FA-45121 / Data systems / Open access
List concatenation copies unused child-buffer prefixes · case 01
List concatenation copies unused child-buffer prefixes.
ROOT CAUSE
list-child-concatenation: List concatenation copies unused child-buffer prefixes.
THE FAILURE
list-child-concatenation: List concatenation copies unused child-buffer prefixes.
Unsuccessful approach: Copying trailing unused child storage still makes the compact output incorrect.
Case contract
Concatenate offset-based list batches into one compact child buffer. Rebase every row offset, copy only each batch referenced child span, preserve parent validity, and preserve child nulls. Output [offsets,visible-child,parent-validity].
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:
out_offsets=[0]; out_child=[]; out_valid=[]
for offsets,child,child_valid,parent_valid in d:
start=0; stop=offsets[-1]
base=len(out_child)
out_child.extend(child[i] if child_valid[i] else None for i in range(start,stop))
out_offsets.extend(base+x-start for x in offsets[1:])
out_valid.extend(parent_valid)
return [out_offsets,out_child,out_valid]
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('two batches', solve([[[0, 2], [1, 2], [True, True], [True]], [[0, 1], [3], [True], [True]]]), [[0, 2, 3], [1, 2, 3], [True, True]])
check('sliced child', solve([[[1, 3], [0, 1, 2, 99], [True, True, True, True], [True]]]), [[0, 2], [1, 2], [True]])
check('null children', solve([[[0, 2], [1, 2], [False, True], [True]]]), [[0, 2], [None, 2], [True]])
check('empty valid row', solve([[[0, 0], [], [], [True]]]), [[0, 0], [], [True]])
check('null parent storage', solve([[[0, 1], [1], [True], [False]]]), [[0, 1], [1], [False]])
check('no batches', solve([]), [[0], [], []])
check('empty batch then row', solve([[[0], [], [], []], [[0, 1], [1], [True], [True]]]), [[0, 1], [1], [True]])
elif N == 2:
check('two batches', solve([[[0, 2], [2, 3], [True, True], [True]], [[0, 1], [4], [True], [True]]]), [[0, 2, 3], [2, 3, 4], [True, True]])
check('sliced child', solve([[[1, 3], [0, 2, 3, 99], [True, True, True, True], [True]]]), [[0, 2], [2, 3], [True]])
check('null children', solve([[[0, 2], [2, 3], [False, True], [True]]]), [[0, 2], [None, 3], [True]])
check('empty valid row', solve([[[0, 0], [], [], [True]]]), [[0, 0], [], [True]])
check('null parent storage', solve([[[0, 1], [2], [True], [False]]]), [[0, 1], [2], [False]])
check('no batches', solve([]), [[0], [], []])
check('empty batch then row', solve([[[0], [], [], []], [[0, 1], [2], [True], [True]]]), [[0, 1], [2], [True]])
elif N == 3:
check('two batches', solve([[[0, 2], [3, 4], [True, True], [True]], [[0, 1], [5], [True], [True]]]), [[0, 2, 3], [3, 4, 5], [True, True]])
check('sliced child', solve([[[1, 3], [0, 3, 4, 99], [True, True, True, True], [True]]]), [[0, 2], [3, 4], [True]])
check('null children', solve([[[0, 2], [3, 4], [False, True], [True]]]), [[0, 2], [None, 4], [True]])
check('empty valid row', solve([[[0, 0], [], [], [True]]]), [[0, 0], [], [True]])
check('null parent storage', solve([[[0, 1], [3], [True], [False]]]), [[0, 1], [3], [False]])
check('no batches', solve([]), [[0], [], []])
check('empty batch then row', solve([[[0], [], [], []], [[0, 1], [3], [True], [True]]]), [[0, 1], [3], [True]])
elif N == 4:
check('two batches', solve([[[0, 2], [4, 5], [True, True], [True]], [[0, 1], [6], [True], [True]]]), [[0, 2, 3], [4, 5, 6], [True, True]])
check('sliced child', solve([[[1, 3], [0, 4, 5, 99], [True, True, True, True], [True]]]), [[0, 2], [4, 5], [True]])
check('null children', solve([[[0, 2], [4, 5], [False, True], [True]]]), [[0, 2], [None, 5], [True]])
check('empty valid row', solve([[[0, 0], [], [], [True]]]), [[0, 0], [], [True]])
check('null parent storage', solve([[[0, 1], [4], [True], [False]]]), [[0, 1], [4], [False]])
check('no batches', solve([]), [[0], [], []])
check('empty batch then row', solve([[[0], [], [], []], [[0, 1], [4], [True], [True]]]), [[0, 1], [4], [True]])
elif N == 5:
check('two batches', solve([[[0, 2], [5, 6], [True, True], [True]], [[0, 1], [7], [True], [True]]]), [[0, 2, 3], [5, 6, 7], [True, True]])
check('sliced child', solve([[[1, 3], [0, 5, 6, 99], [True, True, True, True], [True]]]), [[0, 2], [5, 6], [True]])
check('null children', solve([[[0, 2], [5, 6], [False, True], [True]]]), [[0, 2], [None, 6], [True]])
check('empty valid row', solve([[[0, 0], [], [], [True]]]), [[0, 0], [], [True]])
check('null parent storage', solve([[[0, 1], [5], [True], [False]]]), [[0, 1], [5], [False]])
check('no batches', solve([]), [[0], [], []])
check('empty batch then row', solve([[[0], [], [], []], [[0, 1], [5], [True], [True]]]), [[0, 1], [5], [True]])
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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| two batches | [[0, 2, 3], [1, 2, 3], [True, True]] | [[0, 2, 3], [1, 2, 3], [True, True]] | Passed |
| sliced child | [[0, 3], [0, 1, 2], [True]] | [[0, 2], [1, 2], [True]] | Failed |
| null children | [[0, 2], [None, 2], [True]] | [[0, 2], [None, 2], [True]] | Passed |
| empty valid row | [[0, 0], [], [True]] | [[0, 0], [], [True]] | Passed |
| null parent storage | [[0, 1], [1], [False]] | [[0, 1], [1], [False]] | Passed |
| no batches | [[0], [], []] | [[0], [], []] | Passed |
| empty batch then row | [[0, 1], [1], [True]] | [[0, 1], [1], [True]] | Passed |
SHA-256 / 25d966c8358d8107bcb9f1ef7d3f9a1abecf5c8842d41c1f950083fd0f6b1a3b
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(d):
try:
out_offsets=[0]; out_child=[]; out_valid=[]
for offsets,child,child_valid,parent_valid in d:
start=offsets[0]; stop=len(child)
base=len(out_child)
out_child.extend(child[i] if child_valid[i] else None for i in range(start,stop))
out_offsets.extend(base+x-start for x in offsets[1:])
out_valid.extend(parent_valid)
return [out_offsets,out_child,out_valid]
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('two batches', solve([[[0, 2], [1, 2], [True, True], [True]], [[0, 1], [3], [True], [True]]]), [[0, 2, 3], [1, 2, 3], [True, True]])
check('sliced child', solve([[[1, 3], [0, 1, 2, 99], [True, True, True, True], [True]]]), [[0, 2], [1, 2], [True]])
check('null children', solve([[[0, 2], [1, 2], [False, True], [True]]]), [[0, 2], [None, 2], [True]])
check('empty valid row', solve([[[0, 0], [], [], [True]]]), [[0, 0], [], [True]])
check('null parent storage', solve([[[0, 1], [1], [True], [False]]]), [[0, 1], [1], [False]])
check('no batches', solve([]), [[0], [], []])
check('empty batch then row', solve([[[0], [], [], []], [[0, 1], [1], [True], [True]]]), [[0, 1], [1], [True]])
elif N == 2:
check('two batches', solve([[[0, 2], [2, 3], [True, True], [True]], [[0, 1], [4], [True], [True]]]), [[0, 2, 3], [2, 3, 4], [True, True]])
check('sliced child', solve([[[1, 3], [0, 2, 3, 99], [True, True, True, True], [True]]]), [[0, 2], [2, 3], [True]])
check('null children', solve([[[0, 2], [2, 3], [False, True], [True]]]), [[0, 2], [None, 3], [True]])
check('empty valid row', solve([[[0, 0], [], [], [True]]]), [[0, 0], [], [True]])
check('null parent storage', solve([[[0, 1], [2], [True], [False]]]), [[0, 1], [2], [False]])
check('no batches', solve([]), [[0], [], []])
check('empty batch then row', solve([[[0], [], [], []], [[0, 1], [2], [True], [True]]]), [[0, 1], [2], [True]])
elif N == 3:
check('two batches', solve([[[0, 2], [3, 4], [True, True], [True]], [[0, 1], [5], [True], [True]]]), [[0, 2, 3], [3, 4, 5], [True, True]])
check('sliced child', solve([[[1, 3], [0, 3, 4, 99], [True, True, True, True], [True]]]), [[0, 2], [3, 4], [True]])
check('null children', solve([[[0, 2], [3, 4], [False, True], [True]]]), [[0, 2], [None, 4], [True]])
check('empty valid row', solve([[[0, 0], [], [], [True]]]), [[0, 0], [], [True]])
check('null parent storage', solve([[[0, 1], [3], [True], [False]]]), [[0, 1], [3], [False]])
check('no batches', solve([]), [[0], [], []])
check('empty batch then row', solve([[[0], [], [], []], [[0, 1], [3], [True], [True]]]), [[0, 1], [3], [True]])
elif N == 4:
check('two batches', solve([[[0, 2], [4, 5], [True, True], [True]], [[0, 1], [6], [True], [True]]]), [[0, 2, 3], [4, 5, 6], [True, True]])
check('sliced child', solve([[[1, 3], [0, 4, 5, 99], [True, True, True, True], [True]]]), [[0, 2], [4, 5], [True]])
check('null children', solve([[[0, 2], [4, 5], [False, True], [True]]]), [[0, 2], [None, 5], [True]])
check('empty valid row', solve([[[0, 0], [], [], [True]]]), [[0, 0], [], [True]])
check('null parent storage', solve([[[0, 1], [4], [True], [False]]]), [[0, 1], [4], [False]])
check('no batches', solve([]), [[0], [], []])
check('empty batch then row', solve([[[0], [], [], []], [[0, 1], [4], [True], [True]]]), [[0, 1], [4], [True]])
elif N == 5:
check('two batches', solve([[[0, 2], [5, 6], [True, True], [True]], [[0, 1], [7], [True], [True]]]), [[0, 2, 3], [5, 6, 7], [True, True]])
check('sliced child', solve([[[1, 3], [0, 5, 6, 99], [True, True, True, True], [True]]]), [[0, 2], [5, 6], [True]])
check('null children', solve([[[0, 2], [5, 6], [False, True], [True]]]), [[0, 2], [None, 6], [True]])
check('empty valid row', solve([[[0, 0], [], [], [True]]]), [[0, 0], [], [True]])
check('null parent storage', solve([[[0, 1], [5], [True], [False]]]), [[0, 1], [5], [False]])
check('no batches', solve([]), [[0], [], []])
check('empty batch then row', solve([[[0], [], [], []], [[0, 1], [5], [True], [True]]]), [[0, 1], [5], [True]])
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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| two batches | [[0, 2, 3], [1, 2, 3], [True, True]] | [[0, 2, 3], [1, 2, 3], [True, True]] | Passed |
| sliced child | [[0, 2], [1, 2, 99], [True]] | [[0, 2], [1, 2], [True]] | Failed |
| null children | [[0, 2], [None, 2], [True]] | [[0, 2], [None, 2], [True]] | Passed |
| empty valid row | [[0, 0], [], [True]] | [[0, 0], [], [True]] | Passed |
| null parent storage | [[0, 1], [1], [False]] | [[0, 1], [1], [False]] | Passed |
| no batches | [[0], [], []] | [[0], [], []] | Passed |
| empty batch then row | [[0, 1], [1], [True]] | [[0, 1], [1], [True]] | Passed |
SHA-256 / b5d933aaa9df3c210b850e687aa1f6691195c8ee681a61cadc2deeda1ad97f18
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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Sign in to the archive ↗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 2026-09-29T14:44:19.313794+00:00.
Case digest / 934dfb82eb07a96068817535129db785144b9040c12f6ccd11d93be088670bdd