StructuralIndex, Error>;
fn from_bytes_with(buf: &[u8], opts: BuildOptions) -> Result<StructuralIndex, Error>;

Per-token

impl StructuralIndex {
    fn kind(&self, tok: TokenId) -> TokenKind;
    fn depth(&self, tok: TokenId) -> u16;
    fn byte_offset(&self, tok: TokenId) -> u32;
    fn byte_span(&self, tok: TokenId) -> ByteSpan;
    fn parent(&self, tok: TokenId) -> Option<TokenId>;
    fn close_of(&self, container: TokenId) -> Option<TokenId>;
    fn slice<'a>(&self, bytes: &'a [u8], tok: TokenId) -> &'a [u8];
}

Byte-position lookup

fn container_at_byte(&self, pos: u32) -> Option<TokenId>;
fn ancestors(&self, tok: TokenId) -> Ancestors<'_>;

Mison key layer

fn keys_named(&self, name: &str, depth: Option<u16>) -> KeyHits<'_>;
fn has_key(&self, name: &str) -> bool;
fn keys_seen(&self) -> impl Iterator<Item = &str> + '_;
fn value_for_key(&self, key_tok: TokenId) -> Option<TokenId>;

KeyHits — lazy composable

impl KeyHits<'_> {
    fn at_depth(self, d: u16) -> Self;
    fn and(self, other: Self) -> Self;        // bitmap intersect
    fn or(self, other: Self) -> Self;
    fn count(self) -> u64;                    // O(1) popcount
    fn first(self) -> Option<TokenId>;        // short-circuit
    fn last(self) -> Option<TokenId>;
}
impl Iterator for KeyHits<'_> { type Item = TokenId; }

Fused query primitives

fn find_eq<'a>(idx, bytes, key, literal) -> impl Iterator<Item = TokenId>;
fn find_eq_compound<'a>(idx, bytes, conds) -> impl Iterator<Item = TokenId>;
fn count_key(idx, key) -> u64;

SIMD helpers

fn json_string_eq(value: &[u8], literal: &[u8]) -> bool;     // memchr escape probe
fn json_number_eq(value: &[u8], literal: &[u8]) -> bool;     // numeric semantics
fn parse_f64(bytes: &[u8]) -> Option<f64>;                   // fast-float when "fast-numbers"
fn parse_i64(bytes: &[u8]) -> Option<i64>;

Feature flags

Default: minimal. No external SIMD-JSON dependency — stage-1 of simd-json is fully self-contained.

Status

Pre-1.0. Public API is stable (StructuralIndex, TokenId, fused helpers). Internals (Stage1, KeyBitmaps, StructIndex) are #[doc(hidden)] and may change without semver bumps.

Roadmap

• Stage-1 SIMD scanner (AVX2 + scalar/memchr fallback)
• StructuralIndex + Mison KeyBitmaps
• Public API facade with opaque types
• SIMD helpers: json_string_eq, parse_f64, multi-key, utf8 validation
• NEON stage-1 port (currently scalar+memchr fallback on aarch64)
• Streaming IndexBuilder for NDJSON / huge inputs

License

This repository contain direct copy of Stage 1 from simd-json project.

MIT/Apache-2.0.