[sulaimansuhas]

Unwind a list of datetimes, durations, points, maps, embeddings or paths into a column of that type instead of type-erased cells.

Stacked on #1448 (bot stack main): review and merge #1448 first.

[sulaimansuhas]

Note

AI-generated summary.

Summary

unwoundElementType picks the column type an UNWIND of a list yields. It used an allow-list of six element types (node, edge, string, list, f64, i1/i64). Every other typed list fell into !storage.any cells. The allow-list is gone; the rule is now the type system's own:

 unwoundElementType(list<T>)
-  if T not in {node_id, edge_id, string, list, f64, i1, i64}
-    return !storage.any
-  if T is node_id or edge_id
-    return T
-  return nullable<T>
+  if holdsItsOwnNull(T)                       # any, node_id, edge_id, path
+    return T
+  else if elementTypeToValueType(T) == Invalid  # mixed list, nulls alone
+    return !storage.any
+  return nullable<T>                          # datetime, duration, point, map, embedding, ...

Two follow-ons make that rule reach every case:

literalElementType          DictionaryAttr  -> !storage.map
                            DenseF32ArrayAttr -> !storage.embedding
                            so [{a: 1}, {a: 2}] and [(1, 5), (2, 3)] get a shared element type

sort key dispatch           NLChunkKind::Path used to throw "a path has no order here"
  comparePathColumn         now orders it, the empty (null) path last
    operator<=>(PathView)   lexicographic over IDs, shared with CellOrder's Path case

The path sort key is needed because UNWIND [p, null] AS q ... ORDER BY q used to sort !storage.any cells through CellOrder. It now sorts a path column, which had no comparator.

Evidence

Run locally on 074e4b87, binaries up to date (ninja -n reported no work):

test_query_ir_unwind_typed_list        13 tests  PASSED   (new)
test_query_ir_path_sort_key             2 tests  PASSED   (new)
test_query_ir_list_of_maps             21 tests  PASSED
test_query_ir_datetime_component_cell   7 tests  PASSED
test_query_ir_duration_component_cell   7 tests  PASSED

UnwindTypedListTest checks both the rows and the EXPLAIN (nl) iterator type of each unwind:

UNWIND [duration(1000000), duration(90061000000)] AS d RETURN d.hours, d.seconds
  before: !nl.iter<!nl.chunk<!storage.any>, ...>
  after:  !nl.iter<!nl.chunk<!storage.nullable<!storage.duration>>, ...>   rows (0, 1), (25, 90061)

MATCH p = ... UNWIND [p, null] AS q WITH q ORDER BY q RETURN length(q)
  after:  !storage.path column, rows 1, null

The same holds for datetimes, points, maps, embeddings, collected properties (collect(n.took)) and collected paths. DateTimeComponentCellTest and DurationComponentCellTest gain a case that reads a field off a map value and a mixed-list element, because an unwind no longer reaches the type-erased cell path those tests covered. I did not run the full ctest suite.

Merge Danger

Door: two-way

No stored format or wire format changes. The change only picks a different chunk type at lowering time.

Blast Radius: query-wide

Every query that unwinds a typed list of a type outside the old allow-list now reads a typed column, not !storage.any cells. Any nl op or executor kernel without a case for nullable<datetime|duration|point|map|embedding> or path can now fail on such a query, as the path sort key did. The new tests cover field access, comparison, + duration, DISTINCT, grouping and ORDER BY. Other consumers, such as the list functions over an unwound value, are not covered here.