FA-45651 / Data systems / Open access
Session grouping overwrites the session start on every event · case 01
Session grouping overwrites the session start on every event.
ROOT CAUSE
session-bridge-grouping: Session grouping overwrites the session start on every event.
VERIFIED REPAIR
Preserve the stated physical representation and operation order: Group [key,time,id] events into sessions independently by key. Sort each key by (time,id); consecutive gaps <=gap belong to one transitive session. Emit [key,first-time,last-time,ordered-ids] ordered by key and session time. An intervening bridge may join otherwise distant endpoints.
Unsuccessful approach: Allowing the second event to replace the start still shortens the session interval.
Case contract
Group [key,time,id] events into sessions independently by key. Sort each key by (time,id); consecutive gaps <=gap belong to one transitive session. Emit [key,first-time,last-time,ordered-ids] ordered by key and session time. An intervening bridge may join otherwise distant endpoints.
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:
events,gap=d
out=[]
for key in sorted(set(k for k,t,i in events)):
rows=sorted((t,i) for k,t,i in events if k==key)
start=last=None; ids=[]
for time,ident in rows:
if ids and time-last>gap:
out.append([key,start,last,ids]); ids=[]
start=time
ids.append(ident); last=time
if ids: out.append([key,start,last,ids])
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('bridge chain', solve([[['a', 1, 10], ['a', 3, 11], ['a', 5, 12]], 2]), [['a', 1, 5, [10, 11, 12]]])
check('arrival order', solve([[['a', 3, 10], ['a', 1, 11]], 2]), [['a', 1, 3, [11, 10]]])
check('key separation', solve([[['a', 1, 10], ['b', 1, 11]], 2]), [['a', 1, 1, [10]], ['b', 1, 1, [11]]])
check('separate sessions', solve([[['a', 1, 10], ['a', 6, 11]], 2]), [['a', 1, 1, [10]], ['a', 6, 6, [11]]])
check('equal timestamp', solve([[['a', 1, 11], ['a', 1, 10]], 0]), [['a', 1, 1, [10, 11]]])
check('single event', solve([[['a', 1, 10]], 2]), [['a', 1, 1, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 2:
check('bridge chain', solve([[['a', 2, 10], ['a', 4, 11], ['a', 6, 12]], 2]), [['a', 2, 6, [10, 11, 12]]])
check('arrival order', solve([[['a', 4, 10], ['a', 2, 11]], 2]), [['a', 2, 4, [11, 10]]])
check('key separation', solve([[['a', 2, 10], ['b', 2, 11]], 2]), [['a', 2, 2, [10]], ['b', 2, 2, [11]]])
check('separate sessions', solve([[['a', 2, 10], ['a', 7, 11]], 2]), [['a', 2, 2, [10]], ['a', 7, 7, [11]]])
check('equal timestamp', solve([[['a', 2, 11], ['a', 2, 10]], 0]), [['a', 2, 2, [10, 11]]])
check('single event', solve([[['a', 2, 10]], 2]), [['a', 2, 2, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 3:
check('bridge chain', solve([[['a', 3, 10], ['a', 5, 11], ['a', 7, 12]], 2]), [['a', 3, 7, [10, 11, 12]]])
check('arrival order', solve([[['a', 5, 10], ['a', 3, 11]], 2]), [['a', 3, 5, [11, 10]]])
check('key separation', solve([[['a', 3, 10], ['b', 3, 11]], 2]), [['a', 3, 3, [10]], ['b', 3, 3, [11]]])
check('separate sessions', solve([[['a', 3, 10], ['a', 8, 11]], 2]), [['a', 3, 3, [10]], ['a', 8, 8, [11]]])
check('equal timestamp', solve([[['a', 3, 11], ['a', 3, 10]], 0]), [['a', 3, 3, [10, 11]]])
check('single event', solve([[['a', 3, 10]], 2]), [['a', 3, 3, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 4:
check('bridge chain', solve([[['a', 4, 10], ['a', 6, 11], ['a', 8, 12]], 2]), [['a', 4, 8, [10, 11, 12]]])
check('arrival order', solve([[['a', 6, 10], ['a', 4, 11]], 2]), [['a', 4, 6, [11, 10]]])
check('key separation', solve([[['a', 4, 10], ['b', 4, 11]], 2]), [['a', 4, 4, [10]], ['b', 4, 4, [11]]])
check('separate sessions', solve([[['a', 4, 10], ['a', 9, 11]], 2]), [['a', 4, 4, [10]], ['a', 9, 9, [11]]])
check('equal timestamp', solve([[['a', 4, 11], ['a', 4, 10]], 0]), [['a', 4, 4, [10, 11]]])
check('single event', solve([[['a', 4, 10]], 2]), [['a', 4, 4, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 5:
check('bridge chain', solve([[['a', 5, 10], ['a', 7, 11], ['a', 9, 12]], 2]), [['a', 5, 9, [10, 11, 12]]])
check('arrival order', solve([[['a', 7, 10], ['a', 5, 11]], 2]), [['a', 5, 7, [11, 10]]])
check('key separation', solve([[['a', 5, 10], ['b', 5, 11]], 2]), [['a', 5, 5, [10]], ['b', 5, 5, [11]]])
check('separate sessions', solve([[['a', 5, 10], ['a', 10, 11]], 2]), [['a', 5, 5, [10]], ['a', 10, 10, [11]]])
check('equal timestamp', solve([[['a', 5, 11], ['a', 5, 10]], 0]), [['a', 5, 5, [10, 11]]])
check('single event', solve([[['a', 5, 10]], 2]), [['a', 5, 5, [10]]])
check('empty stream', solve([[], 2]), [])
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 |
|---|---|---|---|
| bridge chain | [['a', 5, 5, [10, 11, 12]]] | [['a', 1, 5, [10, 11, 12]]] | Failed |
| arrival order | [['a', 3, 3, [11, 10]]] | [['a', 1, 3, [11, 10]]] | Failed |
| key separation | [['a', 1, 1, [10]], ['b', 1, 1, [11]]] | [['a', 1, 1, [10]], ['b', 1, 1, [11]]] | Passed |
| separate sessions | [['a', 1, 1, [10]], ['a', 6, 6, [11]]] | [['a', 1, 1, [10]], ['a', 6, 6, [11]]] | Passed |
| equal timestamp | [['a', 1, 1, [10, 11]]] | [['a', 1, 1, [10, 11]]] | Passed |
| single event | [['a', 1, 1, [10]]] | [['a', 1, 1, [10]]] | Passed |
| empty stream | [] | [] | Passed |
SHA-256 / ae92454793e933c36e10aa0f865f9ea65dcb27a9e8fd1b9caee59708711b0616
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(d):
try:
events,gap=d
out=[]
for key in sorted(set(k for k,t,i in events)):
rows=sorted((t,i) for k,t,i in events if k==key)
start=last=None; ids=[]
for time,ident in rows:
if ids and time-last>gap:
out.append([key,start,last,ids]); ids=[]
if len(ids)<=1: start=time
ids.append(ident); last=time
if ids: out.append([key,start,last,ids])
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('bridge chain', solve([[['a', 1, 10], ['a', 3, 11], ['a', 5, 12]], 2]), [['a', 1, 5, [10, 11, 12]]])
check('arrival order', solve([[['a', 3, 10], ['a', 1, 11]], 2]), [['a', 1, 3, [11, 10]]])
check('key separation', solve([[['a', 1, 10], ['b', 1, 11]], 2]), [['a', 1, 1, [10]], ['b', 1, 1, [11]]])
check('separate sessions', solve([[['a', 1, 10], ['a', 6, 11]], 2]), [['a', 1, 1, [10]], ['a', 6, 6, [11]]])
check('equal timestamp', solve([[['a', 1, 11], ['a', 1, 10]], 0]), [['a', 1, 1, [10, 11]]])
check('single event', solve([[['a', 1, 10]], 2]), [['a', 1, 1, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 2:
check('bridge chain', solve([[['a', 2, 10], ['a', 4, 11], ['a', 6, 12]], 2]), [['a', 2, 6, [10, 11, 12]]])
check('arrival order', solve([[['a', 4, 10], ['a', 2, 11]], 2]), [['a', 2, 4, [11, 10]]])
check('key separation', solve([[['a', 2, 10], ['b', 2, 11]], 2]), [['a', 2, 2, [10]], ['b', 2, 2, [11]]])
check('separate sessions', solve([[['a', 2, 10], ['a', 7, 11]], 2]), [['a', 2, 2, [10]], ['a', 7, 7, [11]]])
check('equal timestamp', solve([[['a', 2, 11], ['a', 2, 10]], 0]), [['a', 2, 2, [10, 11]]])
check('single event', solve([[['a', 2, 10]], 2]), [['a', 2, 2, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 3:
check('bridge chain', solve([[['a', 3, 10], ['a', 5, 11], ['a', 7, 12]], 2]), [['a', 3, 7, [10, 11, 12]]])
check('arrival order', solve([[['a', 5, 10], ['a', 3, 11]], 2]), [['a', 3, 5, [11, 10]]])
check('key separation', solve([[['a', 3, 10], ['b', 3, 11]], 2]), [['a', 3, 3, [10]], ['b', 3, 3, [11]]])
check('separate sessions', solve([[['a', 3, 10], ['a', 8, 11]], 2]), [['a', 3, 3, [10]], ['a', 8, 8, [11]]])
check('equal timestamp', solve([[['a', 3, 11], ['a', 3, 10]], 0]), [['a', 3, 3, [10, 11]]])
check('single event', solve([[['a', 3, 10]], 2]), [['a', 3, 3, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 4:
check('bridge chain', solve([[['a', 4, 10], ['a', 6, 11], ['a', 8, 12]], 2]), [['a', 4, 8, [10, 11, 12]]])
check('arrival order', solve([[['a', 6, 10], ['a', 4, 11]], 2]), [['a', 4, 6, [11, 10]]])
check('key separation', solve([[['a', 4, 10], ['b', 4, 11]], 2]), [['a', 4, 4, [10]], ['b', 4, 4, [11]]])
check('separate sessions', solve([[['a', 4, 10], ['a', 9, 11]], 2]), [['a', 4, 4, [10]], ['a', 9, 9, [11]]])
check('equal timestamp', solve([[['a', 4, 11], ['a', 4, 10]], 0]), [['a', 4, 4, [10, 11]]])
check('single event', solve([[['a', 4, 10]], 2]), [['a', 4, 4, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 5:
check('bridge chain', solve([[['a', 5, 10], ['a', 7, 11], ['a', 9, 12]], 2]), [['a', 5, 9, [10, 11, 12]]])
check('arrival order', solve([[['a', 7, 10], ['a', 5, 11]], 2]), [['a', 5, 7, [11, 10]]])
check('key separation', solve([[['a', 5, 10], ['b', 5, 11]], 2]), [['a', 5, 5, [10]], ['b', 5, 5, [11]]])
check('separate sessions', solve([[['a', 5, 10], ['a', 10, 11]], 2]), [['a', 5, 5, [10]], ['a', 10, 10, [11]]])
check('equal timestamp', solve([[['a', 5, 11], ['a', 5, 10]], 0]), [['a', 5, 5, [10, 11]]])
check('single event', solve([[['a', 5, 10]], 2]), [['a', 5, 5, [10]]])
check('empty stream', solve([[], 2]), [])
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 |
|---|---|---|---|
| bridge chain | [['a', 3, 5, [10, 11, 12]]] | [['a', 1, 5, [10, 11, 12]]] | Failed |
| arrival order | [['a', 3, 3, [11, 10]]] | [['a', 1, 3, [11, 10]]] | Failed |
| key separation | [['a', 1, 1, [10]], ['b', 1, 1, [11]]] | [['a', 1, 1, [10]], ['b', 1, 1, [11]]] | Passed |
| separate sessions | [['a', 1, 1, [10]], ['a', 6, 6, [11]]] | [['a', 1, 1, [10]], ['a', 6, 6, [11]]] | Passed |
| equal timestamp | [['a', 1, 1, [10, 11]]] | [['a', 1, 1, [10, 11]]] | Passed |
| single event | [['a', 1, 1, [10]]] | [['a', 1, 1, [10]]] | Passed |
| empty stream | [] | [] | Passed |
SHA-256 / 21b8e4eb30444755cddf711cbe3d80d6de9e4f2e34674234e4967271397b49c1
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(d):
try:
events,gap=d
out=[]
for key in sorted(set(k for k,t,i in events)):
rows=sorted((t,i) for k,t,i in events if k==key)
start=last=None; ids=[]
for time,ident in rows:
if ids and time-last>gap:
out.append([key,start,last,ids]); ids=[]
if not ids: start=time
ids.append(ident); last=time
if ids: out.append([key,start,last,ids])
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('bridge chain', solve([[['a', 1, 10], ['a', 3, 11], ['a', 5, 12]], 2]), [['a', 1, 5, [10, 11, 12]]])
check('arrival order', solve([[['a', 3, 10], ['a', 1, 11]], 2]), [['a', 1, 3, [11, 10]]])
check('key separation', solve([[['a', 1, 10], ['b', 1, 11]], 2]), [['a', 1, 1, [10]], ['b', 1, 1, [11]]])
check('separate sessions', solve([[['a', 1, 10], ['a', 6, 11]], 2]), [['a', 1, 1, [10]], ['a', 6, 6, [11]]])
check('equal timestamp', solve([[['a', 1, 11], ['a', 1, 10]], 0]), [['a', 1, 1, [10, 11]]])
check('single event', solve([[['a', 1, 10]], 2]), [['a', 1, 1, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 2:
check('bridge chain', solve([[['a', 2, 10], ['a', 4, 11], ['a', 6, 12]], 2]), [['a', 2, 6, [10, 11, 12]]])
check('arrival order', solve([[['a', 4, 10], ['a', 2, 11]], 2]), [['a', 2, 4, [11, 10]]])
check('key separation', solve([[['a', 2, 10], ['b', 2, 11]], 2]), [['a', 2, 2, [10]], ['b', 2, 2, [11]]])
check('separate sessions', solve([[['a', 2, 10], ['a', 7, 11]], 2]), [['a', 2, 2, [10]], ['a', 7, 7, [11]]])
check('equal timestamp', solve([[['a', 2, 11], ['a', 2, 10]], 0]), [['a', 2, 2, [10, 11]]])
check('single event', solve([[['a', 2, 10]], 2]), [['a', 2, 2, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 3:
check('bridge chain', solve([[['a', 3, 10], ['a', 5, 11], ['a', 7, 12]], 2]), [['a', 3, 7, [10, 11, 12]]])
check('arrival order', solve([[['a', 5, 10], ['a', 3, 11]], 2]), [['a', 3, 5, [11, 10]]])
check('key separation', solve([[['a', 3, 10], ['b', 3, 11]], 2]), [['a', 3, 3, [10]], ['b', 3, 3, [11]]])
check('separate sessions', solve([[['a', 3, 10], ['a', 8, 11]], 2]), [['a', 3, 3, [10]], ['a', 8, 8, [11]]])
check('equal timestamp', solve([[['a', 3, 11], ['a', 3, 10]], 0]), [['a', 3, 3, [10, 11]]])
check('single event', solve([[['a', 3, 10]], 2]), [['a', 3, 3, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 4:
check('bridge chain', solve([[['a', 4, 10], ['a', 6, 11], ['a', 8, 12]], 2]), [['a', 4, 8, [10, 11, 12]]])
check('arrival order', solve([[['a', 6, 10], ['a', 4, 11]], 2]), [['a', 4, 6, [11, 10]]])
check('key separation', solve([[['a', 4, 10], ['b', 4, 11]], 2]), [['a', 4, 4, [10]], ['b', 4, 4, [11]]])
check('separate sessions', solve([[['a', 4, 10], ['a', 9, 11]], 2]), [['a', 4, 4, [10]], ['a', 9, 9, [11]]])
check('equal timestamp', solve([[['a', 4, 11], ['a', 4, 10]], 0]), [['a', 4, 4, [10, 11]]])
check('single event', solve([[['a', 4, 10]], 2]), [['a', 4, 4, [10]]])
check('empty stream', solve([[], 2]), [])
elif N == 5:
check('bridge chain', solve([[['a', 5, 10], ['a', 7, 11], ['a', 9, 12]], 2]), [['a', 5, 9, [10, 11, 12]]])
check('arrival order', solve([[['a', 7, 10], ['a', 5, 11]], 2]), [['a', 5, 7, [11, 10]]])
check('key separation', solve([[['a', 5, 10], ['b', 5, 11]], 2]), [['a', 5, 5, [10]], ['b', 5, 5, [11]]])
check('separate sessions', solve([[['a', 5, 10], ['a', 10, 11]], 2]), [['a', 5, 5, [10]], ['a', 10, 10, [11]]])
check('equal timestamp', solve([[['a', 5, 11], ['a', 5, 10]], 0]), [['a', 5, 5, [10, 11]]])
check('single event', solve([[['a', 5, 10]], 2]), [['a', 5, 5, [10]]])
check('empty stream', solve([[], 2]), [])
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 |
|---|---|---|---|
| bridge chain | [['a', 1, 5, [10, 11, 12]]] | [['a', 1, 5, [10, 11, 12]]] | Passed |
| arrival order | [['a', 1, 3, [11, 10]]] | [['a', 1, 3, [11, 10]]] | Passed |
| key separation | [['a', 1, 1, [10]], ['b', 1, 1, [11]]] | [['a', 1, 1, [10]], ['b', 1, 1, [11]]] | Passed |
| separate sessions | [['a', 1, 1, [10]], ['a', 6, 6, [11]]] | [['a', 1, 1, [10]], ['a', 6, 6, [11]]] | Passed |
| equal timestamp | [['a', 1, 1, [10, 11]]] | [['a', 1, 1, [10, 11]]] | Passed |
| single event | [['a', 1, 1, [10]]] | [['a', 1, 1, [10]]] | Passed |
| empty stream | [] | [] | Passed |
SHA-256 / c79db6c9a57305db34ffc3dfbb50fd8878c3f4ef7daef4c836fda12d08bc304d
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 2026-09-29T14:44:24.402274+00:00.
Case digest / 935624bb8ebff322c0d7af196f675cd7e4d96e8cb4de15d4442f772c38d20602