✔ PASS Warehouse & Statistical task_118_reversal_interleaved_ledger Scaled: 1M+ Records Ordered: Yes

Financial Ledger Running Total with Transaction Reversal Nullification

Candidate Latency (1M Rows)

103.44 ms

(1.0x slower than golden)

Golden Latency (1M Rows)

100.98 ms

DuckDB in-memory engine

Underlying Data Volume

1,000,000 rows

45.8 MiB across 1 table

Evaluated Model

gemini-3.8-flash-low

Gen Latency: 4.3s

✔ Correctness Verified on 1M+ Records

Candidate SQL output matches ground truth golden query across all multiset rows and numeric tolerances (tol=1e-3). Zero data skew or anti-patterns detected on full dataset scale.

1. Analytical Significance & What It Means

Scenario & Frontier Trap

Business Scenario & Problem

Calculates running account balance where REVERSAL records completely void specific prior transaction IDs, removing both the original transaction and the reversal record from net cumulative balance.

⚡ The Frontier Trap (Why LLMs Fail)

Naive queries sum all records including reversed transactions. In our ledger, naive sum includes entry 2 (+$200) at step 2, temporarily inflating the running balance to $700 before entry 4 subtracts it. True ledger auditing requires excluding voided entries from the active sequence.

Prompt / User Request Given to Model

Calculate the active cumulative balance for each non-reversed transaction.
If a transaction was later reversed (by a record with action = 'REVERSAL' referencing its entry_id), BOTH the original entry AND the reversal record must be completely excluded from the running balance.

Required output columns:
- entry_id (INT)
- account_id (INT)
- amount (DECIMAL)
- net_running_balance (DECIMAL)

Order by entry_id ASC.

2. Underlying Tables, Row Counts & Data Volume

1 Tables (1,000,000 rows • 45.8 MiB)

Production-scale fixtures loaded into the isolated DuckDB sandbox with at least 1,000,000 records per table:

📊 financial_ledger 1,000,000 rows 45.8 MiB Data Volume

entry_id (INTEGER) account_id (INTEGER) action (VARCHAR) reverses_entry_id (INTEGER) amount (DECIMAL(10,2))

Data Preview (showing sample rows from 1,000,000 total rows):

#	entry_id	account_id	action	reverses_entry_id	amount
1	1	100	PAYMENT	NULL	500
2	2	100	PAYMENT	NULL	200
3	3	100	PAYMENT	NULL	150
4	4	100	REVERSAL	2	-200
5	4	100	click	2	0.01
6	5	101	view	3	0.01
7	6	102	add_to_cart	4	109.56
8	7	103	checkout	5	131.98
9	8	104	search	6	493.66
10	9	105	click	7	310.56
11	10	106	view	8	0.01
12	11	107	add_to_cart	9	0.01
13	12	108	checkout	10	291.5
14	13	109	search	11	129.46
15	14	110	click	12	0.01

3. Graphical Query Execution Plan & Cost Bottlenecks

Physical Operator Tree (DuckDB 2.0 Profiler)

Visual flowchart of the physical execution pipeline. Operators with high relative costs (≥ 20% of query runtime or heavy latency) are visually highlighted:

Pipeline Latency Distribution (Total Plan Time: 298.93 ms) Nodes consuming ≥ 20% of query runtime are highlighted with glowing borders

⏳ ORDER_BY 🔥 21.6% Cost

Latency: 64.65 ms

Rows In/Out: 999,997

Data Vol: 30.52 MB

📐 PROJECTION 0.1%

Latency: 0.22 ms

Rows In/Out: 999,997

Data Vol: 30.52 MB

📁 Projections: ['#0', '#1', '#2', ...

🪟 WINDOW 🔥 75.0% Cost

Latency: 224.14 ms

Rows In/Out: 999,997

Data Vol: 30.52 MB

📁 Projections: sum(amount) OVER (P...

📐 PROJECTION 0.0%

Latency: 0.09 ms

Rows In/Out: 999,997

Data Vol: 15.26 MB

📁 Projections: ['#0', '#1', '#2']

🎯 FILTER 0.5%

Latency: 1.59 ms

Rows In/Out: 999,997

Data Vol: 16.33 MB

⚡ HASH_JOIN 2.0%

Latency: 5.96 ms

Rows In/Out: 1,000,000

Data Vol: 16.33 MB

🔍 TABLE_SCAN 0.5%

Latency: 1.64 ms

Rows In/Out: 1,000,000

Data Vol: 15.26 MB

📁 memory.main.financial_ledger

📊 HASH_GROUP_BY 0.2%

Latency: 0.57 ms

Rows In/Out: 2

Data Vol: 8 B

📐 PROJECTION 0.0%

Latency: 0.00 ms

Rows In/Out: 2

Data Vol: 264 B

📁 Projections: entry_id

⚙️ UNION 0.0%

Latency: 0.00 ms

Rows In/Out: 0

Data Vol: 0 B

🔍 TABLE_SCAN 0.0%

Latency: 0.04 ms

Rows In/Out: 1

Data Vol: 260 B

📁 memory.main.financial_ledger

🔍 TABLE_SCAN 0.0%

Latency: 0.02 ms

Rows In/Out: 1

Data Vol: 4 B

📁 memory.main.financial_ledger

Operator	Cost %	Latency	Processed Rows	Data Volume	Details / Table	Status
WINDOW	75.0%	224.14 ms	999,997	30.52 MB	Projections: sum(amount) OVER (PARTITION BY acco	🔥 BOTTLENECK
ORDER_BY	21.6%	64.65 ms	999,997	30.52 MB	-	🔥 BOTTLENECK
HASH_JOIN	2.0%	5.96 ms	1,000,000	16.33 MB	-	Normal
TABLE_SCAN	0.5%	1.64 ms	1,000,000	15.26 MB	memory.main.financial_ledger	Normal
FILTER	0.5%	1.59 ms	999,997	16.33 MB	-	Normal
HASH_GROUP_BY	0.2%	0.57 ms	2	0.00 MB	-	Normal
PROJECTION	0.1%	0.22 ms	999,997	30.52 MB	Projections: ['#0', '#1', '#2', '#3']	Normal
PROJECTION	0.0%	0.09 ms	999,997	15.26 MB	Projections: ['#0', '#1', '#2']	Normal
TABLE_SCAN	0.0%	0.04 ms	1	0.00 MB	memory.main.financial_ledger	Normal
TABLE_SCAN	0.0%	0.02 ms	1	0.00 MB	memory.main.financial_ledger	Normal
PROJECTION	0.0%	0.00 ms	2	0.00 MB	Projections: entry_id	Normal
UNION	0.0%	0.00 ms	0	0.00 MB	-	Normal

4. Queries Executed (Candidate vs Golden Ground Truth)

Beautified & Syntax Highlighted

WITH reversed_entries AS
  (SELECT reverses_entry_id AS entry_id
   FROM financial_ledger
   WHERE action = 'REVERSAL'
     AND reverses_entry_id IS NOT NULL
   UNION SELECT entry_id
   FROM financial_ledger
   WHERE action = 'REVERSAL'),
     valid_ledger AS
  (SELECT entry_id,
          account_id,
          amount
   FROM financial_ledger
   WHERE entry_id NOT IN
       (SELECT entry_id
        FROM reversed_entries))
SELECT entry_id,
       account_id,
       amount,
       sum(amount) OVER (PARTITION BY account_id
                         ORDER BY entry_id ASC ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS net_running_balance
FROM valid_ledger
ORDER BY entry_id ASC;

WITH reversed_ids AS
  (SELECT reverses_entry_id AS void_id
   FROM financial_ledger
   WHERE action = 'REVERSAL'
     AND reverses_entry_id IS NOT NULL
   UNION SELECT entry_id AS void_id
   FROM financial_ledger
   WHERE action = 'REVERSAL'),
     active_entries AS
  (SELECT l.entry_id,
          l.account_id,
          l.amount
   FROM financial_ledger l
   WHERE l.entry_id NOT IN
       (SELECT void_id
        FROM reversed_ids))
SELECT entry_id,
       account_id,
       amount,
       sum(amount) OVER (PARTITION BY account_id
                         ORDER BY entry_id ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS net_running_balance
FROM active_entries
ORDER BY entry_id ASC;

CREATE TABLE financial_ledger (entry_id INT, account_id INT, action VARCHAR, -- 'PAYMENT', 'REFUND', 'REVERSAL'
 reverses_entry_id INT, amount decimal(10, 2));


INSERT INTO financial_ledger
VALUES (1, 100, 'PAYMENT', NULL, 500.00),
       -- Active
 (2, 100, 'PAYMENT', NULL, 200.00),
 -- Reversed by #4!
 (3, 100, 'PAYMENT', NULL, 150.00),
 -- Active
 (4, 100, 'REVERSAL', 2, -200.00); -- Reversal entry

5. Query Results & Expected Ground Truth

Tabular Comparison

Actual Candidate Output (999,997 rows × 4 cols)

#	entry_id	account_id	amount	net_running_balance
1	1	100	500	500
2	3	100	150	650
3	5	101	0.01	0.01
4	6	102	109.56	109.56
5	7	103	131.98	131.98
6	8	104	493.66	493.66
7	9	105	310.56	310.56
8	10	106	0.01	0.01
9	11	107	0.01	0.01
10	12	108	291.5	291.5
11	13	109	129.46	129.46
12	14	110	0.01	0.01
13	15	111	326.99	326.99
14	16	112	47.84	47.84
15	17	113	36.44	36.44
16	18	114	319.41	319.41
17	19	115	11.46	11.46
18	20	116	99.82	99.82
19	21	117	257.08	257.08
20	22	118	0.01	0.01
21	23	119	148.36	148.36
22	24	120	0.01	0.01
23	25	121	10.94	10.94
24	26	122	190.6	190.6
25	27	123	21.12	21.12

Showing first 25 of 999,997 total rows.

Expected Golden Output (999,997 rows × 4 cols)

#	entry_id	account_id	amount	net_running_balance
1	1	100	500	500
2	3	100	150	650
3	5	101	0.01	0.01
4	6	102	109.56	109.56
5	7	103	131.98	131.98
6	8	104	493.66	493.66
7	9	105	310.56	310.56
8	10	106	0.01	0.01
9	11	107	0.01	0.01
10	12	108	291.5	291.5
11	13	109	129.46	129.46
12	14	110	0.01	0.01
13	15	111	326.99	326.99
14	16	112	47.84	47.84
15	17	113	36.44	36.44
16	18	114	319.41	319.41
17	19	115	11.46	11.46
18	20	116	99.82	99.82
19	21	117	257.08	257.08
20	22	118	0.01	0.01
21	23	119	148.36	148.36
22	24	120	0.01	0.01
23	25	121	10.94	10.94
24	26	122	190.6	190.6
25	27	123	21.12	21.12

Showing first 25 of 999,997 total rows.

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