Backend storage in detail¶

httk.store.backend.sql is the database storage layer of httk₂: it stores plain frozen dataclasses in a relational database, makes them queryable through a backend-agnostic search DSL, and serves them through the neutral httk.core.EntryProvider contract (e.g. as an OPTIMADE API via httk-serve). SQL generation and dialect handling run on SQLAlchemy Core internally; the public API exposes no SQLAlchemy types.

Installing¶

The SQL layer is an optional extra (plain import httk.store works without it):

python -m pip install "httk-store[db]"      # SQLite (built into Python) via sqlalchemy
python -m pip install "httk-store[duckdb]"  # additionally the DuckDB backend
python -m pip install "httk-store[postgresql]"  # PostgreSQL backend (psycopg 3)
python -m pip install "httk-store[clickhouse]"  # ClickHouse backend

Backend.postgresql(url) opens a PostgreSQL store from a postgresql:// URL. It is fully transactional and rides the ordinary transactional write profile with no special-casing, and it supports bulk ingestion (store.bulk_ingest()) with the same parity/deferred/parallel behavior as SQLite and DuckDB. Only the psycopg 3 driver is supported: a bare postgresql:// URL is normalized to postgresql+psycopg:// and any other explicit driver is rejected. See the PostgreSQL testing guide for local setup.

Touching a SQL-backed name (such as httk.store.backend.sql.Backend) without the extra installed raises an ImportError naming it.