`new_transaction` sets a transaction's isolation level (for the receipts,
push-actions and purge paths, which ask for a specific level) by calling
`engine.attempt_to_set_isolation_level` before the transaction and resetting it
after. The Rust engine raised `NotImplementedError` there, so those transactions
errored out on the Rust backend.
The shim has no psycopg2-style `conn.set_isolation_level`, so implement it in
SQL: run `SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL <level>` on
the connection. That sets the session's default for *subsequent* transactions,
so it's committed before the caller's transaction begins (SET is transactional);
`new_transaction` resets it to the default (REPEATABLE READ, which the pool
already applies at connection setup) afterwards, scoping the override to the one
transaction — matching psycopg2's behaviour. The level name comes from a fixed
`IsolationLevel` map, not caller input.
Fixes the isolation-level failures in tests.storage.test_event_push_actions,
tests.storage.test_purge and tests.storage.test_receipts on the Rust backend
(20/20 pass); psycopg2 and sqlite are unaffected.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W3G4M92AmwSSZCbmtMJU3d
Turn the Rust backend on with `database.use_rust_driver: true` (alongside
`name: psycopg2`). Keeping `name: psycopg2` means the engine is still selected as
Postgres and all the `isinstance(engine, PostgresEngine)` dialect checks hold;
the flag only swaps the driver implementation.
- `create_engine` returns `RustPostgresEngine` instead of `Psycopg2Engine` when
the flag is set.
- `make_pool` gains a `clock` argument and, for the Rust engine, builds a
`RustConnectionPool` (via `_make_rust_pool`) instead of an adbapi pool:
it derives the libpq DSN from the config `args`, sizes threads/connections
to `cp_max`, passes the engine's synchronous_commit / statement_timeout,
starts the pool, and registers a shutdown hook via the clock. Its declared
return type stays `adbapi.ConnectionPool` — `RustConnectionPool` provides the
`_db_pool` subset `DatabasePool` uses (runWithConnection / threadID /
running / threadpool) — so callers that lean on adbapi-specific methods keep
type-checking.
- `RustConnectionPool` takes synchronous_commit / statement_timeout_ms and
threads them into its pooled connections' session setup.
- `DatabasePool` passes its clock to `make_pool`; the test harness's
`make_fake_db_pool` accepts the new argument.
Tested: create_engine honours the flag (and the Rust engine is still a
PostgresEngine, not a Psycopg2Engine); make_pool builds a started
RustConnectionPool that serves a query as `_db_pool`. psycopg2 and sqlite
homeserver boots remain green. A full homeserver boot on the Rust backend isn't
covered here because the test harness patches `make_pool` with a synchronous
adbapi fake.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W3G4M92AmwSSZCbmtMJU3d
A database engine that drives the Rust Connection/Cursor shim instead of
psycopg2. It subclasses PostgresEngine to reuse the pure SQL-generation and
configuration behaviour, and overrides only the parts that touch a live
connection or are wired to psycopg2 internals:
- `module` points at the Rust backend's DBAPI2 exception hierarchy, which the
transaction driver catches on;
- `convert_param_style` rewrites `?` to `$1, $2, ...` (the shim binds libpq
positional placeholders, not psycopg2's `%s`);
- `in_transaction` / `is_connection_closed` / `attempt_to_set_autocommit` call
the shim's own methods;
- `is_deadlock` matches the Rust `DatabaseError` and its `pgcode`;
- `executescript` uses the shim's multi-statement primitive;
- `on_new_connection` is a no-op — session setup belongs in the Rust pool.
Per-transaction isolation-level overrides raise NotImplementedError for now, and
`check_database` / `server_version` still read psycopg2 attributes; the engine
is not yet selectable via `create_engine`, so neither is reached. Wiring it into
`make_pool` (which also feeds session config to the pool) is the next step.
Tested directly: param-style rewriting, deadlock/pgcode matching, the module
pointer, and — against a live shim connection — in_transaction, is_closed and
autocommit.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W3G4M92AmwSSZCbmtMJU3d
