FA-44521 / Data systems / Open access
An empty left chunk terminates the logical column · case 01
An empty left chunk terminates the logical column.
ROOT CAUSE
chunked-column-zip: An empty left chunk terminates the logical column.
VERIFIED REPAIR
Preserve the stated physical representation and operation order: Assemble two equally long logical columns from independent chunk layouts. Empty chunks carry no rows. Zip by global row ordinal, retain null values, and apply the requested half-open row slice after alignment.
Unsuccessful approach: Skipping empty chunks but filtering null lanes still changes row alignment.
Case contract
Assemble two equally long logical columns from independent chunk layouts. Empty chunks carry no rows. Zip by global row ordinal, retain null values, and apply the requested half-open row slice after alignment.
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:
left,right,start,length=d
a=[v for chunk in left[:next((i for i,c in enumerate(left) if not c),len(left))] for v in chunk]
b=[v for chunk in right for v in chunk]
rows=[[a[i],b[i]] for i in range(len(a))]
rows=rows[start:start+length]
return rows
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('different boundaries', solve([[[1, 2], [3]], [[4], [5, 6]], 0, 3]), [[1, 4], [2, 5], [3, 6]])
check('empty internal chunks', solve([[[1], [], [2]], [[], [3, 4]], 0, 2]), [[1, 3], [2, 4]])
check('global slice', solve([[[1], [2, 3]], [[4, 5], [6]], 1, 2]), [[2, 5], [3, 6]])
check('null field', solve([[[None, 1]], [[2, None]], 0, 2]), [[None, 2], [1, None]])
check('repeated rows', solve([[[1, 1]], [[2, 2]], 0, 2]), [[1, 2], [1, 2]])
check('zero length', solve([[[1]], [[2]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
elif N == 2:
check('different boundaries', solve([[[2, 3], [4]], [[5], [6, 7]], 0, 3]), [[2, 5], [3, 6], [4, 7]])
check('empty internal chunks', solve([[[2], [], [3]], [[], [4, 5]], 0, 2]), [[2, 4], [3, 5]])
check('global slice', solve([[[2], [3, 4]], [[5, 6], [7]], 1, 2]), [[3, 6], [4, 7]])
check('null field', solve([[[None, 2]], [[3, None]], 0, 2]), [[None, 3], [2, None]])
check('repeated rows', solve([[[2, 2]], [[3, 3]], 0, 2]), [[2, 3], [2, 3]])
check('zero length', solve([[[2]], [[3]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
elif N == 3:
check('different boundaries', solve([[[3, 4], [5]], [[6], [7, 8]], 0, 3]), [[3, 6], [4, 7], [5, 8]])
check('empty internal chunks', solve([[[3], [], [4]], [[], [5, 6]], 0, 2]), [[3, 5], [4, 6]])
check('global slice', solve([[[3], [4, 5]], [[6, 7], [8]], 1, 2]), [[4, 7], [5, 8]])
check('null field', solve([[[None, 3]], [[4, None]], 0, 2]), [[None, 4], [3, None]])
check('repeated rows', solve([[[3, 3]], [[4, 4]], 0, 2]), [[3, 4], [3, 4]])
check('zero length', solve([[[3]], [[4]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
elif N == 4:
check('different boundaries', solve([[[4, 5], [6]], [[7], [8, 9]], 0, 3]), [[4, 7], [5, 8], [6, 9]])
check('empty internal chunks', solve([[[4], [], [5]], [[], [6, 7]], 0, 2]), [[4, 6], [5, 7]])
check('global slice', solve([[[4], [5, 6]], [[7, 8], [9]], 1, 2]), [[5, 8], [6, 9]])
check('null field', solve([[[None, 4]], [[5, None]], 0, 2]), [[None, 5], [4, None]])
check('repeated rows', solve([[[4, 4]], [[5, 5]], 0, 2]), [[4, 5], [4, 5]])
check('zero length', solve([[[4]], [[5]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
elif N == 5:
check('different boundaries', solve([[[5, 6], [7]], [[8], [9, 10]], 0, 3]), [[5, 8], [6, 9], [7, 10]])
check('empty internal chunks', solve([[[5], [], [6]], [[], [7, 8]], 0, 2]), [[5, 7], [6, 8]])
check('global slice', solve([[[5], [6, 7]], [[8, 9], [10]], 1, 2]), [[6, 9], [7, 10]])
check('null field', solve([[[None, 5]], [[6, None]], 0, 2]), [[None, 6], [5, None]])
check('repeated rows', solve([[[5, 5]], [[6, 6]], 0, 2]), [[5, 6], [5, 6]])
check('zero length', solve([[[5]], [[6]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
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 |
|---|---|---|---|
| different boundaries | [[1, 4], [2, 5], [3, 6]] | [[1, 4], [2, 5], [3, 6]] | Passed |
| empty internal chunks | [[1, 3]] | [[1, 3], [2, 4]] | Failed |
| global slice | [[2, 5], [3, 6]] | [[2, 5], [3, 6]] | Passed |
| null field | [[None, 2], [1, None]] | [[None, 2], [1, None]] | Passed |
| repeated rows | [[1, 2], [1, 2]] | [[1, 2], [1, 2]] | Passed |
| zero length | [] | [] | Passed |
| no physical chunks | [] | [] | Passed |
SHA-256 / 3e49a40e82e0144e49801c25f3f06cc4124e78783791c83d83ee7585d26e9121
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(d):
try:
left,right,start,length=d
a=[v for chunk in left if chunk for v in chunk if v is not None]
b=[v for chunk in right for v in chunk]
rows=[[a[i],b[i]] for i in range(len(a))]
rows=rows[start:start+length]
return rows
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('different boundaries', solve([[[1, 2], [3]], [[4], [5, 6]], 0, 3]), [[1, 4], [2, 5], [3, 6]])
check('empty internal chunks', solve([[[1], [], [2]], [[], [3, 4]], 0, 2]), [[1, 3], [2, 4]])
check('global slice', solve([[[1], [2, 3]], [[4, 5], [6]], 1, 2]), [[2, 5], [3, 6]])
check('null field', solve([[[None, 1]], [[2, None]], 0, 2]), [[None, 2], [1, None]])
check('repeated rows', solve([[[1, 1]], [[2, 2]], 0, 2]), [[1, 2], [1, 2]])
check('zero length', solve([[[1]], [[2]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
elif N == 2:
check('different boundaries', solve([[[2, 3], [4]], [[5], [6, 7]], 0, 3]), [[2, 5], [3, 6], [4, 7]])
check('empty internal chunks', solve([[[2], [], [3]], [[], [4, 5]], 0, 2]), [[2, 4], [3, 5]])
check('global slice', solve([[[2], [3, 4]], [[5, 6], [7]], 1, 2]), [[3, 6], [4, 7]])
check('null field', solve([[[None, 2]], [[3, None]], 0, 2]), [[None, 3], [2, None]])
check('repeated rows', solve([[[2, 2]], [[3, 3]], 0, 2]), [[2, 3], [2, 3]])
check('zero length', solve([[[2]], [[3]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
elif N == 3:
check('different boundaries', solve([[[3, 4], [5]], [[6], [7, 8]], 0, 3]), [[3, 6], [4, 7], [5, 8]])
check('empty internal chunks', solve([[[3], [], [4]], [[], [5, 6]], 0, 2]), [[3, 5], [4, 6]])
check('global slice', solve([[[3], [4, 5]], [[6, 7], [8]], 1, 2]), [[4, 7], [5, 8]])
check('null field', solve([[[None, 3]], [[4, None]], 0, 2]), [[None, 4], [3, None]])
check('repeated rows', solve([[[3, 3]], [[4, 4]], 0, 2]), [[3, 4], [3, 4]])
check('zero length', solve([[[3]], [[4]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
elif N == 4:
check('different boundaries', solve([[[4, 5], [6]], [[7], [8, 9]], 0, 3]), [[4, 7], [5, 8], [6, 9]])
check('empty internal chunks', solve([[[4], [], [5]], [[], [6, 7]], 0, 2]), [[4, 6], [5, 7]])
check('global slice', solve([[[4], [5, 6]], [[7, 8], [9]], 1, 2]), [[5, 8], [6, 9]])
check('null field', solve([[[None, 4]], [[5, None]], 0, 2]), [[None, 5], [4, None]])
check('repeated rows', solve([[[4, 4]], [[5, 5]], 0, 2]), [[4, 5], [4, 5]])
check('zero length', solve([[[4]], [[5]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
elif N == 5:
check('different boundaries', solve([[[5, 6], [7]], [[8], [9, 10]], 0, 3]), [[5, 8], [6, 9], [7, 10]])
check('empty internal chunks', solve([[[5], [], [6]], [[], [7, 8]], 0, 2]), [[5, 7], [6, 8]])
check('global slice', solve([[[5], [6, 7]], [[8, 9], [10]], 1, 2]), [[6, 9], [7, 10]])
check('null field', solve([[[None, 5]], [[6, None]], 0, 2]), [[None, 6], [5, None]])
check('repeated rows', solve([[[5, 5]], [[6, 6]], 0, 2]), [[5, 6], [5, 6]])
check('zero length', solve([[[5]], [[6]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
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 |
|---|---|---|---|
| different boundaries | [[1, 4], [2, 5], [3, 6]] | [[1, 4], [2, 5], [3, 6]] | Passed |
| empty internal chunks | [[1, 3], [2, 4]] | [[1, 3], [2, 4]] | Passed |
| global slice | [[2, 5], [3, 6]] | [[2, 5], [3, 6]] | Passed |
| null field | [[1, 2]] | [[None, 2], [1, None]] | Failed |
| repeated rows | [[1, 2], [1, 2]] | [[1, 2], [1, 2]] | Passed |
| zero length | [] | [] | Passed |
| no physical chunks | [] | [] | Passed |
SHA-256 / a5e66462f9cdc2df384d1053d6b48ef6a4dee11ab3abf433dfc90606885e90b7
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(d):
try:
left,right,start,length=d
a=[v for chunk in left for v in chunk]
b=[v for chunk in right for v in chunk]
rows=[[a[i],b[i]] for i in range(len(a))]
rows=rows[start:start+length]
return rows
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('different boundaries', solve([[[1, 2], [3]], [[4], [5, 6]], 0, 3]), [[1, 4], [2, 5], [3, 6]])
check('empty internal chunks', solve([[[1], [], [2]], [[], [3, 4]], 0, 2]), [[1, 3], [2, 4]])
check('global slice', solve([[[1], [2, 3]], [[4, 5], [6]], 1, 2]), [[2, 5], [3, 6]])
check('null field', solve([[[None, 1]], [[2, None]], 0, 2]), [[None, 2], [1, None]])
check('repeated rows', solve([[[1, 1]], [[2, 2]], 0, 2]), [[1, 2], [1, 2]])
check('zero length', solve([[[1]], [[2]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
elif N == 2:
check('different boundaries', solve([[[2, 3], [4]], [[5], [6, 7]], 0, 3]), [[2, 5], [3, 6], [4, 7]])
check('empty internal chunks', solve([[[2], [], [3]], [[], [4, 5]], 0, 2]), [[2, 4], [3, 5]])
check('global slice', solve([[[2], [3, 4]], [[5, 6], [7]], 1, 2]), [[3, 6], [4, 7]])
check('null field', solve([[[None, 2]], [[3, None]], 0, 2]), [[None, 3], [2, None]])
check('repeated rows', solve([[[2, 2]], [[3, 3]], 0, 2]), [[2, 3], [2, 3]])
check('zero length', solve([[[2]], [[3]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
elif N == 3:
check('different boundaries', solve([[[3, 4], [5]], [[6], [7, 8]], 0, 3]), [[3, 6], [4, 7], [5, 8]])
check('empty internal chunks', solve([[[3], [], [4]], [[], [5, 6]], 0, 2]), [[3, 5], [4, 6]])
check('global slice', solve([[[3], [4, 5]], [[6, 7], [8]], 1, 2]), [[4, 7], [5, 8]])
check('null field', solve([[[None, 3]], [[4, None]], 0, 2]), [[None, 4], [3, None]])
check('repeated rows', solve([[[3, 3]], [[4, 4]], 0, 2]), [[3, 4], [3, 4]])
check('zero length', solve([[[3]], [[4]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
elif N == 4:
check('different boundaries', solve([[[4, 5], [6]], [[7], [8, 9]], 0, 3]), [[4, 7], [5, 8], [6, 9]])
check('empty internal chunks', solve([[[4], [], [5]], [[], [6, 7]], 0, 2]), [[4, 6], [5, 7]])
check('global slice', solve([[[4], [5, 6]], [[7, 8], [9]], 1, 2]), [[5, 8], [6, 9]])
check('null field', solve([[[None, 4]], [[5, None]], 0, 2]), [[None, 5], [4, None]])
check('repeated rows', solve([[[4, 4]], [[5, 5]], 0, 2]), [[4, 5], [4, 5]])
check('zero length', solve([[[4]], [[5]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
elif N == 5:
check('different boundaries', solve([[[5, 6], [7]], [[8], [9, 10]], 0, 3]), [[5, 8], [6, 9], [7, 10]])
check('empty internal chunks', solve([[[5], [], [6]], [[], [7, 8]], 0, 2]), [[5, 7], [6, 8]])
check('global slice', solve([[[5], [6, 7]], [[8, 9], [10]], 1, 2]), [[6, 9], [7, 10]])
check('null field', solve([[[None, 5]], [[6, None]], 0, 2]), [[None, 6], [5, None]])
check('repeated rows', solve([[[5, 5]], [[6, 6]], 0, 2]), [[5, 6], [5, 6]])
check('zero length', solve([[[5]], [[6]], 0, 0]), [])
check('no physical chunks', solve([[], [], 0, 0]), [])
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 |
|---|---|---|---|
| different boundaries | [[1, 4], [2, 5], [3, 6]] | [[1, 4], [2, 5], [3, 6]] | Passed |
| empty internal chunks | [[1, 3], [2, 4]] | [[1, 3], [2, 4]] | Passed |
| global slice | [[2, 5], [3, 6]] | [[2, 5], [3, 6]] | Passed |
| null field | [[None, 2], [1, None]] | [[None, 2], [1, None]] | Passed |
| repeated rows | [[1, 2], [1, 2]] | [[1, 2], [1, 2]] | Passed |
| zero length | [] | [] | Passed |
| no physical chunks | [] | [] | Passed |
SHA-256 / 2196cf1fdd33c92a742b1de371168062eccca796cbf93d9f8b37ca0f56569df3
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 2026-09-29T14:44:13.048583+00:00.
Case digest / 9c0b589b61ba61cc43431f647266ed292742e34264208b130fb6638026db65d6