An open source multi-tool for exploring and publishing data https://datasette.io
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Claude d7a2ce91cc
Fix concurrency, lifecycle and contract problems from the second review
Schema watcher:
- Scan coalescing is loop-agnostic: in-flight scans are concurrent.futures
  futures any event loop can wait for, taken over only when their loop has
  closed or stopped; each refresh() resolves only its own scans. A write on
  one loop no longer hangs forever when another loop's scan is in flight.
- At most one polling task across event loops; replaced pollers exit.
- A scan or catalog write that fails transiently (internal database locked,
  shared-cache lock, cancellation) re-marks the database and retries it from
  later requests and sweeps, with back-off; requests are never failed by it.
  Write threads mark schema changes directly (under a lock) instead of
  relying on a notification reaching a loop that may have closed.
- add_database() file databases and named in-memory databases use the
  default_schema_watch mode (external unless configured). Named in-memory
  databases can be external: polled with PRAGMA schema_version on their
  write connection. They are not scanned at registration time, which raced
  plugins filling them (datasette-copy-to-memory).
- close() no longer persists a fingerprint for an owned database whose file
  header shows a schema the catalog has not seen.
- The derived-table permission rule (external-content FTS) trusts the
  catalog only when a stat and header read prove it is current; otherwise
  it asks the database, and schedules a rescan if the catalog is behind.

Connections and write threads:
- A BaseException from a write or isolated callback is delivered to the
  caller as a RuntimeError instead of killing the thread silently.
- conn.close() on a write lease raises ConnectionLeaseError, and the write
  thread reopens a connection something else closed.
- Write connections pin PRAGMA recursive_triggers=on (sqlite-utils FTS
  triggers rely on it; idle reopen lost the old drift).
- execute_fn() accepts generators that no longer hold the connection or a
  cursor.
- --crossdb _memory connections count against max_open_connections, are
  reaped, and are discarded when databases are added or removed.

Lifecycle:
- The temp internal database file uses weakref.finalize, not atexit, so
  closed or abandoned instances can be garbage collected.
- The read-pool reaper no longer keeps the last pool alive in its frame.
- The scratch directory is loaded (and locked) at the end of __init__, so a
  failed construction leaves nothing locked.
- config_dir/scratch is used only if empty or created by Datasette; a second
  instance on the same config dir starts without it; sidecar files are never
  deleted the first time a directory is opened.

Regression tests: tests/test_connection_review_fixes.py (24 of 27 fail on
a509b81; the other 3 guard behaviour that must not change).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwkLo2rJWidpkDVT3HkvNv
2026-10-04 08:32:09 +00:00
.github Deploy canned queries to latest.datasette.io again with workaround for #2916 2026-09-15 12:12:22 -07:00
datasette Fix concurrency, lifecycle and contract problems from the second review 2026-10-04 08:32:09 +00:00
demos Fixed an unnecessary f-string 2024-02-04 10:15:21 -08:00
docs Fix concurrency, lifecycle and contract problems from the second review 2026-10-04 08:32:09 +00:00
tests Fix concurrency, lifecycle and contract problems from the second review 2026-10-04 08:32:09 +00:00
.coveragerc Configure code coverage, refs #841, #843 2020-06-13 13:48:23 -07:00
.dockerignore Build Dockerfile with SpatiaLite 5, refs #1249 2021-03-26 21:27:40 -07:00
.git-blame-ignore-revs Ignore Black commits in git blame, refs #1716 2022-04-22 14:58:46 -07:00
.gitattributes New explicit versioning mechanism 2020-10-28 20:38:15 -07:00
.gitignore Ignore ignored/ directory 2026-06-25 21:20:29 -07:00
.isort.cfg Used isort to re-order my imports 2018-05-14 00:04:23 -03:00
.prettierrc .prettierrc, refs #1166 2020-12-31 13:25:44 -08:00
.readthedocs.yaml dependency-groups and uv (#2611) 2025-12-11 17:32:58 -08:00
CODE_OF_CONDUCT.md Add code of conduct again 2022-03-15 08:38:42 -07:00
codecov.yml codecov should not be blocking 2020-07-02 21:29:32 -07:00
Dockerfile Fix Docker release builds on main with Bookworm base image 2026-09-10 18:52:19 -07:00
Justfile Screenshots for reusable modal dialogs docs, plus just shots (#2958) 2026-09-24 15:06:57 -07:00
LICENSE Initial commit 2017-10-22 17:39:03 -07:00
MANIFEST.in Include LICENSE in sdist (#1043) 2020-10-23 13:54:34 -07:00
package-lock.json Bump rollup from 3.29.5 to 3.30.0 (#2651) 2026-03-30 10:54:48 -07:00
package.json Bump rollup from 3.29.5 to 3.30.0 (#2651) 2026-03-30 10:54:48 -07:00
pyproject.toml Screenshots for reusable modal dialogs docs, plus just shots (#2958) 2026-09-24 15:06:57 -07:00
pytest.ini pytest skip tests in ignored/ folder 2026-09-16 16:22:48 -07:00
README.md README: minimum Python is 3.10, not 3.8 (#2878) 2026-09-15 12:38:41 -07:00
ruff.toml Upgrade to ruff>=0.16.0 (#2857) 2026-07-25 15:47:08 -07:00
setup.cfg Switch to ruff and fix all lint errors, refs #2630 2026-01-23 20:43:16 -08:00
test-in-pyodide-with-shot-scraper.sh Test against pyodide/v314.0.0 2026-06-22 10:11:56 -07:00

Datasette

PyPI Changelog Python 3.x Tests Documentation Status License docker: datasette discord

An open source multi-tool for exploring and publishing data

Datasette is a tool for exploring and publishing data. It helps people take data of any shape or size and publish that as an interactive, explorable website and accompanying API.

Datasette is aimed at data journalists, museum curators, archivists, local governments, scientists, researchers and anyone else who has data that they wish to share with the world.

Explore a demo, watch a video about the project or try it out on GitHub Codespaces.

Want to stay up-to-date with the project? Subscribe to the Datasette newsletter for tips, tricks and news on what's new in the Datasette ecosystem.

Installation

If you are on a Mac, Homebrew is the easiest way to install Datasette:

brew install datasette

You can also install it using pip or pipx:

pip install datasette

Datasette requires Python 3.10 or higher. We also have detailed installation instructions covering other options such as Docker.

Basic usage

datasette serve path/to/database.db

This will start a web server on port 8001 - visit http://localhost:8001/ to access the web interface.

serve is the default subcommand, you can omit it if you like.

Use Chrome on OS X? You can run datasette against your browser history like so:

 datasette ~/Library/Application\ Support/Google/Chrome/Default/History --nolock

Now visiting http://localhost:8001/History/downloads will show you a web interface to browse your downloads data:

Downloads table rendered by datasette

metadata.json

If you want to include licensing and source information in the generated datasette website you can do so using a JSON file that looks something like this:

{
    "title": "Five Thirty Eight",
    "license": "CC Attribution 4.0 License",
    "license_url": "http://creativecommons.org/licenses/by/4.0/",
    "source": "fivethirtyeight/data on GitHub",
    "source_url": "https://github.com/fivethirtyeight/data"
}

Save this in metadata.json and run Datasette like so:

datasette serve fivethirtyeight.db -m metadata.json

The license and source information will be displayed on the index page and in the footer. They will also be included in the JSON produced by the API.

datasette publish

If you have Heroku or Google Cloud Run configured, Datasette can deploy one or more SQLite databases to the internet with a single command:

datasette publish heroku database.db

Or:

datasette publish cloudrun database.db

This will create a docker image containing both the datasette application and the specified SQLite database files. It will then deploy that image to Heroku or Cloud Run and give you a URL to access the resulting website and API.

See Publishing data in the documentation for more details.

Datasette Lite

Datasette Lite is Datasette packaged using WebAssembly so that it runs entirely in your browser, no Python web application server required. Read more about that in the Datasette Lite documentation.