[rjb32]

Represent every path, named or shortest, as one GraphPath.

[rjb32]

Note

AI-generated summary.

Summary

A named path and a shortest path held the same thing in two types. Now there is one type for a whole path and one for a walk in flight.

 storage type                                    IR type                 produced by
-EntityList  {EntityType, EntityID}[]            !storage.entity_list    db.make_path
-Path        vector<EntityID>, target first      !storage.path           db.shortest_path
+GraphPath   nodes[], edges[], source first      !storage.path           db.make_path, db.shortest_path
 PathRef     handle into the PathTrie            !storage.path_ref       db.explore_paths

A GraphPath holds one node more than edges. A path with no node is the null path an OPTIONAL MATCH binds.

 enum class ColumnInternalKind : uint32_t {
     BOOL,                 // 4
-    PATH,                 // 5
-    EMBEDDING,            // 6
-    ENTITY_LIST,          // 7
-    LIST_VIEW,            // 8
+    EMBEDDING,            // 5
+    LIST_VIEW,            // 6
     ...                   // every later kind moves down by 2
-    DURATION,             // 23
+    DURATION,             // 21
+    GRAPH_PATH,           // 22: [nodeCount][nodes][edges]
 };

Evidence

• Before: MATCH (a {name: 'A'}), (b {name: 'C'}) SHORTESTPATH(a, b, weight, d, p) RETURN d, p → 3 | 2, 2, 1, 0, 0, target first with no node/edge tags. nodes(p) from Adam to Ghosts → 6, 0, 1.
  After: 3 | (0), [0], (1), [2], (2), the same rendering a named path already had. nodes(p) → 1, 0, 6, relationships(p) → 4, 1.
• New TuringProtoRoundTripTest.RoundTripsGraphPathColumnsAcrossChunkSizes: a null path, a zero-length path and a 40-hop path, at chunk sizes 48, 64, 97 and 256, so a resume lands inside the nodes, between nodes and edges, and inside the edges. Passes.
• ctest: 884/884 passed.
• ctest -R test_net after the renumbering: 18/18 passed.
• Not run: the wasm module, because this machine has no emcc. node --check passes on TuringClient.mjs, client_smoke.mjs and decoder_smoke.js.

Merge Danger

Door: one-way once released

PATH (5) and ENTITY_LIST (7) are deleted and every later wire kind moves down by 2, with GRAPH_PATH added at 22. A client and server on different sides of this PR read almost every column type wrongly, not just paths, so they have to be released together. Reverting the code is easy. Reverting a released wire format is not.

Blast Radius: clients

• JSON shortestPath output changes from [0,1,6] to [{"type":"node","id":0},{"type":"edge","id":1},{"type":"node","id":6}].
• The Python column type name of a named path changes from "EntityList" to "Path".
• The shell renders every path as (0), [1], (6), not (0)-[1]->(6). The shortest path docs are updated to match.
• DISTINCT over a shortest path used to throw and now works.