perf(gfql): seeded typed-hop fast paths use resident indexes (#1658 × #1755)

CHANGELOG.md

@@ -10,6 +10,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Performance
 - **GFQL seeded fast path covers single-alias property RETURNs (LDBC IS5 shape) (#1755)**: `MATCH (m {id})-[:T]->(p) RETURN p.a AS x, p.b` — which lowers to `rows(source=p)+select(items)` rather than a whole-row projection — now takes the seeded typed-hop fast path: the deduped destination rows are renamed/selected directly (value-identical to the rows-pivot + select pipeline; row order may differ). Dtype parity with the full pandas path is exact: non-id properties ride the rows-pivot there, which upcasts int/float to float64 and bool to object, so the lean tail applies the same casts (the id property keeps its dtype); dtype classes not verified against the pivot (datetimes, pandas extension dtypes, categoricals) decline. `res._edges` is the same empty edges frame the full path yields (never None). Conservative declines keep full-path semantics for everything else: cross-alias refs (`RETURN m.x, p.y`), mixed whole-row+property, DISTINCT/ORDER BY/LIMIT (extra lowered ops), expr items, properties absent from the node frame (the full path's null/error semantics must apply), and requested-vs-actual engine mismatches (the full path converts to the requested engine). Differential fast-vs-full sweep across all of the above on pandas + polars: exact parity incl. dtypes and edges, engagement pinned both ways. Measured on LDBC SNB SF1 (dgx, harness row-validated): `message-creator` (IS5) 116.3→38.3 ms on polars (the residue is the seed scan, targeted separately by resident-index coverage).
+- **GFQL seeded typed-hop fast paths use resident indexes (#1658 x #1755)**: with `gfql_index_all()` resident, the seeded fast-path helpers (`_seeded_typed_hop_pandas_cudf`, `_seeded_typed_return_dst_pandas_cudf`, `_seeded_typed_return_dst_polars`) replace their three full-frame scans — O(N) seed-row lookup, O(E) frontier `isin`, O(N) endpoint gather — with positional index lookups (node-id searchsorted + CSR adjacency gather), so a seeded Cypher lookup stops paying graph-size costs entirely. Decline-gated to fall back to the identical scan body: absent/stale index (fingerprint+identity via `get_valid`), non-numeric id families (object/str ids keep the scan path's null semantics), seed not id-filtered. Results identical either way (row order may differ; node-id index implies unique ids). dgx 50k/200k covered-shape: pandas 1.71→0.86ms, polars 2.02→0.69ms (vs Kuzu's same-box 1.06ms); SF1-scale 3.2M/17M polars 47.2→2.25ms — polars numbers measured with a polars-engine index resident, which today requires `gfql_index_all(engine='polars')` on polars frames (until #1767 lands, AUTO index builds swap polars frames to pandas; pandas/cuDF flows are unaffected and independent). Pinned in `TestResidentIndexSeededFastPath` (parity+engagement pandas/polars, string-id decline, stale-index decline, uint64/int64 promote decline, reverse-direction serving).
 - **GFQL seeded typed-hop fast path (#1755)**: a seeded typed 1-hop — native chain `[n({id}), e_forward(), n({type})]` or Cypher `MATCH (m {id})-[:T]->(p) RETURN p` — previously paid the full two-pass chain machinery (~20-40ms: whole-frame combines, full-column type filters, rows-pivot projection). A new seed-first fast path recognizes exactly this shape and reduces the graph to the seed's 1-hop neighborhood before any of that work: native chain 32.6→0.93ms (35×), Cypher RETURN 39.2→1.9ms (20×) on pandas, with cuDF covered via the shared DataFrame API (30.8→4.7ms). Value-identical to the full path by construction (same rows/columns/dtypes; row order and index may differ) — the helpers return `None` and fall through for anything outside the exact shape or carrying full-path side-channels (multi-hop, variable-length, undirected, predicate filters, reverse patterns, missing bindings, list-`labels` columns, policy hooks, same-path WHERE, OPTIONAL MATCH null rows, and WITH..MATCH carried seeds all decline). Null ids/endpoints never link (membership sets are null-dropped, matching the full pipeline's joins). Verified with an independent oracle (results checked against the creator set hand-computed from the raw frames, not merely fast-vs-slow agreement) plus a differential fast-vs-full sweep across shapes × engines in `test_seeded_typed_hop_fastpath.py`.
 - **GFQL seeded typed-hop fast path on polars/polars-gpu (#1755)**: extends the seeded typed-hop Cypher fast path to the polars engines via native polars filters (`_seeded_typed_return_dst_polars`), so a seeded typed 1-hop RETURN also lands in single-digit ms on polars (13.7→3.4ms, 4×) and polars-gpu (24.6→2.5ms, 10×). Dispatch is on the ACTUAL frame type (`is_polars_df`), not the requested engine, because WITH..MATCH reentry can request polars while handing pandas-materialized frames. Same decline contract as the pandas path (undirected/multi-hop/varlen/predicates fall through; value-identical for the covered shape), verified by the per-engine differential sweep and oracle tests in `test_seeded_typed_hop_fastpath.py`.
 - **GFQL two-star grouped-count OLAP queries collect once on polars (#1755)**: profiling showed the residual two-star path (graph-benchmark q5-q7 shapes) spent ~72% of its runtime on the fixed per-op cost of ~27 eager polars operations. When every residual translates natively (see the entry below), the whole plan — base filter_dicts, residual filters, typed-edge filters, semi-joins, group-prop lookup — now composes as ONE `pl.LazyFrame` plan collected once at the join (`filter_by_dict_polars` gains a `filter_expr_by_dict_polars` twin: same column/dtype resolution and typed-error/NIE contract, expression only). Value-identical to the eager lane it replaces (same filters/joins/aggregation), INCLUDING the empty-match boundary: the eager all-left-counts==1 shortcut's single `n=0` row (the openCypher count over no rows) is reproduced — the left-counts frame rides the same single collect. Edges are engine-converted before going lazy, so pandas frames under `engine='polars'` (the WITH..MATCH reentry shape) take the lane instead of crashing; LazyFrame inputs and untranslatable residuals decline to the eager path. Measured on dgx vs warm Kuzu, same session: q5 7.7→3.8ms (flips to a GFQL win vs 5.2), q6 9.8→6.1 (flips vs 7.3), q7 8.7→5.7 (flips vs 6.9) — moving the graph-benchmark scoreboard from 4W/2T/3L to 7W/1T/1L. Differential tests spy the extracted `_connected_join_two_star_fused_polars` helper and ASSERT lane engagement (a `count(*)` query declines the whole two-star path — pinned as a decline shape): fused vs forced-eager exact-row parity (ORDER BY pinned), the ungrouped empty-match n=0 row, pandas-frames-under-polars-engine parity, empty-result shape, pandas oracle.