title	QueryForge Environment Server
emoji	🔍
colorFrom	blue
colorTo	indigo
sdk	docker
pinned	false
app_port	8000
base_path	/web
tags	openenv sql reinforcement-learning

QueryForge — SQL Debugging & Optimisation Environment

Live environment:https://prithvigg-queryforge.hf.spaceInteractive demo:https://prithvigg-queryforge.hf.space/demo/

Try it directly below (HF Space viewer only):

<iframe src="https://prithvigg-queryforge.hf.space/demo/" width="100%" height="700px" frameborder="0"></iframe>

SQL is the language that runs the world's data infrastructure. Yet SQL bugs are silent killers — a missing JOIN condition inflates totals by 3×, a correlated subquery scans a million rows once per row, a typo in a keyword stops production cold. These bugs are rarely caught by linters, rarely surfaced by error messages, and routinely shipped to production.

QueryForge is an OpenEnv-compatible reinforcement learning environment where an agent learns to debug and optimise SQL queries. The agent receives a broken or slow query, submits fixes, and receives graded feedback from a deterministic DuckDB engine combined with an Anthropic AI quality judge — a smooth, informative reward signal across the full 0.0 → 1.0 range.

---

Why SQL Debugging as an RL Environment?

LLMs can write SQL. What they struggle with is the iterative, feedback-driven debugging loop that real engineers do:

• Read the error message
• Form a hypothesis about the root cause
• Patch the query
• Check if the output is now correct
• Refine until it's both correct and efficient

This is precisely the loop that RL is built for. QueryForge provides the environment that closes this loop with a graded, multi-stage reward signal — not just "correct / incorrect" but partial credit for syntax validity, execution success, row correctness, and code quality.

---

Environment Overview

Property	Value
Task type	SQL debugging & optimisation
Action space	Single SQL query string
Observation space	Task description + graded feedback
Reward range	0.0 – 1.0 (continuous)
Episode termination	Score ≥ 0.90, no improvement for 2 steps, or max steps
Grading engine	DuckDB (deterministic) + Anthropic AI judge
Concurrent sessions	Supported

---

Reward Scale

The grading pipeline has four stages that produce a smooth partial-progress signal:

Score	Meaning
0.00	Syntax error — query could not be parsed
0.15	Syntax valid but runtime error
0.30	Executes but returns 0 rows or wrong row count
0.30 – 0.80	Partial row correctness (deterministic, DuckDB)
0.80 – 1.00	Correct rows + AI quality assessment (Anthropic)

The AI judge scores on three axes: Correctness (0–0.50), Optimization (0–0.30 — penalises cartesian products, correlated subqueries), Code quality (0–0.20 — readability, aliases, formatting).

Offline mode: If ANTHROPIC_API_KEY is not set, the AI judge is skipped and scoring is fully deterministic (capped at 0.80). The done threshold self-adjusts to 0.80 in this case so episodes still terminate correctly.

---

Action Space

classSQLAction(Action):
sql: str# The SQL query to submit for grading

One field. The agent submits a SQL string. No multi-statement queries (; separated) are allowed — rejected with score 0.0.

---

Observation Space

classSQLObservation(Observation):
# Task context (set on reset, constant within an episode)task_id: str# e.g. "task_easy_syntax"task_level: str# "easy" | "medium" | "hard" | "custom"task_title: str# Human-readable titletask_description: str# Full context: schema, broken query, error, goal# Per-step grading signalssyntax_valid: bool# True if query parsed without errorexecution_success: bool# True if query ran to completion in DuckDBexecution_error: str# Runtime error message, if anyrows_returned: int# Number of rows returned# Feedbackfeedback: str# Detailed grading feedback (DuckDB + AI judge)hint: str# Actionable hint (suppressed once score >= 0.90)# Episode progressattempt: int# Number of queries submitted this episodebest_score: float# Highest score achieved so fardone: boolreward: float# Score for this specific step (0.0 – 1.0)

---

Built-in Tasks

ID	Level	Title	Max Steps
task_easy_syntax	easy	Fix Syntax Errors	5
task_medium_join	medium	Fix the Cartesian JOIN	5
task_hard_cte	hard	Rewrite Correlated Subquery as CTE	6
task_expert_rank	expert	Fix the Tie-Breaking Window Function	6
task_expert_recursive	expert	Traverse Org Chart with Recursive CTE	7
task_expert_window	expert	Fix Two Broken Window Functions	6

Easy — Fix Syntax Errors

Three SQL keywords are misspelled (SELEC, FORM, WEHRE). The agent must identify and correct them.

Schema:users(id, name, age, city) — 6 rows Goal: Return name and age of users older than 30 in New York, ordered by name

Medium — Fix the Cartesian JOIN

A missing JOIN condition (o.product_id = p.id) causes a cartesian product, inflating every total by 3×. The agent must rewrite using explicit INNER JOIN … ON syntax.

Schema:orders, users, products — e-commerce dataset Goal: Correct per-(user, product) total amount spent, ordered by total DESC

Hard — Rewrite Correlated Subquery as CTE

A semantically correct but O(N²) query re-executes AVG(salary) for every employee row. The agent must rewrite using a WITH clause that computes department averages exactly once.

Schema:departments, employees — 9 employees across 3 departments Goal: Employees who earn strictly above their department average, ordered by dept/salary

Expert — Fix the Tie-Breaking Window Function (2 bugs)

Two layered bugs: ROW_NUMBER() drops tied reps AND ORDER BY revenue ASC picks the lowest earners instead of the highest. Agent must fix the sort order AND switch to RANK()/DENSE_RANK() — fixing only one still produces wrong results.

Schema:sales_reps(id, name, region, revenue) — 6 reps across 2 regions with ties Goal: All reps whose revenue is the highest in their region

Expert — Traverse Org Chart with Recursive CTE (2 bugs)

Two layered bugs: the anchor uses WHERE id = 3 (includes VP Eng himself in results) AND the query is a hardcoded two-level CTE that misses deeper employees. Agent must fix the anchor to WHERE manager_id = 3 AND convert to WITH RECURSIVE.

Schema:employees(id, name, manager_id) — 14 employees, 4 levels deep Goal: All 8 subordinates of VP Eng at any depth (excluding VP Eng), ordered by id

Expert — Fix Broken Window Functions (3 bugs)

Three layered bugs: both SUM and RANK window functions are missing PARTITION BY, they need different ORDER BY clauses, AND the data contains tied revenue values (West Q3=Q4=16000) that must be ranked correctly.

Schema:quarterly_sales(region, quarter, revenue) — 8 rows across 2 regions with ties Goal: Per-region running total (ORDER BY quarter) and within-region revenue rank (ORDER BY revenue DESC) with correct tie handling

Structural penalties are enforced per task level/id to prevent gaming:

• hard: requires WITH clause (−0.30 if absent)
• medium: requires explicit JOIN (−0.20 if absent)
• task_expert_recursive: requires WITH RECURSIVE (−0.30) + correct anchor via manager_id (−0.15)
• task_expert_rank: penalises ROW_NUMBER() (−0.20) + penalises ASC ordering without DESC (−0.15)
• task_expert_window: requires PARTITION BY in both window functions (−0.20 if absent, −0.10 if only one)

---

Custom Tasks

Register any SQL task at runtime — no code changes needed.

Via Python

fromtasksimportREGISTRY, task_from_dictREGISTRY.register(task_from_dict({
"id": "my_window_task",
"level": "hard",
"title": "Rank Employees by Salary",
"schema_ddl": "CREATE TABLE emp (id INT, name VARCHAR, dept VARCHAR, salary DECIMAL); INSERT INTO emp VALUES ...",
"broken_query": "SELECT name, salary FROM emp ORDER BY salary DESC",
"expected_rows": [{"name": "Alice", "rank": 1}, ...],
"hint": "Use ROW_NUMBER() OVER (PARTITION BY dept ORDER BY salary DESC)",
"solution_query": "SELECT name, RANK() OVER (ORDER BY salary DESC) AS rank FROM emp",
}))

Via REST API (when server is running)

# Register a custom task
curl -X POST http://localhost:8000/tasks \
-H "Content-Type: application/json" \
-d '{"id": "my_task", "schema_ddl": "...", "expected_rows": [...]}'# List all tasks
curl http://localhost:8000/tasks
# Remove a custom task
curl -X DELETE http://localhost:8000/tasks/my_task

Via JSON file

REGISTRY.load_from_json("my_tasks.json")

---

Quickstart

Install dependencies

python -m venv .venv
.venv/bin/pip install -e ".[dev]"

Run the local playbook (no server needed)

Tests all three built-in tasks directly, with progressive SQL attempts:

ANTHROPIC_API_KEY=your_key .venv/bin/python playbook.py

Run the inference script

Runs any OpenAI-compatible LLM as an agent against all 6 tasks and reports scores:

# Against HuggingFace routerexport API_BASE_URL=https://router.huggingface.co/v1
export MODEL_NAME=meta-llama/Llama-3.1-8B-Instruct
export HF_TOKEN=your_hf_token
export ENV_URL=http://127.0.0.1:8000 # or the live HF Space URL
python inference.py
# Against the live HF Space (no local server needed)export ENV_URL=https://prithvigg-queryforge.hf.space
python inference.py

Run the HTTP server

uvicorn server.app:app --reload --host 0.0.0.0 --port 8000

---

Baseline Results

The following scores were produced by running meta-llama/Llama-3.1-8B-Instruct (via HuggingFace router) as the agent against all 6 tasks with the full AI judge active.

Task	Level	Steps Used	Best Score
Fix the Syntax Errors	easy	1	1.000
Fix the Cartesian JOIN	medium	1	0.900
Rewrite Correlated Subquery as CTE	hard	1	0.900
Fix the Tie-Breaking Window Function	expert	1	1.000
Traverse Org Chart with Recursive CTE	expert	2	0.900
Fix Two Broken Window Functions	expert	3	0.900
Average			0.933

The easy–hard tasks and the rank/recursive expert tasks were solved in 1–2 steps. The dual-window expert task required 3 steps, demonstrating the feedback loop produces training-relevant multi-step trajectories for harder tasks.

---

API Endpoints

Method	Endpoint	Description
POST	/reset	Start a new episode. Pass {"task_id": "..."} to pin to a task
POST	/step	Submit a SQL query: {"sql": "SELECT ..."}
GET	/state	Current episode ID and step count
GET	/schema	Action and observation JSON schemas
POST	/tasks	Register a custom task
GET	/tasks	List all registered tasks
DELETE	/tasks/{task_id}	Remove a custom task (built-ins protected)
WS	/ws	WebSocket endpoint for persistent low-latency sessions
GET	/health	Container health check
GET	/docs	Interactive OpenAPI documentation

Examples

BASE=https://prithvigg-queryforge.hf.space # or http://localhost:8000 for local# Start an episode pinned to the hard task
curl -X POST $BASE/reset \
-H "Content-Type: application/json" \
-d '{"task_id": "task_hard_cte"}'# Submit a query
curl -X POST $BASE/step \
-H "Content-Type: application/json" \
-d '{"sql": "WITH dept_avg AS (SELECT department_id, AVG(salary) AS avg_salary FROM employees GROUP BY department_id) SELECT e.name, e.department_id, e.salary FROM employees e JOIN dept_avg d ON e.department_id = d.department_id WHERE e.salary > d.avg_salary ORDER BY e.department_id, e.salary DESC"}'# List all available tasks
curl $BASE/tasks

---

Python Client

fromqueryforgeimportQueryforgeEnv, SQLActionwithQueryforgeEnv(base_url="http://localhost:8000") asenv:
# Pin to a specific taskobs=env.reset(task_id="task_medium_join")
print(obs.task_description)
# Submit a fixresult=env.step(SQLAction(sql=""" SELECT u.name, p.title, SUM(o.amount) AS total_spent FROM orders o INNER JOIN users u ON o.user_id = u.id INNER JOIN products p ON o.product_id = p.id GROUP BY u.name, p.title ORDER BY total_spent DESC """))
print(f"Score: {result.reward:.3f}")
print(f"Feedback: {result.observation.feedback}")
print(f"Done: {result.done}")
# Register and use a custom taskenv.register_task(TaskSpec(
id="my_task",
schema_ddl="CREATE TABLE ...; INSERT INTO ...",
expected_rows=[{"col": "val"}],
title="My Custom Task",
))
obs=env.reset(task_id="my_task")

---

Project Structure

queryforge/
├── __init__.py # Public exports (SQLAction, SQLObservation, TaskSpec, REGISTRY)
├── models.py # SQLAction, SQLObservation, TaskSpec Pydantic models
├── tasks.py # Built-in tasks (easy→expert) + thread-safe TaskRegistry
├── judge.py # 4-stage grading pipeline (DuckDB + Anthropic)
├── client.py # QueryforgeEnv client with task management helpers
├── playbook.py # Local test runner (no server required)
├── inference.py # Baseline inference script (any OpenAI-compatible LLM)
├── demo.py # Gradio interactive demo (mounted at /demo)
├── Dockerfile # Container image
├── openenv.yaml # OpenEnv manifest
├── pyproject.toml # Project metadata and dependencies
├── uv.lock # Locked dependencies
└── server/
├── app.py # FastAPI app — core + /tasks REST endpoints + Gradio mount
├── queryforge_environment.py # Environment class (reset, step, state)
└── requirements.txt # Server dependencies

---

Deployment

Hugging Face Spaces (recommended)

UV_CACHE_DIR=/tmp/uv-cache openenv push . --repo-id <hf-username>/queryforge

Add ANTHROPIC_API_KEY as a Space secret after deployment. Without it, the environment runs in deterministic-only mode (scores capped at 0.80, done threshold self-adjusts accordingly).

Docker

docker build -t queryforge:latest .
docker run -p 8000:8000 -e ANTHROPIC_API_KEY=$ANTHROPIC_API_KEY queryforge:latest

The deployed environment exposes:

• /web — Interactive UI for exploring the environment
• /docs — Full OpenAPI / Swagger interface
• /ws — WebSocket endpoint for persistent agent sessions
• /health — Container health monitoring

---

Environment Design Notes

Why DuckDB? DuckDB runs fully in-memory with no external process or network dependency. Each step() call creates an isolated connection, seeds it with the task's schema, runs the agent's query, then closes — complete isolation with zero shared state between steps.

Why a 4-stage reward? Binary correct/incorrect rewards give an agent no gradient to climb when its query is simply broken. The 4-stage pipeline means every improvement — fixing a typo, avoiding a runtime error, returning the right row count, getting the right rows, writing clean SQL — is rewarded. This produces a smooth loss landscape for policy gradient methods.

Why structural penalties? Without them, an agent could achieve 0.80 on the hard CTE task by submitting the original correlated subquery verbatim (rows match, but the task was never solved). Structural penalties enforce that the agent actually learned what to change, not just that rows matched.