FA-100321 / Dataset deduplication grouping / Open access

Dataset deduplication: hash collision merges distinct records · case 01

hash collision merges distinct records.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The candidate bucket is treated as proof of equality.

THE FAILURE

The candidate bucket is treated as proof of equality.

Unsuccessful approach: Checking only record length still merges unequal values of equal length.

Case contract

Given rows [hash,key,id], return IDs of distinct full keys, retaining first occurrence order even when hashes collide.

Why this case matters

This deterministic toy operation makes one dataset equivalence or representative rule explicit.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(rows):
    seen=set(); out=[]
    for h,k,i in rows:
     if h not in seen: seen.add(h); out.append(i)
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('collision distinct keys',solve([[N,'aa','a'],[N,'bb','b']]),['a','b'])
check('exact duplicate',solve([[N,'same','a'],[N,'same','b']]),['a'])
check('same key different hash',solve([[1,'x','a'],[2,'x','b']]),['a'])
check('empty',solve([]),[])
check('length collision',solve([[0,'aa','a'],[0,'bb','b']]),['a','b'])
check('source order',solve([[1,'z','z'],[1,'a','a']]),['z','a'])
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
collision distinct keys	`['a']`	`['a', 'b']`	Failed
exact duplicate	`['a']`	`['a']`	Passed
same key different hash	`['a', 'b']`	`['a']`	Failed
empty	`[]`	`[]`	Passed
length collision	`['a']`	`['a', 'b']`	Failed
source order	`['z']`	`['z', 'a']`	Failed

SHA-256 / 41f7618274b360cf47307cb972d8d7970505f40acdfa9428434edd346103add4

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(rows):
    seen=set(); out=[]
    for h,k,i in rows:
     if (h,len(k)) not in seen: seen.add((h,len(k))); out.append(i)
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('collision distinct keys',solve([[N,'aa','a'],[N,'bb','b']]),['a','b'])
check('exact duplicate',solve([[N,'same','a'],[N,'same','b']]),['a'])
check('same key different hash',solve([[1,'x','a'],[2,'x','b']]),['a'])
check('empty',solve([]),[])
check('length collision',solve([[0,'aa','a'],[0,'bb','b']]),['a','b'])
check('source order',solve([[1,'z','z'],[1,'a','a']]),['z','a'])
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
collision distinct keys	`['a']`	`['a', 'b']`	Failed
exact duplicate	`['a']`	`['a']`	Passed
same key different hash	`['a', 'b']`	`['a']`	Failed
empty	`[]`	`[]`	Passed
length collision	`['a']`	`['a', 'b']`	Failed
source order	`['z']`	`['z', 'a']`	Failed

SHA-256 / 07cf908b1b36cade11262e65b3e7c59fa34bb512e8a6f797542205bfdd0d5e54

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 6 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.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

Verification & scope

Inputs are small in-memory fixtures with the stated contract; results do not claim production deduplication quality. 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 2026-09-30T16:48:34.472079+00:00.

Case digest / 48c843d7182e0bdeb9e09c6dfdc394b85a338b8744219c1b137062412abce032