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FA-44431 / Data systems / Open access

List gather sorts its physical row selection · case 01

List gather sorts its physical row selection.

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

ROOT CAUSE

list-offset-slice: List gather sorts its physical row selection.

THE FAILURE

list-offset-slice: List gather sorts its physical row selection.

Unsuccessful approach: Sorting and deduplicating still changes requested order and multiplicity.

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 sorted(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[[1, 2], [3]][[3], [1, 2]]Failed
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 / d4eccac81d9a6dde98d98d39ddc52b472b536b5da11a800a1bb1dfe034e70fb0

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 sorted(set(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[[1, 2], [3]][[3], [1, 2]]Failed
null child[[None, 2]][[None, 2]]Passed
hidden null list[None][None]Passed
empty valid list[[], [1]][[], [1]]Passed
repeated list[[2]][[2], [2]]Failed
no rows[][]Passed
nonzero physical origin[[1, 2]][[1, 2]]Passed

SHA-256 / 8a3e34131a494bb3ef820ae7f0eaf703b5b185d0b66790088fd2e7fc065de1a4

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 7 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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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 2026-09-29T14:44:12.425733+00:00.

Case digest / 6d143574ab888107ce1fe1bce3ac069a87a4636c2a676537ca2eeedb9d9be563