Add opt-in database creation strategies by DeoLeung · Pull Request #1487 · dbfixtures/pytest-postgresql

DeoLeung · 2026-11-02T00:49:21Z

Add create_strategy to postgresql_proc and postgresql_noproc, with matching CLI and ini options for wal_log, file_copy and clone. Leaving it unset preserves existing behavior for synchronous and asynchronous clients.

Client factories translate these modes into PostgreSQL strategy and copy_method options before constructing a janitor. Janitors accept the raw options, enforce their pairing constraint, compose SQL safely and let PostgreSQL report unknown or unsupported values. The session-local file-copy setting is applied on the same connection as database creation. Initial and layered template creation keep the server default.

README usage examples live with the Advanced Usage examples after Configuration, with a short reflink caveat and links to the official PostgreSQL documentation. Configuration remains compatible with existing keyword and positional constructors.

Validation on PostgreSQL 18.6: the full native suite passed with two xdist workers (250 passed, 11 platform skips). All 20 selected configuration/factory scenarios passed without pytest-asyncio, including sync-only execution of the copied client examples. Applicable pre-commit checks, including Ruff, formatting and full-project mypy, passed. Real-server assertions cover both factories and client types, SQL/session selection, invalid option pairs, server compatibility errors and template data isolation.

Documentation follow-up: applicable README pre-commit hooks, source/wheel builds and PyPI README rendering passed.

Closes #1260.

Summary by CodeRabbit

New Features
- Added configurable PostgreSQL database creation strategies: PostgreSQL’s default, wal_log, file_copy and clone.
- Configure a strategy through the command line, pytest.ini, or process and no-process factories. Factory settings take precedence over global configuration.
- Synchronous and asynchronous client fixtures now use the configured strategy when cloning databases.
- Added guidance on PostgreSQL version and operating-system requirements, filesystem considerations and performance benchmarking.

coderabbitai · 2026-11-02T00:49:41Z

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Walkthrough

The change adds create_strategy configuration for synchronous and asynchronous client database creation. It supports PostgreSQL’s default, wal_log, file_copy, and clone strategies through factory arguments, pytest options, and janitors.

Changes: Database creation strategy

Layer / File(s)	Summary
Configure the strategy `pytest_postgresql/config.py`, `pytest_postgresql/plugin.py`, `README.rst`, `newsfragments/1260.feature.rst`	Configuration accepts `None`, `wal_log`, `file_copy`, or `clone`. The CLI, ini setting, README, and feature notice describe these options and their defaults.
Resolve and propagate factory settings `pytest_postgresql/executors/`, `pytest_postgresql/factories/`, `tests/test_create_strategy.py`, `tests/test_pg_exe.py`	Process and noproc factory arguments take precedence over the configured value. The selected strategy passes through executors to synchronous and asynchronous client janitors. Tests cover validation, configuration precedence, and propagation.
Apply the strategy during database creation `pytest_postgresql/janitor.py`, `tests/test_create_strategy.py`	The janitors generate strategy-specific creation SQL and, when required, set `file_copy_method` before creating a database. Integration tests cover synchronous and asynchronous creation, supported-feature errors, template data, and database creation without a template.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant ClientFixture
  participant DatabaseJanitor
  participant PostgreSQL
  ClientFixture->>DatabaseJanitor: pass create_strategy
  DatabaseJanitor->>PostgreSQL: set file_copy_method when required
  DatabaseJanitor->>PostgreSQL: create database with selected strategy

Suggested reviewers: fizyk, tboy1337

Merge Risk: Low · previous review cc5a2

Code constructing PostgreSQLConfig directly may need to pass the new field. Give it a default to preserve compatibility; the PostgreSQL 14 test workflow remains intact.

Pre-merge checks: 6

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely summarises the main change: adding opt-in database creation strategies.
Linked Issues check		Issue `#1260` asks whether PostgreSQL 18 `file_copy_method=clone` can speed up test database copies in this library. The issue is a question. Its implicit coding requirement is that the library can use …
Out of Scope Changes check		All changed areas support the `create_strategy` feature: `config.py` (validation and `PostgreSQLConfig` field), `plugin.py` (`--postgresql-create-strategy` and `postgresql_create_strategy`), `factorie…
Docstring Coverage		Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…
Newsfragment Check		A newsfragment was added at `newsfragments/1260.feature.rst`. The `pyproject.toml` configuration defines `feature` as a valid Towncrier type, and the filename follows the required `[issue_number].[typ…

Full details: Linked Issues check

Explanation

Issue #1260 asks whether PostgreSQL 18 file_copy_method=clone can speed up test database copies in this library. The issue is a question. Its implicit coding requirement is that the library can use this copy mode for test database creation. The PR adds an opt-in create_strategy option (wal_log, file_copy, clone) to postgresql_proc and postgresql_noproc, with CLI and ini equivalents. In pytest_postgresql/janitor.py at the reviewed head, _build_file_copy_method_sql returns SET file_copy_method = copy or SET file_copy_method = clone for file_copy or clone, only when cloning from a template. DatabaseJanitor.init and AsyncDatabaseJanitor.init execute this statement on the same cursor before CREATE DATABASE ... STRATEGY FILE_COPY. _build_create_database_sql adds WAL_LOG or FILE_COPY only when template_dbname is set and the janitor is not a template. Unset leaves the server default. The PR does not claim a measured speed gain on XFS, and the issue does not require one. Test-module and README coverage is described in the PR but was not independently re-run here.

Full details: Out of Scope Changes check

Explanation

All changed areas support the create_strategy feature: config.py (validation and PostgreSQLConfig field), plugin.py (--postgresql-create-strategy and postgresql_create_strategy), factories/process.py and factories/noprocess.py (factory argument and forwarding), executors/proc.py and executors/noop.py (stored value), factories/client.py (passes the value to the janitors), janitor.py (SQL generation), tests/test_create_strategy.py and the one-line tests/test_pg_exe.py change (create_strategy=None in make_config), README.rst (documentation of the new option), and newsfragments/1260.feature.rst. No change is unrelated to issue #1260 or the stated feature. The janitor source at the reviewed head matches the PR description and the summary.

Full details: Docstring Coverage

Explanation

Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 21 functions across 10 files. (2 skipped: 2 unsupported.)

Full details: Newsfragment Check

Explanation

A newsfragment was added at newsfragments/1260.feature.rst. The pyproject.toml configuration defines feature as a valid Towncrier type, and the filename follows the required [issue_number].[type].rst format.

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Inline comments:
Review comments at @pytest_postgresql/config.py:
- Line 41: Update the PostgreSQLConfig field order so create_strategy follows
drop_test_database, and give it a None default. Preserve the existing positional
argument meanings and allow callers using the previous fields to construct
PostgreSQLConfig without specifying a strategy.

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pytest_postgresql/config.py
pytest_postgresql/executors/noop.py
pytest_postgresql/executors/proc.py
pytest_postgresql/factories/client.py
pytest_postgresql/factories/noprocess.py
pytest_postgresql/factories/process.py
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fizyk · 2026-11-03T12:54:04Z

        self._connection_timeout = connection_timeout
        self.isolation_level = isolation_level
        self.autocommit = autocommit
+        self.create_strategy = validate_create_strategy(create_strategy)


do we need to validate the strategies at janitor level?

I think I'd pass exact knobs to the janitor instead. strategy: None| WAL_LOG| COPY, copy_method: None | clone | copy With the requirement that copy method be None for the first two strategy options, and not null for the copy strategy 🤔

Janitor, I thinkI'd like to have the exact postgresql options passed

Updated in e438c48. Client factories now translate the public create_strategy modes into PostgreSQL options before constructing the janitor: (None, None), ('WAL_LOG', None), ('FILE_COPY', 'copy'), or ('FILE_COPY', 'clone').

Janitors accept strategy and copy_method directly, no longer import or validate the public mode, and only enforce the requested pairing rule: a copy method is present exactly when the strategy is FILE_COPY. Option values are composed safely as SQL literals; PostgreSQL still reports unknown or unsupported values. Template creation keeps its existing behavior.

Expanded real-server coverage verifies all modes through both factories and sync/async clients, including same-backend SET/CREATE statements. Local validation passed: 250 tests in each serial/xdist run, 201 without the async extra, 48 Docker executions, and applicable pre-commit/full-project mypy checks.

codecov · 2026-11-03T13:01:00Z

Codecov Report

❌ Patch coverage is 99.54955% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
tests/test_create_strategy.py	99.40%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

fizyk · 2026-11-04T13:49:18Z

+inheriting the strategy of the fixture named by ``depends_on``.
+
+Filesystem and performance considerations
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


I'd trim this section and mostly defer to the official documentation where we can.

This summary though useful belongs to some additonal pages of a documentation (we don't have, apart from README) or official documentation for the postgresql/filesystems.... :/ I'm just afraid it'll clutter the README

Addressed in 9eeb73a. Removed the extended filesystem, Docker and benchmarking discussion. The README now keeps a short reflink/performance caveat and links to the official PostgreSQL CREATE DATABASE and file_copy_method documentation for the details. Applicable README pre-commit hooks (including rstcheck), source/wheel builds and PyPI README rendering pass.

fizyk · 2026-11-04T13:50:31Z

 By default, it connects to ``127.0.0.1:5432``.

+Choosing how test databases are cloned
+--------------------------------------


I'd move this whole section to advanced usage after config.

Moved in 9eeb73a. The complete creation-strategy section now sits with the existing Advanced Usage examples after Configuration, immediately before the DatabaseJanitor examples.

fizyk · 2026-11-04T13:53:39Z

+
+@pytest.mark.parametrize("factory_name", ["postgresql_proc", "postgresql_noproc"])
+@pytest.mark.parametrize("factory_strategy", [None, "clone"])
+def test_factory_create_strategy_precedence(


For this test, I'd write regular one, without pytester,

Updated in 6b1652a. This is now a regular parametrized test using real proc/noproc fixtures and the pytest request, without pytester. It checks explicit factory arguments against global configuration and checks that a chained noproc fixture uses its own configuration rather than its parent's strategy. CLI/ini parsing remains covered separately by the pytester integration tests.

fizyk · 2026-11-04T13:57:17Z

+    )
+    suffix = "" if strategy is None else f" STRATEGY '{strategy}'"
+    async_available = importlib.util.find_spec("pytest_asyncio") is not None
+    pytester.makepyfile(


use copy_example instead of writing python in sql

Updated in 6b1652a. Extracted the configuration and sync/async client scenarios into tests/examples and load them with copy_example. Per-case values are written as JSON data instead of generated Python. The seeded-data and same-session SET/CREATE assertions remain, including the optional async skip when pytest-asyncio is absent. Validation passed: 250 tests with two xdist workers (11 skips), 20 selected configuration/factory scenarios without pytest-asyncio, and applicable pre-commit checks including full-project mypy.

Add opt-in database creation strategies (refs dbfixtures#1260)

cc5a2d3

coderabbitai Bot reviewed Nov 2, 2026

View reviewed changes

Comment thread pytest_postgresql/config.py Resolved

Preserve PostgreSQLConfig constructor compatibility

185c397

fizyk reviewed Nov 3, 2026

View reviewed changes

Pass PostgreSQL creation options directly to janitors

e438c48

fizyk approved these changes Nov 4, 2026

View reviewed changes

Trim cloning documentation and move it to advanced usage

9eeb73a

fizyk reviewed Nov 5, 2026

View reviewed changes

Simplify strategy tests and use pytester examples

6b1652a

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