SQL Benchmarks Lab MCP server

SQL Benchmarking Laboratory

A deterministic, orchestrated harness for verifying database performance at scale. Developed by Ramona C. Truta

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The Mission: "Ground Truth" as Code

This platform is a specialized laboratory for testing SQL performance hypotheses. It transforms query tuning from intuition into a reproducible science.

The core of the system is a Deterministic Orchestration Harness that guarantees that if the logic or the environment changes, the benchmark result changes. If they do not, the result is addressable and cached.

Scope: the focus to date is synthetic and canonical (TPC-H) data, which is the right instrument for mechanism experiments — where controlled, reproducible data isolates the variable under test. Real-data support exists but is experimental; see the FAQ for the synthetic-vs-real rationale, the container model, and the roadmap (AI-security testbed, real-data trust chain).

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Key Features & Innovations

1. Context-Aware Semantic Hashing (The Experiment ID)

The Heart of the system is the Experiment ID, an 8-character hash that governs the entire lifecycle. This hash is a SHA-256 fingerprint generated from:

• The Config: Every dimension in your YAML (rows, skew, parameters).
• The SQL Logic: The actual content of the benchmarked scripts.
• The Code: All measurement-relevant Python — orchestration (assets/), engine clients (resources/), and data generators (plugins/).

Semantic Normalization: The hashing engine distinguishes between a logic change and a formatting change.

• SQL: Comments, whitespace, and case are normalized before hashing.
• Python: Orchestration scripts are parsed into an Abstract Syntax Tree (AST) to strip docstrings and formatting variations, ensuring the Experiment ID only changes when execution logic changes.

2. Multi-Layer Cold-Cache Isolation

To ensure IO-bound performance is not masked by memory buffers, engine-level buffers are cleared before every query:

• Postgres: Mandatory Docker Container Restarts clear shared buffers.
• Versioned DuckDB (duckdb_1_5, duckdb_2_0): every query runs in a fresh worker process, so DuckDB's buffer pool starts empty.

OS page cache: not evicted. Engines call thrash_os_cache, which dirties an anonymous memory region (half of available RAM, capped at 4 GB). On macOS this was measured to leave a cached 1 GB file fully resident, so measurements should be read as warm at the OS level. DuckDB clients take a required cold argument, and cold=True raises until a verified eviction step exists.

3. Agentic AI Integration

The platform is built for the future of Autonomous Engineering. The Experiment ID allows AI agents to treat the laboratory as a Deterministic Performance API.

• See AGENTS.md for the full Agentic Benchmarking Protocol.

4. Declarative Matrix Orchestration

Benchmarks are defined as N-dimensional matrices in YAML. The platform expands these into a Cartesian product of Independent Dagster Partitions. This allows for parallel dispatch and granular retries.

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Usage & Technical Setup

Prerequisites

• uv: the project's Python environment & dependency manager (fast, modern). setup.sh uses it, and it can install Python 3.11 for you.
• Python 3.11+: core runtime (uv provisions it if missing).
• Docker: for the containerized engines (Postgres, TypeDB), which the harness manages itself — not required for the DuckDB-only quickstart.

Installation & Setup

From PyPI — the lab is installable, which gives you the tooling and the sqlbench CLI:

pip install sqlbenchdag

From source — clone the repo to also get the published capsules (sql_benchmarks/experiments/results/) and the full harness. The laboratory includes a comprehensive setup script that manages virtual environments, dependencies, and directory initialization.

# 1. Automate Setup
chmod +x setup.sh && ./setup.sh

# 2. Activate Laboratory
source venv/bin/activate

The Execution Workflow (CLI)

While the system is powered by Dagster, the primary interface is the CLI for automated workflows.

# QUICKSTART: DuckDB only, no Docker required — runs in seconds
./run.sh sql_benchmarks/experiments/queue/quickstart.yaml --auto

# FULL BENCHMARK: Run all queued experiments (requires Docker for Postgres)
./run.sh queue --auto

# SINGLE EXPERIMENT: Pass a specific config path
./run.sh sql_benchmarks/experiments/queue/quack_execution_modes.yaml --auto

To write your own experiment, start from the annotated template and see the catalog of published runs in docs/experiments.md.

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Project Structure

Managed with a strict separation between Harness and Scenario:

/sql_benchmarks
├── /assets                 # THE HARNESS: Dagster factories & pipeline logic
├── /resources              # THE INFRASTRUCTURE: DB drivers & Docker management
├── /scripts/sql            # THE SCENARIOS: Raw SQL partitioned by scenario
├── /plugins                # THE DATA: Declarative generators & scenario providers
├── /utils                  # THE BRAIN: AST-hashing, common logic, & system primitives
└── /experiments            # THE LABORATORY
    ├── active.yaml         # LOCAL runtime staging — the coordinator overwrites
    │                       #   this on every run (gitignored; not shared state)
    ├── /queue              # Staging area for new experiment configs
    ├── /archive            # Library of previously defined experiment templates
    ├── /configs            # Registry of immutable, hash-addressed experiment capsules
    └── /results            # Data capsules: fragments, CSVs, and Dashboards

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Published Experiments — the Quack investigation

The first published study with this lab: an independent measurement of DuckDB's Quack client-server protocol (beta, v1.5.3). Each row links the runnable config to its committed, verifiable capsule. Full numbers, scaling exponents, and verification steps in docs/published_capsules.md.

Act	Question	Config	Capsule	Finding
I	What does the protocol cost?	quack_execution_modes.yaml	b8e2bfaf	Attach-mode overhead grows with scan size (2.6× → 9.5× at 10M rows); pushdown stays flat at ~2×.
II	Why is pushdown ~2× and not 1×?	quack_residual_threads.yaml	25b0e134	The residual tracks reduced server-side parallelism (~2–4 of 8 threads), not transport.
III	Does it generalize to joins?	tpch_quack_validation.yaml	b198363e	On canonical TPC-H Q3, pushdown holds (~1.9×); attach mode cannot run the join at all (DNF).
IV	Does it beat the incumbent?	quack_vs_postgres.yaml	902d1277	DuckDB-over-Quack (pushdown) beats PostgreSQL by up to 13.2×, and the gap widens with scale.

Act 0 (b82b4eae) is the exploratory scout that started it — see docs/published_capsules.md.

The lab also ships scenario suites for other studies — selectivity/, null_logic/, null_sentinel/, recursion/, sort_spill/, tpch/, and more under sql_benchmarks/scripts/sql/ — each runnable across the engine matrix.

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Naming & Provenance

The lab works at two layers, named two different ways. Keeping them distinct is the difference between a number you can trace and a number you have to trust.

Layer	What it is	Named by	Example
Capsule	one experiment's complete results	its Experiment ID — an 8-char SHA-256 of the question (config + SQL + measurement code), assigned by the machine	48c92f31
Release	a signed set of capsules backing a publication	a human name: sqlbenchdag-<topic>-v<N>-<YYYYMMDD>	sqlbenchdag-quack-v1-20260614

A release contains capsules; a capsule is one experiment. The machine names capsules (hashes you can't forge); the author names releases (words that mean something). sqlbenchdag is the lab's maker's mark — sql + bench + dag (Dagster, the orchestration that distinguishes this lab from a bare query timer). It is carried on every release this lab produces.

Two hashes, two jobs (a capsule contains both — they are not the same thing):

• the Experiment ID (8 chars) is an address — it names the capsule, and the same question always produces the same address;
• the integrity seal (64 chars, in integrity.seal) is a checksum — it verifies the capsule's contents are untouched. You file by the address; the seal is the tamper-evident lid.

Reproducibility is pinned to the release. Because the Experiment ID hashes the measurement code, it is stable only at a fixed code revision — which is exactly what the signed release tag freezes. To reproduce a published capsule, check out its release tag and re-run its config; the same question yields the same ID, or the comparison is refused by construction.

Provenance roadmap: a per-capsule generator stamp (sqlbenchdag@<commit>) will record the exact build that produced each capsule. It writes through the finalization code, which lives inside the Experiment-ID hash, so it ships with a future release rather than re-numbering capsules already published.

See docs/published_capsules.md for the full trust chain (reproducibility, integrity, timestamp, authorship) and how to verify each. Reproducibility and integrity are automatic on every run; timestamp and signature are optional steps you add only when publishing — the producer workflow is docs/PUBLISHING.md.

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License

Copyright 2025-2026 Ramona C. Truta. Licensed under the Apache License 2.0.

Built with Dagster, Polars, Docker, DuckDB, and Postgres.