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GFQL Cypher: var-length path trail semantics + lane-dependent cardinality (round-005 umbrella) #1903
Description
Activity
Umbrella verified served on master
e6625ed28— recommending close after review, with one bookkeeping dependency noted below.pandas: 13/13 hand-oracled checks pass — the silent-wrong lanes are gone:
- one-MATCH three-lanes now agree (
y-only=[d,d],count=2, two-alias=2) - 3-cycle undirected
[*2]→[b,c]; self-loop[*2]→ 0 rows - cross-element relationship-uniqueness → 0; parallel-edge 2-hop → 2
- undirected self-loop rows=count=1; shortest-path unreachable → 0 rows
[*0..1]keeps the zero-hop row;[*..2]parses
polars: every lane that used to return wrong values now raises a typed NotImplementedError instead — fwd/rev min_hops>1 lanes cite #1748 by number; undirected min_hops>1 cites the deferred-features NIE (tracked in #1906). Where polars answers, values match the pandas oracle. So: no silent-wrong remains; all residual work is split into open issues.
Bookkeeping: #1748's own filed defect is now resolved-by-decline (verified separately), but the polars NIE messages cite #1748 as the tracker for native hop-gating — if #1748 is closed, that native-polars feature needs a successor tracker (or fold it into #1906) so the citation doesn't dangle.
- one-MATCH three-lanes now agree (
Round-005 path probe (76 queries × both engines @ d8668fd, hand-computed trail-semantics oracles, twice-verified; scripts in session scratchpad probe-paths/). Fixtures: diamond, directed 3-cycle, self-loop, parallel edges, typed, disconnected.
SILENT-WRONG:
[*2]):RETURN y.id→1 row,count(*)→2,RETURN x.id, y.id→2. Single-alias endpoint projections compile to a reachability lane that collapses path multiplicity.[*2]→ [] vs oracle [b,c]); the two-alias row lane gets it right — pandas disagrees with itself.[*2]on self-loop returns (s,s), count 2 vs oracle 1; yet[*3]→ 0 — neither walk nor trail).(x)-[]->(m)-[]-(y)on a single-edge graph reuses the edge → 1 row vs oracle 0; parallel-edge 2-hop 6 vs 4.[*0..1]silently drops the zero-hop seed (pandas correct; polars' own NIE text lists include_zero_hop_seed as must-error, but these forms don't raise).TYPED-GAP: 8.
[*..3](valid openCypher omitted-lower-bound) → GFQLSyntaxError; parser grammar (~904-953) lacks the*..Mproduction; also blocks bounded shortestPath.Honest NIEs and a solid correct inventory (cycle termination exact, typed alternation, shortestPath ties/typed/min-bound) in the probe report. Net: path counting is only trustworthy via multi-alias row projections or grouped aggregates on acyclic neighborhoods. Successor context: #1748 (polars var-length), #1658 (CSR engagement).