h2hdb

h2hdb is the database and coordination core for the H2HDB multi-repository system. It owns the SQLite/MariaDB schema, bounded transactional workflows, and backend-neutral application facades. Komga and OPDS use the catalog facade; ingest uses the transaction-owning ingest facade and downloader uses the queue facade.

It deliberately does not scan files, parse galleryinfo.txt, manipulate images, choose filesystem paths, serve HTTP, serialize OPDS documents, or depend on hbrowser. Those responsibilities belong to consumer adapters and sibling packages.

Greenfield BCNF schema

The current schema is a clean epoch-2 design:

361 catalog data-plane base relations checked as BCNF, plus 82 generated logical views for read-oriented projections. Fifty-three generic sealed vertical families keep every new base at its semantic key plus at most one value.
28 declared decompositions, each checked as lossless and dependency-preserving.
75 operational control-plane base relations checked as BCNF, plus one derived activation view. The base count includes the epoch-control relation; the generated CREATE-only provider owns the other 74 bases and the view.
One generated physical schema for SQLite and MariaDB, with backend-specific SQL rendered from the same closed-world manifests.
A separate physical-width gate requires each catalog_* base table to have its semantic primary key plus at most one atomic non-key value. It currently reports all 361 bases compliant with no width debt; logical views are excluded from that policy.
The closed catalog physical-domain authority contains exactly 320 relations: 260 mutation relations and 60 read-only views. The complete publication graph is inside that closure, including permanent finalization replay state.
The generated provider installs exactly 4,646 typed bootstrap rows per backend, including all 17 fixed 256-shard cleanup ranges.

The logical sources of truth are verification/schema/catalog.toml and verification/schema/operational.toml. They declare functional dependencies, keys, decompositions, bootstrap facts, and semantic obligations. Deterministic generators derive the physical manifests, Lean schema proofs, and the wheel-resident runtime provider. Generated SQL is not a second schema-authoring surface.

This is a greenfield cutover. There is no v1-v7 upgrade or adoption path, no legacy-epoch compatibility layer, and no dual write. Read-only logical views inside epoch 2 are deliberate read models. A previous or foreign database must be replaced with an empty database and rebuilt from source data.

The numbered migration runner, monolithic H2HDB facade, and their hand-written legacy repositories are not shipped. In particular, the old catalog_build_discoveries relation is not part of the package or generated schema. Production SQL relation names are checked against the two physical manifests in both source and built-wheel verification, so a second hand-written catalog_* or operational_* schema cannot silently bypass the manifest audit.

Schema epoch

The active identity is epoch=2, schema_version=1. The singleton h2hdb_schema_epoch row binds the exact generated DDL, bootstrap-seed, and semantic-obligation manifests into one durable checksum.

Initialization follows a fail-closed state machine:

A truly empty database is admitted and recorded as BUILDING.
Idempotent generated DDL and bootstrap rows are applied in deterministic slices.
The complete object set, bootstrap facts, and activation obligations are validated.
The exact manifest is atomically marked READY.

If construction is interrupted, rerunning migrate may resume only the same checksum-matching BUILDING epoch. A READY rerun validates the exact current epoch. Drift, an unknown control residue, or any other non-empty database is rejected without adoption or destructive repair.

The command name migrate is retained as the administration interface, but it constructs or resumes this single manifest-bound greenfield epoch; it does not run numbered historical migrations.

Core responsibilities

MariaDB and SQLite connectors, read/write transactions, and connector-enforced read-only access.
Manifest-bound schema construction, full validation, and O(1) readiness checks.
Normalized catalog identities, immutable revisions, publication preparation, and revision-pinned reads.
Durable download-to-ingest handoff, exact attempt/lease fencing, and coordinated completion.
Bounded source-build, analysis, publication, cleanup, maintenance-gate, canonical-value, event, and hash-cache workflows.

Cross-table workflows use one connector and one managed transaction. Mutable authority is represented by normalized heads, generations, leases, seals, and receipts rather than by caller-supplied counts, cursors, digests, names, or tokens. Long-running work advances through bounded, replayable batches; pointer publication validates sealed scalar state in a short transaction.

Installation

This repository uses a src layout and an independent uv environment. It is not part of a uv workspace, and uv.lock is intentionally ignored.

uv venv --python 3.14
uv pip install -e ".[dev]"

Rebuild the local environment after toolchain changes with:

./scripts/rebuild-env.sh

Configuration

{
  "database": {
    "sql_type": "sqlite",
    "database": "/var/lib/h2hdb/catalog.sqlite3",
    "access_mode": "read-write"
  },
  "maintenance": {
    "optimize_enabled": true
  },
  "logger": {
    "level": "INFO",
    "file": null
  }
}

For MariaDB, also set host, port, user, password, and database. Read-only consumers should use "access_mode": "read-only" and a database account limited to the metadata/read privileges required by schema validation and application reads.

JSON string values consisting exactly of ${ENV_NAME} are resolved from the process environment before validation. Variable names must match [A-Za-z_][A-Za-z0-9_]*; missing or invalid variables stop startup without including their values in the error. Inline interpolation such as db-${INSTANCE} is deliberately unsupported, and unknown JSON fields are rejected.

Schema administration

The CLI exposes exactly three operations:

uv run --no-sync python -m h2hdb migrate --config config.json
uv run --no-sync python -m h2hdb check --config config.json
uv run --no-sync python -m h2hdb ready --config config.json

Choose the operation from database state:

Database state or caller	Operation
Truly empty database	Run `migrate` to construct epoch 2/version 1
Matching interrupted `BUILDING` epoch	Rerun `migrate` to resume
Matching `READY` epoch	Run read-only `check` for the full audit
Consumer startup	Run `check`; never initialize schema
Frequent readiness probe	Run the O(1) read-only `ready` check
Previous, foreign, or drifted schema	Create a new empty database and rebuild

The wheel-resident generated provider must resolve every required runtime validator and recurring writer binding before it opens or mutates a database; the public administration API does not accept a substitute provider. check holds a read transaction while validating the complete READY schema; ready validates only the exact epoch/version/manifest marker.

Applications can use the same administration boundary directly:

from h2hdb import VNextDatabaseAdminFacade, load_config

config = load_config("config.json")
admin = VNextDatabaseAdminFacade(config)
admin.initialize()  # deployment init job only
admin.check()  # full read-only audit
admin.check_readiness()  # lightweight probe

Public application API

Consumers should import the public facades and immutable domain values from h2hdb; they must not import connector, repository, generated-schema, or table implementation modules.

Revision-pinned catalog reads use open_database, which performs the full manifest-bound READY audit before returning a VNextCatalogFacade:

from h2hdb import load_config, open_database

catalog = open_database(load_config("readonly-config.json"))
revision = catalog.get_catalog_revision()
page = catalog.list_publications(
    revision=revision,
    offset=0,
    limit=50,
    require_artifact=True,
)
publication = catalog.get_publication("42", revision=revision)

Download request creation, bounded listing, and exact-request completion use VNextDownloadQueueFacade:

from h2hdb import VNextDownloadQueueFacade, load_config

queue = VNextDownloadQueueFacade(load_config("writer-config.json"))
request = queue.request_download(42, "https://example.invalid/gallery/42")
pending = queue.list_download_requests(limit=100)
queue.complete_download_request(request)

Each facade call owns a fresh connection and one bounded read or write transaction. Repository methods that accept connectors or units of work remain internal coordination surfaces.

Deliberate current limits

A nonblank catalog search query fails closed until a normalized, revision-pinned search index is part of the manifest and reader contract.
The durable contract needed to derive CatalogPublication.redownload_required for a pinned revision is not closed. Readers therefore do not infer it from transient operational rows.
Core defines and orchestrates the typed artifact-preparation/storage boundary, but concrete filesystem and object-storage behavior remains in the consumer adapter.

Verification

The schema workflow and implementation checks are:

uv run --no-sync python scripts/verify-formal.py coverage --validate-only
uv run --no-sync python scripts/verify-formal.py schema
uv run --no-sync python scripts/verify-formal.py lean
uv run --no-sync python scripts/verify-schema-surface.py
uv run --no-sync black --check src tests scripts
uv run --no-sync ruff check src tests scripts
uv run --no-sync mypy src tests scripts
uv run --no-sync pytest
uv run --no-sync python -m build

verify-formal.py schema checks manifest validity and generator drift for the physical, Lean, operational-refinement, and runtime-provider artifacts. The Lean target proves the declared closed-world BCNF and decomposition statements under their explicit assumptions; it does not by itself prove SQL/runtime refinement.

coverage --validate-only validates the evidence-index structure while still reporting unresolved production blockers. Plain coverage is the strict production-readiness gate and must remain nonzero until every reported blocker has real evidence. Schema and Lean success must not be presented as strict coverage success.

SQLite tests run locally. Set H2HDB_TEST_MARIADB=1 with a working Docker daemon to include MariaDB testcontainer cases.

The distribution boundary can be checked with:

uv run --no-sync python scripts/build-and-verify-distributions.py \
  --output-directory /path/to/empty/output-directory

It builds in a fresh temporary directory, verifies the wheel's closed schema surface and removed-module boundary, and confirms that the installed CLI exposes only migrate, check, and ready.

Local release gate

Install the versioned Git hooks once per clone:

./scripts/install-git-hooks.sh

The installer refuses to disable an existing hooks path or executable legacy hook; compose those hooks explicitly before switching this clone to .githooks. VS Code's built-in Git and command-line Git honor the installed hooks. GitHub web edits and clones where the installer has not run do not.

Ordinary commits and merges do not run the expensive release suite. When the staged project.version in pyproject.toml increases, the pre-commit or pre-merge-commit hook requires the candidate tree to have no unstaged or untracked files and automatically runs the complete local release gate:

Black, Ruff, and mypy;
coverage-contract and generated-schema drift checks;
Lean proofs and the required small TLC profiles;
the complete SQLite and MariaDB test suite; and
the installed-distribution boundary check.

The gate requires the development environment, Docker for MariaDB, the Lean toolchain declared by lean-toolchain, and either host Java or Docker for TLC. Deep TLC remains an explicit manual check. A successful gate writes a local, non-versioned receipt under the repository's Git metadata and binds it to the exact staged tree and project version. The pre-push hook allows a version-increasing master push only when that receipt is valid, so retrying the same commit does not rerun the suite.

To verify an already committed clean HEAD explicitly, or to force a fresh verification, run:

uv run --no-sync python scripts/release-gate.py run
uv run --no-sync python scripts/release-gate.py run --refresh

GitHub-hosted formal verification is manual-only. The PyPI workflow rechecks the version transition, builds and smoke-tests the distributions, and publishes them; the expensive correctness evidence is owned by the local release gate.

Multi-repository development

The repositories remain independent projects. For an isolated editable-install smoke environment, run:

./scripts/rebuild-multirepo-integration.sh

See docs/multi-repo-deployment.md for the database ownership, initialization, and consumer-adapter deployment boundary.

License

GNU Affero General Public License v3 or later. See LICENSE.

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