AS OF SYSTEM TIME NULL combined with any WHERE predicate returns zero rows

[mkhairi]

Tested against: origin/main @ 8e84501a (post-v0.3.0 main head, 2026-07-07)

Severity: High — per-record history reads are the primary query shape on
a BITEMPORAL collection; every such read silently returns empty, making the
audit surface unusable while writes keep succeeding.

Summary

On a BITEMPORAL document_strict collection, a version-history scan
(AS OF SYSTEM TIME NULL) that also carries a WHERE predicate
returns 0 rows silently. The bare AS OF SYSTEM TIME NULL scan on
the same collection returns the full version set with correct
_ts_system / _ts_valid_from / _ts_valid_until projections, so the
versioned store itself is intact — only the predicate-carrying scan
path drops everything. ORDER BY makes no difference. The result also
comes back with a placeholder result column header instead of the
collection's columns, suggesting the query resolves to an empty
synthetic result rather than a filtered scan.

Regression relative to 67c4572d, where AS OF SYSTEM TIME NULL WHERE id = ... returned that record's versions; plausibly fallout of the
recent unification of bitemporal document scans onto a shared pipeline.

Repro

CREATE COLLECTION asof_repro (id TEXT PRIMARY KEY, v TEXT, BITEMPORAL) ENGINE = document_strict;
INSERT INTO asof_repro (id, v) VALUES ('a','one');
UPDATE asof_repro SET v = 'two' WHERE id = 'a';

SELECT * FROM asof_repro AS OF SYSTEM TIME NULL;
--  id | _ts_system    | _ts_valid_from       | _ts_valid_until     | v
--  a  | 1783400895366 | -9223372036854775808 | 9223372036854775807 | one
--  a  | 1783400895370 | -9223372036854775808 | 9223372036854775807 | two
-- (2 rows)                          -- full history, correct

SELECT * FROM asof_repro AS OF SYSTEM TIME NULL WHERE id = 'a';
--  result
-- (0 rows)                          -- WRONG: expected the same 2 versions

SELECT * FROM asof_repro AS OF SYSTEM TIME NULL WHERE id = 'a' ORDER BY _ts_system;
-- (0 rows)                          -- WRONG

Expected

1. AS OF SYSTEM TIME NULL + WHERE returns the version rows matching
   the predicate — filtering a history scan must not differ semantically
   from filtering a plain scan.
2. The result carries the collection's real column set (as the bare
   scan already does), not a placeholder result column.

Files (best-guess)

• nodedb/src/data/executor/handlers/document/read/fetch.rs — new
  shared fetch pipeline; the predicate path appears not to be wired for
  all-versions scans.
• nodedb/src/data/executor/dispatch/document.rs — dispatch may route
  predicate-carrying AS OF reads to a path that ignores the version
  store.

Operational context

The whole point of a BITEMPORAL collection is answering "what did this
record look like over time" — i.e. AS OF SYSTEM TIME NULL WHERE <key>.
With that shape returning empty, audit-trail consumers must scan the
entire history of every record and filter client-side, which is
unbounded on a growing audit log.