FAILURE MAP
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FA-44526 / Data systems / Open access

Only the first physical right chunk participates in row assembly · case 01

Only the first physical right chunk participates in row assembly.

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

ROOT CAUSE

chunked-column-zip: Only the first physical right chunk participates in row assembly.

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: Reversing chunk order restores length but changes global positions.

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 for v in chunk]
        b=(right[0] if right else []) + [None]*sum(map(len,right[1:]))
        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 fixtureActualExpectedOutcome
different boundaries[[1, 4], [2, None], [3, None]][[1, 4], [2, 5], [3, 6]]Failed
empty internal chunks[[1, None], [2, None]][[1, 3], [2, 4]]Failed
global slice[[2, 5], [3, None]][[2, 5], [3, 6]]Failed
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 / 649b0c163fac49cf8cc74b58fd92c34ac8ee0a7e9dde1708e04db389c0ad8699

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 for v in chunk]
        b=[v for chunk in reversed(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 fixtureActualExpectedOutcome
different boundaries[[1, 5], [2, 6], [3, 4]][[1, 4], [2, 5], [3, 6]]Failed
empty internal chunks[[1, 3], [2, 4]][[1, 3], [2, 4]]Passed
global slice[[2, 4], [3, 5]][[2, 5], [3, 6]]Failed
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 / dab514de5598d1606cb7120c1298279cf6a293e8c2983c905f18226c5b1326ea

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 fixtureActualExpectedOutcome
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 2026-09-29T14:44:13.097048+00:00.

Case digest / bb1ff66606dfb0d203d173c364bd4ee7d5cacaed5f9f37faf0651f0436dc26b6