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FA-44451 / Data systems / Open access

A null list exposes its physically retained child values · case 01

A null list exposes its physically retained child values.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

list-offset-slice: A null list exposes its physically retained child values.

VERIFIED REPAIR

Preserve the stated physical representation and operation order: Gather selected list rows from offset-based child storage. Parent nullness hides child storage; empty valid lists remain []; child nulls remain None. Preserve repeated selected rows and list element order.

Unsuccessful approach: Replacing null lists with empty lists confuses absence with cardinality zero.

Case contract

Gather selected list rows from offset-based child storage. Parent nullness hides child storage; empty valid lists remain []; child nulls remain None. Preserve repeated selected rows and list element order.

Why this case matters

A bounded deterministic data engine model makes representation and changelog faults reproducible.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(d):
    try:
        offsets,child,parents,valid,selection=d
        out=[]
        for row in selection:
            lo=offsets[row]
            hi=offsets[row+1]
            items=[child[i] if valid[i] else None for i in range(lo,hi)]
            out.append(items)
        return out
    except (IndexError, KeyError, ValueError, StopIteration) as exc:
        return {"representation_error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
if N == 1:
    check('shared child offsets', solve([[0, 2, 3], [1, 2, 3], [True, True], [True, True, True], [1, 0]]), [[3], [1, 2]])
    check('null child', solve([[0, 2], [1, 2], [True], [False, True], [0]]), [[None, 2]])
    check('hidden null list', solve([[0, 2], [1, 2], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [1], [True, True], [True], [0, 1]]), [[], [1]])
    check('repeated list', solve([[0, 1, 2], [1, 2], [True, True], [True, True], [1, 1]]), [[2], [2]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 1, 2], [True], [True, True, True], [0]]), [[1, 2]])
elif N == 2:
    check('shared child offsets', solve([[0, 2, 3], [2, 3, 4], [True, True], [True, True, True], [1, 0]]), [[4], [2, 3]])
    check('null child', solve([[0, 2], [2, 3], [True], [False, True], [0]]), [[None, 3]])
    check('hidden null list', solve([[0, 2], [2, 3], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [2], [True, True], [True], [0, 1]]), [[], [2]])
    check('repeated list', solve([[0, 1, 2], [2, 3], [True, True], [True, True], [1, 1]]), [[3], [3]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 2, 3], [True], [True, True, True], [0]]), [[2, 3]])
elif N == 3:
    check('shared child offsets', solve([[0, 2, 3], [3, 4, 5], [True, True], [True, True, True], [1, 0]]), [[5], [3, 4]])
    check('null child', solve([[0, 2], [3, 4], [True], [False, True], [0]]), [[None, 4]])
    check('hidden null list', solve([[0, 2], [3, 4], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [3], [True, True], [True], [0, 1]]), [[], [3]])
    check('repeated list', solve([[0, 1, 2], [3, 4], [True, True], [True, True], [1, 1]]), [[4], [4]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 3, 4], [True], [True, True, True], [0]]), [[3, 4]])
elif N == 4:
    check('shared child offsets', solve([[0, 2, 3], [4, 5, 6], [True, True], [True, True, True], [1, 0]]), [[6], [4, 5]])
    check('null child', solve([[0, 2], [4, 5], [True], [False, True], [0]]), [[None, 5]])
    check('hidden null list', solve([[0, 2], [4, 5], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [4], [True, True], [True], [0, 1]]), [[], [4]])
    check('repeated list', solve([[0, 1, 2], [4, 5], [True, True], [True, True], [1, 1]]), [[5], [5]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 4, 5], [True], [True, True, True], [0]]), [[4, 5]])
elif N == 5:
    check('shared child offsets', solve([[0, 2, 3], [5, 6, 7], [True, True], [True, True, True], [1, 0]]), [[7], [5, 6]])
    check('null child', solve([[0, 2], [5, 6], [True], [False, True], [0]]), [[None, 6]])
    check('hidden null list', solve([[0, 2], [5, 6], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [5], [True, True], [True], [0, 1]]), [[], [5]])
    check('repeated list', solve([[0, 1, 2], [5, 6], [True, True], [True, True], [1, 1]]), [[6], [6]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 5, 6], [True], [True, True, True], [0]]), [[5, 6]])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
shared child offsets[[3], [1, 2]][[3], [1, 2]]Passed
null child[[None, 2]][[None, 2]]Passed
hidden null list[[1, 2]][None]Failed
empty valid list[[], [1]][[], [1]]Passed
repeated list[[2], [2]][[2], [2]]Passed
no rows[][]Passed
nonzero physical origin[[1, 2]][[1, 2]]Passed

SHA-256 / 64aa4b05bce9fd1c39ad3ab14a4f48903534d40da2d0dc7527066d20b6353142

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(d):
    try:
        offsets,child,parents,valid,selection=d
        out=[]
        for row in selection:
            lo=offsets[row]
            hi=offsets[row+1]
            items=[child[i] if valid[i] else None for i in range(lo,hi)]
            out.append(items if parents[row] else [])
        return out
    except (IndexError, KeyError, ValueError, StopIteration) as exc:
        return {"representation_error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
if N == 1:
    check('shared child offsets', solve([[0, 2, 3], [1, 2, 3], [True, True], [True, True, True], [1, 0]]), [[3], [1, 2]])
    check('null child', solve([[0, 2], [1, 2], [True], [False, True], [0]]), [[None, 2]])
    check('hidden null list', solve([[0, 2], [1, 2], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [1], [True, True], [True], [0, 1]]), [[], [1]])
    check('repeated list', solve([[0, 1, 2], [1, 2], [True, True], [True, True], [1, 1]]), [[2], [2]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 1, 2], [True], [True, True, True], [0]]), [[1, 2]])
elif N == 2:
    check('shared child offsets', solve([[0, 2, 3], [2, 3, 4], [True, True], [True, True, True], [1, 0]]), [[4], [2, 3]])
    check('null child', solve([[0, 2], [2, 3], [True], [False, True], [0]]), [[None, 3]])
    check('hidden null list', solve([[0, 2], [2, 3], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [2], [True, True], [True], [0, 1]]), [[], [2]])
    check('repeated list', solve([[0, 1, 2], [2, 3], [True, True], [True, True], [1, 1]]), [[3], [3]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 2, 3], [True], [True, True, True], [0]]), [[2, 3]])
elif N == 3:
    check('shared child offsets', solve([[0, 2, 3], [3, 4, 5], [True, True], [True, True, True], [1, 0]]), [[5], [3, 4]])
    check('null child', solve([[0, 2], [3, 4], [True], [False, True], [0]]), [[None, 4]])
    check('hidden null list', solve([[0, 2], [3, 4], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [3], [True, True], [True], [0, 1]]), [[], [3]])
    check('repeated list', solve([[0, 1, 2], [3, 4], [True, True], [True, True], [1, 1]]), [[4], [4]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 3, 4], [True], [True, True, True], [0]]), [[3, 4]])
elif N == 4:
    check('shared child offsets', solve([[0, 2, 3], [4, 5, 6], [True, True], [True, True, True], [1, 0]]), [[6], [4, 5]])
    check('null child', solve([[0, 2], [4, 5], [True], [False, True], [0]]), [[None, 5]])
    check('hidden null list', solve([[0, 2], [4, 5], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [4], [True, True], [True], [0, 1]]), [[], [4]])
    check('repeated list', solve([[0, 1, 2], [4, 5], [True, True], [True, True], [1, 1]]), [[5], [5]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 4, 5], [True], [True, True, True], [0]]), [[4, 5]])
elif N == 5:
    check('shared child offsets', solve([[0, 2, 3], [5, 6, 7], [True, True], [True, True, True], [1, 0]]), [[7], [5, 6]])
    check('null child', solve([[0, 2], [5, 6], [True], [False, True], [0]]), [[None, 6]])
    check('hidden null list', solve([[0, 2], [5, 6], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [5], [True, True], [True], [0, 1]]), [[], [5]])
    check('repeated list', solve([[0, 1, 2], [5, 6], [True, True], [True, True], [1, 1]]), [[6], [6]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 5, 6], [True], [True, True, True], [0]]), [[5, 6]])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
shared child offsets[[3], [1, 2]][[3], [1, 2]]Passed
null child[[None, 2]][[None, 2]]Passed
hidden null list[[]][None]Failed
empty valid list[[], [1]][[], [1]]Passed
repeated list[[2], [2]][[2], [2]]Passed
no rows[][]Passed
nonzero physical origin[[1, 2]][[1, 2]]Passed

SHA-256 / 896a7292fadb5363f179268906925045c26b71b68c99c7a30d46ed2de517e338

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(d):
    try:
        offsets,child,parents,valid,selection=d
        out=[]
        for row in selection:
            lo=offsets[row]
            hi=offsets[row+1]
            items=[child[i] if valid[i] else None for i in range(lo,hi)]
            out.append(items if parents[row] else None)
        return out
    except (IndexError, KeyError, ValueError, StopIteration) as exc:
        return {"representation_error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
if N == 1:
    check('shared child offsets', solve([[0, 2, 3], [1, 2, 3], [True, True], [True, True, True], [1, 0]]), [[3], [1, 2]])
    check('null child', solve([[0, 2], [1, 2], [True], [False, True], [0]]), [[None, 2]])
    check('hidden null list', solve([[0, 2], [1, 2], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [1], [True, True], [True], [0, 1]]), [[], [1]])
    check('repeated list', solve([[0, 1, 2], [1, 2], [True, True], [True, True], [1, 1]]), [[2], [2]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 1, 2], [True], [True, True, True], [0]]), [[1, 2]])
elif N == 2:
    check('shared child offsets', solve([[0, 2, 3], [2, 3, 4], [True, True], [True, True, True], [1, 0]]), [[4], [2, 3]])
    check('null child', solve([[0, 2], [2, 3], [True], [False, True], [0]]), [[None, 3]])
    check('hidden null list', solve([[0, 2], [2, 3], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [2], [True, True], [True], [0, 1]]), [[], [2]])
    check('repeated list', solve([[0, 1, 2], [2, 3], [True, True], [True, True], [1, 1]]), [[3], [3]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 2, 3], [True], [True, True, True], [0]]), [[2, 3]])
elif N == 3:
    check('shared child offsets', solve([[0, 2, 3], [3, 4, 5], [True, True], [True, True, True], [1, 0]]), [[5], [3, 4]])
    check('null child', solve([[0, 2], [3, 4], [True], [False, True], [0]]), [[None, 4]])
    check('hidden null list', solve([[0, 2], [3, 4], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [3], [True, True], [True], [0, 1]]), [[], [3]])
    check('repeated list', solve([[0, 1, 2], [3, 4], [True, True], [True, True], [1, 1]]), [[4], [4]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 3, 4], [True], [True, True, True], [0]]), [[3, 4]])
elif N == 4:
    check('shared child offsets', solve([[0, 2, 3], [4, 5, 6], [True, True], [True, True, True], [1, 0]]), [[6], [4, 5]])
    check('null child', solve([[0, 2], [4, 5], [True], [False, True], [0]]), [[None, 5]])
    check('hidden null list', solve([[0, 2], [4, 5], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [4], [True, True], [True], [0, 1]]), [[], [4]])
    check('repeated list', solve([[0, 1, 2], [4, 5], [True, True], [True, True], [1, 1]]), [[5], [5]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 4, 5], [True], [True, True, True], [0]]), [[4, 5]])
elif N == 5:
    check('shared child offsets', solve([[0, 2, 3], [5, 6, 7], [True, True], [True, True, True], [1, 0]]), [[7], [5, 6]])
    check('null child', solve([[0, 2], [5, 6], [True], [False, True], [0]]), [[None, 6]])
    check('hidden null list', solve([[0, 2], [5, 6], [False], [True, True], [0]]), [None])
    check('empty valid list', solve([[0, 0, 1], [5], [True, True], [True], [0, 1]]), [[], [5]])
    check('repeated list', solve([[0, 1, 2], [5, 6], [True, True], [True, True], [1, 1]]), [[6], [6]])
    check('no rows', solve([[0], [], [], [], []]), [])
    check('nonzero physical origin', solve([[1, 3], [0, 5, 6], [True], [True, True, True], [0]]), [[5, 6]])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
shared child offsets[[3], [1, 2]][[3], [1, 2]]Passed
null child[[None, 2]][[None, 2]]Passed
hidden null list[None][None]Passed
empty valid list[[], [1]][[], [1]]Passed
repeated list[[2], [2]][[2], [2]]Passed
no rows[][]Passed
nonzero physical origin[[1, 2]][[1, 2]]Passed

SHA-256 / 8b82b4b1704df7570994e3cdfa1520cd2e8d47c877862c456aa26cb0a9a578b7

Verification & scope

Offline stipulated semantics over valid small inputs; no performance, concurrency, or production-engine conformance claim. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:44:12.384642+00:00.

Case digest / 149e7377a4189a92ebaab93cf0e60584434e5d91d0bd593fcf47d30944b7225e